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Potential Tropical Cyclone Twenty-Two Discussion Number   5
NWS National Hurricane Center Miami FL       AL222023
400 PM EST Fri Nov 17 2023
 
The disturbance continues to have a broad and elongated circulation 
with a vorticity maximum in the vicinity of western Jamaica and all 
of the associated deep convection east of the trough axis.  Earlier 
ASCAT passes differed on the strength of the system's winds, with 
the B instrument showing 35-40 kt within the Jamaica Channel and the 
C instrument only showing 25-30 kt.  The intensity remains 30 kt 
based on a blend of these data.

The system is accelerating northeastward with an initial motion of 
050/15 kt.  An additional acceleration toward the northeast--close 
to 30 kt by 36-48 hours--is expected as the disturbance gets picked 
up by a shortwave trough moving across Florida toward the 
southwestern Atlantic.  The updated NHC forecast remains near the 
fastest model solutions, and is generally a blend of the previous 
forecast with the latest GFS model.  As noted earlier, the 
disturbance's motion across the Greater Antilles is likely to be 
discontinuous.

The chance for the system to become a tropical cyclone continues to 
decrease and in fact now appears unlikely due to a combination of 
the system's broad structure, the terrain of the Greater Antilles, 
strong southwesterly shear, and mid-level dry air.  However, with 
the strongest surface winds near or just below 35 kt, there is 
still some chance that the system could produce 
tropical-storm-force winds over areas within the tropical storm 
watch, especially within heavy rainfall.  The NHC forecast still 
shows the possibility, albeit small, for the system to become a 
tropical storm in 24-36 hours mainly based on continuity.  After 
that, the system should become extratropical by 48 hours and 
absorbed by a front by 60 hours.  Advisories on this system could be
discontinued at any time if there is no longer a risk of 
tropical-storm-force winds within the tropical storm watch areas.
 
Despite the decreasing chance of tropical cyclone formation, there
is high confidence that heavy rainfall and flooding will remain a
distinct and serious threat across Jamaica, southeastern Cuba, and
Hispaniola.  Additional rainfall amounts of 4 to 8 inches, with
isolated areas as high as 16 inches, are forecast in these areas
and are likely to produce life-threatening flash flooding and
mudslides.
 
 
KEY MESSAGES:
 
1.  Potential Tropical Cyclone Twenty-Two could produce tropical
storm conditions, especially in areas of heavy rainfall, across
southeastern Cuba, Haiti, the southeastern Bahamas, and the Turks 
and Caicos Islands through Saturday, and tropical storm watches are 
in effect for these areas.
 
2.  Heavy rains will impact portions of Jamaica, southeast Cuba, and 
southern Hispaniola through Sunday. This rainfall is likely to 
produce flash flooding, along with mudslides in areas of higher 
terrain.  Lighter amounts across the southeastern Bahamas as 
well as the Turks and Caicos Islands may lead to flash flooding in 
urban areas.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  17/2100Z 18.7N  77.7W   30 KT  35 MPH...POTENTIAL TROP CYCLONE
 12H  18/0600Z 20.7N  75.3W   30 KT  35 MPH...POTENTIAL TROP CYCLONE
 24H  18/1800Z 23.4N  71.3W   35 KT  40 MPH...TROPICAL STORM
 36H  19/0600Z 26.5N  66.0W   35 KT  40 MPH
 48H  19/1800Z 30.1N  60.8W   35 KT  40 MPH...POST-TROP/EXTRATROP
 60H  20/0600Z...ABSORBED BY A FRONT
 
$$
Forecaster Berg
 
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