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Subtropical Storm Andrea Forecast Discussion


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588 
WTNT41 KNHC 202234
TCDAT1

Subtropical Storm Andrea Special Discussion Number   1
NWS National Hurricane Center Miami FL       AL012019
630 PM AST Mon May 20 2019

Satellite and aircraft data indicate that the area of low pressure
that the National Hurricane Center has been monitoring to the
southwest of Bermuda has developed into a subtropical storm.
The Air Force Hurricane Hunters have recently exited the cyclone and
found that the system has developed a well-defined center and has a
minimum pressure of about 1006 mb. The maximum adjusted flight-level
and surface SFMR winds support an intensity of about 35 kt.  The
cyclone is considered subtropical at this time because it is
interacting with an upper-level low pressure system to its west,
has a relatively large radius of maximum wind, and its overall
appearance in satellite images.

Based on satellite and aircraft fixes today, the initial motion of
Andrea is estimated to be northward at 12 kt as it has been moving
in the flow between a subtropical ridge to its east and a mid- to
upper-level low to its west.  The models show Andrea slowing down
and gradually turning to the northeast on Tuesday and eastward by
Tuesday night as it moves on the northern periphery of the ridge.

Andrea could strengthen slightly through early Tuesday while it
remains in a fairly moist and unstable atmosphere.  However, after
that time, gradual weakening should commence due to less favorable
conditions, and all of the reliable models show Andrea opening into
a trough and becoming absorbed by a cold front on Wednesday.  The
NHC official track forecast lies near the middle of the guidance
envelope.


FORECAST POSITIONS AND MAX WINDS

INIT  20/2230Z 28.8N  68.7W   35 KT  40 MPH
 12H  21/0600Z 30.2N  68.9W   40 KT  45 MPH
 24H  21/1800Z 31.1N  68.3W   35 KT  40 MPH
 36H  22/0600Z 31.5N  66.4W   30 KT  35 MPH
 48H  22/1800Z...DISSIPATED

$$
Forecaster Cangialosi