Tropical Storm Ernesto Discussion Number   8
NWS National Hurricane Center Miami FL       AL052024
1100 AM AST Tue Aug 13 2024

Ernesto's center passed near or over Guadeloupe and Montserrat this
morning and is now located just south of St. Kitts and Nevis.
Aircraft data, satellite images, and radar data show that the storm
is becoming better organized, and there are some indications that
an inner core is developing.  Earlier NOAA Hurricane Hunter data
supported maximum winds of 40 kt, and given the improved structure
since then (and consensus T3.0 Dvorak estimates from TAFB and SAB),
the initial intensity is set at 45 kt.

Ernesto has turned toward the west-northwest, and now has an
initial motion of 290/16 kt.  A break in the subtropical ridge over
the western Atlantic is expected to cause Ernesto to turn toward
the northwest and then north during the next couple of days, with
the storm's center passing near or over the Virgin Islands this
evening and then moving northeast and north of Puerto Rico
overnight and on Wednesday.  A northward to north-northeastward
motion is forecast after 48 hours as Ernesto interacts with a
deep-layer trough off the U.S. East Coast, but this trough ends up
bypassing Ernesto, resulting in the storm slowing down a bit when
it is in the vicinity of Bermuda.  The track guidance has been very
consistent, and no changes were required to the official track
forecast compared to the previous issuance.

Sea surface temperatures near Ernesto in the northeastern Caribbean
Sea are very warm--on the order of 29-30 degrees Celsius--and
vertical shear in the atmosphere is relatively light.  Combined
with the thought that Ernesto is developing an inner core, these
ingredients favor quick strengthening over the next day or so.
SHIPS and the HFIP Corrected Consensus models indicate that Ernesto
could be near or at hurricane strength in about 24 hours, and
several of the Rapid Intensification (RI) indices are notably high.
As a result, the updated NHC intensity forecast is more aggressive
than the previous forecast, and brings Ernesto to hurricane
strength by 24 hours when the center is north of Puerto Rico.
Because there is some risk of the storm becoming a hurricane before
that time, a Hurricane Watch has been issued for the Virgin
Islands, Culebra, and Vieques.  After moving north of Puerto Rico,
additional strengthening is likely, and the NHC forecast is near the
high end of the guidance.  Ernesto is also likely to grow in size
while over the western Atlantic, and that is reflected in the
official forecast.


Key Messages:

1. Tropical storm conditions are expected to continue over portions
of the Leeward Islands today and spread westward to the Virgin
Islands and Puerto Rico later today and tonight.  Hurricane
conditions are also possible on the Virgin Islands, Culebra, and
Vieques this evening and tonight.

2. Heavy rainfall may result in locally considerable flash flooding
and mudslides in areas of the Leeward Islands through today, and
over the Virgin Islands into Puerto Rico by later today through
Wednesday.

3. Ernesto is likely to bring impacts to Bermuda late this week, 
and interests there should monitor the progress of this system.


FORECAST POSITIONS AND MAX WINDS

INIT  13/1500Z 16.9N  62.6W   45 KT  50 MPH
12H  14/0000Z 18.0N  64.6W   55 KT  65 MPH
24H  14/1200Z 19.8N  66.6W   65 KT  75 MPH
36H  15/0000Z 22.0N  68.0W   75 KT  85 MPH
48H  15/1200Z 24.3N  68.5W   85 KT 100 MPH
60H  16/0000Z 26.3N  68.1W   90 KT 105 MPH
72H  16/1200Z 28.2N  67.0W   95 KT 110 MPH
96H  17/1200Z 31.4N  65.2W   95 KT 110 MPH
120H  18/1200Z 34.9N  64.5W   90 KT 105 MPH

$$
Forecaster Berg