Official Discussion issued by the National Hurricane Center

Isaias (AL092020) DATA RELEASED: 8/4/2020 9:00:00 PM UTC

Copy of official data

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.


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