Tropical Storm Ernesto Discussion Number   9
NWS National Hurricane Center Miami FL       AL052024
500 PM AST Tue Aug 13 2024

Ernesto's structure continues to gradually increase in organization. 
There has been some indication of dry air within the circulation 
and possibly some westerly shear--likely related to the system's 
continued fast motion--but the maximum winds have been increasing 
during the day nonetheless.  An Air Force Reserve Hurricane Hunter 
aircraft measured peak 850-mb flight-level winds of 57 kt and 
believable SFMR winds of 45-50 kt northeast of the center, and 
dropsonde data showed that the central pressure had fallen to 1001 
mb.  Based on these data, the initial intensity is set at 50 kt.  
Some satellite estimates suggest the intensity could be slightly 
higher, but there will be both Air Force and NOAA aircraft in the 
storm later this evening to confirm these trends.

The recent aircraft fixes indicate that Ernesto continues to turn 
to the right and is moving west-northwestward, or 300/16 kt.  This 
turn is expected to continue for the next couple of days as Ernesto 
moves toward a break in the western Atlantic subtropical ridge.  On 
this track, Ernesto's center should pass over the Virgin Islands 
later this evening and then pass 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 continues to 
be very consistent, and again no significant changes were required 
to the official track forecast compared to the previous issuance.

Very warm sea surface temperatures and generally low shear favor 
continued strengthening over the next few days.  SHIPS and the HFIP 
Corrected Consensus models continue to suggest that Ernesto could 
reach hurricane strength by 12 hours, and several of the Rapid 
Intensification (RI) indices are still well above climatology.  As a 
result, the NHC intensity forecast shows Ernesto becoming a 
hurricane by tonight and then peaking at an intensity at or just 
below major hurricane strength in 60-72 hours.  Since there is some 
chance of Ernesto becoming a hurricane while it is near the Virgin 
Islands, a Hurricane Watch remains in effect for the Virgin Islands, 
Culebra, and Vieques.


Key Messages:

1. Tropical storm conditions are expected to continue over portions
of the northern Leeward Islands this evening and spread westward to 
the Virgin Islands and Puerto Rico this evening 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 this evening, 
and over the Virgin Islands into Puerto Rico by this evening 
through Wednesday.

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

4. Swells generated by Ernesto are expected to affect portions of 
the Virgin Islands, Puerto Rico, the Dominican Republic, the Turks 
and Caicos, and the Bahamas during the next few days and then reach 
the east coast of the United States and Bermuda late this week and 
into the weekend.  These swells are likely to cause 
life-threatening surf and rip current conditions.


FORECAST POSITIONS AND MAX WINDS

INIT  13/2100Z 18.0N  64.1W   50 KT  60 MPH
12H  14/0600Z 19.3N  65.9W   65 KT  75 MPH
24H  14/1800Z 21.3N  67.6W   75 KT  85 MPH
36H  15/0600Z 23.4N  68.6W   85 KT 100 MPH
48H  15/1800Z 25.4N  68.7W   90 KT 105 MPH
60H  16/0600Z 27.2N  67.9W   95 KT 110 MPH
72H  16/1800Z 29.1N  66.7W   95 KT 110 MPH
96H  17/1800Z 32.7N  65.3W   90 KT 105 MPH
120H  18/1800Z 36.8N  64.1W   90 KT 105 MPH

$$
Forecaster Berg