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Tropical Storm Karen Forecast Discussion Number 3
2019-09-22 22:37:57| National Hurricane Center (Atlantic)
Issued at 500 PM AST Sun Sep 22 2019 ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM Tropical Storm Karen Discussion Number 3 NWS National Hurricane Center Miami FL AL122019 500 PM AST Sun Sep 22 2019 The convective structure of Karen has continued to lose organization this afternoon, with the center becoming exposed to the north and northwest of the primary convective band. An Air Force Reconnaissance aircraft investigating the storm has found a well-defined circulation, and flight-level and SFMR winds to support an intensity of around 30 kt. The plane, however, has not fully sampled the storm so the initial intensity remains 35 kt which is between the wind speeds indicated in earlier ASCAT data and the recent in situ observations. The upper-level environment ahead of Karen is forecast to remain unfavorable with the global models and SHIPS guidance predicting an increase in northeasterly shear by Monday. This is expected to prevent the storm from strengthening, and Karen may even have trouble maintaining tropical cyclone status while it moves over the eastern Caribbean Sea. After the system moves north of Puerto Rico around midweek, it is forecast to reach more favorable upper-level conditions, and the NHC intensity forecast again calls for strengthening later in the forecast period. The new intensity forecast, however, is slightly more conservative than the previous one at days 3-5, and is a little above the latest intensity consensus (IVCN) model). The tropical storm is moving west-northwestward or 295/11 kt. The track forecast philosophy is unchanged from earlier today. Karen should turn northwestward, and then northward during the next day or so as it begins to respond to a weakness in the subtropical ridge over the western Atlantic. This motion should bring the center of Karen over Puerto Rico or the Virgin Islands on Tuesday. By late in the forecast period, the dynamical models build a strong deep-layer ridge over the southeast United States that extends northeastward over the western Atlantic. This pattern is likely to cause Karen to slow its northward progression by days 4 and 5. The track guidance remains in very good agreement, and only slight adjustments to the previous official forecast were required. Key Messages: 1. Tropical-storm-force winds and heavy rainfall will continue to affect the southern Windward Islands through tonight. 2. Karen is forecast to approach Puerto Rico, and the U.S. and British Virgin Islands on Tuesday, and a tropical storm watch has been issued. Tropical-storm-force winds, heavy rainfall, and flash flooding is possible on these islands. FORECAST POSITIONS AND MAX WINDS INIT 22/2100Z 12.9N 62.7W 35 KT 40 MPH 12H 23/0600Z 13.7N 63.8W 35 KT 40 MPH 24H 23/1800Z 14.9N 64.8W 35 KT 40 MPH 36H 24/0600Z 16.3N 65.4W 35 KT 40 MPH 48H 24/1800Z 18.0N 65.9W 35 KT 40 MPH 72H 25/1800Z 21.5N 65.7W 40 KT 45 MPH 96H 26/1800Z 24.3N 65.5W 45 KT 50 MPH 120H 27/1800Z 26.0N 66.3W 50 KT 60 MPH $$ Forecaster Brown NNNN
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