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Hurricane Delta Discussion Number   8
NWS National Hurricane Center Miami FL       AL262020
1100 AM EDT Tue Oct 06 2020
 
Satellite imagery and recent NOAA Hurricane Hunter aircraft data
show that Delta is a very symmetric and compact hurricane.  The
aircraft reported a tiny 5-nmi-wide eye, which has also been
seen in radar imagery from the Cayman Islands, and there is a hint
of a pinhole eye in infrared satellite data.  The central pressure
has continued to fall, with the lastest center dropwindsonde data 
supporting a pressure of 955 mb.  The plane has reported a peak 
flight-level winds of 109 kt, and believable SFMR winds of 102 kt. 
Therefore, the initial intensity is set at 100 kt, making Delta the 
third major hurricane of the 2020 Atlantic hurricane season.
 
Delta has continued to rapidly strengthen over the past 24 hours,
with an estimated 55-kt increase in wind speed between 1200 UTC
Monday and 1200 UTC today.  Environmental conditions of low 
vertical wind shear, deep warm waters, and sufficient mid-level
moisture are expected to support additional rapid intensification
through today, and the only reason that the strengthening could
slow is if a difficult-to-predict eyewall replace cycle begins.
The SHIPS Rapid intensification index continues to indicate a high
likelihood of at least an additional 25-30 kt of intensity increase 
before the system reaches the northeastern portion of the Yucatan
Peninsula. Given that, the NHC intensity forecast is above the 
various intensity aids and call for Delta to be an extremely 
dangerous category 4 hurricane when it nears the Yucatan.  It could 
be stronger than indicated below since landfall is predicted to 
occur between the 12 and 24 h forecast points. Some reduction in 
intensity is likely when Delta moves over land, but the 
environmental conditions over the southern Gulf of Mexico are 
expected to support re-strengthening, and the NHC intensity 
forecast shows a second peak in 48-72 hours.  As mentioned before, 
increasing southwesterly shear and cooler shelf waters near the 
northern Gulf coast are expected to cause some reduction in wind 
speed, but Delta is still expected to be a dangerous hurricane when 
it nears the northern Gulf coast.
 
Delta is moving west-northwestward at about 14 kt.  A mid-level
ridge that extends westward across Florida and the northeastern
Gulf of Mexico should continue to steer Delta west-northwestward to
northwestward during the next couple of days. As the hurricane
nears the western portion of the ridge it should slow down. By
day three a developing trough over the south-central United States
is expected to cause Delta to turn northward toward the northern
Gulf coast. The track guidance is tightly clustered through 48
hours, but there is still a fair amount of spread thereafter
regarding the timing and details of the northward turn.  The ECMWF
and its ensemble mean are well west of the bulk of the remainder of
the guidance. The NHC track lies near the TVCA multi-model consensus 
which is close to a blend of the GFS, HWRF, UKMET ensemble mean.
 
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. 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 
monitor updates to the forecast.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  06/1500Z 18.2N  82.6W  100 KT 115 MPH
 12H  07/0000Z 19.4N  84.5W  120 KT 140 MPH
 24H  07/1200Z 21.0N  87.2W  120 KT 140 MPH
 36H  08/0000Z 22.3N  89.6W  105 KT 120 MPH
 48H  08/1200Z 23.4N  91.3W  110 KT 125 MPH
 60H  09/0000Z 24.6N  92.3W  115 KT 130 MPH
 72H  09/1200Z 26.3N  92.5W  110 KT 125 MPH
 96H  10/1200Z 30.5N  91.2W   70 KT  80 MPH...INLAND
120H  11/1200Z 34.5N  87.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Brown
 
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