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Hurricane Laura Discussion Number  25
NWS National Hurricane Center Miami FL       AL132020
1000 PM CDT Tue Aug 25 2020
 
Laura's cloud pattern is becoming better organized on satellite
images, with a banding feature over the eastern portion of the
circulation and an expanding central dense overcast with cloud tops
of -80C or colder.  The upper-level outflow is becoming better
established over the northwestern quadrant.  Flight-level and
SFMR-observed surface winds from NOAA and Air Force Hurricane
Hunter aircraft indicate that the maximum winds have increased to
near 80 kt, and the central pressure is falling.  The hurricane is
expected to remain over SSTs near 30 deg C until it nears the coast,
with only moderate vertical shear.  The SHIPS Rapid Intensification
Index shows a significant probability for a 25-30 kt increase in
strength during the next 24 hours, and this is reflected in the
official forecast.  This is also between the simple and corrected
intensity model consensus predictions.  Laura will weaken rapidly
after landfall, but it will likely bring hurricane-force winds well
inland over extreme western Louisiana and eastern Texas.
 
Aircraft and satellite fixes show a continued west-northwestward
track with an initial motion estimate near 300/15 kt.  The track
forecast reasoning has not changed.  The hurricane should gradually
turn toward the northwest and north over the next day or two as it
moves around the western periphery of a mid-level high and into a
weakness into the subtropical ridge.  Later in the forecast period
the cyclone should turn toward the east-northeast and move with
increasing forward speed while embedded within the westerlies. The
official track forecast is very similar to the previous one and
also very close to the simple and corrected consensus track model
predictions.
 
Users are again reminded not to focus on the exact details of the
track or intensity forecasts as the average NHC track error at 36 h
is around 60 miles and the average intensity error is close to 10
mph. In addition, wind, storm surge, and rainfall hazards will
extend far from the center.
 
Key Messages:
 
1. There is a danger of life-threatening storm surge with large and
dangerous waves producing potentially catastrophic damage from San
Luis Pass, Texas, to the Mouth of the Mississippi River, including
areas inside the Port Arthur Hurricane Flood Protection system.
This surge could penetrate up to 30 miles inland from the immediate
coastline in southwestern Louisiana and far southeastern Texas.
Actions to protect life and property should be rushed to completion, 
as water levels will begin to rise on Wednesday.
 
2. Hurricane-force winds are expected Wednesday night in the warning
area from San Luis Pass, Texas, to west of Morgan City, Louisiana,
and the strongest winds associated with Laura's eyewall will occur
somewhere within this area.  Hurricane-force winds and widespread
damaging wind gusts are also expected to spread well inland into
portions of eastern Texas and western Louisiana early Thursday.
 
3. Widespread flash flooding along small streams, urban areas, and 
roadways is expected to begin Wednesday night into Thursday across 
far eastern Texas, Louisiana, and Arkansas.  This will also lead to 
minor to isolated moderate river flooding.  The heavy rainfall 
threat and localized 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  26/0300Z 25.2N  89.5W   80 KT  90 MPH
 12H  26/1200Z 26.5N  91.4W   95 KT 110 MPH
 24H  27/0000Z 28.7N  93.1W  105 KT 120 MPH
 36H  27/1200Z 31.2N  93.8W   70 KT  80 MPH...INLAND
 48H  28/0000Z 33.7N  93.6W   40 KT  45 MPH...INLAND
 60H  28/1200Z 36.0N  92.3W   30 KT  35 MPH...INLAND
 72H  29/0000Z 37.2N  89.5W   25 KT  30 MPH...INLAND
 96H  30/0000Z 38.0N  78.0W   30 KT  35 MPH...POST-TROP/EXTRATROP
120H  31/0000Z 42.0N  65.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
 
$$
Forecaster Pasch
 
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