000 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