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