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Tropical Storm Josephine Forecast Discussion Number 14
2020-08-15 04:37:13| National Hurricane Center (Atlantic)
Issued at 1100 PM AST Fri Aug 14 2020 000 WTNT41 KNHC 150237 TCDAT1 Tropical Storm Josephine Discussion Number 14 NWS National Hurricane Center Miami FL AL112020 1100 PM AST Fri Aug 14 2020 Josephine continues to produce bursts of deep convection near and to the northeast of its center, however, there is little evidence of any banding features. A fortuitous ASCAT-A overpass has revealed peak winds of 35-40 kt over the northern semicircle of the storm, and the scatterometer ambiguities along with the earlier reconnaissance aircraft data suggest that the circulation is still closed. Based on the scatterometer data, the initial wind speed has been set at 40 kt. The intensity forecast reasoning remains unchanged from the previous forecast. The moderate to strong southwesterly vertical wind shear that is affecting the cyclone is forecast to increase over the weekend and reach values of around 30 kt on Sunday. This is expected to result in gradual weakening by the latter portion of the weekend, and Josephine is predicted to weaken to a tropical depression in about 48 hours, and become a remnant low in 3-4 days. A plausible alternate scenario that is suggested by some of the global models is for the circulation to open up into a trough of low pressure, resulting in dissipation of the tropical cyclone within the next few days. The timely ASCAT data was very helpful in determining Josephine's center location. Based on that and the earlier aircraft fixes, the cyclone continues to move west-northwestward or 300/14 kt. A subtropical ridge to the north of Josephine should steer the cyclone west-northwestward during the next 24-48 hours. After that time, Josephine should turn northwestward, and then northward as a weakness develops in the ridge over the western Atlantic. By late in the period, Josephine or its remnants are expected to turn north-northeastward as it becomes embedded within the mid-latitude westerlies. The latest official forecast is near the middle of the tightly clustered dynamical track models, and is very similar to the previous NHC advisory. KEY MESSAGES: 1. Josephine should pass far enough to the northeast of the Leeward Islands over the weekend to prevent major impacts. However, interests there should continue to monitor its progress until the storm has passed north of that area. 2. Locally heavy rainfall is possible in the northern Leeward Islands, the Virgin Islands, and Puerto Rico as Josephine passes by to the northeast. Isolated minor flooding is possible in Puerto Rico through Monday. FORECAST POSITIONS AND MAX WINDS INIT 15/0300Z 18.3N 57.4W 40 KT 45 MPH 12H 15/1200Z 19.2N 59.3W 40 KT 45 MPH 24H 16/0000Z 20.4N 61.6W 40 KT 45 MPH 36H 16/1200Z 21.7N 63.9W 35 KT 40 MPH 48H 17/0000Z 23.2N 65.8W 30 KT 35 MPH 60H 17/1200Z 24.7N 67.2W 25 KT 30 MPH 72H 18/0000Z 26.4N 67.7W 25 KT 30 MPH 96H 19/0000Z 29.5N 67.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 20/0000Z 33.0N 64.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown
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