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Hurricane Delta Discussion Number   7
NWS National Hurricane Center Miami FL       AL262020
500 AM EDT Tue Oct 06 2020
 
Delta has maintained a very deep central dense overcast during the
past several hours, with overshooting cloud-top temperatures to
-90C, and perhaps hints of an eye trying to emerge.  On the last 
pass through the center, the Air Force plane reported a 4-mb 
pressure fall in one hour to 968 mb, with believable SFMR values of 
80-85 kt.  Thus, the initial wind speed is set to 85 kt.
 
The hurricane is in the midst of a very impressive rapid
intensification episode, having strengthened over 50 kt during the 
past 24 hours.  I honestly don't see much that will stop it until it
reaches Yucatan, due to low vertical wind shear, high deep-layer
moisture, and the very warm and deep waters of the northwestern
Caribbean.  This is also supported by SHIPS rapid intensification 
probabilities that are well above 50 percent for most categories.  
Thus, the intensity forecast is raised to 115 kt near Yucatan 
landfall, closest to the HWRF forecast model, which has been a 
good performer this year, especially after ingesting NOAA radar 
data.  Some weakening is expected due to land interaction, but 
conditions look ripe for re-intensification over the Gulf of Mexico. 
Almost all the guidance is higher, now showing Delta reaching 
category 4 status in the 2-to-3 day time frame, and the new NHC 
intensity forecast reflects this likelihood.  However, an increase 
in southwesterly shear and cooler shelf waters near the northern 
Gulf coast should promote weakening, and little change has been made 
to the intensity forecast near landfall.  

Delta is moving much faster this morning to the west-northwest, with 
the latest estimates at about 13 kt.  A strengthening mid-level 
ridge across Florida should steer the hurricane to the 
west-northwest or northwest during the next couple of days.  Likely 
because of the deterioration of Gamma, model guidance is showing 
less poleward motion before Yucatan, and the official track is 
shifted to the west for the first day or so.  Over the Gulf of 
Mexico, Delta should slow down and turn northward ahead of a trough 
moving eastward across Texas in a few days.  Model guidance has 
again shifted westward, like the last cycle, and the official 
forecast is trended in that direction. However, it remains slightly 
east of the model consensus, due to a notable westward bias in some 
of the guidance during this hurricane season.

Users are reminded to not focus on the details of the track or
intensity forecasts, as the average 4-day track error is around 150
miles and the average 4-day intensity error is close to 15 mph.
 
Key Messages:
 
1. Extremely dangerous storm surge and hurricane conditions are
expected within portions of the northern Yucatan Peninsula of
Mexico beginning tonight, and a Hurricane Warning is in effect.
 
2. Heavy rainfall will affect portions of the Cayman Islands, 
western Cuba and the northern Yucatan Peninsula through midweek. 
This rainfall could lead to significant flash flooding and 
mudslides. The potential for heavy rain and flash flooding will 
increase across portions of the central Gulf Coast, Tennessee 
Valley, and southeastern United States as Delta moves inland later 
this week.
 
3. 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 a significant 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  06/0900Z 17.5N  81.3W   85 KT 100 MPH
 12H  06/1800Z 18.7N  83.1W  100 KT 115 MPH
 24H  07/0600Z 20.4N  85.8W  115 KT 130 MPH
 36H  07/1800Z 21.8N  88.5W  105 KT 120 MPH
 48H  08/0600Z 23.0N  90.4W  110 KT 125 MPH
 60H  08/1800Z 24.2N  91.5W  115 KT 130 MPH
 72H  09/0600Z 25.8N  92.0W  110 KT 125 MPH
 96H  10/0600Z 29.8N  91.1W   85 KT 100 MPH...INLAND
120H  11/0600Z 34.0N  88.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Blake
 
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