Tropical Storm Delta Discussion Number   5
NWS National Hurricane Center Miami FL       AL262020
500 PM EDT Mon Oct 05 2020

Visible satellite imagery shows that the convective banding of Delta has continued to quickly improve since this morning. The primary convective band now wraps entirely around the center, with what appears to be a banding-type eye feature occasionally noted.  There are some dry slots between the convective bands but those appear to be gradually filling in.  A NOAA Hurricane Hunter aircraft currently collecting data in the storm environment found peak SFMR winds of 55 kt during its first pass through the center from northwest to southeast.  The plane also reported a minimum pressure of 983 mb, much lower than previously estimated.  The aircraft also observed an 18 nmi-wide-eye that was open to the west-northwest.   Assuming that there are stronger winds yet to be sampled in the northeastern quadrant, the initial intensity has been raised to 60 kt. 

Delta is situated within a very conducive environment for
strengthening.  The storm will be moving over SSTs of 29-30 degrees
Celsius and the vertical wind shear is forecast to remain 5 kt or
less while Delta traverses the northwestern Caribbean. These
conditions are expected to allow for rapid strengthening over the
next 24 to 36 hours.  The SHIPS Rapid Intensification Index gives a
better than 50 percent chance of a 35-40 kt increase in wind speed
over the next 24 hours.  The NHC intensity forecast follow suit by
calling for rapid intensification over the next day or so, and 
Delta is forecast to be a major hurricane when is passes near or 
over the northeastern portion of the Yucatan peninsula.  Once 
the storm reaches the central Gulf of Mexico in 60-72 hours, 
increasing southwestern vertical wind shear and cooler shelf waters 
over the northern Gulf are likely to result in some reduction in 
wind speed as the system nears the northern Gulf coast.  Although 
there is still significant uncertainty regarding Delta's intensity 
when it nears the northern Gulf coast, it is becoming increasing 
likely that the system will pose a significant wind and storm surge
threat to a portion of that area.

The center has jogged southward again this afternoon, which appears 
to be primarily due to the system organizing rather than a true 
storm motion.  The initial motion estimate remains an uncertain 
275/7 kt. Delta should begin moving west-northwestward this evening, and a west-northwestward to northwestward motion around the southwestern portion of a deep-layer ridge to its northeast is 
expected over the next couple of days. The more southward initial 
position and more ridging over the eastern Gulf of Mexico has 
resulted in a significant westward shift in the track envelope 
through the first 60-72 hours.  The NHC has been adjusted in that 
direction, and this has required the issuance of a Hurricane Warning for the northeastern portion of the Yucatan peninsula of Mexico.   After 72 hours, a mid- to upper-level trough is forecast to develop over Texas which should cause Delta to turn northward and then north-northeastward toward the northern Gulf Coast.  Although the track forecast has not changed much during the latter portion of the period, there is more cross-track spread in the model guidance than before, which has increased the uncertainty regarding potential landfall and the timing of Delta's approach to the northern Gulf Coast.

Key Messages:

1. Dangerous storm surge and hurricane conditions are expected 
within portions of the northern Yucatan Peninsula of Mexico and are 
possible in extreme western Cuba beginning Tuesday night, and a 
Hurricane Warning is in effect.

2. Heavy rainfall will affect portions of Jamaica, the Cayman 
Islands, western Cuba and the northern Yucatan Peninsula during the 
next few days. This rainfall could lead to significant flash 
flooding and mudslides.  

3. Tropical storm conditions are expected in portions of the Cayman 
Islands beginning tonight or early Tuesday, and a Tropical Storm 
Warning is in effect.  

4. Delta is forecast to approach the northern Gulf Coast late this 
week as a hurricane. While there is large uncertainty in the track 
and intensity forecasts, there is an increasing risk of dangerous 
storm surge, wind, and rainfall hazards along the coast from 
Louisiana to the western Florida Panhandle beginning Thursday night 
or Friday. Residents in these areas should ensure they have their 
hurricane plan in place and monitor updates to the forecast of 
Delta.

FORECAST POSITIONS AND MAX WINDS

INIT  05/2100Z 16.2N  79.4W   60 KT  70 MPH
 12H  06/0600Z 17.1N  80.9W   75 KT  85 MPH
 24H  06/1800Z 19.0N  83.5W   95 KT 110 MPH
 36H  07/0600Z 21.0N  86.2W  105 KT 120 MPH
 48H  07/1800Z 22.6N  88.7W  105 KT 120 MPH
 60H  08/0600Z 23.7N  90.6W  105 KT 120 MPH
 72H  08/1800Z 24.8N  91.5W   95 KT 110 MPH
 96H  09/1800Z 28.5N  91.5W   85 KT 100 MPH
120H  10/1800Z 33.0N  89.0W   40 KT  45 MPH...INLAND

$$
Forecaster Brown