Tropical Storm Rafael Forecast Discussion

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WTNT43 KNHC 050300
TCDAT3

Tropical Storm Rafael Discussion Number   6
NWS National Hurricane Center Miami FL       AL182024
1000 PM EST Mon Nov 04 2024

After a period of intensification this afternoon, Rafael has taken a 
brief pause on further development. Tonight's Air Force Reserve 
Aircraft sampled the tropical storm from 2330-0130 UTC, finding the 
structure still somewhat broad with a minimum central pressure of 
996 mb from the last fix, only slightly lower than this afternoon. 
Earlier AMSR2 and GMI microwave imagery did show the outer core 
structure of Rafael is gradually organizing, with plenty of curved 
convective bands on the 37-GHz channel along the the eastern flank, 
though some dry air appears to be undercutting the cirrus outflow 
to the west and preventing organized convection from fully wrapping 
around the center. Aircraft flight-level winds at 850 mb were not 
all that impressive (40 kt peak), though peak SFMR values in the 
same realm still support a maximum intensity of about 40 kt for 
this advisory. Another Air Force Reconnaissance mission is in route 
to sample the storm again later tonight. 

Rafael appears to be turning more northwestward with a faster 
forward motion, estimated tonight at 335/10 kt. The track forecast 
for the next 48 h is fairly straightforward, as mid-level ridging 
builds in to the northeast of Rafael, which should maintain steering 
that should continue a northwestward track, bringing the tropical 
storm on its closest approach to Jamaica Tuesday morning, passing 
through the Cayman Islands Tuesday night, and nearing the Caribbean 
coast of western Cuba on Wednesday. After Rafael crosses Cuba and 
moves into the eastern Gulf of Mexico, the track forecast remains a 
challenge. The spread in ensemble track solutions is notable, and 
appears not just related to the vertical depth of Rafael, but also 
the synoptic pattern over the United States. A large deep-layer 
cutoff low is expected to dig into the four corners region of the 
U.S., and how progressive this feature is moving into the central 
U.S. will likely determine how much ridging remains over the Gulf of 
Mexico in 4-5 days. The latest NHC track forecast is similar to the 
prior track for the first 36 h, but is a shade farther right beyond 
that time, slightly favoring the GFS and Canadian model solutions 
over the UKMET and ECMWF tracks. However, the 200-850 mb steering 
flow depicted in the Gulf of Mexico also shows the possibility of a 
bifurcation point near 25N 86W in 3 days, and where Rafael ends up 
at the time could determine if it stays in the eastern Gulf of 
Mexico or moves much further westward into the central or western 
Gulf. Needless to say, this is a low confidence track forecast in 5 
days. 

The inner core of Raphael still appears to be in the formative stage 
tonight, as convection has yet to become axis-symmetrical around the 
low-level circulation, which lacks a tighter wind field. Thus, the 
rate of intensification over the next day or so should be slower 
than in the final 24 h before Raphael reaches Cuba. Environmental 
conditions remain very favorable in the northwestern Caribbean, and 
SHIPS rapid intensification guidance still indicates that the 
cyclone has a 40-50 percent chance of a 45 kt increase in the next 
36 h. The NHC intensity forecast will show 40 kt of intensification 
over the next 36 h, with some additional intensification possible 
before Raphael moves over Cuba. Once in the Gulf of Mexico, westerly 
shear increases to 15-25 kt, which could halt intensification and 
ultimately lead to weakening as it imports very dry air into Raphael 
by the end of the forecast. The NHC intensity forecast is similar to 
the prior advisory, and remains on the high side of the overall 
intensity guidance.

Key Messages:

1. Rafael is forecast to be near hurricane intensity when it passes 
near or over the Cayman Islands by Tuesday night where damaging 
hurricane-force winds, a dangerous storm surge, and destructive 
waves are expected. Rafael should reach western Cuba and the Isle of 
Youth on Wednesday. A hurricane warning is in effect for this 
region, where a dangerous storm surge and destructive waves are 
also expected. 

2. Tropical storm conditions are expected in Jamaica tonight and 
Tuesday. Tropical storm conditions are possible in the Lower and 
Middle Florida Keys beginning late Wednesday or Wednesday night.

3. It is too soon to determine what, if any, impacts Rafael could
bring to portions of the northern Gulf Coast.  Residents in this
area should regularly monitor updates to the forecast.

4. Rafael will bring areas of heavy rain to portions of the western
Caribbean, including Jamaica and Cuba through mid-week, where
flooding and landslides are possible.  Heavy rainfall will spread
into Florida and adjacent areas of the Southeast United States mid
to late week.


FORECAST POSITIONS AND MAX WINDS

INIT  05/0300Z 16.3N  77.2W   40 KT  45 MPH
 12H  05/1200Z 17.6N  78.3W   50 KT  60 MPH
 24H  06/0000Z 19.4N  79.9W   60 KT  70 MPH
 36H  06/1200Z 21.4N  81.6W   80 KT  90 MPH
 48H  07/0000Z 23.3N  83.1W   80 KT  90 MPH
 60H  07/1200Z 24.6N  84.3W   80 KT  90 MPH
 72H  08/0000Z 25.4N  85.3W   75 KT  85 MPH
 96H  09/0000Z 26.6N  87.6W   65 KT  75 MPH
120H  10/0000Z 27.1N  89.9W   45 KT  50 MPH

$$
Forecaster Papin