[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 110251
TCDAT2

Tropical Storm Paulette Discussion Number  17
NWS National Hurricane Center Miami FL       AL172020
1100 PM AST Thu Sep 10 2020

Paulette has been fighting off intense vertical wind shear, which is
analyzed by UW-CIMSS to be on the order of 35-40 kt out of the
southwest. Deep convection with cold cloud tops of -70 to -80
degrees C have persisted near and to the northeast of the center
throughout the evening. A late arriving ASCAT overpass revealed that
Paulette is stronger than previously analyzed, with believable wind
vectors of 50-55 kt in the northeastern quadrant. There were some
values even higher than these. However, the ASCAT ambiguities and
satellite imagery suggest most of those are either rain contaminated
or too close to the edge of the ASCAT pass to be trustworthy.
Nonetheless, the other values indicate that the initial intensity is
now at least 55 kt.

The SHIPS guidance suggests that the current shear over Paulette
will begin to gradually decrease tomorrow and continue to decrease
into the weekend. By late Saturday the guidance indicates the shear
could fall to 10 kt or less. By that time, the cyclone is forecast
to be traversing over waters with SSTs near 29 C. The only negative
environmental factor could be some dry air in the vicinity of the
system. However that same dry air has not seemed to have that much
of an effect on Paulette as of late. With shear expected to remain
fairly strong the next 24 h, no strengthening is anticipated during
that time. After 24 h, Paulette should gradually intensify into
early next week. The NHC intensity forecast for this advisory has
been increased across the board. In the near term this change is due
to the adjusted initial intensity. Beyond 24 h, the latest NHC
forecast is close to a blend of the multi-model consensus values,
including the HFIP corrected consensus and the Florida State
Superensemble.

Paulette is now moving northwest, or 305/09 kt. There is no change
to the forecast track reasoning from the previous advisory. The
forecast models are in good agreement between a generally northwest
to west-northwestward motion over the next 3-4 days as the cyclone
is steered around a subtropical ridge to its north. Around day 4,
about the same time the system would be making its closest approach
to Bermuda, a turn to the northeast is expected as the system
rounds the western periphery of the ridge. The latest NHC track
forecast is little changed from the previous one, and is near the
tracks of the various consensus aids. It should be noted that there
is sufficient spread in the track guidance such that it is too soon
to know what types of impacts Paulette could have on Bermuda early
next week.


Key Messages:

1.  Paulette is expected to approach Bermuda as a hurricane this
weekend and make its closest approach to the island on Monday and
Tuesday.  While the exact details of Paulette's track and intensity
near the island are not yet known, the risk of strong winds, storm
surge, and heavy rainfall on Bermuda continues to increase.

2.  Swells produced by Paulette are expected to affect portions of
the Leeward Islands, the Greater Antilles, the Bahamas, Bermuda,
and the southeastern United States into the weekend.  These swells
could cause life-threatening surf and rip current conditions.


FORECAST POSITIONS AND MAX WINDS

INIT  11/0300Z 22.7N  50.9W   55 KT  65 MPH
 12H  11/1200Z 23.4N  52.4W   55 KT  65 MPH
 24H  12/0000Z 24.6N  54.1W   55 KT  65 MPH
 36H  12/1200Z 26.1N  55.8W   60 KT  70 MPH
 48H  13/0000Z 27.6N  57.6W   65 KT  75 MPH
 60H  13/1200Z 28.9N  59.9W   70 KT  80 MPH
 72H  14/0000Z 30.0N  62.3W   80 KT  90 MPH
 96H  15/0000Z 32.6N  65.0W   85 KT 100 MPH
120H  16/0000Z 35.0N  62.5W   90 KT 105 MPH

$$
Forecaster Latto
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