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Tropical Storm Elsa Discussion Number  16
NWS National Hurricane Center Miami FL       AL052021
500 AM EDT Sun Jul 04 2021
 
The last pass from the Air Force Hurricane Hunters provided 
interesting and somewhat confusing data on Elsa.  The flight-level 
winds and SFMR data indicate that Elsa's intensity remains around 55 
kt, but the wind center is located well to the east of the previous 
fixes.  However, the minimum pressure observed with this new wind 
center is a few millibars higher than the fixes that were made 
further west last night.  The new center is now beneath the 
strongest convection, so it seems likely that the mid-level 
circulation has built downward to the surface and led to this center 
reformation. Elsa does appear a little better organized in 
geostationary satellite and microwave images, and it now has a 
central dense overcast that is fairly symmetric around the center. 
The NOAA Hurricane Hunters will be investigating Elsa shortly, and 
the data the aircraft collects will be very helpful in understanding 
these structural changes and the new intensity information.
 
Elsa appears to have slowed down, and smoothing through the latest
center reformation yields an initial motion of 285/12 kt.  Despite
the changes to the initial motion and position, the overall track
forecast reasoning has not changed much.  Elsa is expected to move
west-northwestward and track near or over Jamaica and eastern Cuba
later this morning and then across or just south of the central and
western portions of Cuba later today through early Monday.  By early
Monday, however, Elsa should be making a turn to the north as it
moves between the subtropical ridge over the western Atlantic and a
trough over the Gulf of Mexico.  This motion should take the storm
near the Florida Keys by late Monday and near or over the west coast
of Florida on Tuesday.  After that time, the storm is forecast to
turn northeastward and increase its forward speed as it tracks
across the southeast U.S. and over the western Atlantic on the
northwest side of the ridge.  The NHC track forecast is a little
slower than the previous one, due in part to the initial motion and
position.
 
The short term intensity forecast is very dependent on Elsa's exact 
track.  If the core of the storm moves directly over Jamaica or 
Cuba, the small vortex would likely be very disrupted due to the 
mountainous islands.  However, if the storm manages to pass between 
those islands today, some strengthening seems possible given the 
improved appearance in satellite images.  Weakening is forecast to 
occur on Monday due to a combination of land interaction with Cuba 
and an increase in vertical wind shear.  After the storm moves over 
the Florida Straits and the eastern Gulf of Mexico, only a small 
amount of restrengthening is expected due to continued moderate wind 
shear.  The NHC intensity forecast is largely an update of the 
previous one and in line with the majority of the typically skillful 
intensity aids.
 
Key Messages:
 
1. Widespread heavy rain will move across southern Haiti and Jamaica
tonight into Sunday where isolated to scattered flash flooding and
mudslides will be possible. Heavy rain will then impact the Cayman
Islands and Cuba Sunday into Monday resulting in significant
flooding and mudslides over Cuba. As Elsa approaches the Florida
Keys and Florida Peninsula early next week, isolated flash flooding
and minor river flooding will be possible.
 
2. Tropical storm conditions and dangerous storm surge are expected
with hurricane conditions possible in portions of eastern Cuba
later this morning. Tropical storm conditions are possible in
central and western Cuba tonight and Monday.
 
3. There is an increasing risk of tropical storm conditions, storm
surge, and rainfall impacts beginning late Monday in the Florida 
Keys, and a Tropical Storm Watch is in effect for portions of the
Florida Keys.
 
4. There is a risk of tropical storm conditions, storm surge,
and rainfall impacts along the Florida Peninsula Monday night
through Wednesday and the coasts of Georgia and the Carolinas
Wednesday and Thursday.  However, uncertainty in the forecast
remains larger than usual due to Elsa's potential interaction with
Cuba.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  04/0900Z 18.1N  75.5W   55 KT  65 MPH
 12H  04/1800Z 19.5N  77.4W   60 KT  70 MPH...NEAR CUBA
 24H  05/0600Z 21.5N  79.4W   60 KT  70 MPH...NEAR CUBA
 36H  05/1800Z 23.0N  81.0W   50 KT  60 MPH...INLAND
 48H  06/0600Z 24.6N  82.2W   45 KT  50 MPH...OVER WATER
 60H  06/1800Z 25.9N  82.8W   50 KT  60 MPH
 72H  07/0600Z 27.8N  82.9W   50 KT  60 MPH...NEAR FLORIDA COAST
 96H  08/0600Z 33.2N  80.0W   40 KT  45 MPH...INLAND
120H  09/0600Z 38.4N  72.7W   35 KT  40 MPH...OVER WATER
 
$$
Forecaster Cangialosi/Reinhart
 
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