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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
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