ATL: BILL - Advisories

[cycloneye]

BULLETIN
Tropical Depression Two Advisory Number 1
NWS National Hurricane Center Miami FL AL022021
1100 AM EDT Mon Jun 14 2021

...TROPICAL DEPRESSION FORMS OFFSHORE OF NORTH CAROLINA...
...HEADING AWAY FROM THE UNITED STATES...


SUMMARY OF 1100 AM EDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...35.0N 73.7W
ABOUT 105 MI...165 KM E OF CAPE HATTERAS NORTH CAROLINA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...NE OR 50 DEGREES AT 21 MPH...33 KM/H
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES


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


DISCUSSION AND OUTLOOK
----------------------
At 1100 AM EDT (1500 UTC), the center of Tropical Depression Two was
located near latitude 35.0 North, longitude 73.7 West. The
depression is moving toward the northeast near 21 mph (33 km/h), and
this general motion is expected through Wednesday with increasing
forward speed.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
The depression is expected to become a tropical storm by tonight
and could continue to strengthen on Tuesday. The system should
begin to weaken by Tuesday night and is expected to dissipate on
Wednesday.

The estimated minimum central pressure is 1006 mb (29.71 inches).


HAZARDS AFFECTING LAND
----------------------
None


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

$$
Forecaster Blake


Tropical Depression Two Discussion Number 1
NWS National Hurricane Center Miami FL AL022021
1100 AM EDT Mon Jun 14 2021

Satellite and radar images show that the low pressure area that NHC
has been following since yesterday off the coast of North Carolina
has become better organized, with a small central dense overcast
over the center and more prominent banding features. The low also
has advanced ahead of a nearby diffuse stationary front, with that
boundary lying northwest of the center. Considering the small core
of the low, ample deep convection, satellite pattern, and that the
low is feeding off of the thunderstorm activity (and not the front)
-- it is now classified as a tropical depression. The initial
intensity is set to 30 kt, which is our best estimate assuming
strengthening from the 20-25 kt overnight ASCAT and surface
observations.

The depression is moving northeastward at about 18 kt. A large
mid-latitude trough digging across eastern North America should
cause the cyclone to continue moving generally northeastward, but
faster, over the next couple of days. In about 48 hours, the system
is forecast to dissipate near Newfoundland as it is absorbed by a
larger extratropical low. Model guidance is in very good agreement
on this scenario, and the NHC forecast lies near the track
consensus.

The depression has about 24 hours over marginally warm waters in
low-to-moderate shear to strengthen before it moves north of the
Gulf Stream and decays. Almost all of the intensity guidance shows
the system becoming a tropical storm tonight, and considering the
healthy initial structure, the official forecast follows that
guidance. The low should lose tropical characteristics in about 36
hours due to very cold waters and dissipate near Newfoundland in
about 2 days.

FORECAST POSITIONS AND MAX WINDS

INIT 14/1500Z 35.0N 73.7W 30 KT 35 MPH
12H 15/0000Z 36.6N 70.9W 40 KT 45 MPH
24H 15/1200Z 39.8N 65.3W 45 KT 50 MPH
36H 16/0000Z 43.6N 59.7W 40 KT 45 MPH...POST-TROP/EXTRATROP
48H 16/1200Z...DISSIPATED

$$
Forecaster Blake

[cycloneye]

BULLETIN
Tropical Depression Two Advisory Number 2
NWS National Hurricane Center Miami FL AL022021
500 PM EDT Mon Jun 14 2021

...DEPRESSION EXPECTED TO BECOME A TROPICAL STORM TONIGHT...


SUMMARY OF 500 PM EDT...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...35.5N 72.0W
ABOUT 200 MI...320 KM E OF CAPE HATTERAS NORTH CAROLINA
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...NE OR 55 DEGREES AT 18 MPH...30 KM/H
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES


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


DISCUSSION AND OUTLOOK
----------------------
At 500 PM EDT (2100 UTC), the center of Tropical Depression Two was
located near latitude 35.5 North, longitude 72.0 West. The
depression is moving toward the northeast near 18 mph, and
this general motion is expected through Wednesday with increasing
forward speed.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
The depression is expected to become a tropical storm by tonight
and could continue to strengthen on Tuesday. The system is
expected to become a post-tropical low and dissipate on Wednesday.

The estimated minimum central pressure is 1006 mb (29.71 inches).


HAZARDS AFFECTING LAND
----------------------
None


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

$$
Forecaster Blake


Tropical Depression Two Discussion Number 2
NWS National Hurricane Center Miami FL AL022021
500 PM EDT Mon Jun 14 2021

Deep convection has weakened some this afternoon near the center of
the depression, and the cloud pattern definitely is showing signs of
shear. However, visible satellite imagery still indicates that it
has a tight circulation, and past experience suggests with that kind
of low-level structure, the depression is close to becoming a
tropical storm. None of the conventional intensity estimates,
however, show the system as a storm yet, and since scatterometer
data also totally missed this morning, 30 kt will stay as the
initial wind speed. No change is made to the intensity forecast from
the last advisory, with the system having about 24 hours of time
over marginally warm water to intensify. Afterwards, the cyclone
should quickly lose convection and transition into an extratropical
low, and dissipate near Newfoundland. This forecast is somewhat
higher than the the guidance consensus on this cycle, but given that
I was on the low side on the first forecast compared to guidance, I
decided to hold steady and not waffle like the models are prone to
doing.

The depression is moving northeastward at about 16 kt, a little
slower than before. Model guidance is in excellent agreement on
large trough over eastern North America causing the depression to
accelerate quite a bit in that general direction during the next
day or two. The northeastward track is forecast to continue until
the system dissipates near Newfoundland on Wednesday while it is
absorbed by a larger extratropical low. The model guidance has
shifted a little south of the previous advisory, and the NHC track
prediction is shifted in that direction.


FORECAST POSITIONS AND MAX WINDS

INIT 14/2100Z 35.5N 72.0W 30 KT 35 MPH
12H 15/0600Z 37.5N 68.3W 40 KT 45 MPH
24H 15/1800Z 40.9N 62.5W 45 KT 50 MPH
36H 16/0600Z 45.0N 57.0W 40 KT 45 MPH...POST-TROP/EXTRATROP
48H 16/1800Z...DISSIPATED

$$
Forecaster Blake

[cycloneye]

Tropical Storm Bill Advisory Number 3
NWS National Hurricane Center Miami FL AL022021
1100 PM AST Mon Jun 14 2021

...DEPRESSION STRENGTHENS INTO TROPICAL STORM BILL...
...LIKELY TO BE SHORT-LIVED...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...36.7N 69.8W
ABOUT 335 MI...540 KM ENE OF CAPE HATTERAS NORTH CAROLINA
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...NE OR 55 DEGREES AT 23 MPH...37 KM/H
MINIMUM CENTRAL PRESSURE...1003 MB...29.62 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 Tropical Storm Bill was
located near latitude 36.7 North, longitude 69.8 West. Bill is
moving toward the northeast near 23 mph (37 km/h), and this general
motion is expected through Wednesday with increasing forward speed.

Satellite-derived wind data indicate that the maximum sustained
winds have increased to near 45 mph (75 km/h) with higher gusts.
Some additional strengthening is possible on Tuesday, however the
system is expected to become a post-tropical low and dissipate on
Wednesday.

Tropical-storm-force winds extend outward up to 70 miles (110 km)
from the center.

The estimated minimum central pressure is 1003 mb (29.62 inches).


HAZARDS AFFECTING LAND
----------------------
None


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

$$
Forecaster Pasch

Tropical Storm Bill Discussion Number 3
NWS National Hurricane Center Miami FL AL022021
1100 PM AST Mon Jun 14 2021

Deep convection has increased in a cluster to the northeast of the
estimated center. Scatterometer measurements showed a couple of
40-41 kt vectors over the southeastern quadrant of the cyclone. On
this basis, the estimated intensity is increased to 40 kt, which
makes this the second tropical storm of the season, albeit a rather
high-latitude one. The system is in an environment of fairly
strong southwesterly shear, but the diffluent upper-level flow has
apparently contributed to some strengthening in a seemingly hostile
environment. Some additional short-term strengthening could occur
but by 36 hours, the cyclone should merge with a baroclinic zone
while approaching Newfoundland and become extratropical. This
transition is also shown by the FSU cyclone phase analyses of the
GFS model fields.

Bill is moving fairly swiftly northeastward, or 055/20 kt. The
track forecast appears to be straightforward. The flow ahead of a
large mid-tropospheric trough near the United States east coast
should accelerate the system northeastward for the next day or two,
and until the system dissipates. The NHC track forecast is similar
to the previous one and not far from the model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT 15/0300Z 36.7N 69.8W 40 KT 45 MPH
12H 15/1200Z 38.9N 65.1W 45 KT 50 MPH
24H 16/0000Z 42.6N 59.6W 40 KT 45 MPH
36H 16/1200Z 46.5N 54.5W 35 KT 40 MPH...POST-TROP/EXTRATROP
48H 17/0000Z...DISSIPATED

$$
Forecaster Pasch

[cycloneye]

BULLETIN
Tropical Storm Bill Advisory Number 4
NWS National Hurricane Center Miami FL AL022021
500 AM AST Tue Jun 15 2021

...BILL STRENGTHENS A LITTLE MORE...
...EXPECTED TO BE A SHORT-LIVED TROPICAL STORM...


SUMMARY OF 500 AM AST...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...38.5N 67.2W
ABOUT 240 MI...385 KM SE OF NANTUCKET MASSACHUSETTS
ABOUT 460 MI...740 KM SSW OF HALIFAX NOVA SCOTIA
MAXIMUM SUSTAINED WINDS...50 MPH...85 KM/H
PRESENT MOVEMENT...NE OR 50 DEGREES AT 31 MPH...50 KM/H
MINIMUM CENTRAL PRESSURE...999 MB...29.50 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 Tropical Storm Bill was
located near latitude 38.5 North, longitude 67.2 West. Bill is
moving rapidly toward the northeast near 31 mph (50 km/h), and
this general motion is expected to continue through Wednesday.

Maximum sustained winds have increased to near 50 mph (85 km/h)
with higher gusts. Little change in strength is expected today,
followed by gradual weakening tonight and Wednesday morning when
Bill will be moving over colder water. The system is forecast to
become a post-tropical low by tonight and dissipate on Wednesday.

Tropical-storm-force winds extend outward up to 90 miles (150 km)
from the center.

The estimated minimum central pressure is 999 mb (29.50 inches).


HAZARDS AFFECTING LAND
----------------------
None.


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

$$
Forecaster Stewart


Tropical Storm Bill Discussion Number 4
NWS National Hurricane Center Miami FL AL022021
500 AM AST Tue Jun 15 2021

Bill has developed an impressive convective shear pattern to be so
far north in latitude. AMSU-A temperature data around 0117 UTC
indicated that Bill has a marginal mid-level warm core, suggesting
that the cyclone might be a hybrid low pressure system. A
late-arriving ASCAT scatterometer pass indicated surface winds up to
42 kt in the southeastern about 40 nmi from the center, plus an
expansion of the 34-kt wind field in that quadrant as well.
Convection has continued to increase since the time of that earlier
ASCAT data as indicated by a 0600Z Dvorak satellite data-T estimate
of 3.0/45 kt from TAFB. Therefore, the initial intensity has been
increased to 45 kt.

Bill's motion is more rapidly toward the northeast now, or 055/27
kt. The latest track forecast is nearly identical to the previous
advisory. Bill is embedded within southwesterly flow ahead of an
approaching deep-layer trough and associated cold front, and this
steering pattern is expected to persist until Bill dissipates as an
extratropical low near eastern Newfoundland in 36 h or less. The new
NHC track forecast lies down the middle of the very tightly packed
guidance model suite.

Despite strong southwesterly deep-layer vertical wind shear in
excess of 30 kt, Bill has managed to maintain deep convection while
passing over marginal sea-surface temperatures (SST) of 26.5 deg C.
However, the cyclone will be moving over SSTs near 20 deg C by 12 h
and over sharply colder waters thereafter while the wind shear
concurrently increases. As a result, Bill is expected to transition
to an extratropical low pressure system and possible gale area at or
shortly after the 12-h period, followed by dissipation by 36 h when
the cyclone will be near eastern Newfoundland. The new intensity
forecast is similar to the previous advisory, and closely follows a
blend of the IVCN and HCCA consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT 15/0900Z 38.5N 67.2W 45 KT 50 MPH
12H 15/1800Z 41.0N 62.9W 45 KT 50 MPH
24H 16/0600Z 44.7N 57.6W 40 KT 45 MPH...POST-TROP/EXTRATROP
36H 16/1800Z 48.6N 52.6W 35 KT 40 MPH...POST-TROP/EXTRATROP
48H 17/0600Z...DISSIPATED

$$
Forecaster Stewart

[cycloneye]

Tropical Storm Bill Discussion Number 5
NWS National Hurricane Center Miami FL AL022021
1100 AM AST Tue Jun 15 2021

Bill remains a fairly well organized tropical storm. Microwave
satellite data indicate that the cyclone still has a fairly tight
core and curved bands on the north and west sides of the
circulation. However, drier air is wrapping into the southeast
portion of the storm, and convection has been decreasing in
intensity over the past couple of hours. A very recent ASCAT-A pass
showed maximum winds of 45-50 kt southeast of the center.
Therefore, the initial intensity is nudged up to 50 kt.

The tropical storm is racing northeastward, and the latest initial
motion is estimated to be 055/33 kt. Bill is embedded in the
mid-latitude jet stream and a continued fast northeastward motion
is expected during the next day or two. This motion should take
the storm over much cooler waters on the north side of the Gulf
Stream Current in about 12 hours. These cold waters, drier air,
and mid-latitude dynamics should cause Bill to transition to an
extratropical cyclone later today. All of the models agree that
the extratropical cyclone should dissipate in 24 to 36 hours over
or near Atlantic Canada.

Bill will likely remain at about the same intensity until it
dissipates by late Wednesday. It should be noted that given the
fast forward speed, most of the strong winds will be on the
southeast side of the system.


FORECAST POSITIONS AND MAX WINDS

INIT 15/1500Z 40.5N 62.0W 50 KT 60 MPH
12H 16/0000Z 43.4N 58.5W 50 KT 60 MPH...POST-TROP/EXTRATROP
24H 16/1200Z 47.5N 54.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
36H 17/0000Z...DISSIPATED

$$
Forecaster Cangialosi

[cycloneye]

Tropical Storm Bill Discussion Number 6
NWS National Hurricane Center Miami FL AL022021
500 PM AST Tue Jun 15 2021

Bill is well on its way to becoming an extratropical cyclone. The
convective pattern has become quite asymmetric with the center
exposed to the southwest of the weakening thunderstorms. The
center itself has become stretched, and in fact, surrounding
observations suggest that the surface center may no longer
be closed. In addition, a warm front appears to be forming on
the storm's southeast side. Based on these trends, it seems very
likely that Bill won't be around for long as a tropical storm. The
initial intensity is held at 50 kt based on the earlier ASCAT data,
but that could be a little generous.

The initial motion remains a very fast 055/31 kt. A continued fast
east-northeast to northeast motion in the mid-latitude jet stream
is expected until the cyclone dissipates within the next 12-24
hours near Atlantic Canada. Some weakening seems likely prior to
dissipation due to the cyclone moving over much colder SSTs while
remaining in a strong wind shear environment.

Due to the system's fast forward speed, the strong winds will
remain confined to the south and east sides of the cyclone.

FORECAST POSITIONS AND MAX WINDS

INIT 15/2100Z 41.6N 59.6W 50 KT 60 MPH
12H 16/0600Z 44.7N 55.9W 45 KT 50 MPH...POST-TROP/EXTRATROP
24H 16/1800Z...DISSIPATED

$$
Forecaster Cangialosi

[cycloneye]

Post-Tropical Cyclone Bill Discussion Number 7
NWS National Hurricane Center Miami FL AL022021
1100 PM AST Tue Jun 15 2021

Satellite imagery indicates that Bill has become extratropical over
the north Atlantic. A partial scatterometer overpass showed 35-40
kt winds to the east-southeast of the center, so the initial
intensity is lowered to a possibly generous 45 kt. The
extratropical low should continue to weaken and move quickly toward
the northeast until it weakens to a trough between 12-24 h.

This is the last advisory on Bill by the National Hurricane Center.
Additional information on this system can be found in High Seas
Forecasts issued by the National Weather Service, under AWIPS
header NFDHSFAT1, WMO header FZNT01 KWBC, and online at
ocean.weather.gov/shtml/NFDHSFAT1.php

FORECAST POSITIONS AND MAX WINDS

INIT 16/0300Z 43.5N 57.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
12H 16/1200Z 46.5N 53.9W 40 KT 45 MPH...POST-TROP/EXTRATROP
24H 17/0000Z...DISSIPATED

$$
Forecaster Beven