[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 050258
TCDAT5

Tropical Storm Elsa Discussion Number  19
NWS National Hurricane Center Miami FL       AL052021
1100 PM EDT Sun Jul 04 2021

Similar to this time last night, Elsa has undergone another
convective bursting pattern, except that tonight this has translated
into at least some slight strengthening. An Air Force Reserve
reconnaissance aircraft investigating the cyclone this evening has
found maximum 850-mb flight-level winds of 55 kt and reliable SFMR
surface winds of about 55 kt. Although there have been SFMR winds of
60 kt or more reported northeast and north of the center, those
values appear to be contaminated by shoaling and/or breaking waves
owing to the shallow water flowing in and around the offshore Cayo
Anclitas and Cayo Pingues archipelagos. The estimated center
pressure of 1004 mb based on dropsonde data also does a higher
intensity of 60 kt. Therefore, based on the most reliable data, the
intensity has been increased to 55 kt.

The initial motion estimate is 310/13 kt.  There remains no
significant change to the previous few track forecasts and synoptic
reasonings. Elsa is expected to move northwestward and then
northward around the western periphery of a mid-level subtropical
ridge during the next 3 days, followed by acceleration toward the
northeast on days 4 and 5 as the cyclone moves near the southeast
U.S. coast and then over the northwestern Atlantic. The new NHC
track forecast is basically just an update and extension of the
previous advisory track, and lies close to a blend of the tightly
packed corrected consensus model HCCA and the simple consensus
models TVCA and GFEX.

Cuban radar data from Pilan and Camaguey have occasionally revealed
an eye-like feature in the low -and mid-levels of the cyclone where
cloud top temperatures have been colder than -80C and also where
significant lightning activity has been occurring. Given that the
circulation centers have become better aligned and the upper-level
outflow pattern is well-established and steadily improving, some
additional strengthening during the next 12 h is forecast, which
calls for Elsa to be near hurricane strength before landfall occurs
along the south-central coast of Cuba tomorrow. Over the eastern
Gulf of Mexico late Monday and Tuesday, some restrengthening is
forecast after Elsa clears Cuba, but southwesterly vertical wind
shear is expected to hinder the intensification process.  The
official intensity forecast remains on the high side of the
numerical model guidance, and follows a blend of the HCCA intensity
consensus model, and the LGEM and and Decay-SHIPS
statistical-dynamical models.

Key Messages:

1. Widespread heavy rain will continue to affect portions of Jamaica
tonight where isolated to scattered flash flooding and mudslides
will be possible. Heavy rain will then impact the Cayman Islands and
Cuba tonight into Monday resulting in significant flooding and
mudslides over Cuba. As Elsa approaches the Florida Keys, Florida
Peninsula, and coastal Georgia Monday through Wednesday, heavy
rainfall may result in isolated flash, urban, and minor river
flooding.  Mid to late week, heavy rains across coastal South
Carolina may result in isolated flash flooding.

2. Tropical storm conditions and a dangerous storm surge are
expected with hurricane conditions possible in portions of eastern
Cuba tonight.  Tropical storm conditions are expected in portions
of central and western Cuba tonight and Monday, and will spread
into portions of the Florida Keys by late Monday.

3. Tropical Storm and Surge Surge Watches are in effect for
portions of the west coast of the Florida peninsula where tropical
storm conditions and a dangerous storm surge are possible beginning
as early as Monday night and continuing into Tuesday.

4. There is a risk of tropical storm conditions, storm surge,
and rainfall impacts along the remainder of the Florida Peninsula
Tuesday night through Wednesday and the coasts of Georgia and the
Carolinas Wednesday and Thursday.


FORECAST POSITIONS AND MAX WINDS

INIT  05/0300Z 20.6N  79.2W   55 KT  65 MPH
 12H  05/1200Z 21.9N  80.7W   60 KT  70 MPH
 24H  06/0000Z 23.5N  82.1W   50 KT  60 MPH
 36H  06/1200Z 25.1N  82.9W   50 KT  60 MPH
 48H  07/0000Z 27.1N  83.2W   50 KT  60 MPH
 60H  07/1200Z 29.2N  82.8W   45 KT  50 MPH...INLAND
 72H  08/0000Z 31.5N  81.6W   35 KT  40 MPH...INLAND
 96H  09/0000Z 36.0N  76.0W   35 KT  40 MPH...INLAND
120H  10/0000Z 41.0N  66.8W   40 KT  45 MPH...OVER WATER

$$
Forecaster Stewart
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