[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT41 KNHC 152034
TCDAT1

Tropical Storm Josephine Discussion Number  17
NWS National Hurricane Center Miami FL       AL112020
500 PM AST Sat Aug 15 2020

Josephine continues to feel the effects of westerly shear, and the
low cloud swirl denoting the center is partly exposed at the western
edge of the convection.  Satellite intensity estimates have not
changed significantly since the earlier recon flight, so the initial
intensity remains 40 kt.  Animation of satellite imagery suggests
that the low-level circulation is at best barely closed, but there
is insufficient evidence right now to justify a downgrade to a
tropical wave.  Another aircraft is scheduled to investigate the
system near 0000Z.

The initial motion is west-northwestward or 295/15 kt.  It sounds
like a broken record, but there is little change to either the
forecast guidance or the forecast track since the last advisory. For
the next 36-48 h, Josephine or its remnants are likely to continue
to move west-northwestward on the southwest side of the subtropical
ridge.  After that, the system is forecast to recurve to the north
and north-northeast through a break in the western portion of the
ridge.  As before, the new NHC forecast lies near the the center of
the tightly-clustered guidance and near the various consensus
models.

Josephine is expected to remain in an environment of moderate to
strong westerly shear for at least the next 48-60 h which should
cause the system to weaken.  The intensity forecast, which assumes
some sort of closed circulation will last for 5 days, now calls for
the system to weaken to a depression between 24-36 h and become a
remnant low by 60 h.  An alternative scenario is that the system
degenerates to a tropical wave, which could occur at almost any time
given the state of the circulation.  There is a chance that
Josephine or its remnants could encounter a less hostile environment
after 72 h.  However, it remains unclear at this time whether there
will be enough left of the system to take advantage of those
favorable conditions.


KEY MESSAGES:

1. Josephine is passing far enough to the northeast of the Leeward
Islands 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  15/2100Z 20.0N  61.6W   40 KT  45 MPH
 12H  16/0600Z 20.8N  63.4W   35 KT  40 MPH
 24H  16/1800Z 22.1N  65.5W   35 KT  40 MPH
 36H  17/0600Z 23.4N  67.4W   30 KT  35 MPH
 48H  17/1800Z 24.9N  68.6W   30 KT  35 MPH
 60H  18/0600Z 26.3N  69.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  18/1800Z 28.0N  69.4W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  19/1800Z 30.5N  68.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  20/1800Z 33.0N  65.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven
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