Tropical Storm Ernesto Discussion Number   5
NWS National Hurricane Center Miami FL       AL052024
500 PM AST Mon Aug 12 2024

Satellite images and data from the Air Force Hurricane Hunters 
indicate that a center of circulation has now formed, and deep 
convection is gradually organizing in bands around that feature.  A 
combination of flight-level wind and SFMR data from the aircraft 
support increasing the winds to 35 kt.  Since the system meets the 
definition of a tropical cyclone and has winds of tropical storm 
force, it is now designated Tropical Storm Ernesto.

Based on the latest satellite images and aircraft data, the center 
has formed about 30 n mi north of the previous track.  This makes 
the initial motion uncertain, but our best estimate is 285/24 kt. 
This fast forward speed is due to a strong low- to mid-level ridge 
situated just north of the system over the subtropical Atlantic.  A 
fast west-northwestward motion is expected to continue, taking the 
storm across the northern Leeward Islands overnight and near or over 
the Virgin Islands and Puerto Rico Tuesday afternoon or Tuesday 
night.  After that time, a significant slowdown and a turn to the 
north over the Atlantic is expected as a deep-layer trough pushes 
off the U.S. east coast, causing the ridge to shift eastward. The 
NHC track forecast is a little to the right of the previous one in 
the short term and lies on the left edge of the guidance through 
Ernesto's track across the Caribbean.  This forecast is closer to 
the middle of the guidance envelope while it is over the western and 
central Atlantic.

Since Ernesto now has a center and a slightly improved circulation, 
strengthening seems likely.  However, the rate of intensification 
will likely be slow during the next day or two due to the system's 
broad structure and ragged convective pattern.  More significant 
strengthening is forecast after Ernesto exits the Caribbean, when 
nearly all of the environmental conditions appear conducive.  The 
NHC intensity forecast is a little higher than the previous one in 
the short term, trending toward the latest consensus aids.


Key Messages:

1. Ernesto is expected to bring tropical storm conditions to
portions of the Leeward Islands late tonight and Tuesday and to the 
Virgin Islands and Puerto Rico by late Tuesday. Tropical Storm 
Warnings are in effect for this entire area.

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

3. It is too soon to know what impacts Ernesto could bring to 
Bermuda late this week, and interests there should monitor the 
progress of this system.

FORECAST POSITIONS AND MAX WINDS

INIT  12/2100Z 16.0N  57.5W   35 KT  40 MPH
12H  13/0600Z 16.2N  60.3W   40 KT  45 MPH
24H  13/1800Z 16.9N  63.4W   45 KT  50 MPH
36H  14/0600Z 18.5N  65.6W   50 KT  60 MPH
48H  14/1800Z 20.9N  67.1W   60 KT  70 MPH
60H  15/0600Z 22.9N  67.8W   70 KT  80 MPH
72H  15/1800Z 25.0N  68.0W   80 KT  90 MPH
96H  16/1800Z 29.4N  66.0W   95 KT 110 MPH
120H  17/1800Z 32.5N  64.3W   95 KT 110 MPH

$$
Forecaster Cangialosi