Tropical Depression Eighteen Forecast Discussion

000
WTNT43 KNHC 041440
TCDAT3

Tropical Depression Eighteen Discussion Number   4
NWS National Hurricane Center Miami FL       AL182024
1000 AM EST Mon Nov 04 2024

Data from the Air Force Hurricane Hunters, satellite images, and
surface observations indicate that the low pressure system over the
south-central Caribbean Sea has developed a well-defined center and
is producing organized deep convection. Therefore, the system now
meets the criteria of a tropical depression. The maximum
flight-level winds from the aircraft support holding the initial
wind speed steady at 30 kt. Deep convection is gradually organizing
near the center and in bands around it, especially on the south and
east sides of the circulation.

The depression has jogged a bit to the right of the previous track,
and the initial motion estimate is now 010/8 kt. A turn to the
northwest is expected later today, and that motion is forecast to
continue during the next few days as a ridge builds over the
southwestern Atlantic and northeastern Caribbean. This motion should
take the center of the system near Jamaica tonight, near or over the
Cayman Islands by late Tuesday, and across western Cuba on
Wednesday. After that time, when the system reaches the Gulf of
Mexico, the model solutions diverge, which appears to be due to
differences in the steering patterns and vertical depth of the
storm. The NHC track forecast is largely an update of the previous
one and remains close to the various consensus models.  However, it
should be noted that the track forecast over the Gulf of Mexico is
of low confidence.

The environmental factors of low wind shear, high moisture, and warm
SSTs support intensification, and since the system now has a well
organized circulation, there is increasing confidence of steady
strengthening until the system reaches Cuba or the southeastern Gulf
of Mexico. In 3 or 4 days, when the system reaches the central Gulf,
a sharp increase in southwesterly vertical wind shear, drier air,
and slightly cooler waters should end the strengthening trend and
induce weakening. The NHC intensity forecast lies near the middle of
the guidance envelope, fairly close to the HCCA and IVCN consensus
aids.


Key Messages:

1. Hurricane conditions are expected in the Cayman Islands on
Tuesday and are possible in portions of Cuba early Wednesday, where
Hurricane Warnings and Watches are in effect. There is a risk of
dangerous impacts from hurricane-force winds and storm surge in the
Cayman Islands and portions of western Cuba. Tropical storm
conditions are expected in Jamaica this evening.

2. Interests in the Florida Keys should closely monitor this system
as tropical storm watches could be required for portions of these
areas later today.

3. The system is forecast to enter the Gulf of Mexico later this
week, but given significant uncertainties in the long-range forecast
track and intensity, it is too soon to determine what, if any,
impacts could occur. Residents in this area should regularly monitor
updates to the forecast.

4. The system will bring areas of heavy rain across portions of the
western Caribbean, including Jamaica and portions of Cuba through
mid-week. Flooding and mudslides are possible in these areas.  Heavy
rainfall will spread north into Florida and adjacent areas of the
Southeast United States mid to late week.


FORECAST POSITIONS AND MAX WINDS

INIT  04/1500Z 15.2N  76.9W   30 KT  35 MPH
 12H  05/0000Z 16.5N  77.6W   35 KT  40 MPH
 24H  05/1200Z 18.2N  79.0W   45 KT  50 MPH
 36H  06/0000Z 19.9N  80.7W   60 KT  70 MPH
 48H  06/1200Z 21.7N  82.4W   70 KT  80 MPH
 60H  07/0000Z 23.4N  83.9W   70 KT  80 MPH
 72H  07/1200Z 24.6N  85.1W   70 KT  80 MPH
 96H  08/1200Z 26.1N  87.4W   65 KT  75 MPH
120H  09/1200Z 27.4N  89.5W   55 KT  65 MPH

$$
Forecaster Cangialosi/Kelly