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Hurricane Laura Discussion Number  29
NWS National Hurricane Center Miami FL       AL132020
1000 PM CDT Wed Aug 26 2020
 
Extremely dangerous Laura has the signature of a classic hurricane
on satellite images, with a well-defined eye surrounded by very
deep convection.  There is little evidence of shear, and the
upper-level outflow pattern is extremely well defined, while the
cyclone is over sea surface temperatures near 30 deg C.
Observations from both NOAA and Air Force Hurricane Hunter
aircraft show that Laura continued to strengthen during the
evening.  Using a blend of adjusted flight-level and SFMR-observed 
surface winds, the intensity estimate is 130 kt for this advisory.  
Since there is now little time remaining for the system over water, 
no significant change in intensity is anticipated until the center 
crosses the coastline.  Laura will weaken rapidly after it begins 
to move over land, but destructive winds should spread well inland, 
more than 100 miles, along its path.  Later in the forecast period, 
the ECMWF and U.K. Met. Office global models indicate some 
baroclinic re-intensification as the remnants of Laura move off the 
U.S. East coast, and this is reflected in the NHC forecast.
 
Laura has begun to turn northward as it moves around the western
side of a subtropical high pressure area, and the initial motion is
about 340/13 kt.  The track forecast is essentially unchanged
from the previous advisories.  The cyclone should move through a
weakness in the ridge and turn to the northeast over the next day
or two.  Then the system should accelerate toward the
east-northeast while embedded in the westerlies.  The official 
track forecast remains close to both the simple and the corrected 
dynamical model consensus predictions, TVCA and HCCA.
 
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 overnight tonight 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  27/0300Z 29.0N  93.2W  130 KT 150 MPH
 12H  27/1200Z 31.0N  93.7W   95 KT 110 MPH...INLAND
 24H  28/0000Z 33.8N  92.9W   50 KT  60 MPH...INLAND
 36H  28/1200Z 35.6N  91.5W   35 KT  40 MPH...INLAND
 48H  29/0000Z 36.8N  88.2W   25 KT  30 MPH...INLAND
 60H  29/1200Z 37.5N  82.7W   25 KT  30 MPH...POST-TROP/INLAND
 72H  30/0000Z 38.5N  75.5W   30 KT  35 MPH...POST-TROP/EXTRATROP
 96H  31/0000Z 45.0N  60.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  01/0000Z 52.0N  46.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 
$$
Forecaster Pasch
 
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