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Hurricane Delta Discussion Number  11
NWS National Hurricane Center Miami FL       AL262020
400 AM CDT Wed Oct 07 2020
 
Satellite images show very deep convection associated with Delta, 
with extremely cold cloud-top temperatures to -97C noted southwest 
of the center overnight.  However, this structure has not resulted 
in a stronger cyclone, and the full NOAA Hurricane Hunter aircraft 
mission actually indicated that Delta has significantly weakened 
since earlier today.  The maximum flight-level winds were 98 kt, 
with SFMR values near 90 kt.  Early in the mission, the flight 
director indicated that the eyewall had dissipated, but on the last 
fix, she noted that the eyewall had re-formed.  Recent Cuban radar 
data also indicate that at least a partial eyewall is present, so 
the initial wind speed is generously kept at 100 kt.

Delta should begin to re-intensify late today as it moves into an 
area of fairly warm and deep waters, with fairly light shear.  The 
regional hurricane models all show Delta attaining category 4 status 
in 36-48 hours, and so does the NHC forecast. As Delta approaches 
the Louisiana coast, lower oceanic heat content and an increase in 
shear is likely to cause some weakening before landfall. The NHC 
intensity forecast is very similar to the previous one, and leans on 
the stronger regional hurricane models.  I should also note that all 
of the guidance show Delta becoming considerably larger than it is 
now by the time it reaches the northern Gulf coast, so even if 
weakening occurs there, the hurricane will likely bring a sizable 
area of hazardous conditions to the coast. 
 
Fixes from the aircraft and Cuban radar data indicate the storm is 
moving faster to the northwest or 305/15 kt.  Delta should make 
landfall during the next few hours between Cozumel and Cancun, and 
move quickly across northeastern Yucatan before emerging in the 
southern Gulf of Mexico early this afternoon.  The hurricane is 
then expected to move to the northwest or west-northwest around the 
southwestern and western portion of the subtropical ridge for about 
the next 36 hours.  Thereafter, Delta will likely turn northward by 
early Friday between the ridge and a mid-level trough over Texas.  
While there is broad agreement on the synoptic pattern, subtle 
differences in the subtropical ridge and the depth of the cyclone 
are causing some challenges.  The ECMWF and its ensembles, for 
instance, are showing a stronger ridge and a weaker storm, which 
results in a slower track toward southwestern Louisiana.  The GFS 
and UKMET, on the other hand, are showing a deeper cyclone, which 
would feel stronger upper-level winds, and move Delta faster to the 
coast.  Given the expectation of a powerful cyclone at landfall, the 
NHC forecast is shaded toward the latter two models, which results 
in a slightly faster and westward-shifted forecast from before, not 
too different from the model consensus. 
 
Key Messages:
 
1. Life-threatening storm surge and dangerous winds are expected 
within portions of the northern Yucatan Peninsula of Mexico during 
the next few hours. Now is the time to be in your storm shelter.
 
2. Heavy rainfall will affect portions of western Cuba and the 
northern Yucatan Peninsula through early Thursday. This rainfall 
could lead to significant flash flooding and mudslides. Flash, 
urban, and small stream flooding, along with minor river flooding is 
likely Friday through Saturday across portions of the central Gulf 
Coast north into portions of the Lower Mississippi Valley. The heavy 
rainfall will spread northeastward into the Tennessee Valley and 
interior southeastern United States this weekend into early next 
week. 
 
3. There is an increasing likelihood of life-threatening storm surge
and dangerous hurricane-force winds, especially along the coasts of
Louisiana and Mississippi, beginning on Friday. Residents in these
areas should ensure they have their hurricane plan in place and
follow advice given by local officials.  Storm surge and hurricane
watches will likely be issued for portions of the northern Gulf
Coast later today.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/0900Z 20.6N  86.4W  100 KT 115 MPH
 12H  07/1800Z 21.9N  88.4W   90 KT 105 MPH
 24H  08/0600Z 23.3N  90.8W   95 KT 110 MPH
 36H  08/1800Z 24.9N  92.4W  105 KT 120 MPH
 48H  09/0600Z 26.7N  92.9W  115 KT 130 MPH
 60H  09/1800Z 29.2N  92.3W  100 KT 115 MPH
 72H  10/0600Z 32.0N  91.0W   50 KT  60 MPH...INLAND
 96H  11/0600Z 35.5N  87.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  12/0600Z 38.5N  82.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Blake
 
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