[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 250237
TCDAT2

Tropical Storm Karen Discussion Number  12
NWS National Hurricane Center Miami FL       AL122019
1100 PM AST Tue Sep 24 2019

During the afternoon and early evening hours, satellite images
indicated that the cloud pattern associated with Karen was
becoming a little better organized. Then, surface observations from
the area just east of Puerto Rico indicated that the pressures
were falling, and a center was apparently becoming better defined.
The presence of this center was confirmed by a reconnaissance
plane which was able to fix a tight small circulation of about 1002
or 1003 mb.  This, by no means, indicates that the overall
circulation of the cyclone is well organized. Winds are still swirly
on the western portion of the circulation and are responding to an
elongated trough of low pressure north of Puerto Rico. In fact, I
would not be surprised if another center reforms father to west
within the trough or the large cyclonic envelope, and the center we
are tracking dissipates. In any case, preliminary analysis indicates
that the center of Karen that we were tracking moved very near or
over Vieques around 2100 UTC and then over Culebra a little bit
later. This small center could also have been a meso-vortex within
the larger circulation.

Data from the reconnaissance plane and satellite intensity estimates
yield an initial intensity of 40 kt. These winds are occurring
primarily to the southeast of the center. Karen is heading toward a
shear environment that is not ideal at all for significant
intensification. As previously indicated, the NHC forecast calls for
a very modest increase in intensity during the next 3 to 5 days as
indicated by the HCCA model.  However, some of the statistical
guidance brings Karen to hurricane status by the end of the
forecast period.

Satellite and reconnaissance fixes indicate that Karen is moving
toward the north-northeast or 015 degrees at 12 kt. This motion
however, is highly uncertain because it includes the reformation of
the center.  The circulation of Karen is trapped between a
subtropical high over the Atlantic and a mid-level trough over the
Bahamas. This flow pattern will continue to steer Karen in this same
generaldirection for the next 3 days. After that time, the steering
flow is forecast to collapse, and Karen, if it is still a cyclone,
will begin to meander. This would allow another ridge to develop
north of the cyclone and force it to move westward. This is the
solution provided by most of the global models.


Key Messages:

1.  Karen will continue to bring heavy rainfall, flash floods and
mudslides to Puerto Rico, Vieques and the U.S. and British Virgin
Islands into Wednesday even as the center moves away from the
region.

FORECAST POSITIONS AND MAX WINDS

INIT  25/0300Z 19.1N  65.0W   40 KT  45 MPH
 12H  25/1200Z 20.8N  64.6W   45 KT  50 MPH
 24H  26/0000Z 23.2N  64.0W   45 KT  50 MPH
 36H  26/1200Z 25.5N  63.4W   50 KT  60 MPH
 48H  27/0000Z 27.0N  62.5W   55 KT  65 MPH
 72H  28/0000Z 26.8N  61.5W   55 KT  65 MPH
 96H  29/0000Z 26.5N  61.5W   55 KT  65 MPH
120H  30/0000Z 26.0N  65.5W   55 KT  65 MPH

$$
Forecaster Avila
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