[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 220900
TCDAT2

Tropical Storm Karen Discussion Number   1
NWS National Hurricane Center Miami FL       AL122019
500 AM AST Sun Sep 22 2019

Scatterometer surface wind data and observations from the Windward
Islands indicate that the low pressure system just east of Tobago
has become better defined. Infrared and microwave satellite imagery
also show that deep convection has increased and has become better
organized around the center. Barbados recently reported a 10-minute
wind of 32 kt gusting to 39 kt, and the earlier scatterometer data
showed a large field of 30-32 kt winds in the eastern semicircle.
Based on these data, the low has been upgraded to Tropical Storm
Karen. Tropical Storm Warnings have been issued for the southern
Windward Islands as a result.

The initial motion estimate is an uncertain 285/10 kt. The latest
NHC model guidance is in very good agreement on Karen moving
northwestward around the southwestern periphery of a deep-layer
ridge for the next 24-36 hours, followed by a turn toward the north
into a break in the ridge currently located over the northern
Leeward Islands and Puerto Rico. In the 72-96 hour period, Karen is
forecast to slow down and possibly even stall and turn westward on
day 5 as another large ridge moves eastward across the southeastern
United States and builds to the north of the cyclone. The official
track forecast lies close to the tightly packed consensus track
models TVCN, NOAA-HCCA, and TVCX.

Little, if any, change in intensity is expected for the next 48
hours due to strong northeasterly vertical wind shear. However, the
upper-level flow is expected to be difluent, which should help Karen
maintain its current intensity despite the otherwise unfavorable
shear conditions. By 72 hours and beyond, Karen is forecast to move
underneath an upper-level anticyclone, which should result in a
significant decrease in the shear and also enhance the upper-level
outflow, allowing for some strengthening to occur. The NHC intensity
forecast closely follows a blend of the the intensity consensus
models IVCN and HCCA, and the Decay-SHIPS model.

A Tropical Storm Watch will likely be required for Puerto Rico and
the Virgin Islands later today, and Tropical Storm Warnings may be
issued for other areas in the Windward Islands later this morning.

FORECAST POSITIONS AND MAX WINDS

INIT  22/0900Z 11.9N  60.2W   35 KT  40 MPH
 12H  22/1800Z 12.5N  61.6W   35 KT  40 MPH
 24H  23/0600Z 13.4N  63.1W   35 KT  40 MPH
 36H  23/1800Z 14.7N  64.1W   35 KT  40 MPH
 48H  24/0600Z 16.1N  65.1W   35 KT  40 MPH
 72H  25/0600Z 19.9N  65.5W   45 KT  50 MPH
 96H  26/0600Z 23.4N  65.0W   50 KT  60 MPH
120H  27/0600Z 25.6N  65.6W   55 KT  65 MPH

$$
Forecaster Stewart
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