000 WTNT42 KNHC 230254 TCDAT2 Tropical Storm Karen Discussion Number 4 NWS National Hurricane Center Miami FL AL122019 1100 PM AST Sun Sep 22 2019 Karen remains poorly organized this evening, with the low-level center exposed to the north of the main convective mass due to the effects of 15-20 kt of northeasterly vertical shear. The initial intensity will be held at 35 kt based on earlier Air Force Reserve Hurricane Hunter data that included maximum 1500 ft flight-level winds of 42 kt and SFMR surface wind estimates near 35 kt. The initial motion is 295/10. The track guidance is in excellent agreement that Karen should turn northwestward during the next 6-12 h in response to a break in a ridge to the north of the storm, followed by a northward motion that would take the center near Puerto Rico and the Virgin Islands into the Atlantic between 36-48 h. Late in the forecast period, the steering currents are expected to weaken as a strong deep-layer ridge builds eastward from the United States into the western Atlantic. This should cause Karen to slow its forward motion. The new forecast track is little changed from the previous track and is near the center of the guidance envelope and the various consensus models. The upper-level winds are currently not favorable for significant development, and the current shear might get stronger during the next 12-24 h. Thus, little change in strength is forecast while Karen crosses the eastern Caribbean, and the system may have trouble maintaining tropical cyclone status. The environment becomes more favorable for development from 48 h on, and the intensity forecast calls for slow strengthening during this time. The new intensity forecast has only minor adjustments from the previous forecasts. Key Messages: 1. Heavy rainfall will continue to affect portions of 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 is in effect. Tropical-storm-force winds, heavy rainfall, and flash flooding are possible on these islands. FORECAST POSITIONS AND MAX WINDS INIT 23/0300Z 13.1N 63.5W 35 KT 40 MPH 12H 23/1200Z 13.9N 64.5W 35 KT 40 MPH 24H 24/0000Z 15.3N 65.2W 35 KT 40 MPH 36H 24/1200Z 16.9N 65.8W 35 KT 40 MPH 48H 25/0000Z 18.7N 66.0W 35 KT 40 MPH 72H 26/0000Z 22.4N 65.7W 40 KT 45 MPH 96H 27/0000Z 25.0N 66.0W 45 KT 50 MPH 120H 28/0000Z 26.0N 67.0W 55 KT 65 MPH $$ Forecaster Beven