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Tropical Depression Nine Discussion Number   2
NWS National Hurricane Center Miami FL       AL092021
500 PM EDT Thu Aug 26 2021
 
The overall satellite presentation of the tropical cyclone has 
continued to gradually improve today.  Visible imagery and very 
recent observations from an Air Force Reserve reconnaissance 
aircraft indicate that the circulation has continued to become 
better defined.  In addition, the convective activity has become a 
little better organized in a band around the northeastern and 
eastern portions of the circulation, and the system is likely near 
tropical storm strength.  However, the initial intensity remains 30 
kt pending the aircraft fully sampling the eastern portion of the 
circulation.
  
The initial motion estimate is northwestward or 325/12 kt. The 1200 
UTC dynamical model guidance continues to take the system 
northwestward around the southwestern side of well-established 
deep-layer ridge over the western Atlantic.  On the forecast track, 
the system is expected to move over portions of western Cuba late 
Friday, over the southeastern and central Gulf of Mexico on 
Saturday, and approach the northern Gulf coast on Sunday.  Although 
the track guidance envelope has tightened this cycle, increasing 
confidence in the overall forecast scenario, some shifts in the 
track are still likely until the system consolidates and becomes 
better defined.  Users are reminded to not focus on the exact 
forecast track as storm surge, wind, and rainfall hazards will 
extend far from the center, and the average NHC track forecast error 
at day 3 is around 120 miles. The lastest NHC track forecast is 
close to the previous official forecast, and lies between the TCVA 
and HCCA consensus aids.
 
There is some evidence of some light to moderate southerly shear 
over the system, but with the cyclone moving over the high ocean 
heat content waters of the northwestern Caribbean Sea the shear 
should not hinder intensification, with steady strengthening 
anticipated during the next 12 to 24 hours.  Once the system moves 
over the Gulf of Mexico, it will be traversing a warm eddy, and this 
feature, combined with a favorable upper-level wind pattern and a 
moist atmosphere, is likely to result in steady to rapid 
strengthening on Saturday and Saturday night.  The NHC intensity 
forecast again brings the system to near major hurricane strength 
when it approaches the northern Gulf coast on Sunday.  This is 
supported by the HWRF and CTCI models, and the global model guidance 
that has consistently showed significant deepening of the system 
over the Gulf of Mexico over the past several model cycles.  
Therefore, as mentioned this morning, there is higher-than-normal 
confidence that a strengthening tropical cyclone will be moving over 
the Gulf of Mexico this weekend.
 
Key Messages:
 
1. Tropical storm conditions are expected in portions of the Cayman 
Islands tonight and in portions of western Cuba and the Isle of 
Youth Friday. Dangerous storm surge is possible Friday in portions 
of western Cuba, including the Isle of Youth, in areas of onshore 
flow. 

2. Life-threatening heavy rains, flash flooding and mudslides are 
expected across Jamaica, the Cayman Islands, and western Cuba, 
including the Isle of Youth.

3. The system is forecast to approach the northern Gulf coast at or 
near major hurricane intensity on Sunday, where there is an 
increasing risk of life-threatening storm surge, damaging 
hurricane-force winds, and heavy rainfall Sunday and Monday, 
especially along the coast of Louisiana.  Storm Surge and Hurricane 
watches will likely be issued for a portion of this area later 
tonight or Friday morning.  Interests in these areas should closely 
monitor the progress of this system and follow any advice given by 
local officials. 

FORECAST POSITIONS AND MAX WINDS
 
INIT  26/2100Z 18.0N  79.8W   30 KT  35 MPH
 12H  27/0600Z 19.7N  81.0W   45 KT  50 MPH
 24H  27/1800Z 21.7N  82.8W   55 KT  65 MPH...INLAND
 36H  28/0600Z 23.7N  84.8W   60 KT  70 MPH...OVER WATER
 48H  28/1800Z 25.6N  87.0W   70 KT  80 MPH
 60H  29/0600Z 27.2N  88.8W   85 KT 100 MPH
 72H  29/1800Z 28.9N  90.4W   95 KT 110 MPH
 96H  30/1800Z 31.9N  91.4W   50 KT  60 MPH...INLAND
120H  31/1800Z 34.6N  90.0W   25 KT  30 MPH...INLAND
 
$$
Forecaster Brown
 
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