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Tropical Storm Elsa Discussion Number  15
NWS National Hurricane Center Miami FL       AL052021
1100 PM EDT Sat Jul 03 2021
 
Elsa is undergoing a convective bursting pattern the past few 
hours, with some cold overshooting tops of -90 deg C east and 
northeast of the center. However, data from an Air Force Reserve 
reconnaissance aircraft indicate that this convective increase has 
not translated into an intensity increase. To the contrary, 5000-ft 
flight-level and SFMR surface winds have decreased while the central 
pressure has increased to 1004 mb. Based on the latest recon data, 
the intensity has been lowered to 55 kt. The aircraft has now 
climbed to 10,000 ft for safety reasons and will be penetrating the 
area of intense convection to check for stronger winds there.
 
The initial motion estimate is now 295/15 kt.  Elsa is forecast to 
gradually move around the western periphery of a deep-layer 
subtropical ridge over the next 96 hours, accompanied by an 
additional decrease in forward speed. The latest model guidance has 
continued to converge along the previous advisory track, with the 
corrected-consensus models HCCA and FSSE nearly on top of each 
other. The TCVA simple consensus model is also similar to the HCCA 
and FSSE models. However, out of respect for the slightly more 
westward GFS and GFS-ensemble models, which have performed 
admirably thus far with Elsa, the new official forecast lies a tad 
west of the aforementioned consensus models and lies nearly on top 
of the previous advisory track.

After interacting with the mountainous terrain of southwestern 
Haiti, which could have caused some disruption in the low-level 
field despite the center remaining offshore, little change in 
intensity is expected tonight. However, some slight restrengthening 
could occur by Sunday afternoon as Elsa approaches the south-central 
coast of Cuba where the sea-surface temperatures are quite warm at 
more than 30 deg C and the water is deep. Weakening is expected 
after the cyclone moves across west-central Cuba, followed again by 
some slight restrengthening after Elsa emerges over the warm Gulf 
Stream in the Straits of Florida. Westerly vertical wind shear 
increasing to near 20 kt by 96 hours should prevent any significant 
strengthening from occurring. Elsa should become a very  
asymmetrical tropical cyclone late on day 3 and on day 4 with most 
of the heavy rain and strongest winds displaced along and to the 
east of the forecast track. The initial intensity is similar to the 
previous advisory and closely follows the simple and corrected 
consensus models.
 
Given the remaining uncertainty in the track forecast and the degree 
of land interaction with Hispaniola and Cuba, users are urged to 
factor in some of this uncertainty.  For reference, average NHC 
track errors at days 3 and 4 are 125 miles and 150 miles, 
respectively.  The average NHC intensity errors are around 15 mph 
for both days 3 and 4.
 
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
beginning early Sunday, with tropical storm conditions possible in
central and western Cuba Sunday night and Monday.
 
3. There is an increasing risk of tropical storm conditions, storm
surge, and rainfall impacts beginning Monday in the Florida Keys and
the southern Florida Peninsula, and a Tropical Storm Watch is now
in effect for portions of the Florida Keys. This risk will spread
northward along the Florida Peninsula through Wednesday and reach
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 the islands of Hispaniola and
Cuba. Interests elsewhere in Florida and along the southeast U.S.
coast should monitor Elsa's progress and updates to the forecast.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  04/0300Z 17.9N  75.3W   55 KT  65 MPH
 12H  04/1200Z 19.2N  77.3W   55 KT  65 MPH
 24H  05/0000Z 20.9N  79.4W   60 KT  70 MPH
 36H  05/1200Z 22.5N  81.0W   50 KT  60 MPH...INLAND
 48H  06/0000Z 24.1N  82.2W   45 KT  50 MPH...OVER WATER
 60H  06/1200Z 26.0N  82.8W   50 KT  60 MPH
 72H  07/0000Z 28.0N  83.0W   50 KT  60 MPH
 96H  08/0000Z 32.7N  81.0W   45 KT  50 MPH...INLAND
120H  09/0000Z 37.7N  74.9W   35 KT  40 MPH...OVER WATER
 
$$
Forecaster Stewart/Papin
 
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