Tropical Storm Paulette Discussion Number  24
NWS National Hurricane Center Miami FL       AL172020
500 PM AST Sat Sep 12 2020

Convective cloud tops have cooled again as deep convection has 
redeveloped since this morning, with an eye-like feature noted in 
visible satellite imagery.  Since the storm is still being affected 
by 20-25 kt of southerly shear, it is assumed that the low-level 
center is still displaced to the south of this feature a bit.  But 
it won't be surprising if the low- and mid-level centers become 
collocated soon as the shear drops significantly during the next 
6-12 hours.  The initial intensity remains 60 kt, and we should get 
a much better handle on Paulette's maximum winds and structure once 
the first Air Force Hurricane Hunter aircraft reaches the storm this 
evening.

The motion remains northwestward (305/13 kt) due to a break in the 
subtropical ridge to the north-northeast of Paulette.  A 
mid-tropospheric high currently centered near the U.S. Mid-Atlantic 
coast is expected to slide eastward to the north of Paulette during 
the next 24 hours, which should cause the cyclone to turn 
west-northwestward tonight.  Once the high becomes established over 
the central Atlantic, Paulette is expected to recurve around its 
western periphery toward a longwave trough over the northeastern 
United States Sunday night through Monday night.  On days 3 through 
5 of the forecast period, Paulette should be accelerating 
northeastward toward the north Atlantic, embedded in the 
mid-latitude westerlies.  The new NHC track forecast is embedded 
among the very tightly clustered guidance envelope, and no 
significant changes were made from the morning forecast.

As stated above, deep-layer shear is expected to be 10 kt or less 
between 12 and 48 hours.  While ocean waters are plenty warm at 
28-29 degrees Celsius, the main possible limiting factor for 
strengthening would be mid-level dry air, with the SHIPS model 
diagnosing ambient relative humidities of 30-40 percent for the next 
couple of days.  But, if the shear remains low enough, that dry air 
is unlikely to infiltrate the circulation, and Paulette is 
therefore expected to intensify during the next 2-3 days.  The NHC 
intensity forecast is close to the SHIPS, HCCA, and HWRF solutions, 
showing a peak intensity just under the major hurricane threshold 
in 2-3 days, when Paulette should be starting to move away from 
Bermuda.


Key Messages:

1. Paulette is expected to approach Bermuda as a hurricane on
Sunday and be near the island Sunday night and Monday.  A prolonged
period of strong winds, storm surge, and heavy rainfall is expected
on Bermuda beginning Sunday evening, and a hurricane warning
is in effect for the island.  Preparations to protect life and
property should be rushed to completion.

2. Swells produced by Paulette are affecting portions of the
Leeward Islands, the Greater Antilles, the Bahamas, and Bermuda,
and are expected to spread westward to the east coast of the United
States during the next day or two. These swells could cause
life-threatening surf and rip current conditions.


FORECAST POSITIONS AND MAX WINDS

INIT  12/2100Z 28.4N  58.5W   60 KT  70 MPH
12H  13/0600Z 29.2N  60.4W   65 KT  75 MPH
24H  13/1800Z 30.3N  62.8W   75 KT  85 MPH
36H  14/0600Z 31.8N  64.6W   85 KT 100 MPH
48H  14/1800Z 33.5N  64.9W   90 KT 105 MPH
60H  15/0600Z 35.3N  63.2W   95 KT 110 MPH
72H  15/1800Z 37.0N  59.8W   95 KT 110 MPH
96H  16/1800Z 40.0N  52.0W   85 KT 100 MPH
120H  17/1800Z 43.5N  44.0W   70 KT  80 MPH

$$
Forecaster Berg