[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 030838
TCDAT5

Hurricane Elsa Discussion Number  12
NWS National Hurricane Center Miami FL       AL052021
500 AM AST Sat Jul 03 2021

Elsa appears less organized this morning.  Satellite images show an
asymmetric cloud pattern with the low-level center located near the
northwestern edge of the main area of thunderstorms.  This satellite
presentation is indicative of moderate-to-strong northwesterly
shear that is likely caused by the tropical cyclone's fast forward
motion. The initial intensity is lowered to 65 kt following a blend
of the latest Dvorak estimates. The hurricane passed by NOAA buoy
42059 a few hours ago, and the storm's minimum pressure was
adjusted a few millibars higher based on the buoy's data. Another
Air Force Hurricane Hunter aircraft will be flying through Elsa in
a couple of hours, and the data the plane collects will provide a
better estimate of Elsa's intensity and structure.

Elsa continues to move very quickly to the west-northwest at about
27 kt.  A subtropical ridge to the north of the hurricane should
keep it on a west-northwest path, albeit at a slightly slower pace
through the weekend.  This should take the core of the storm just
south of or over southern Hispaniola later today and near or
across Jamaica and eastern Cuba on Sunday.  Shortly after that time,
Elsa is expected to near the western edge of the ridge and move
toward a weakness over the southeastern U.S.  In response to this
pattern change, Elsa should slow down some more and turn to the
north.  The models appear to be slowly converging on a solution in
showing the cyclone making the northward turn somewhere over Cuba on
Monday and then heading in the vicinity of Florida or the
eastern Gulf of Mexico late Monday through Wednesday. Although the
models are in better agreement compared to previous days, there is
still a considerable amount of spread in the GFS and ECMWF ensemble
members, and the details of the long-term track are still uncertain.

Some mid-level wind shear associated with Elsa's fast forward speed
appears to be affecting the hurricane now.  However, since the
cyclone is expected to slow down and move beneath an upper-level
anticyclone later this weekend, it seems likely that the vortex will
become better aligned in the vertical.  The big question is will
Elsa be interacting with the mountainous islands of Hispaniola and
Cuba when the environmental winds become conducive for
strengthening.  If the cyclone manages to stay south of those
islands, Elsa could have an opportunity to restrengthen. Conversely,
if the storm tracks directly over the islands, weakening would very
likely occur.  As a compromise, the NHC intensity forecast shows
little change in strength through tonight, followed by slow
weakening on Sunday and early Monday.  Slight restrengthening is
forecast when Elsa moves north of Cuba and  across the eastern Gulf
of Mexico.  This forecast is a little lower than the previous one in
the short term, but is largely unchanged at the longer forecast
times.

Given that there is still 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. Hurricane conditions and dangerous storm surge are expected
within the Hurricane Warning areas in Haiti and the Dominican
Republic later today and in Jamaica beginning Sunday.

2. Widespread heavy rain will move across southern Hispaniola and
Jamaica today 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 with mudslides in Cuba. As Elsa approaches the Florida Keys
and southern Florida early next week, isolated flash flooding and
minor river flooding will be possible.

3. Hurricane conditions and dangerous storm surge are possible in
portions of eastern Cuba beginning early Sunday where a Hurricane
Watch is in effect. There is an increasing risk of wind, storm
surge, and rainfall impacts elsewhere in Cuba Sunday and Monday.

4. There is an increasing risk of storm surge, wind, and rainfall
impacts beginning Monday in the Florida Keys and spreading northward
along the Florida Peninsula through Tuesday. However, the forecast
uncertainty remains larger than usual due to Elsa's potential
interaction with the islands of Hispaniola and Cuba this weekend.
Interests throughout Florida should monitor Elsa's progress and
updates to the forecast.


FORECAST POSITIONS AND MAX WINDS

INIT  03/0900Z 16.2N  69.0W   65 KT  75 MPH
 12H  03/1800Z 17.5N  72.3W   65 KT  75 MPH
 24H  04/0600Z 19.0N  75.4W   65 KT  75 MPH
 36H  04/1800Z 20.5N  77.8W   60 KT  70 MPH
 48H  05/0600Z 22.1N  79.7W   55 KT  65 MPH...INLAND
 60H  05/1800Z 23.4N  81.2W   50 KT  60 MPH...OVER WATER
 72H  06/0600Z 24.7N  82.2W   55 KT  65 MPH
 96H  07/0600Z 28.2N  83.0W   55 KT  65 MPH
120H  08/0600Z 33.7N  80.2W   35 KT  40 MPH...INLAND

$$
Forecaster Cangialosi/Berg
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