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| #1011031 (Received by flhurricane at: 11:05 PM 03.Aug.2020) TCDAT4 Hurricane Isaias Discussion Number 28 NWS National Hurricane Center Miami FL AL092020 1100 PM EDT Mon Aug 03 2020 NWS Doppler radar data and reports from an Air Force Reserve Hurricane Hunter aircraft indicate that Isaias re-intensified to a hurricane despite a less than impressive appearance in satellite imagery. The aircraft reported 117 kt winds at 700 mb to the east of the center, but these were not mixed to the surface by the weak convection in that area, as the maximum SFMR winds were 75 kt. Based on these data, the initial intensity is raised to 75 kt. The hurricane is moving 020/19, and a faster forward speed is expected as the system moves farther into the mid-latitude southwesterly flow. This should bring the center onshore in southern North Carolina shortly, followed by a track through the mid-Atlantic and western New England states Tuesday and Tuesday night and into southeastern Canada early Wednesday. Interaction with a strong jet stream suggests that Isaias should weaken more slowly than normal as it moves through the eastern United States, and this should produce very strong wind gusts along the mid-Atlantic coast tomorrow. As a result, the gust factors at 24-48 h have been increased above the standard 20 percent in the Forecast/Advisory (TCMAT4). The cyclone is forecast to be absorbed by a larger extratropical low over Canada in about 72 h. Key Messages: 1. There is the danger of life-threatening storm surge inundation along portions of the immediate coastline and adjacent waterways of northeastern South Carolina and the North Carolina coast, including portions of Pamlico and Albemarle Sounds. Residents in these areas should follow advice given by local emergency officials. 2. Hurricane conditions are spreading into the southern portion of the hurricane Warning area and should spread northward through tonight and early tomorrow morning. 3. Isaias is expected to bring widespread sustained tropical storm force winds and wind gusts to hurricane force to the mid-Atlantic coast, including portions of the Chesapeake Bay region, later tonight and on Tuesday, which could cause tree damage and power outages. Tropical storm conditions are expected to spread across New England late Tuesday into early Wednesday. 4. Heavy rainfall along the East Coast near the path of Isaias will result in flash and urban flooding, some of which may be significant in the eastern Carolinas, mid-Atlantic and northeast through Wednesday. Widespread minor to moderate river flooding is possible across portions of the Carolinas and the Mid-Atlantic. Quick- responding rivers in the northeast will also be susceptible to minor river flooding. FORECAST POSITIONS AND MAX WINDS INIT 04/0300Z 33.8N 78.5W 75 KT 85 MPH 12H 04/1200Z 37.0N 76.8W 60 KT 70 MPH...INLAND 24H 05/0000Z 42.0N 73.8W 50 KT 60 MPH...INLAND 36H 05/1200Z 46.8N 70.4W 40 KT 45 MPH...INLAND 48H 06/0000Z 50.8N 68.3W 30 KT 35 MPH...POST-TROP/EXTRATROP 60H 06/1200Z 52.9N 66.3W 25 KT 30 MPH...POST-TROP/EXTRATROP 72H 07/0000Z...DISSIPATED $$ Forecaster Beven |