ATL: SAM - Advisories

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Re: ATL: SAM - Advisories

#21 Postby cycloneye » Mon Sep 27, 2021 9:36 pm

BULLETIN
Hurricane Sam Advisory Number 22
NWS National Hurricane Center Miami FL AL182021
1100 PM AST Mon Sep 27 2021

...SAM EXPECTED TO REMAIN A POWERFUL HURRICANE FOR SEVERAL MORE
DAYS...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...16.8N 53.2W
ABOUT 660 MI...1060 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...120 MPH...195 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...956 MB...28.23 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 1100 PM AST (0300 UTC), the center of Hurricane Sam was located
near latitude 16.8 North, longitude 53.2 West. Sam is moving toward
the northwest near 9 mph (15 km/h), and this motion is expected to
continue for the next few days, with an increase in forward speed
beginning on Thursday. A turn to the north is expected by Friday.
On the forecast track, Sam will pass well to the northeast of the
northern Leeward Islands Wednesday and Thursday.

Data from a NOAA Hurricane Hunter plane indicate that maximum
sustained winds remain near 120 mph (195 km/h) with higher gusts.
Sam is a category 3 hurricane on the Saffir-Simpson Hurricane Wind
Scale. The hurricane could strengthen some overnight, and Sam is
anticipated to be a category 3 or 4 hurricane for the next several
days.

Hurricane-force winds extend outward up to 40 miles (65 km) from the
center and tropical-storm-force winds extend outward up to 125 miles
(205 km).

The estimated minimum central pressure from NOAA aircraft data is
956 mb (28.23 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Sam can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC.

SURF: Swells generated by Sam will impact the Lesser Antilles for
the next several days. Swells are expected to reach Bermuda and the
Bahamas mid-to-late week, and then spread to the United States east
coast late this week. These swells could cause life-threatening
surf and rip current conditions. Please consult products from your
local weather office.


NEXT ADVISORY
-------------
Next complete advisory at 500 AM AST.

$$
Forecaster Blake



Hurricane Sam Discussion Number 22
NWS National Hurricane Center Miami FL AL182021
1100 PM AST Mon Sep 27 2021

The NOAA Hurricane Hunters have been flying through Sam tonight,
with radar and wind observations showing broken concentric eyewalls
at times. The maximum 700-mb flight-level winds on the mission
were 114 kt, with peak SFMR values to 103 kt and a central pressure
around 956 mb, so the initial wind speed will remain 105 kt. While
the overall intensity doesn't seem to have changed much in the past
several hours, the aircraft data show that the hurricane has grown
in size, and that is reflected in the initial wind radii.

The future intensity of Sam is hard to pinpoint. Eyewall cycles
will likely play a key role in determining its second peak intensity
since the hurricane should remain in low- or moderate-shear and
warm-water environments for the next few days. Those cycles are
basically impossible to forecast, but there is some suggestion on
satellite that a larger eye is trying to form, which could allow for
some increase in strength in the near term. It seems likely that
Sam will be a category 3 or 4 hurricane given the conducive
environment for most of the forecast period, so the new NHC forecast
is similar to the previous one, with the most significant change
showing a larger hurricane consistent with the latest guidance.

Sam continues to move northwestward, or 315/8 kt. The hurricane
should move in that direction for the next few days around the
southwestern portion of the subtropical high. A turn to the north
is likely as Sam meets the western edge of the high, with a gradual
acceleration to the northeast anticipated by the weekend due to an
incoming mid-latitude trough from the west. While there are some
speed differences in the models, especially near and after
recurvature, the NHC forecast leans toward the faster GFS solution
over the slower ECMWF, given the magnitude of the strong
southwesterly flow that Sam should encounter at long range, plus a
nod to the superior performance of late for the American model. The
new forecast is adjusted a bit to the right and faster beyond day 3,
with no significant changes made before that time.


Key Messages:

1. Large swells generated by Sam are affecting the Leeward Islands
and will spread to portions of the Virgin Islands, Puerto Rico,
Hispaniola, the Bahamas, and Bermuda by Thursday or Friday.
Significant swells will likely reach the east coast of the United
States and Atlantic Canada by the weekend. These swells will likely
cause life-threatening surf and rip current conditions, and
beachgoers and other interests along these coasts are urged to
follow the advice of lifeguards and local officials through the
upcoming weekend.


FORECAST POSITIONS AND MAX WINDS

INIT 28/0300Z 16.8N 53.2W 105 KT 120 MPH
12H 28/1200Z 17.5N 54.0W 115 KT 130 MPH
24H 29/0000Z 18.4N 55.1W 115 KT 130 MPH
36H 29/1200Z 19.3N 56.4W 110 KT 125 MPH
48H 30/0000Z 20.6N 58.0W 110 KT 125 MPH
60H 30/1200Z 22.2N 59.7W 110 KT 125 MPH
72H 01/0000Z 24.3N 61.0W 110 KT 125 MPH
96H 02/0000Z 29.6N 61.5W 105 KT 120 MPH
120H 03/0000Z 37.5N 56.9W 100 KT 115 MPH

$$
Forecaster Blake
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Re: ATL: SAM - Advisories

#22 Postby cycloneye » Tue Sep 28, 2021 3:54 am

BULLETIN
Hurricane Sam Advisory Number 23
NWS National Hurricane Center Miami FL AL182021
500 AM AST Tue Sep 28 2021

...AIR FORCE HURRICANE HUNTERS FIND SAM HAS STRENGTHENED...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...17.2N 53.9W
ABOUT 610 MI...980 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...130 MPH...215 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...953 MB...28.15 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 500 AM AST (0900 UTC), the center of Hurricane Sam was located
near latitude 17.2 North, longitude 53.9 West. Sam is moving toward
the northwest near 9 mph (15 km/h), and this motion is expected to
continue for the next few days, with an increase in forward speed
beginning on Thursday. A turn toward the north is expected by
Friday. On the forecast track, Sam will pass well to the northeast
of the northern Leeward Islands on Wednesday and Thursday.

Data from an Air Force Reserve Hurricane Hunter aircraft indicate
that maximum sustained winds have increased to near 130 mph (215
km/h) with higher gusts. Sam is a category 4 hurricane on the
Saffir-Simpson Hurricane Wind Scale. Some fluctuations in intensity
are expected during the next couple of days, but Sam is forecast to
remain a major hurricane through late this week.

Hurricane-force winds extend outward up to 40 miles (65 km) from the
center and tropical-storm-force winds extend outward up to 125 miles
(205 km).

The estimated minimum central pressure based on dropsonde data from
the aircraft is 953 mb (28.15 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Sam can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC.

SURF: Swells generated by Sam will impact the Lesser Antilles for
the next several days. Swells are expected to reach Bermuda and the
Bahamas in a couple of days, and then spread to the United States
east coast late this week. These swells could cause
life-threatening surf and rip current conditions. Please consult
products from your local weather office.


NEXT ADVISORY
-------------
Next complete advisory at 1100 AM AST.

$$
Forecaster Reinhart


Hurricane Sam Discussion Number 23
NWS National Hurricane Center Miami FL AL182021
500 AM AST Tue Sep 28 2021

The Air Force Reserve Hurricane Hunters that investigated Sam early
this morning found evidence that the hurricane has strengthened.
Peak 700-mb flight-level winds of 126 kt were reported in the
northeastern quadrant, which after the standard adjustment would
support an intensity of 110-115 kt. Satellite data also indicate
that Sam's structure has improved overnight. Sam's inner core
appears to have consolidated into a single, primary eyewall in
recent GMI and AMSR2 microwave imagery, and the latest GOES-16
infrared imagery shows a colder ring of convective cloud tops
developing around the eye of Sam. This has brought the latest
UW-CIMSS ADT and SATCON estimates up to around 115 kt. Based on the
flight-level wind data and ongoing satellite trends, the initial
intensity is raised to 115 kt for this advisory. The minimum central
pressure of 953 mb is based on a center dropsonde of 954 mb with
12-kt surface winds.

In the short-term, internal dynamic processes that are difficult to
predict could cause some fluctuations in Sam's intensity. If Sam's
eyewall is able to contract today, some additional strengthening
could occur, and this possibility is reflected in the latest NHC
intensity forecast. Thereafter, the warm sea-surface temperatures
and weak to moderate vertical wind shear along Sam's forecast track
suggest it should remain a major hurricane for the next several
days. Thus, the NHC forecast only shows gradual weakening through
72-96 h, in agreement with the consensus aids IVCN and HCCA. By days
4-5, increasing southerly wind shear along with decreasing SSTs
should increase Sam's rate of weakening as it recurves deeper into
the mid-latitudes.

Aircraft and microwave data indicate that Sam is slightly tilted in
the vertical, with the low-level center displaced just a bit to the
south of the mid-level eye. Based on recent aircraft fixes, Sam's
initial motion is northwestward, or 310/8 kt. This motion is
expected to continue for the next few days as Sam moves around the
southwestern periphery of the subtropical ridge. A mid- to
upper-level trough is forecast to dig southward over the western
Atlantic later this week, which should steer Sam toward the north by
Friday. Then, Sam is expected to accelerate north-northeastward
within the deep-layer southerly flow ahead of the trough this
weekend. The official NHC track forecast is very similar to the
previous one, with just a slight adjustment to the left based on the
latest track guidance consensus aids. The along-track spread in the
guidance noticeably increases as Sam recurves over the western
Atlantic, with the ECMWF much slower than the GFS. Once again, the
NHC forecast trends closer to the faster GFS solution at longer
ranges, given its better overall performance this season.


Key Messages:

1. Large swells generated by Sam are affecting the Leeward Islands
and will spread to portions of the Virgin Islands, Puerto Rico,
Hispaniola, the Bahamas, and Bermuda by Thursday or Friday.
Significant swells will likely reach the east coast of the United
States and Atlantic Canada by the weekend. These swells will likely
cause life-threatening surf and rip current conditions, and
beachgoers and other interests along these coasts are urged to
follow the advice of lifeguards and local officials through the
upcoming weekend.


FORECAST POSITIONS AND MAX WINDS

INIT 28/0900Z 17.2N 53.9W 115 KT 130 MPH
12H 28/1800Z 17.9N 54.7W 120 KT 140 MPH
24H 29/0600Z 18.8N 55.9W 115 KT 130 MPH
36H 29/1800Z 19.9N 57.4W 115 KT 130 MPH
48H 30/0600Z 21.3N 59.0W 110 KT 125 MPH
60H 30/1800Z 23.2N 60.5W 110 KT 125 MPH
72H 01/0600Z 25.6N 61.5W 110 KT 125 MPH
96H 02/0600Z 31.4N 60.7W 105 KT 120 MPH
120H 03/0600Z 39.0N 56.0W 95 KT 110 MPH

$$
Forecaster Reinhart
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Re: ATL: SAM - Advisories

#23 Postby cycloneye » Tue Sep 28, 2021 9:35 am

BULLETIN
Hurricane Sam Advisory Number 24
NWS National Hurricane Center Miami FL AL182021
1100 AM AST Tue Sep 28 2021

...SAM REMAINS A POWERFUL CATEGORY 4 HURRICANE OVER THE TROPICAL
ATLANTIC...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...17.5N 54.3W
ABOUT 580 MI...935 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...130 MPH...215 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 8 MPH...13 KM/H
MINIMUM CENTRAL PRESSURE...952 MB...28.12 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 1100 AM AST (1500 UTC), the eye of Hurricane Sam was located near
latitude 17.5 North, longitude 54.3 West. Sam is moving toward the
northwest near 8 mph (13 km/h) and this motion with an increase in
forward is expected during the next couple of days. A turn toward
the north is forecast to occur by Friday. On the forecast track,
Sam will pass well to the east of the northern Leeward Islands
through Wednesday.

Maximum sustained winds remain near 130 mph (215 km/h) with higher
gusts. Sam is a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Some fluctuations in intensity are expected
during the next couple of days, but Sam is forecast to remain a
major hurricane through late this week.

Hurricane-force winds extend outward up to 40 miles (65 km) from the
center and tropical-storm-force winds extend outward up to 140 miles
(220 km).

The estimated minimum central pressure is 952 mb (28.12 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Sam can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC.

SURF: Swells generated by Sam will impact the Lesser Antilles
during the next several days. Swells are expected to reach Bermuda
and the Bahamas in a couple of days, and then spread to the United
States east coast late this week. These swells could cause
life-threatening surf and rip current conditions. Please consult
products from your local weather office.


NEXT ADVISORY
-------------
Next complete advisory at 500 PM AST.

$$
Forecaster Cangialosi


Hurricane Sam Discussion Number 24
NWS National Hurricane Center Miami FL AL182021
1100 AM AST Tue Sep 28 2021

Satellite images indicate that Sam has been generally steady in
strength during the past several hours, and it remains a powerful
category 4 hurricane on the Saffir-Simpson Hurricane Wind Scale.
The storm has a well-defined eye, and the convective pattern
surrounding the center is fairly symmetric. A 1043 UTC SSMIS pass
showed a closed and symmetric eyewall, with no indication of a
concentric eyewall. The latest Dvorak classifications from TAFB
and SAB were 5.5/102 kt and the CIMSS automated technique is
currently 6.2/120 kt. Based on these satellite estimates and the
overnight reconnaissance data, the initial intensity is held at
115 kt. Another Air Force Hurricane Hunter aircraft is scheduled to
investigate Sam this afternoon.

The major hurricane is moving slowly northwestward, with the initial
motion estimated to be 305/7 kt. A mid-level ridge situated to the
north-northeast of Sam is expected to shift eastward as a deep-layer
trough digs southeastward over the western Atlantic. This change in
the large-scale pattern should cause Sam to speed up and gradually
turn toward the north in 2 or 3 days and then to the northeast in 4
to 5 days. The models are in fairly good agreement, and the new
forecast track is essentially an update of the previous one. Based
on the forecast, Sam should pass well east of the northern Leeward
Island through Wednesday and east of Bermuda Friday night and
Saturday.

Sam is expected to remain in favorable environmental conditions for
it to maintain its intensity, or perhaps strengthen slightly, during
the next day or two. However, after that time, a gradual increase
in southerly shear should promote a slow weakening trend, and Sam
will likely be beginning its transition to an extratropical cyclone
toward the end of the forecast period. The NHC intensity forecast
is also an update of the previous one and in line with the various
consensus aids. Sam is expected to remain a major hurricane during
the next several days.

The initial wind radii have been adjusted based on a 1114 UTC
ASCAT-A pass.

Key Messages:

1. Large swells generated by Sam are affecting the Leeward Islands
and will spread to portions of the Virgin Islands, Puerto Rico,
Hispaniola, the Bahamas, and Bermuda by Thursday or Friday.
Significant swells will likely reach the east coast of the United
States and Atlantic Canada by the weekend. These swells will likely
cause life-threatening surf and rip current conditions, and
beachgoers and other interests along these coasts are urged to
follow the advice of lifeguards and local officials through the
upcoming weekend.


FORECAST POSITIONS AND MAX WINDS

INIT 28/1500Z 17.5N 54.3W 115 KT 130 MPH
12H 29/0000Z 18.2N 55.1W 120 KT 140 MPH
24H 29/1200Z 19.2N 56.5W 115 KT 130 MPH
36H 30/0000Z 20.5N 58.1W 115 KT 130 MPH
48H 30/1200Z 22.0N 59.6W 110 KT 125 MPH
60H 01/0000Z 24.0N 60.9W 110 KT 125 MPH
72H 01/1200Z 26.6N 61.5W 110 KT 125 MPH
96H 02/1200Z 32.5N 59.7W 100 KT 115 MPH
120H 03/1200Z 39.2N 54.8W 90 KT 105 MPH

$$
Forecaster Cangialosi
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Re: ATL: SAM - Advisories

#24 Postby cycloneye » Tue Sep 28, 2021 3:41 pm

BULLETIN
Hurricane Sam Advisory Number 25
NWS National Hurricane Center Miami FL AL182021
500 PM AST Tue Sep 28 2021

...SAM MAINTAINING CATEGORY 4 INTENSITY OVER THE TROPICAL
ATLANTIC...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...17.9N 55.0W
ABOUT 530 MI...855 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...130 MPH...215 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...947 MB...27.97 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 500 PM AST (2100 UTC), the eye of Hurricane Sam was located by
an Air Force Reserve Unit Hurricane Hunter aircraft near latitude
17.9 North, longitude 55.0 West. Sam is moving toward the northwest
near 9 mph (15 km/h), and this general motion with an increase in
forward speed is expected during the next couple of days. A turn
toward the north is forecast by Friday. On the forecast track, Sam
will pass well to the east or northeast of the northern Leeward
Islands through Wednesday.

Maximum sustained winds are near 130 mph (215 km/h) with higher
gusts. Sam is a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Some fluctuations in intensity are expected
during the next couple of days, but Sam is forecast to remain a
major hurricane through late this week.

Hurricane-force winds extend outward up to 40 miles (65 km) from the
center and tropical-storm-force winds extend outward up to 140 miles
(220 km).

The minimum central pressure estimated from Air Force Hurricane
Hunter aircraft observations is 947 mb (27.97 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Sam can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC.

SURF: Swells generated by Sam will impact the Lesser Antilles
during the next several days. Swells are expected to reach Bermuda
and the Bahamas in a couple of days, and then spread to the United
States east coast late this week. These swells could cause
life-threatening surf and rip current conditions. Please consult
products from your local weather office.


NEXT ADVISORY
-------------
Next complete advisory at 1100 PM AST.

$$
Forecaster Pasch




Hurricane Sam Discussion Number 25
NWS National Hurricane Center Miami FL AL182021
500 PM AST Tue Sep 28 2021

Sam has looked a little less impressive on satellite imagery this
afternoon, particularly on the infrared channels where the eye is
not very well-defined. However, observations from the Air Force
Hurricane Hunters indicate that the hurricane is maintaining
category 4 intensity since a blend of the latest flight-level and
SFMR-observed surface winds support maintaining 115-kt winds. The
aircraft also measured a quite low central pressure of 947 mb on
two passes through the eye. Upper-level outflow remains well
defined except over the southwest quadrant of the circulation, and
several arc clouds are seen emanating from the system over the
western semicircle, indicative of some dry mid-level air in the
environment. However, this dry air is apparently not significantly
affecting the inner core of Sam, given that it has remained a
powerful hurricane.

Center fixes yield a continued slow northwestward motion of around
305/8 kt. There is little change to the track forecast reasoning
from the previous advisories. Sam is likely to move around the
southwestern periphery of a subtropical ridge for the next couple of
days. A turn toward the north, ahead of a large mid-tropospheric
trough moving off the United States east coast, is forecast around
day 3. Later in the forecast period, the hurricane is expected to
accelerate northeastward within the flow on the eastern side of the
trough. There is good agreement among most of the guidance models
on this general track, and the official forecast is very close
to the model consensus.

Since Sam will remain in a low-shear environment and over a warm
ocean surface for the next few days, some re-intensification is
possible, and the system is likely to remain a major hurricane
for the next 4 days or so. The official intensity forecast is not
much different from the latest NOAA corrected consensus forecast,
HCCA.


Key Messages:

1. Large swells generated by Sam are affecting the Leeward Islands
and will spread to portions of the Virgin Islands, Puerto Rico,
Hispaniola, the Bahamas, and Bermuda by Thursday or Friday.
Significant swells will likely reach the east coast of the United
States and Atlantic Canada by the weekend. These swells will likely
cause life-threatening surf and rip current conditions, and
beachgoers and other interests along these coasts are urged to
follow the advice of lifeguards and local officials through the
upcoming weekend.


FORECAST POSITIONS AND MAX WINDS

INIT 28/2100Z 17.9N 55.0W 115 KT 130 MPH
12H 29/0600Z 18.6N 55.9W 120 KT 140 MPH
24H 29/1800Z 19.7N 57.4W 115 KT 130 MPH
36H 30/0600Z 21.0N 59.1W 115 KT 130 MPH
48H 30/1800Z 22.8N 60.6W 110 KT 125 MPH
60H 01/0600Z 25.0N 61.6W 110 KT 125 MPH
72H 01/1800Z 27.7N 62.0W 110 KT 125 MPH
96H 02/1800Z 33.5N 59.0W 100 KT 115 MPH
120H 03/1800Z 40.0N 53.5W 90 KT 105 MPH

$$
Forecaster Pasch
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Re: ATL: SAM - Advisories

#25 Postby cycloneye » Tue Sep 28, 2021 9:36 pm

BULLETIN
Hurricane Sam Advisory Number 26
NWS National Hurricane Center Miami FL AL182021
1100 PM AST Tue Sep 28 2021

...SAM SLOWLY STRENGTHENING WITH 140-MPH WINDS...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...18.4N 55.6W
ABOUT 490 MI...790 KM E OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...140 MPH...220 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...944 MB...27.88 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 1100 PM AST (0300 UTC), the eye of Hurricane Sam was located
near latitude 18.4 North, longitude 55.6 West. Sam is moving toward
the northwest near 9 mph (15 km/h), and this general motion with an
increase in forward speed is expected during the next couple of
days. A turn toward the north is forecast by Friday. On the
forecast track, Sam will pass well to the east and northeast of
the northern Leeward Islands through Wednesday.

Maximum sustained winds are near 140 mph (220 km/h) with higher
gusts. Sam is a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Some fluctuations in intensity are expected
during the next couple of days, but Sam is forecast to remain a
major hurricane through late this week.

Hurricane-force winds extend outward up to 40 miles (65 km) from the
center and tropical-storm-force winds extend outward up to 140 miles
(220 km).

The estimated minimum central pressure is 944 mb (27.88 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Sam can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC.

SURF: Swells generated by Sam will impact the Lesser Antilles
during the next several days. Swells are expected to reach Bermuda
and the Bahamas in a couple of days, and then spread to the United
States east coast late this week. These swells could cause
life-threatening surf and rip current conditions. Please consult
products from your local weather office.


NEXT ADVISORY
-------------
Next complete advisory at 500 AM AST.

$$
Forecaster Blake


Hurricane Sam Discussion Number 26
NWS National Hurricane Center Miami FL AL182021
1100 PM AST Tue Sep 28 2021

Satellite images suggest that Sam has strengthened. The eyewall of
the hurricane has become more intense, with a warmer eye noted
during the past several hours since the last reconnaissance aircraft
departed. The initial wind speed is nudged upward to 120 kt, a
little above what the previous aircraft mission from this afternoon
supported. Another Air Force Reserve Hurricane Hunter plane is
scheduled to fly through Sam in a few hours for a better look at the
intensity.

Sam is forecast to move into an area with somewhat lower wind shear
and higher ocean heat content by late Wednesday. In addition, the
hurricane will likely be moving a little faster, which decreases the
upwelling potential under the storm. These factors lead me to
believe Sam isn't quite done intensifying, and could reach another
peak sometime late Wednesday or Thursday. The one fly-in-the-
ointment to this forecast is another eyewall replacement cycle
potentially beginning, although recent microwave data doesn't give
that impression. Thus, the new forecast is raised from the last
one during the first couple of days, on the higher side of the
guidance. A more consistent weakening trend is expected late week,
due to cooler SSTs and increasing shear, and no significant
changes were made to the official forecast at long range.

The hurricane continues moving northwestward at about 8 kt. Models
are locked into this track continuing for the next day or two at a
faster pace around the southwestern portion of a strengthening
Atlantic subtropical ridge. Thereafter, Sam should turn northward
on Friday and northeastward this weekend, likely a fair distance
east of Bermuda, due to a large mid-latitude trough moving off of
the United States east coast. Model guidance remains in close
agreement on almost all of the forecast, and the only significant
change from the last advisory is an eastward adjustment on Day 5 due
to guidance suggesting that Sam gets shunted more eastward by the
trough, rather than captured by it.


Key Messages:

1. Large swells generated by Sam are affecting the Leeward Islands
and will spread to portions of the Virgin Islands, Puerto Rico,
Hispaniola, the Bahamas, and Bermuda by Thursday or Friday.
Significant swells will likely reach the east coast of the United
States and Atlantic Canada by the weekend. These swells will likely
cause life-threatening surf and rip current conditions, and
beachgoers and other interests along these coasts are urged to
follow the advice of lifeguards and local officials through the
upcoming weekend.


FORECAST POSITIONS AND MAX WINDS

INIT 29/0300Z 18.4N 55.6W 120 KT 140 MPH
12H 29/1200Z 19.1N 56.7W 120 KT 140 MPH
24H 30/0000Z 20.2N 58.2W 125 KT 145 MPH
36H 30/1200Z 21.8N 59.9W 125 KT 145 MPH
48H 01/0000Z 23.9N 61.2W 120 KT 140 MPH
60H 01/1200Z 26.4N 61.9W 115 KT 130 MPH
72H 02/0000Z 29.1N 61.8W 110 KT 125 MPH
96H 03/0000Z 35.0N 58.0W 100 KT 115 MPH
120H 04/0000Z 40.0N 52.0W 85 KT 100 MPH

$$
Forecaster Blake
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Re: ATL: SAM - Advisories

#26 Postby cycloneye » Wed Sep 29, 2021 4:45 am

Hurricane Sam Discussion Number 27
NWS National Hurricane Center Miami FL AL182021
500 AM AST Wed Sep 29 2021

The eye of Sam has become cloud filled in infrared satellite
imagery overnight, but the ring of deep convection surrounding the
eye has cooled. There appears to be a southwest-to-northeast tilt to
Sam's circulation as some modest southwesterly shear seems to be
impinging on the hurricane. An Air Force Reserve Hurricane
Hunter aircraft that has been investigating Sam overnight shows
that the hurricane continues to fluctuate in intensity. The
aircraft has reported a peak flight-level wind of 124 kt and SFMR
winds of 108 kt. Therefore the initial wind speed has been set at
115 kt, which leans toward the higher flight-level-to-surface wind
reduction. The aircraft also reported a minimum pressure of 950 mb,
which is up a few millibars from the flight yesterday afternoon.
The fluctuations in intensity that Sam has experienced over the
past couple of days are fairly typical for hurricanes of this
strength.

As mentioned in the previous advisory, Sam will be moving into a
lower vertical wind shear environment, and the expected faster
forward speed decreases the potential for upwelling beneath the
storm. As a result, some re-intensification is forecast, but
difficult-to-predict eyewall replacement cycles could cause
additional fluctuations in intensity over the next day or two.
After 60 to 72 hours, a more pronounced weakening trend is likely
to begin as the storm moves over cooler SSTs and the vertical
shear increases. The global models indicate that Sam will begin its
transition into a powerful extratropical cyclone late in the
period, but that transition will likely not be completed until
after 120 h.

Sam is moving northwestward at about 8 kt. The track guidance
remains in excellent agreement through 96 hours as Sam should move
northwestward and then northward around the western portion of the
subtropical ridge over the eastern Atlantic during the next few
days. By Saturday, Sam is forecast to turn northeastward between
the aforementioned ridge and a deep-layer trough over the
northeastern U.S. and Nova Scotia. By late in the period, there
is an increase in spread in the guidance which is related to how
Sam interacts with the deep-layer trough. For now, the NHC track
forecast at days 4 and 5 lies between the TVCA multi-model
consensus and the HFIP corrected consensus aid. Overall, little
change to the previous NHC track forecast was required for this
advisory.


Key Messages:

1. Large swells generated by Sam are affecting the Leeward Islands
and will spread to portions of the Virgin Islands, Puerto Rico,
Hispaniola, the Bahamas, and Bermuda by Thursday or Friday.
Significant swells will likely reach the east coast of the United
States and Atlantic Canada by the weekend. These swells will likely
cause life-threatening surf and rip current conditions, and
beachgoers and other interests along these coasts are urged to
follow the advice of lifeguards and local officials through the
upcoming weekend.


FORECAST POSITIONS AND MAX WINDS

INIT 29/0900Z 18.9N 56.2W 115 KT 130 MPH
12H 29/1800Z 19.7N 57.3W 120 KT 140 MPH
24H 30/0600Z 21.0N 58.9W 120 KT 140 MPH
36H 30/1800Z 22.8N 60.4W 120 KT 140 MPH
48H 01/0600Z 25.2N 61.5W 115 KT 130 MPH
60H 01/1800Z 27.9N 62.0W 115 KT 130 MPH
72H 02/0600Z 30.8N 61.5W 110 KT 125 MPH
96H 03/0600Z 35.8N 57.5W 95 KT 110 MPH
120H 04/0600Z 40.8N 52.0W 80 KT 90 MPH

$$
Forecaster Brown
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Re: ATL: SAM - Advisories

#27 Postby cycloneye » Wed Sep 29, 2021 9:53 am

BULLETIN
Hurricane Sam Advisory Number 28
NWS National Hurricane Center Miami FL AL182021
1100 AM AST Wed Sep 29 2021

...POWERFUL SAM CONTINUES MOVING SLOWLY NORTHWESTWARD...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...19.4N 57.0W
ABOUT 405 MI...655 KM ENE OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...130 MPH...215 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...949 MB...28.03 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 1100 AM AST (1500 UTC), the center of Hurricane Sam was located
near latitude 19.4 North, longitude 57.0 West. Sam is moving toward
the northwest near 9 mph (15 km/h), and this general motion with an
increase in forward speed is expected during the next couple of
days. A turn toward the north is forecast by Friday. On the
forecast track, Sam will pass well to the east-northeast of the
northern Leeward Islands through tonight.

Maximum sustained winds are near 130 mph (215 km/h) with higher
gusts. Sam is a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Some fluctuations in intensity are expected
during the next couple of days, but Sam is forecast to remain a
major hurricane through late this week.

Hurricane-force winds extend outward up to 40 miles (65 km) from the
center and tropical-storm-force winds extend outward up to 125 miles
(205 km).

The minimum central pressure estimated from NOAA Hurricane Hunter
aircraft observations is 949 mb (28.03 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Sam can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC.

SURF: Swells generated by Sam will impact the Lesser Antilles
during the next several days. Swells are expected to reach Bermuda
and the Bahamas in a day or so, and then spread to the United
States east coast by this weekend. These swells could cause
life-threatening surf and rip current conditions. Please consult
products from your local weather office.


NEXT ADVISORY
-------------
Next complete advisory at 500 PM AST.

$$
Forecaster Pasch




Hurricane Sam Discussion Number 28
NWS National Hurricane Center Miami FL AL182021
1100 AM AST Wed Sep 29 2021

Sam has a well-organized cloud pattern on satellite imagery, with a
90 n mi-wide Central Dense Overcast surrounded by numerous
convective banding features. Upper-level outflow has now become
better established to the southeast of the hurricane. A NOAA
Hurricane Hunter mission from a couple of hours ago reported a 20 n
mi-wide diameter circular eye. The current intensity is held at 115
kt for this advisory, which is a little higher than the maximum
winds observed in the earlier aircraft mission. However, since the
estimated minimum central pressure of 949 is a little lower than it
was earlier this morning and Sam's intensity has been fluctuating,
it is considered prudent not to lower the winds at this time. An
Air Force Hurricane Hunter aircraft is scheduled to investigate the
hurricane soon and will provide another intensity estimate.

Sam continues its slow northwestward trek with the current motion
remaining near 310/8 kt. Sam should move northwestward and then
northward around the western portion of the subtropical ridge over
the eastern Atlantic during the next few days, and turn toward
the north-northeast and northeast later in the forecast period.
The track guidance models are in very good agreement through 72
hours or so, with some increase in model spread thereafter. This
increase in spread is largely due to how Sam will interact with a
strong mid-latitude trough moving through Atlantic Canada. Some
of the guidance suggests that this trough could partially bypass
the hurricane around the end of the period and beyond, but this
is not yet clear. The current NHC forecast track is not much
different from the previous one and is in good agreement with the
dynamical model consensus, TVCA.

The hurricane will continue to move over warm waters and in an
environment of low vertical shear and diffluent upper-level flow
for the next 1-2 days. Thus, it would not be surprising to soon
see some restrengthening. The official intensity forecast is
essentially a blend of the latest Decay-SHIPS and LGEM predictions,
and is very similar to the previous NHC forecast. Sam is likely to
remain a major hurricane into this weekend.


Key Messages:

1. Large swells generated by Sam are affecting the Leeward Islands
and will spread to portions of the Virgin Islands, Puerto Rico,
Hispaniola, the Bahamas, and Bermuda by Thursday or Friday.
Significant swells will likely reach the east coast of the United
States and Atlantic Canada by the weekend. These swells will likely
cause life-threatening surf and rip current conditions, and
beachgoers and other interests along these coasts are urged to
follow the advice of lifeguards and local officials through the
upcoming weekend.


FORECAST POSITIONS AND MAX WINDS

INIT 29/1500Z 19.4N 57.0W 115 KT 130 MPH
12H 30/0000Z 20.3N 58.1W 120 KT 140 MPH
24H 30/1200Z 21.8N 59.6W 120 KT 140 MPH
36H 01/0000Z 23.9N 61.0W 120 KT 140 MPH
48H 01/1200Z 26.6N 61.8W 115 KT 130 MPH
60H 02/0000Z 29.4N 61.8W 110 KT 125 MPH
72H 02/1200Z 32.0N 60.9W 105 KT 120 MPH
96H 03/1200Z 36.2N 57.3W 90 KT 105 MPH
120H 04/1200Z 39.5N 53.0W 75 KT 85 MPH

$$
Forecaster Pasch
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Re: ATL: SAM - Advisories

#28 Postby cycloneye » Wed Sep 29, 2021 3:57 pm

BULLETIN
Hurricane Sam Advisory Number 29
NWS National Hurricane Center Miami FL AL182021
500 PM AST Wed Sep 29 2021

...CATEGORY 4 HURRICANE SAM PASSING WELL TO THE EAST-NORTHEAST OF
THE NORTHERN LEEWARD ISLANDS...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...20.2N 57.6W
ABOUT 385 MI...620 KM ENE OF THE NORTHERN LEEWARD ISLANDS
MAXIMUM SUSTAINED WINDS...130 MPH...215 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 9 MPH...15 KM/H
MINIMUM CENTRAL PRESSURE...945 MB...27.91 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 500 PM AST (2100 UTC), the center of Hurricane Sam was located
near latitude 20.2 North, longitude 57.6 West. Sam is moving toward
the northwest near 9 mph (15 km/h), and this general motion with an
increase in forward speed is expected during the next couple of
days. A turn toward the north is forecast by Friday. On the
forecast track, Sam will continue to pass well to the
east-northeast of the northern Leeward Islands through tonight.

Maximum sustained winds are near 130 mph (215 km/h) with higher
gusts. Sam is a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Some fluctuations in intensity are expected
during the next couple of days, but Sam is forecast to remain a
major hurricane through late this week.

Hurricane-force winds extend outward up to 40 miles (65 km) from the
center and tropical-storm-force winds extend outward up to 140 miles
(220 km).

An Air Force Reserve Unit Hurricane Hunter aircraft reported a
minimum central pressure of 945 mb (27.91 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Sam can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC.

SURF: Swells generated by Sam will impact the Lesser Antilles
during the next several days. Swells are expected to reach Bermuda
and the Bahamas in a day or so, and then spread to the United
States east coast by this weekend. These swells could cause
life-threatening surf and rip current conditions. Please consult
products from your local weather office.


NEXT ADVISORY
-------------
Next complete advisory at 1100 PM AST.

$$
Forecaster Pasch



Hurricane Sam Discussion Number 29
NWS National Hurricane Center Miami FL AL182021
500 PM AST Wed Sep 29 2021

Sam continues to exhibit a well-organized cloud pattern on satellite
imagery, although there is some asymmetry of the coldest-topped
convection around the center. The hurricane is also maintaining
numerous banding features with well-defined upper-level
anticyclonic outflow. Observations from an Air Force Hurricane
Hunter plane showed peak 700 mb fight-level winds of 130 kt in the
northeast quadrant which, using the standard reduction, corresponds
to maximum surface winds of 117 kt. However, the maximum
SFMR-observed surface winds were 103 kt. Based on these data, with
more emphasis on the flight-level winds, the current intensity
estimate is held at 115 kt. The aircraft also measured a minimum
central pressure of 945 mb by dropsonde.

Since the hurricane is forecast to remain in an environment of low
vertical shear and to remain over warm waters through 48 hours, Sam
could restrengthen a little more during the next day or so. Since
the Hurricane Hunters reported a concentric eyewall,
short-term strengthening may be curtailed until the eyewall
replacement cycle completes. Later in the forecast period, gradual
weakening is likely due to cooler SSTs and increasing shear. The
official intensity forecast is in very good agreement with the
latest corrected consensus prediction. Sam will likely be close to
extratropical transition around day 5.

The initial motion is still northwestward, or 310/8 kt. During
the next few days, Sam is likely to move northwestward and then
northward around the western periphery of a large subtropical high
pressure system centered over the eastern Atlantic. A turn to the
north-northeast and northeast is expected later in the forecast
period as Sam begins to encounter the flow on the southern side of
a large mid-tropospheric trough moving through Atlantic Canada.
The track guidance models remain in excellent agreement through 72
hours, including the time that Sam passes by Bermuda. At days 4-5
there is some divergence of the model guidance, apparently due to
how Sam may interact with the trough. Most notably the ECMWF is a
lot slower than the other global models suggesting that the trough
will at least partially bypass it in that case. Not much change
has been made to the previous official forecast, however, and the
NHC track remains very close to the TVCN dynamical model consensus.


Key Messages:

1. Swells generated by Sam will impact the Lesser Antilles during
the next several days. Swells are expected to reach Bermuda
and the Bahamas in a day or so, and then spread to the United
States east coast by this weekend. These swells could cause
life-threatening surf and rip current conditions. Please consult
products from your local weather office.


FORECAST POSITIONS AND MAX WINDS

INIT 29/2100Z 20.2N 57.6W 115 KT 130 MPH
12H 30/0600Z 21.2N 58.9W 120 KT 140 MPH
24H 30/1800Z 23.1N 60.4W 120 KT 140 MPH
36H 01/0600Z 25.6N 61.4W 120 KT 140 MPH
48H 01/1800Z 28.3N 61.9W 115 KT 130 MPH
60H 02/0600Z 31.0N 61.3W 110 KT 125 MPH
72H 02/1800Z 33.6N 59.9W 100 KT 115 MPH
96H 03/1800Z 37.5N 55.0W 85 KT 100 MPH
120H 04/1800Z 42.0N 48.5W 70 KT 80 MPH

$$
Forecaster Pasch
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Re: ATL: SAM - Advisories

#29 Postby cycloneye » Wed Sep 29, 2021 10:01 pm

Hurricane Sam Discussion Number 30
NWS National Hurricane Center Miami FL AL182021
1100 PM AST Wed Sep 29 2021

Sam is intensifying tonight after completing an eyewall replacement
cycle. A recent NOAA Hurricane Hunter aircraft showed peak 700 mb
flight-level winds of 138 kt, multiple SFMR surface winds of 120 kt
or greater, plus falling central pressure to about 940 mb. This
deepening trend is also seen on recent satellite imagery, with
significant warming within the eye noted. These data support
raising the initial intensity to 125 kt for this advisory. It is
of note that the NOAA mission has been quite helpful for both the
size and intensity analysis, with dropsondes and SFMR data showing
that the hurricane has grown quite a bit since earlier today,
mostly on the eastern side. Additionally, reflectivity data
from the core confirmed the end of the eyewall replacement cycle.

The hurricane could strengthen a little more overnight while it
moves over a warm ocean eddy in fairly light shear. Afterward,
gradually cooling SSTs, falling ocean heat content, and the
inevitable future eyewall replacement cycles should cause a
weakening trend. However, this will likely not be as steady as
shown below, and significant deviations (upward or downward) from
the forecast can be expected. Faster weakening is expected by the
weekend due to cool SSTs and increasing shear. The new forecast is
close to the intensity consensus, and is a little higher than the
previous NHC prediction early on, primarily due to the initial wind
speed.

Sam has sped up tonight, now estimated at 315/10 kt. It sounds like
a broken record, but there are no changes to the forecast during the
first few days as model guidance is in excellent agreement on a
gradually rightward-curving track, passing a couple of hundred n mi
or more east of Bermuda. Afterward, guidance is actually in worse
agreement over the weekend, with widely divergent solutions from an
upper-level trough picking up Sam and turning it north toward
Newfoundland or the trough leaving Sam behind, causing a slow
eastward motion. The trend in the guidance is for a slower motion
at long range, so I've elected to keep the day 4 and 5 points almost
the same as the previous advisory, just a hair faster than the
latest consensus aids.


Key Messages:

1. Swells generated by Sam will impact the Lesser Antilles during
the next several days. Swells are expected to reach Bermuda
and the Bahamas in a day or so, and then spread to the United
States east coast by this weekend. These swells could cause
life-threatening surf and rip current conditions. Please consult
products from your local weather office.

2. A Tropical Storm Watch could be required for Bermuda on
Thursday, and interests there should monitor the progress of Sam.


FORECAST POSITIONS AND MAX WINDS

INIT 30/0300Z 20.6N 58.4W 125 KT 145 MPH
12H 30/1200Z 21.9N 59.6W 130 KT 150 MPH
24H 01/0000Z 24.1N 60.9W 125 KT 145 MPH
36H 01/1200Z 26.8N 61.8W 120 KT 140 MPH
48H 02/0000Z 29.6N 61.8W 115 KT 130 MPH
60H 02/1200Z 32.2N 60.7W 110 KT 125 MPH
72H 03/0000Z 34.3N 59.2W 100 KT 115 MPH
96H 04/0000Z 37.5N 54.5W 85 KT 100 MPH
120H 05/0000Z 42.0N 48.5W 70 KT 80 MPH

$$
Forecaster Blake
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Re: ATL: SAM - Advisories

#30 Postby cycloneye » Thu Sep 30, 2021 4:24 am

Hurricane Sam Discussion Number 31
NWS National Hurricane Center Miami FL AL182021
500 AM AST Thu Sep 30 2021

Sam is a very impressive hurricane in infrared satellite imagery
this morning. The 25-nm-wide eye remains very distinct and is
surrounded by a ring of convection with cloud tops around -65C.
The outflow is also well established in all quadrants. An Air Force
Reserve Hurricane Hunter aircraft that performed three eyewall
penetrations overnight has reported peak 700-mb flight-level winds
of 139 kt in the northeastern, southeastern, and eastern eyewall,
and peak SFMR surface winds of 119 kt. These data still support an
initial wind speed of 125 kt. Sam's minimum pressure has fallen a
few millibars since the NOAA aircraft mission last evening. The
latest estimated pressure from dropsonde data gathered by the Air
Force is 937 mb. NOAA buoy 41044 has recently reported a peak
one-minute wind of 68 kt with a gust to 86 kt in the northeastern
eyewall of Sam. The buoy has also reported peak seas of 40 ft.

Sam could still strengthen a little today as it continues to move
over a warm ocean eddy and remains in low vertical wind shear
conditions. After that time, difficult-to-predict eyewall cycles
however, could cause some fluctuations in intensity. After 48
hours, gradually decreasing SSTs and ocean heat content are likely
to cause a more definitive weakening trend, with a faster rate of
weakening likely after day 3. Sam is forecast to complete its
extratropical transition by day 5, and it is predicted by the
global model guidance to become a large and powerful extratropical
low over the north Atlantic.

Sam is moving northwestward or 320/10 kt. The track forecast
reasoning is again unchanged from the previous advisory. Sam will
move northwestward, and then northward around the western portion
of a subtropical ridge during the next 48 hours. After that time,
Sam is predicted to turn northeastward between the ridge and a
large mid-latitude trough over the northeastern United States. As
that trough lifts northeastward by day 3, Sam is forecast to
continue on a northeastward heading, but it is not likely to
accelerate as much as a typical recurving tropical cyclone over
the north-central Atlantic. The dynamical model guidance remains
in excellent agreement through 72 hours, but there is increasing
spread after that time. The latest runs of the GFS and ECMWF
models have come into somewhat better agreement at days 3 through
5, and the NHC track forecast is near the consensus of those
typically reliable models.

Although the core of Sam is forecast to pass east of Bermuda early
Saturday, the tropical-storm-force wind field is forecast to expand
and could pass very close to the island beginning late Friday night
or early Saturday. Therefore, the Bermuda Weather Service has issued
a Tropical Storm Watch for Bermuda.


Key Messages:

1. Swells generated by Sam will impact the Northern Leeward Islands
and the Greater Antilles, including Puerto Rico, during the next
few days. Swells are expected to reach Bermuda and the Bahamas by
Friday, and then spread to the United States east coast by this
weekend. These swells could cause life-threatening surf and rip
current conditions. Please consult products from your local
weather office.

2. Tropical storm conditions are possible on Bermuda beginning
Friday night or early Saturday, and a Tropical Storm Watch has
been issued for that island.


FORECAST POSITIONS AND MAX WINDS

INIT 30/0900Z 21.5N 59.1W 125 KT 145 MPH
12H 30/1800Z 23.0N 60.2W 130 KT 150 MPH
24H 01/0600Z 25.6N 61.4W 125 KT 145 MPH
36H 01/1800Z 28.4N 61.8W 120 KT 140 MPH
48H 02/0600Z 31.1N 61.3W 115 KT 130 MPH
60H 02/1800Z 33.5N 59.9W 105 KT 120 MPH
72H 03/0600Z 35.5N 58.0W 95 KT 110 MPH
96H 04/0600Z 38.7N 52.6W 80 KT 90 MPH
120H 05/0600Z 44.3N 45.0W 65 KT 75 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown
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Re: ATL: SAM - Advisories

#31 Postby cycloneye » Thu Sep 30, 2021 9:59 am

BULLETIN
Hurricane Sam Advisory Number 32
NWS National Hurricane Center Miami FL AL182021
1100 AM AST Thu Sep 30 2021

...SAM EXPECTED TO CAUSE LARGE SWELLS AND HIGH SURF OVER A LARGE
PORTION OF THE WESTERN ATLANTIC SHORELINE...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...22.6N 60.0W
ABOUT 365 MI...585 KM NNE OF THE NORTHERN LEEWARD ISLANDS
ABOUT 730 MI...1175 KM SSE OF BERMUDA
MAXIMUM SUSTAINED WINDS...145 MPH...230 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...937 MB...27.67 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Watch is in effect for...
* Bermuda

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area, generally within 48 hours.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 1100 AM AST (1500 UTC), the center of Hurricane Sam was located
near latitude 22.6 North, longitude 60.0 West. Sam is moving toward
the northwest near 13 mph (20 km/h), and a turn toward the
north-northwest with an increase in forward speed is expected
tonight. A turn toward the north is anticipated by late Friday, and
a northeastward motion is forecast to begin on Saturday. On the
forecast track, the core of Sam will pass to the east of Bermuda
early Saturday.

Maximum sustained winds are near 145 mph (230 km/h) with higher
gusts. Sam is a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Some fluctuations in intensity are expected
during the next couple of days, but Sam is forecast to remain a
major hurricane through Saturday, with more significant weakening
anticipated later in the weekend.

Hurricane-force winds extend outward up to 60 miles (95 km) from the
center and tropical-storm-force winds extend outward up to 150 miles
(240 km).

The estimated minimum central pressure is 937 mb (27.67 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Sam can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC,
and on the web at hurricanes.gov/graphics_at3.shtml?key_messages.

WIND: Tropical storm conditions are possible on Bermuda beginning
Friday night or early Saturday.

SURF: Swells generated by Sam will impact the northern Leeward
Islands and the Greater Antilles, including Puerto Rico, during the
next few days. Swells are expected to reach Bermuda and the Bahamas
by Friday, and then spread to the United States east coast by this
weekend. These swells could cause life-threatening surf and rip
current conditions. Please consult products from your local
weather office.


NEXT ADVISORY
-------------
Next intermediate advisory at 200 PM AST.
Next complete advisory at 500 PM AST.

$$
Forecaster Pasch


Hurricane Sam Discussion Number 32
NWS National Hurricane Center Miami FL AL182021
1100 AM AST Thu Sep 30 2021

Sam continues to look quite impressive on satellite images, with a
20-25 n mi wide eye surrounded by very deep convection. The
system's convective banding features and upper-level anticyclonic
outflow also remain well-defined, with particularly strong outflow
to the northwest and north. Subjective and objective Dvorak
intensity estimates have not changed significantly since earlier
this morning, so the advisory intensity will remain at 125 kt.
Interestingly, aircraft observations show that Sam has been a
little stronger than indicated by satellite-derived intensity
estimates, which underscores the value of aerial reconnaissance
of tropical cyclones. Another Air Force Hurricane Hunter aircraft
is scheduled to investigate the hurricane later today.

Sam should continue to move over waters of high oceanic heat
content and within a low-shear atmospheric environment for the next
24 hours or so. Thus, it could still strengthen a little today and
tonight. By 48 hours, decreasing SSTs and increasing shear should
lead to a gradual weakening trend. Around day 5, global model
fields suggest that Sam will be merging with a baroclinic zone and
transition into a large and powerful extratropical cyclone over the
north Atlantic. The official intensity forecast is in good
agreement with the HCCA corrected consensus model prediction.

The hurricane is moving a little faster toward the northwest, or at
about 320/11 kt. During the next couple of days, a gradual turn
toward the north is likely as Sam rounds the western end of a large
subtropical anticyclone over the eastern and central Atlantic.
Thereafter, Sam is forecast to move generally northeastward in the
flow between the anticyclone and a trough near Atlantic Canada.
The NHC forecast is very similar to a consensus of the typically
reliable GFS and ECMWF predictions, with a little bit of smoothing
around days 3-4.

Although the core of Sam is forecast to pass east of Bermuda early
Saturday, the tropical-storm-force wind field is forecast to expand
and could pass very close to the island beginning late Friday night
or early Saturday. Therefore, a Tropical Storm Watch is in effect
for Bermuda.


Key Messages:

1. Swells generated by Sam will impact the Northern Leeward Islands
and the Greater Antilles, including Puerto Rico, during the next
few days. Swells are expected to reach Bermuda and the Bahamas by
Friday, and then spread to the United States east coast by this
weekend. These swells could cause life-threatening surf and rip
current conditions. Please consult products from your local
weather office.

2. Tropical storm conditions are possible on Bermuda beginning
Friday night or early Saturday, and a Tropical Storm Watch has
been issued for that island.


FORECAST POSITIONS AND MAX WINDS

INIT 30/1500Z 22.6N 60.0W 125 KT 145 MPH
12H 01/0000Z 24.4N 60.8W 130 KT 150 MPH
24H 01/1200Z 27.2N 61.7W 125 KT 145 MPH
36H 02/0000Z 30.2N 61.6W 115 KT 130 MPH
48H 02/1200Z 32.7N 60.8W 105 KT 120 MPH
60H 03/0000Z 34.9N 59.2W 95 KT 110 MPH
72H 03/1200Z 36.9N 57.0W 90 KT 105 MPH
96H 04/1200Z 40.0N 51.0W 80 KT 90 MPH
120H 05/1200Z 44.5N 45.5W 65 KT 75 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch
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Re: ATL: SAM - Advisories

#32 Postby cycloneye » Thu Sep 30, 2021 3:58 pm

BULLETIN
Hurricane Sam Advisory Number 33
NWS National Hurricane Center Miami FL AL182021
500 PM AST Thu Sep 30 2021

...INTENSE HURRICANE SAM EXPECTED TO BRING LARGE SWELLS AND
DANGEROUS HIGH SURF TO A LARGE PORTION OF THE WESTERN ATLANTIC
SHORELINE...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...23.6N 60.9W
ABOUT 645 MI...1040 KM SSE OF BERMUDA
MAXIMUM SUSTAINED WINDS...145 MPH...230 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...938 MB...27.70 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

The Bermuda Weather Service has issued a Tropical Storm Warning for
Bermuda.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* Bermuda

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 500 PM AST (2100 UTC), the eye of Hurricane Sam was located by
an Air Force Hurricane Hunter aircraft near latitude 23.6 North,
longitude 60.9 West. Sam is moving toward the northwest near 14
mph (22 km/h), and a turn toward the north-northwest with an
additional increase in forward speed is expected tonight. A turn
toward the north is anticipated on Friday, and a northeastward
motion is forecast to begin on Saturday. On the forecast track, the
core of Sam will pass to the east of Bermuda early Saturday.

Maximum sustained winds are near 145 mph (230 km/h) with higher
gusts. Sam is a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Some fluctuations in intensity are expected
during the next couple of days, but Sam is forecast to remain a
major hurricane into Saturday, with more significant weakening
anticipated later in the weekend.

Hurricane-force winds extend outward up to 60 miles (95 km) from the
center and tropical-storm-force winds extend outward up to 150 miles
(240 km).

The minimum central pressure reported by the Hurricane Hunters is
938 mb (27.70 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Sam can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC,
and on the web at hurricanes.gov/graphics_at3.shtml?key_messages.

WIND: Tropical storm conditions are expected on Bermuda beginning
Friday night or early Saturday.

SURF: Swells generated by Sam will impact the northern Leeward
Islands and the Greater Antilles, including Puerto Rico, during the
next few days. Swells are expected to reach Bermuda and the Bahamas
by Friday, and then spread to the United States east coast by this
weekend. These swells could cause life-threatening surf and rip
current conditions. Please consult products from your local
weather office.


NEXT ADVISORY
-------------
Next intermediate advisory at 800 PM AST.
Next complete advisory at 1100 PM AST.

$$
Forecaster Pasch




Hurricane Sam Discussion Number 33
NWS National Hurricane Center Miami FL AL182021
500 PM AST Thu Sep 30 2021

Sam remains a formidable hurricane, with a well-organized
cloud pattern on satellite imagery. The 25 n mi wide eye is
surrounded by a fairly symmetric pattern of deep convective cloud
tops, and the upper-level outflow pattern is very well defined. An
Air Force Reserve Unit Hurricane Hunter aircraft investigated the
system and found peak 700-mb flight level winds of 133 kt, and a
highest unflagged SFMR-observed surface wind of 125 kt. Based on
these observations, the advisory intensity is kept at 125 kt.
Measurements from the aircraft also showed that the central
pressure remains quite low, near 938 mb.

Sam will continue to traverse waters of high oceanic heat content
for another 12-18 hours, and the shear should remain fairly low for
the next few days. Therefore, some intensification could still
occur overnight. In any event, the system is expected to maintain
major hurricane status for the next 36-48 hours. Over the weekend,
a gradual weakening trend should commence due to cooler SSTs.
However, Sam will likely remain a powerful cyclone with hurricane-
force winds until the end of the forecast period. By 120 hours,
simulated satellite imagery from the ECMWF and GFS models forecast
the system's cloud pattern to resemble that of an extratropical low,
and this is reflected in the official forecast, which shows
extratropical status at that time. The official intensity forecast
remains close to the HCCA corrected consensus model solution.

Center fixes continue to show a gradual increase in forward speed,
and the hurricane is moving northwestward, or about 320/12 kt.
During the next 24-36 hours, Sam should turn toward the north as it
moves around the western periphery of a large subtropical high over
the eastern and central Atlantic. Then, the cyclone is expected to
move generally northeastward in the flow between the anticyclone and
a trough near Atlantic Canada. There is fairly close agreement in
the track models through 60 hours or so. However, there are some
significant differences in the model-predicted track of Sam at
higher latitudes, probably due to variations in how the system
interacts with the trough in the various guidance. The NHC track
forecast follows the latest model consensus, TVCN.

Although the core of Sam is predicted to pass east of Bermuda early
Saturday, the tropical-storm-force wind field is forecast to expand
and could pass very close to the island beginning late Friday night
or early Saturday. Therefore, a Tropical Storm Warning has been
issued for Bermuda.


Key Messages:

1. Swells generated by Sam will impact the Northern Leeward Islands
and the Greater Antilles, including Puerto Rico, during the next
few days. Swells are expected to reach Bermuda and the Bahamas by
Friday, and then spread to the United States east coast by this
weekend. These swells could cause life-threatening surf and rip
current conditions. Please consult products from your local
weather office.

2. Tropical storm conditions are expected on Bermuda beginning
Friday night or early Saturday, and a Tropical Storm Warning has
been issued for that island.


FORECAST POSITIONS AND MAX WINDS

INIT 30/2100Z 23.6N 60.9W 125 KT 145 MPH
12H 01/0600Z 25.6N 61.5W 130 KT 150 MPH
24H 01/1800Z 28.5N 61.9W 125 KT 145 MPH
36H 02/0600Z 31.3N 61.4W 110 KT 125 MPH
48H 02/1800Z 33.8N 60.1W 100 KT 115 MPH
60H 03/0600Z 35.8N 58.3W 90 KT 105 MPH
72H 03/1800Z 37.4N 56.2W 85 KT 100 MPH
96H 04/1800Z 42.5N 50.0W 75 KT 85 MPH
120H 05/1800Z 47.5N 46.0W 65 KT 75 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch
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Re: ATL: SAM - Advisories

#33 Postby cycloneye » Thu Sep 30, 2021 6:50 pm

WTNT33 KNHC 302343
TCPAT3

BULLETIN
Hurricane Sam Intermediate Advisory Number 33A
NWS National Hurricane Center Miami FL AL182021
800 PM AST Thu Sep 30 2021

...POWERFUL HURRICANE SAM NOW MOVING NORTH-NORTHWEST...
...DANGEROUS SURF EXPECTED FOR A LARGE PORTION OF THE WESTERN
ATLANTIC SHORELINE...


SUMMARY OF 800 PM AST...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...24.3N 61.0W
ABOUT 600 MI...965 KM SSE OF BERMUDA
MAXIMUM SUSTAINED WINDS...145 MPH...230 KM/H
PRESENT MOVEMENT...NNW OR 340 DEGREES AT 14 MPH...22 KM/H
MINIMUM CENTRAL PRESSURE...938 MB...27.70 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* Bermuda

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 800 PM AST (0000 UTC), the eye of Hurricane Sam was located near
latitude 24.3 North, longitude 61.0 West. Sam is moving toward the
north-northwest near 14 mph (22 km/h), and this continued motion
with an additional increase in forward speed is expected tonight. A
turn toward the north is anticipated on Friday, and a northeastward
motion is forecast to begin on Saturday. On the forecast track, the
core of Sam will pass to the east of Bermuda early Saturday.

Maximum sustained winds remain near 145 mph (230 km/h) with higher
gusts. Sam is a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Some fluctuations in intensity are expected
during the next couple of days, but Sam is forecast to remain a
major hurricane into Saturday, with more significant weakening
anticipated later in the weekend.

Hurricane-force winds extend outward up to 60 miles (95 km) from
the center and tropical-storm-force winds extend outward up to 150
miles (240 km).

The estimated minimum central pressure is 938 mb (27.70 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Sam can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC,
and on the web at hurricanes.gov/graphics_at3.shtml?key_messages.

WIND: Tropical storm conditions are expected on Bermuda beginning
Friday night or early Saturday.

SURF: Swells generated by Sam will impact the northern Leeward
Islands and the Greater Antilles, including Puerto Rico, during the
next few days. Swells are expected to reach Bermuda and the Bahamas
by Friday, and then spread to the United States east coast by this
weekend. These swells could cause life-threatening surf and rip
current conditions. Please consult products from your local
weather office.


NEXT ADVISORY
-------------
Next complete advisory at 1100 PM AST.

$$
Forecaster Papin
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Re: ATL: SAM - Advisories

#34 Postby cycloneye » Thu Sep 30, 2021 9:54 pm

BULLETIN
Hurricane Sam Advisory Number 34
NWS National Hurricane Center Miami FL AL182021
1100 PM AST Thu Sep 30 2021

...SAM STILL A POWERFUL 145 MPH HURRICANE...
...DANGEROUS SURF EXPECTED FOR A LARGE PORTION OF THE WESTERN
ATLANTIC SHORELINE...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...25.0N 61.2W
ABOUT 550 MI...885 KM SSE OF BERMUDA
MAXIMUM SUSTAINED WINDS...145 MPH...230 KM/H
PRESENT MOVEMENT...NNW OR 345 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...938 MB...27.70 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* Bermuda

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 1100 PM AST (0300 UTC), the center of Hurricane Sam was located
near latitude 25.0 North, longitude 61.2 West. Sam is moving toward
the north-northwest near 16 mph (26 km/h) and this motion with an
slight increase in forward speed is expected tonight. A turn toward
the north is anticipated on Friday, and a northeastward motion is
forecast to begin on Saturday. On the forecast track, the core of
Sam will pass to the east of Bermuda early Saturday.

Maximum sustained winds remain near 145 mph (230 km/h) with higher
gusts. Sam is a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Some fluctuations in intensity are expected
during the next day or so, followed by gradual weakening. Sam is
forecast to remain a major hurricane into Saturday, with additional
weakening forecast later in the weekend.

Hurricane-force winds extend outward up to 60 miles (95 km) from the
center and tropical-storm-force winds extend outward up to 150 miles
(240 km).

The estimated minimum central pressure is 938 mb (27.70 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Sam can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC,
and on the web at hurricanes.gov/graphics_at3.shtml?key_messages.

WIND: Tropical storm conditions are expected on Bermuda beginning
Friday night or early Saturday.

SURF: Swells generated by Sam will impact the northern Leeward
Islands and the Greater Antilles, including Puerto Rico, during the
next few days. Swells are expected to reach Bermuda and the Bahamas
tomorrow, and then spread to the United States east coast by this
weekend. These swells could cause life-threatening surf and rip
current conditions. Please consult products from your local
weather office.


NEXT ADVISORY
-------------
Next intermediate advisory at 200 AM AST.
Next complete advisory at 500 AM AST.

$$
Forecaster Papin




Hurricane Sam Discussion Number 34
NWS National Hurricane Center Miami FL AL182021
1100 PM AST Thu Sep 30 2021

Sam's satellite structure on infrared remains quite impressive this
evening, with a circular eye staying quite warm (+10-20C) in
comparison to the ring of cold cloud tops associated with the
eyewall (-60 to -70C). The most recent microwave imagery was a SSMIS
pass at 1957 UTC, which indicated the eyewall remains quite intense,
if just a little asymmetric with a stronger western semicircle. This
eyewall asymmetry is consistent with a touch of light southerly
shear affecting the cyclone as diagnosed by ECMWF-SHIPS. However,
this shear does not appear to be having a significant impact on the
hurricane's intensity. While there have not been any recent aircraft
data to determine Sam's intensity since the last mission departed
the hurricane at around 2000 UTC, the satellite intensity estimates
have not changed much this evening. Thus, the initial intensity has
been held at 125-kt this advisory. Another Air Force Reserve
Reconnaissance Mission will be flying into Sam overnight to get a
better sense of the current intensity.

Following Sam's eye tonight, the hurricane is beginning to make a
gradual turn northward at a faster motion, with the latest estimate
now north-northwest at 345/14 kt. The track guidance in the
short-term remains in good agreement that Sam should continue to
turn to the north, north-northeast, and then northeastward as it is
steered around the western edge of a large subtropical ridge over
the central Atlantic. This track should take the hurricane east of
Bermuda. While there is a large deep-layer trough located north of
Sam, this feature will not initially capture the cyclone, as this
trough first de-amplifies and merges with a larger deep-layer
trough located over the far eastern Provinces of Canada. In fact,
Sam's forward motion to the northeast in 48-72 hours may even slow a
tad as it remains just south of the stronger upper-level
westerlies. However, by 96-120 hours, the deep-layer low over Canada
is expected to dig southeastward into North Atlantic, and will
likely capture Sam as the hurricane rapidly accelerates ahead of
this amplifying trough. It is in the 72-120 hour time-frame that a
lot of the track guidance diverges, mostly related to the timing and
degree of Sam's interaction of with this trough ejecting out of
Canada. For now, the official NHC track forecast has elected to
stay close to the track consensus TVCN, which has preformed well
with this hurricane so far. This latest track is just a bit
northeast and faster than the previous one after 72 hours.

Sam still has another 24 hours under warm 28-29 C sea-surface
temperatures while the southerly vertical wind shear is expected to
remain light. Thus, the hurricane is expected to maintain Category 4
intensity over the next day or so, with short-term intensity changes
likely to be controlled by inner core dynamics (such as eyewall
replacement cycles). Thereafter, sea surface temperatures decrease
markedly as southerly shear is also expected to gradually increase.
This combination should lead to steady weakening. After 72 hours,
the rate of weakening has actually been slowed a tad, since the
ECMWF, GFS, and Canadian models all show Sam receiving significant
baroclinic support as it undergoes a dynamic extratropical
transition while the hurricane phases with the large baroclinic
trough emerging off Canada. Simulated satellite imagery from these
models suggest that Sam's transition to an extratropical cyclone
should take place between 96-120 hours, with the resulting cyclone
producing a large wind footprint across the North Atlantic basin.


Key Messages:

1. Swells generated by Sam will impact the Northern Leeward Islands
and the Greater Antilles, including Puerto Rico, during the next
few days. Swells are expected to reach Bermuda and the Bahamas by
tomorrow, and then spread to the United States east coast by this
weekend. These swells could cause life-threatening surf and rip
current conditions. Please consult products from your local
weather office.

2. Tropical storm conditions are expected on Bermuda beginning
Friday night or early Saturday, and a Tropical Storm Warning is in
effect for the island.


FORECAST POSITIONS AND MAX WINDS

INIT 01/0300Z 25.0N 61.2W 125 KT 145 MPH
12H 01/1200Z 27.2N 61.8W 125 KT 145 MPH
24H 02/0000Z 30.2N 61.6W 115 KT 130 MPH
36H 02/1200Z 32.9N 60.5W 105 KT 120 MPH
48H 03/0000Z 35.0N 58.9W 95 KT 110 MPH
60H 03/1200Z 36.6N 56.8W 85 KT 100 MPH
72H 04/0000Z 38.7N 53.8W 80 KT 90 MPH
96H 05/0000Z 44.6N 47.2W 75 KT 85 MPH
120H 06/0000Z 48.9N 42.5W 70 KT 80 MPH...POST-TROP/EXTRATROP

$$
Forecaster Papin
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Re: ATL: SAM - Advisories

#35 Postby cycloneye » Fri Oct 01, 2021 4:32 am

Hurricane Sam Discussion Number 35
NWS National Hurricane Center Miami FL AL182021
500 AM AST Fri Oct 01 2021

An Air Force Reserve Hurricane Hunter aircraft investigated Sam a
few hours ago and found that the already-intense hurricane had
strengthened a bit since yesterday afternoon's reconnaissance
flight. The plane measured a peak 700-mb flight-level wind of 147
kt in the northeastern eyewall, and using a typical 90-percent
reduction from that altitude, the intensity is estimated to be 130
kt. Dropsondes released in the eye also indicated that the central
pressure had fallen to 934 mb. This drop in pressure is likely due
to a combination of the strengthening and an expansion of the
tropical-storm- and hurricane-force wind fields, which was
confirmed by the aircraft and scatterometer data from last evening.

Sam is moving a little faster toward the north-northwest (345/15
kt) as it curves around the western periphery of a mid-tropospheric
ridge located over the eastern and central subtropical Atlantic.
The hurricane is expected to turn northward later today and then
northeastward by Saturday night--passing well to the east of
Bermuda--when it begins to move between the ridge and a mid- to
upper-level low located over the northeastern United States and
Atlantic Canada. Interaction and a possible merger with the
aforementioned low during extratropical transition is likely to
cause a sudden north-northeastward acceleration to the southeast of
Newfoundland on day 4, followed by a slower motion toward the
east-northeast on day 5. The track models are very tightly
clustered for much of the 5-day forecast period, yielding high
confidence in the NHC track forecast. The new NHC forecast is
relatively unchanged from the previous forecast, and closely
follows the GFEX and TVCA consensus aids.

Although fluctuations in intensity will still be possible, a
general weakening trend is anticipated in the coming days as Sam
moves over a gradually cooler ocean, reaching sub-26C waters by day
3. However, the weakening is not expected to be rapid due to
continued upper-level divergence and only light-to-moderate
deep-layer shear, and Sam could remain a major hurricane at least
through Saturday night. Global models now indicate that Sam should
complete extratropical transition by day 4, and baroclinic forcing
is likely to keep the system as a potent hurricane-force
post-tropical cyclone through the end of the forecast period. The
NHC intensity forecast is essentially an update of the previous
forecast, lying close to the HCCA and IVCN consensus aids.


Key Messages:

1. Swells generated by Sam will impact the northern Leeward Islands
and the Greater Antilles, including Puerto Rico, during the next
couple of days. Swells are expected to reach Bermuda and the
Bahamas today, and then spread to the United States east coast and
Atlantic Canada this weekend. These swells could cause
life-threatening surf and rip current conditions. Please consult
products from your local weather office.

2. Tropical storm conditions are expected on Bermuda beginning
tonight or early Saturday, and a Tropical Storm Warning is in effect
for the island.


FORECAST POSITIONS AND MAX WINDS

INIT 01/0900Z 26.6N 61.7W 130 KT 150 MPH
12H 01/1800Z 28.8N 62.0W 125 KT 145 MPH
24H 02/0600Z 31.7N 61.2W 115 KT 130 MPH
36H 02/1800Z 34.2N 59.7W 105 KT 120 MPH
48H 03/0600Z 36.0N 57.8W 95 KT 110 MPH
60H 03/1800Z 37.7N 55.0W 90 KT 105 MPH
72H 04/0600Z 40.1N 51.4W 85 KT 100 MPH
96H 05/0600Z 47.7N 44.8W 75 KT 85 MPH...POST-TROP/EXTRATROP
120H 06/0600Z 50.1N 38.1W 65 KT 75 MPH...POST-TROP/EXTRATROP

$$
Forecaster Berg
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Re: ATL: SAM - Advisories

#36 Postby cycloneye » Fri Oct 01, 2021 6:48 am

BULLETIN
Hurricane Sam Intermediate Advisory Number 35A
NWS National Hurricane Center Miami FL AL182021
800 AM AST Fri Oct 01 2021

...SAM REMAINS A POWERFUL CATEGORY 4 HURRICANE OVER THE CENTRAL
ATLANTIC...
...TROPICAL STORM CONDITIONS EXPECTED ON BERMUDA BY TONIGHT OR
EARLY SATURDAY...


SUMMARY OF 800 AM AST...1200 UTC...INFORMATION
----------------------------------------------
LOCATION...27.5N 61.8W
ABOUT 380 MI...610 KM SSE OF BERMUDA
MAXIMUM SUSTAINED WINDS...150 MPH...240 KM/H
PRESENT MOVEMENT...NNW OR 345 DEGREES AT 17 MPH...28 KM/H
MINIMUM CENTRAL PRESSURE...934 MB...27.58 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* Bermuda

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 800 AM AST (1200 UTC), the eye of Hurricane Sam was located near
latitude 27.5 North, longitude 61.8 West. Sam is moving toward the
north-northwest near 17 mph (28 km/h). A turn toward the north and
north-northeast, at a similar forward speed, is expected later today
and tonight, followed by a northeastward motion Saturday night
through Monday. On the forecast track, the center of Sam will pass
well to the east of Bermuda tonight.

Maximum sustained winds are near 150 mph (240 km/h) with higher
gusts. Sam is a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Although fluctuations in intensity are still
possible today, weakening is forecast during the next couple of
days. However, Sam is expected to remain a major hurricane through
at least Saturday night.

Hurricane-force winds extend outward up to 70 miles (110 km) from
the center and tropical-storm-force winds extend outward up to 175
miles (280 km).

The estimated minimum central pressure is 934 mb (27.58 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Sam can be found in the Tropical Cyclone Discussion
under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC, and on the
web at hurricanes.gov/graphics_at3.shtml?key_messages.

WIND: Tropical storm conditions are expected on Bermuda beginning
tonight or early Saturday.

SURF: Swells generated by Sam will impact the northern Leeward
Islands and the Greater Antilles, including Puerto Rico, during the
next couple of days. Swells are expected to reach Bermuda and the
Bahamas later today, and then spread to the United States east
coast and Atlantic Canada this weekend. These swells could cause
life-threatening surf and rip current conditions. Please consult
products from your local weather office.


NEXT ADVISORY
-------------
Next complete advisory at 1100 AM AST.

$$
Forecaster Cangialosi
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Re: ATL: SAM - Advisories

#37 Postby cycloneye » Fri Oct 01, 2021 10:08 am

Hurricane Sam Discussion Number 36
NWS National Hurricane Center Miami FL AL182021
1100 AM AST Fri Oct 01 2021

Sam remains a powerful category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale over the subtropical central Atlantic.
Satellite images show that the hurricane still has a circular and
quite distinct eye and closed eyewall. However, an 0827 UTC SSMIS
pass indicated that a dry slot was present on the eastern side of
the circulation between the eyewall and rainbands. The latest
Dvorak classifications from TAFB, SAB, and CIMSS at the University
of Wisconsin range from 102-115 kt. However, Air Force
reconnaissance data from earlier this morning showed that the winds
were much higher, and in fact, the Dvorak estimates have had a low
bias compared to the Hurricane Hunter data for the past 24-36 hours.
Therefore, the initial intensity is held at 130 kt for now. Another
Air Force Hurricane Hunter aircraft is scheduled to investigate Sam
this afternoon. An ASCAT-A pass from around 12Z indicated that
Sam's tropical-storm-force wind radii have expanded, and the initial
wind radii were adjusted based on that data. In addition, the eye
of Sam passed about 60 n mi east of NOAA buoy 41049 earlier this
morning. The buoy reported a minimum pressure of 998 mb, maximum
winds of around 45 kt, gusts to 62 kt, and maximum seas of about 22
ft.

The major hurricane has turned to the north and is now moving
faster. The latest initial motion estimate is 355/18 kt. The
large-scale pattern consists of a deep-layer ridge to the northeast
of Sam and a large low pressure system centered over Atlantic
Canada. The steering flow between these features should cause Sam
to move northeastward at a sightly slower pace this weekend. By
early next week, the deep-layer low is expected to retreat
northward, which should cause Sam to turn a little more to the
right. The models are in fairly good agreement, but there are some
notable speed differences with the UKMET model being a fast outlier.
The new NHC track forecast is slightly to the right of the previous
one at 60 and 72 h, but is otherwise very similar. This forecast
lies near the middle of the guidance envelope.

Sam is expected to slowly weaken during the next several days as it
moves over progressively cooler waters and into an environment of
stronger shear. The hurricane will likely begin extratropical
transition in a couple of days when it crosses the 26 degree C
isotherm, and this transition is expected to be completed by 96
hours. All of the model guidance shows steady weakening through the
forecast period, and so does the NHC forecast. This prediction is
close to the IVCN, IVDR, and HCCA models in the short term and near
the GFS model during the extratropical portion of the forecast.
Even though Sam is likely to weaken, it is still expected to be a
significant storm over the next several days.


Key Messages:

1. Swells generated by Sam will impact the northern Leeward Islands
and the Greater Antilles, including Puerto Rico, during the next
couple of days. Swells are expected to reach Bermuda and the
Bahamas this afternoon, and then spread to the United States east
coast and Atlantic Canada on Saturday. These swells could cause
life-threatening surf and rip current conditions. Please consult
products from your local weather office.

2. Tropical storm conditions are possible on Bermuda beginning
tonight or early Saturday, and a Tropical Storm Warning is in effect
for the island.


FORECAST POSITIONS AND MAX WINDS

INIT 01/1500Z 28.4N 61.8W 130 KT 150 MPH
12H 02/0000Z 30.7N 61.5W 125 KT 145 MPH
24H 02/1200Z 33.4N 60.2W 110 KT 125 MPH
36H 03/0000Z 35.6N 58.4W 100 KT 115 MPH
48H 03/1200Z 37.2N 56.0W 95 KT 110 MPH
60H 04/0000Z 38.7N 52.9W 90 KT 105 MPH
72H 04/1200Z 41.9N 48.6W 85 KT 100 MPH
96H 05/1200Z 49.0N 42.2W 75 KT 85 MPH...POST-TROP/EXTRATROP
120H 06/1200Z 51.0N 34.3W 60 KT 70 MPH...POST-TROP/EXTRATROP

$$
Forecaster Cangialosi/Nepaul
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Re: ATL: SAM - Advisories

#38 Postby cycloneye » Fri Oct 01, 2021 3:38 pm

BULLETIN
Hurricane Sam Advisory Number 37
NWS National Hurricane Center Miami FL AL182021
500 PM AST Fri Oct 01 2021

...CORE OF SAM FORECAST TO PASS WELL EAST OF BERMUDA TONIGHT...
...SWELLS EXPECTED TO REACH THE EAST COAST OF THE U.S. AND ATLANTIC
CANADA ON SATURDAY...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...30.0N 61.8W
ABOUT 240 MI...385 KM SE OF BERMUDA
MAXIMUM SUSTAINED WINDS...150 MPH...240 KM/H
PRESENT MOVEMENT...N OR 355 DEGREES AT 20 MPH...31 KM/H
MINIMUM CENTRAL PRESSURE...937 MB...27.67 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for...
* Bermuda

A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.

For storm information specific to your area, please monitor
products issued by your national meteorological service.


DISCUSSION AND OUTLOOK
----------------------
At 500 PM AST (2100 UTC), the eye of Hurricane Sam was located
near latitude 30.0 North, longitude 61.8 West. Sam is moving toward
the north near 20 mph (31 km/h). A turn toward the north-northeast,
at a slightly slower forward speed, is expected by tonight, followed
by a northeastward motion Saturday night through Monday. On the
forecast track, the center of Sam will pass well to the east of
Bermuda tonight.

Maximum sustained winds are near 150 mph (240 km/h) with higher
gusts. Sam is a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Although fluctuations in intensity are still
possible, weakening is forecast during the next couple of days.
However, Sam is expected to remain a major hurricane through at
least Saturday night.

Hurricane-force winds extend outward up to 60 miles (95 km) from the
center and tropical-storm-force winds extend outward up to 205 miles
(335 km).

The estimated minimum central pressure is 937 mb (27.67 inches).


HAZARDS AFFECTING LAND
----------------------
Key messages for Sam can be found in the Tropical Cyclone Discussion
under AWIPS header MIATCDAT3 and WMO header WTNT43 KNHC, and on the
web at hurricanes.gov/graphics_at3.shtml?key_messages.

WIND: Tropical storm conditions are possible on Bermuda beginning
tonight or early Saturday.

SURF: Swells generated by Sam will impact the northern Leeward
Islands, the Greater Antilles, the Bahamas, and Bermuda during the
next couple of days. Swells are expected to reach the United States
east coast and Atlantic Canada on Saturday. These swells could
cause life-threatening surf and rip current conditions. Please
consult products from your local weather office.


NEXT ADVISORY
-------------
Next intermediate advisory at 800 PM AST.
Next complete advisory at 1100 PM AST.

$$
Forecaster Cangialosi/Nepaul



Hurricane Sam Discussion Number 37
NWS National Hurricane Center Miami FL AL182021
500 PM AST Fri Oct 01 2021

Sam remains a powerful hurricane. The eye is still very distinct
and there are several mesovorticies evident in satellite imagery.
In addition, microwave images show a closed and symmetric eyewall.
Data from the Air Force Hurricane Hunters indicate that Sam has been
maintaining its category 4 intensity. The aircraft measured peak
flight-level winds at 700 mb of 152 kt, which corresponds to a
135-140 kt surface wind. However, the peak SFMR winds are around 115
kt. Dropsonde data from the aircraft show a sharp decrease in winds
around the 925 mb level, which could mean that the strongest winds
are not reaching the surface. The minimum pressure in the eye
remains very low though at 937 mb. Based on all of this data, the
initial intensity is held at 130 kt, but there is some uncertainty
in that estimate.

The major hurricane continues northward and the latest initial
motion estimate is 355/17 kt. The large-scale pattern consists of a
deep-layer ridge to the northeast of Sam and a large low pressure
system centered over Atlantic Canada. The steering flow between
these features should cause Sam to move northeastward at a sightly
slower pace this weekend. By early next week, the deep-layer low is
expected to retreat northward, which should cause Sam to turn a
little more to the right. The models are in fairly good agreement,
but there are some notable speed differences with the UKMET on the
faster side and the GFS on the slower side of the guidance envelope.
No major changes were made to the NHC track forecast, and it remains
near the consensus aids.

Sam is expected to slowly weaken during the next several days as it
moves over progressively cooler waters and into an environment of
stronger shear. The hurricane will likely begin extratropical
transition in a couple of days when it crosses the 26 degree C
isotherm, and this transition is expected to be completed shortly
after 72 hours. All of the model guidance shows steady weakening
through the forecast period, and so does the NHC forecast. This
prediction is close to the IVCN, IVDR, and HCCA models in the short
term and near the GFS model during the extratropical portion of the
forecast. Even though Sam is likely to weaken, it is still expected
to be a significant storm over the next several days.


Key Messages:

1. Swells generated by Sam will impact the northern Leeward Islands
the Greater Antilles, the Bahamas, and Bermuda during the next
couple of days. Swells are expected to reach the United States
east coast and Atlantic Canada on Saturday. These swells could
cause life-threatening surf and rip current conditions. Please
consult products from your local weather office.

2. Tropical storm conditions are possible on Bermuda beginning
tonight or early Saturday, and a Tropical Storm Warning is in effect
for the island.


FORECAST POSITIONS AND MAX WINDS

INIT 01/2100Z 30.0N 61.8W 130 KT 150 MPH
12H 02/0600Z 32.3N 61.0W 120 KT 140 MPH
24H 02/1800Z 34.8N 59.4W 110 KT 125 MPH
36H 03/0600Z 36.7N 57.3W 100 KT 115 MPH
48H 03/1800Z 38.6N 54.2W 95 KT 110 MPH
60H 04/0600Z 41.1N 50.1W 90 KT 105 MPH
72H 04/1800Z 44.9N 45.6W 85 KT 100 MPH
96H 05/1800Z 50.5N 40.5W 70 KT 80 MPH...POST-TROP/EXTRATROP
120H 06/1800Z 52.6N 30.7W 50 KT 60 MPH...POST-TROP/EXTRATROP

$$
Forecaster Cangialosi/Nepaul
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Re: ATL: SAM - Advisories

#39 Postby cycloneye » Fri Oct 01, 2021 9:51 pm

Hurricane Sam Discussion Number 38
NWS National Hurricane Center Miami FL AL182021
1100 PM AST Fri Oct 01 2021

The satellite appearance of Sam has degraded slightly during the
past few hours, with the eye becoming more cloud filled and the
eyewall cloud tops become a little less symmetric. Various
subjective and objective satellite intensity estimates are in the
115-130 kt range, and based on the slight decay the initial
intensity is lowered to 125 kt. An Air Force Reserve Hurricane
Hunter aircraft is currently enroute to investigate Sam.

Sam is making its forecast turn toward the north-northeast with the
initial motion now 020/15 kt. There is no change to the track
forecast philosophy and little change to the forecast track from the
previous advisory. The steering flow between a deep-layer ridge to
the northeast and east of Sam and a large mid-latitude low pressure
system centered over Atlantic Canada should cause Sam to turn
northeastward during the next 24 h, followed by a continued
northeastward motion as the system become entrained in southwesterly
mid-latitude flow. The models are in fairly good agreement,
although there is some spread in both the track and the speed due to
model differences in the cyclone's evolution as it becomes
extratropical. The new forecast track lies close to the center of
the guidance envelope and the various consensus models.

Slow weakening is expected to continue during the next 2-3 days as
Sam moves over cooler sea surface temperatures and begins
extratropical transition. This is likely to be complete by 72 h,
with the global models suggesting that Sam will evolve into a
warm-core seclusion extratropical low. Based on this and the
guidance, it is likely that the cyclone will maintain hurricane
strength until after the transition is done. By the end of the
forecast period, the extratropical low is expected to be decaying
over the far north Atlantic. The new intensity forecast lies at the
upper edge of the intensity guidance.


Key Messages:

1. Swells generated by Sam will impact the northern Leeward Islands
the Greater Antilles, the Bahamas, and Bermuda during the next
couple of days. Swells are expected to reach the United States
east coast and Atlantic Canada on Saturday. These swells could
cause life-threatening surf and rip current conditions. Please
consult products from your local weather office.

2. Tropical storm conditions are possible on Bermuda during the
next several hours, and a Tropical Storm Warning is in effect for
the island.


FORECAST POSITIONS AND MAX WINDS

INIT 02/0300Z 31.4N 61.2W 125 KT 145 MPH
12H 02/1200Z 33.5N 60.2W 120 KT 140 MPH
24H 03/0000Z 35.8N 58.3W 110 KT 125 MPH
36H 03/1200Z 37.7N 55.6W 100 KT 115 MPH
48H 04/0000Z 39.6N 52.2W 95 KT 110 MPH
60H 04/1200Z 43.0N 47.3W 90 KT 105 MPH
72H 05/0000Z 47.2N 43.2W 80 KT 90 MPH...POST-TROP/EXTRATROP
96H 06/0000Z 50.5N 38.0W 65 KT 75 MPH...POST-TROP/EXTRATROP
120H 07/0000Z 54.5N 27.5W 50 KT 60 MPH...POST-TROP/EXTRATROP

$$
Forecaster Beven
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Re: ATL: SAM - Advisories

#40 Postby cycloneye » Sat Oct 02, 2021 4:29 am

Hurricane Sam Discussion Number 39
NWS National Hurricane Center Miami FL AL182021
500 AM AST Sat Oct 02 2021

The Air Force Reserve Hurricane Hunters conducted their final
mission into Sam a few hours ago and found that the hurricane is
still of category 4 intensity, but the maximum winds have decreased
some. The crew reported a peak 700-mb flight-level wind of 130 kt
(equating to surface winds of 115-120 kt) and unflagged SFMR winds
of 110-115 kt. Based on these wind data, Sam's intensity is now
estimated to be 115 kt. This value is at the upper end of the
latest satellite estimates, which range from 100-115 kt. The
hurricane's central pressure has also risen to 945 mb.

Sam is still moving toward the north-northeast with a motion of
020/15 kt. The hurricane is entering the area between a deep-layer
ridge to the east and a large mid- to upper-level low over Atlantic
Canada, and this flow should cause Sam to turn toward the northeast
by tonight and then maintain that general heading for much of the
forecast period. The storm is also expected to accelerate,
reaching a peak forward speed of more than 25 kt in 60-72 hours.
The track guidance is tightly clustered through day 3, but there is
significantly more spread on days 4 and 5 due to uncertainty on
exactly how Sam will interact with the aforementioned
mid-/upper-level low. The NHC forecast has been placed near a
blend of the GFS-ECMWF mean and the HCCA consensus aid, which
necessitated a northward shift from the previous forecast only on
days 4 and 5.

Deep-layer southerly shear of 15-20 kt appears to be contributing
to Sam's current weakening. Continued shear and cooler waters
along Sam's path should lead to additional weakening in the coming
days, although not at a rapid rate due to some baroclinic forcing.
Global models suggest that Sam will begin extratropical transition
in about 48 hours, with that process completing by 72 hours. The
NHC intensity forecast closely follows the HCCA and IVCN consensus
aids during Sam's tropical phase, but then transitions to a blend of
the GFS and ECMWF global model guidance on days 3 through 5 during
its extratropical phase. Sam is expected to continue producing
hurricane-force winds through at least day 3, with more significant
weakening occurring on days 4 and 5 once it is a vertically stacked
occluded low.


Key Messages:

1. Swells generated by Sam will impact the northern Leeward Islands
the Greater Antilles, the Bahamas, and Bermuda during the next
couple of days. Swells are expected to reach the United States
east coast and Atlantic Canada today. These swells could cause
life-threatening surf and rip current conditions. Please consult
products from your local weather office.

2. Although the Tropical Storm Warning for Bermuda has been
discontinued, a few wind gusts to tropical storm force will still
be possible on the island during the morning.


FORECAST POSITIONS AND MAX WINDS

INIT 02/0900Z 32.8N 60.5W 115 KT 130 MPH
12H 02/1800Z 34.6N 59.3W 100 KT 115 MPH
24H 03/0600Z 36.6N 57.1W 95 KT 110 MPH
36H 03/1800Z 38.4N 54.2W 90 KT 105 MPH
48H 04/0600Z 40.7N 50.0W 85 KT 100 MPH
60H 04/1800Z 44.4N 44.8W 80 KT 90 MPH
72H 05/0600Z 48.9N 40.7W 75 KT 85 MPH...POST-TROP/EXTRATROP
96H 06/0600Z 53.4N 34.7W 55 KT 65 MPH...POST-TROP/EXTRATROP
120H 07/0600Z 58.7N 26.4W 45 KT 50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Berg
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