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Hurricane Delta Discussion Number  15
NWS National Hurricane Center Miami FL       AL262020
400 AM CDT Thu Oct 08 2020
 
Satellite images indicate that Delta remains a well organized
hurricane with a central dense overcast feature and curved bands
beyond that.  There is still no indication of an eye, however, in
geostationary satellite images. The Air Force Hurricane Hunters
were in Delta a few hours ago and toward the end of that mission,
they reported maximum flight-level winds of 102 kt and SFMR winds of
77 kt.  Based on a blend of this data, the initial intensity was
increased to 85 kt at 0600 UTC.  Since the cyclone appears to be
generally steady in strength since that time, the wind speed is held
at that value.  Both the NOAA and Air Force Hurricane Hunters will
be investigating Delta later today, and that data will help us
assess its strength and structure.
 
The track forecast reasoning is unchanged.  Delta is currently 
moving northwestward at 13 kt on the southwestern periphery of an 
Atlantic subtropical ridge.  The western portion of the ridge is 
expected to weaken later today as a trough moves eastward across 
the south-central United States. This change in the steering 
pattern should cause Delta to turn northward by late tonight and 
north-northeastward by Friday night.  This motion should take the 
core of the hurricane to the Louisiana coast in a little more than 
36 hours (sometime Friday afternoon or evening).  After landfall, a 
turn to the northeast is forecast as a larger trough approaches 
Delta from the west. The models are in very good agreement, and the 
NHC track forecast is just an update of the previous one.
 
Delta is expected to continue gradually strengthening during the 
next 24 hours while it remains over warm deep waters and in an 
environment of low wind shear and a high amount of moisture.  Based 
on these favorable environmental conditions and the trend in the 
models, Delta is forecast to regain major hurricane status by 
tonight.  Just prior to making landfall, the cyclone is forecast to 
level off in strength or weaken slightly as it moves over the cooler 
shelf waters and into somewhat less favorable atmospheric 
conditions.  Rapid weakening is forecast after Delta moves inland.  
The intensity models are in fairly good agreement, and the NHC 
intensity forecast lies near the middle of the guidance envelope. It 
should be noted that the NHC 1-2 day intensity forecasts are subject 
to errors of around 1 Saffir-Simpson category.
 
The aircraft and fairly recent scatterometer data indicate that
Delta is gradually growing in size. This trend is expected to
continue as Delta approaches the Louisiana coast. The NHC wind
radii forecast follows a consensus of the global and hurricane
regional models.
 
Key Messages:
 
1. Delta is expected to grow in size as it approaches the northern
Gulf Coast, where life-threatening storm surge and dangerous
hurricane-force winds are likely beginning Friday, particularly for
portions of the Louisiana coast.  Storm Surge and Hurricane Warnings
are in effect, and residents in these areas should follow advice
given by local officials and rush preparedness actions to
completion.
 
2. Significant flash, urban, small stream and minor to isolated 
moderate river flooding is likely Friday and Saturday from portions 
of the central Gulf Coast into portions of the Lower Mississippi 
Valley. As Delta moves farther inland, heavy rainfall is expected in 
the Ohio Valley and Mid-Atlantic this weekend. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0900Z 23.4N  91.8W   85 KT 100 MPH
 12H  08/1800Z 24.6N  93.0W   95 KT 110 MPH
 24H  09/0600Z 26.4N  93.7W  100 KT 115 MPH
 36H  09/1800Z 28.8N  93.4W   90 KT 105 MPH
 48H  10/0600Z 31.3N  92.4W   55 KT  65 MPH...INLAND
 60H  10/1800Z 33.3N  90.9W   30 KT  35 MPH...INLAND
 72H  11/0600Z 34.6N  89.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  12/0600Z...DISSIPATED
 
$$
Forecaster Cangialosi
 
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