[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 262051
TCDAT3

Hurricane Laura Discussion Number  28
NWS National Hurricane Center Miami FL       AL132020
400 PM CDT Wed Aug 26 2020

Laura has continued to rapidly strengthen today with recent
visible satellite imagery revealing a very distinct 25 nautical-
mile-wide eye embedded in a symmetric central dense overcast. The
upper-level outflow has also become well established in all
quadrants.  An Air Force Reserve hurricane hunter aircraft that
is still investigating the hurricane has reported peak 700-mb
flight-level winds of 136 kt and SFMR winds of 121 kt in the
northeast eyewall.  These data support an initial intensity of
125 kt, which is an increase of 55 kt over the past 24 hours.  The
minimum pressure has fallen to around 947 mb.  The well-defined eye
is now within range of the NWS Lake Charles WSR-88D radar, and
hourly Tropical Cyclone Updates began at 1900 UTC (2 PM CDT) and
will continue through landfall and beyond overnight.

Laura still has about 12 hours remaining over the warm waters of the
northwest Gulf of Mexico waters, but increasing southwesterly shear
around the time of landfall and the possibility of an eyewall
replacement could result in some fluctuations in intensity this
evening, but Laura is expected to remain an extremely dangerous
category 4 hurricane through landfall tonight.  Although rapid
weakening is expected on Thursday as Laura moves inland, the
hurricane is expected to bring a swath of damaging winds well inland
over western Louisiana and extreme eastern Texas.  The cyclone or
its remnants are forecast to move off Mid-Atlantic coast over the
weekend and there remains some possibility that Laura will
re-intensify as a tropical cyclone offshore of the United States
east before it merges with a frontal boundary later in the forecast
period.

Recent satellite and aircraft fixes show that Laura is moving
northwestward at about 13 kt.  Laura is nearing the western extent
of a mid-level ridge that is located over the southeastern United
States.  The hurricane should turn north-northwestward this evening
and northward on Thursday between the ridge and a weak trough over
the south-central United States. By Friday the cyclone should turn
northeastward and then east-northeastward as it becomes embedded in
the mid-latitude westerlies. The track model guidance continues to
be in good agreement through 72, but there are some forward speed
differences thereafter.  The new NHC track is very close to the
previous advisory and is near the middle of the guidance envelope.

Laura is a large hurricane and users are reminded to not focus on
the precise track forecast since wind, storm surge, and rainfall
hazards extend far from the center.

Key Messages:

1. Unsurvivable storm surge with large and destructive waves will
cause catastrophic damage from Sea Rim State Park, Texas, to
Intracoastal City, Louisiana, including Calcasieu and Sabine Lakes.
This surge could penetrate up to 40 miles inland from the immediate
coastline, and flood waters will not fully recede for several days
after the storm.

2. Hurricane-force winds are expected tonight in portions of the
hurricane warning area, with catastrophic wind damage expected
where Laura's eyewall moves onshore. Hurricane-force winds and
widespread damaging wind gusts will spread well inland into portions
of extreme eastern Texas and western Louisiana early Thursday.

3. Widespread flash flooding along small streams, urban areas, and
roadways is expected to begin this afternoon into Thursday from far
eastern Texas into Louisiana and Arkansas. This will also lead to
minor to moderate freshwater river flooding. The heavy rainfall
threat and flash and urban flooding potential will spread
northeastward into the middle-Mississippi, lower Ohio, and Tennessee
Valleys Friday night and Saturday.

FORECAST POSITIONS AND MAX WINDS

INIT  26/2100Z 27.9N  92.8W  125 KT 145 MPH
 12H  27/0600Z 29.7N  93.6W  130 KT 150 MPH
 24H  27/1800Z 32.5N  93.5W   60 KT  70 MPH...INLAND
 36H  28/0600Z 34.8N  92.7W   35 KT  40 MPH...INLAND
 48H  28/1800Z 36.5N  90.1W   25 KT  30 MPH...INLAND
 60H  29/0600Z 37.3N  85.6W   25 KT  30 MPH...INLAND
 72H  29/1800Z 38.0N  79.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  30/1800Z 43.2N  64.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  31/1800Z 51.0N  49.0W   45 KT  50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown
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