Tropical Storm Josephine Forecast Discussion

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238 
WTNT41 KNHC 150237
TCDAT1

Tropical Storm Josephine Discussion Number  14
NWS National Hurricane Center Miami FL       AL112020
1100 PM AST Fri Aug 14 2020

Josephine continues to produce bursts of deep convection near and 
to the northeast of its center, however, there is little evidence 
of any banding features.  A fortuitous ASCAT-A overpass has 
revealed peak winds of 35-40 kt over the northern semicircle of the 
storm, and the scatterometer ambiguities along with the earlier 
reconnaissance aircraft data suggest that the circulation is still 
closed.  Based on the scatterometer data, the initial wind speed 
has been set at 40 kt.  

The intensity forecast reasoning remains unchanged from the 
previous forecast. The moderate to strong southwesterly vertical 
wind shear that is affecting the cyclone is forecast to increase 
over the weekend and reach values of around 30 kt on Sunday. This is 
expected to result in gradual weakening by the latter portion of the 
weekend, and Josephine is predicted to weaken to a tropical 
depression in about 48 hours, and become a remnant low in 3-4 days. 
A plausible alternate scenario that is suggested by some of the 
global models is for the circulation to open up into a trough of 
low pressure, resulting in dissipation of the tropical cyclone 
within the next few days.  

The timely ASCAT data was very helpful in determining Josephine's 
center location.  Based on that and the earlier aircraft fixes, 
the cyclone continues to move west-northwestward or 300/14 kt.  A 
subtropical ridge to the north of Josephine should steer the cyclone 
west-northwestward during the next 24-48 hours.  After that time, 
Josephine should turn northwestward, and then northward as a 
weakness develops in the ridge over the western Atlantic. By late 
in the period, Josephine or its remnants are expected to turn 
north-northeastward as it becomes embedded within the mid-latitude 
westerlies.  The latest official forecast is near the middle of the 
tightly clustered dynamical track models, and is very similar to the 
previous NHC advisory. 

KEY MESSAGES:

1. Josephine should pass far enough to the northeast of the Leeward
Islands over the weekend to prevent major impacts.  However,
interests there should continue to monitor its progress until the
storm has passed north of that area.

2. Locally heavy rainfall is possible in the northern Leeward
Islands, the Virgin Islands, and Puerto Rico as Josephine passes by
to the northeast. Isolated minor flooding is possible in Puerto
Rico through Monday.


FORECAST POSITIONS AND MAX WINDS

INIT  15/0300Z 18.3N  57.4W   40 KT  45 MPH
 12H  15/1200Z 19.2N  59.3W   40 KT  45 MPH
 24H  16/0000Z 20.4N  61.6W   40 KT  45 MPH
 36H  16/1200Z 21.7N  63.9W   35 KT  40 MPH
 48H  17/0000Z 23.2N  65.8W   30 KT  35 MPH
 60H  17/1200Z 24.7N  67.2W   25 KT  30 MPH
 72H  18/0000Z 26.4N  67.7W   25 KT  30 MPH
 96H  19/0000Z 29.5N  67.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  20/0000Z 33.0N  64.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Brown




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