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Tropical Depression FOURTEEN

Tropical Depression Fourteen Discussion Number   6
NWS National Hurricane Center Miami FL       AL142020
500 PM EDT Fri Aug 21 2020
Since this morning's advisory, the low-level swirl on which the Air 
Force reconnaissance plane made its last fix has apparently become 
the new center of circulation of the depression.  A little bit of 
deep convection has developed over this new center during the past 
few hours, but on the whole there is very little convective activity 
in the central region of the circulation.  The strongest and most 
persistent convection is located within a band that extends across 
the Cayman Islands toward western Cuba.  An ASCAT pass from this 
morning showed winds of 25-30 kt to the northeast of the new center, 
so 30 kt remains the initial intensity on this advisory.

It is a bit of a mystery why the depression has struggled to 
develop much central convection, given a seemingly low-shear 
environment and warm waters.  Since these conditions are expected 
to continue for the next few days, intensification is still 
indicated in the official forecast, although the rate of 
strengthening has been muted a bit while the system approaches 
the Yucatan Peninsula given its current structure.  After the 
center moves over the Gulf of Mexico, many of the models still show 
the cyclone reaching hurricane intensity in about 3 days, including 
the intensity consensus, and that possibility is still shown in the 
NHC forecast.  By day 4, the cyclone is likely to be blasted by 
30-40 kt of southwesterly shear, which would lead to weakening 
while it approaches the northwestern Gulf coast.  The official 
forecast has been reduced at that time, although it's noteworthy to 
mention that it still lies above all the guidance on day 4.

Now that there is more confidence in the initial position, the new 
motion estimate is a little to the right from before, but still 
toward the northwest, or 325/11 kt.  A deep-layer trough over the 
Gulf of Mexico is forecast to be shoved aside by the Atlantic 
subtropical ridge building westward over the next 2 days.  Even 
with this pattern change, the cyclone is expected to move generally 
northwestward for the entire 5-day forecast period.  However, there 
has been a notable westward bend in some of the track models, 
(particularly the GFS and ECMWF) from days 3-5, which is likely 
due those models having a weaker cyclone steered more by the 
low-level ridge at that time.  Since the NHC intensity forecast is 
mirroring this particular model trend, the track forecast has been 
shifted westward from the previous prediction on days 4 and 5 
toward the GFS and ECMWF solutions.  The track forecast is still of 
rather low confidence, with the spread among the model guidance 
being larger than normal at every forecast time period.
Key Messages:
1. Tropical Depression Fourteen is expected to strengthen over the
northwestern Caribbean Sea through Saturday, and it could still be
near hurricane strength when it reaches the east coast of the 
Yucatan Peninsula of Mexico late Saturday.  A Hurricane Watch
and a Tropical Storm Warning are in effect for portions of that
2. The system is expected to move into the south-central Gulf of
Mexico as a tropical storm on Sunday.  Although some strengthening 
is anticipated Sunday and Monday, weakening is forecast as the 
system approaches the northwestern Gulf coast on Tuesday.  It is 
still too soon to know exactly the location and magnitude of impacts 
the system will produce along the central or northwestern Gulf 
Coast, and interests in that area should continue monitoring the 
progress of this system over the next few days.
INIT  21/2100Z 17.7N  84.3W   30 KT  35 MPH
 12H  22/0600Z 18.6N  85.0W   35 KT  40 MPH
 24H  22/1800Z 19.8N  85.9W   45 KT  50 MPH
 36H  23/0600Z 21.2N  87.1W   55 KT  65 MPH...INLAND
 48H  23/1800Z 22.9N  88.7W   55 KT  65 MPH...OVER WATER
 60H  24/0600Z 24.6N  90.4W   60 KT  70 MPH
 72H  24/1800Z 26.2N  92.2W   65 KT  75 MPH
 96H  25/1800Z 28.5N  95.0W   50 KT  60 MPH
120H  26/1800Z 30.0N  97.5W   30 KT  35 MPH...INLAND
Forecaster Berg