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Tropical Storm Isaias Forecast Discussion Number 31
2020-08-04 22:57:11| National Hurricane Center (Atlantic)
Issued at 500 PM EDT Tue Aug 04 2020 000 WTNT44 KNHC 042057 TCDAT4 Tropical Storm Isaias Discussion Number 31 NWS National Hurricane Center Miami FL AL092020 500 PM EDT Tue Aug 04 2020 NOAA Doppler radar data from Islip, New York (KOKX), indicated 70-kt winds just off the surface south of Long Island earlier this afternoon, along with buoy reports from New York Harbor Inlet (44065) that supported lowering the intensity to 55 kt, so that value is used for this advisory. The motion remains north-northeastward or 020/35 kt. Isaias will continue moving north-northeastward through tonight, accompanied by a gradual decrease in forward speed. In 12 hours or, the cyclone is expected to interact with a larger extratropical over southeastern Canada and degenerate into a post-tropical cyclone near western Maine. By 24 hours, Isaias is expected to transition to an extratropical low, and dissipate or become absorbed by the aforementioned larger extratropical low. The new NHC track forecast is just an extension of the previous advisory, and lies very close to the tightly clustered consensus track models. Isaias will continue to gradually spin down and lose its tropical characteristics. The precipitation has decreased in size and also has become more stratiform in appearance, which are indications that the cyclone is gradually weakening. This downward trend should continue until Isais becomes an extratropical low in 12-24 hours. There also remains a risk of tornadoes across portions of New England this afternoon and evening Key Messages: 1. Tropical storm force winds that could cause tree damage and power outages will continue to spread across New England tonight. 2. Heavy rainfall near the path of Isaias, through the Hudson River Valley, is likely to result in flash flooding, particularly through urban areas and the surrounding terrain of the Catskills, Adirondack and Green Mountain Ranges through Tuesday night. Scattered minor to moderate river flooding is likely across portions of the Mid-Atlantic. Quick-responding rivers in the Northeast will also be susceptible to minor and possible moderate river flooding. 3. The threat of tornadoes will spread into New England this afternoon and evening. FORECAST POSITIONS AND MAX WINDS INIT 04/2100Z 42.7N 74.2W 55 KT 65 MPH 12H 05/0600Z 46.3N 72.4W 35 KT 40 MPH...POST-TROP/INLAND 24H 05/1800Z 50.7N 71.1W 30 KT 35 MPH...POST-TROP/EXTRATROP 36H 06/0600Z 53.3N 70.0W 25 KT 30 MPH...POST-TROP/EXTRATROP 48H 06/1800Z 54.1N 67.8W 20 KT 25 MPH...POST-TROP/EXTRATROP 60H 07/0600Z...DISSIPATED $$ Forecaster Stewart
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