093 WTNT44 KNHC 010245 TCDAT4 Hurricane Isaias Discussion Number 16 NWS National Hurricane Center Miami FL AL092020 1100 PM EDT Fri Jul 31 2020 Isaias has a somewhat asymmetrical appearance on satellite images, with lots of deep convection over the eastern semicircle and not as much over the western part of the circulation. Reports from an Air Force Hurricane Hunter aircraft indicate that the central pressure has dropped a few mb, and flight-level and SFMR-observed surface wind observations from the aircraft indicate an intensity of near 70 kt. The hurricane is experiencing some westerly shear, and this is likely to limit intensification. However, some strengthening is still possible on Saturday. When Isais moves farther north in a couple of days, the shear should cause a gradual weakening trend to begin. The official intensity forecast is about the same as the previous one, and a little above the model consensus. The hurricane continues moving northwestward at a bit slower pace, or 310/13 kt. The general track forecast philosophy has not changed. Isais should continue to move northwestward on the southwest side of a mid-level ridge through Saturday and begin to turn north-northwestward through a weakness in the ridge on Sunday. Thereafter, a turn toward the north-northeast and northeast with an increase in forward speed is likely during days 3 to 5. The official track forecast is close to the previous one and also very close to the latest dynamical model consensus. The hurricane warning has been extended northward along the Florida east coast. Key Messages: 1. Hurricane conditions and dangerous storm surge are expected in portions of the Bahamas through Saturday, and Hurricane Warnings are in effect. 2. Hurricane conditions are expected along portions of the Florida east coast late Saturday and Saturday night, and a Hurricane Warning has been issued. Preparations to protect life and property should be rushed to completion. 3. Dangerous storm surge is possible along the Florida east coast from Jupiter Inlet to Ponte Vedra Beach where water rises of 2 to 4 feet above ground level are possible along the immediate coastline and adjacent waterways. Residents in these areas should follow advice given by local emergency officials. 4. Isaias will produce heavy rains and potentially life-threatening flash and urban flooding, especially in low-lying and poorly drained areas, across South to east-Central Florida, and across the Carolinas to the mid Atlantic. Isolated minor river flooding is possible across the eastern Carolinas and into Virginia early next week. 5. There is a risk of impacts from winds, heavy rainfall, and storm surge spreading along much of the the U.S. east coast through early next week, and interests there should monitor the progress of Isaias and updates to the forecast. FORECAST POSITIONS AND MAX WINDS INIT 01/0300Z 23.3N 76.4W 70 KT 80 MPH 12H 01/1200Z 24.5N 77.8W 75 KT 85 MPH 24H 02/0000Z 25.9N 79.1W 75 KT 85 MPH 36H 02/1200Z 27.1N 80.0W 70 KT 80 MPH 48H 03/0000Z 28.5N 80.5W 65 KT 75 MPH 60H 03/1200Z 30.2N 80.5W 60 KT 70 MPH 72H 04/0000Z 33.1N 78.9W 60 KT 70 MPH 96H 05/0000Z 41.0N 72.5W 55 KT 65 MPH 120H 06/0000Z 47.5N 64.0W 45 KT 50 MPH...POST-TROP/EXTRATROP $$ Forecaster Pasch