[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 180904
TCDAT5

Tropical Storm Jerry Discussion Number   4
NWS National Hurricane Center Miami FL       AL102019
500 AM AST Wed Sep 18 2019

Enhanced BD-curve infrared imagery and a 0431 UTC AMSR2 microwave
pass indicate that the cyclone has become better organized during
the pass several hours.  Although the surface center is still
situated near the northeastern edge of the convective mass, the
deep convection has expanded in the form of curve bands in the south
portion of the cyclone.  Based on the increased subjective and
objective satellite intensity estimates, and the improved microwave
presentation, the initial intensity is raised to 40 kt making the
system the tenth named storm of the season.

Even though the shear is low and the sea surface temperatures are
warm, GOES-16 sounder data and the GFS/ECMWF SHIPS intensity models
indicate that the environment surrounding the cyclone is still a
little dry and stable.  Therefore, only gradual intensification is
forecast.  The shear is forecast to increase after 24 hours or so,
to the point where it should slow, or halt development, and this is
reflected in the official forecast.  It should be noted that the
forecast still calls for the cyclone to become a hurricane as it
approaches the northern Leeward Islands.

The initial motion is estimated to be west-northwestward, or 290/11
kt, within the low to mid-tropospheric steering flow produced by a
subtropical ridge to the north of the tropical storm.  This general
motion is expected to continue during the next 3 to 4 days.
Afterward, a northwest to north-northwestward turn, influenced by a
growing weakness in the aforementioned ridge, is expected.  The NHC
track forecast is basically an update from the previous advisory and
lies in the middle of the guidance suite, and hedged toward the HCCA
multi-model consensus.


Key Messages:

1. Jerry is expected to strengthen and be a hurricane when
its moves near the northern Leeward Islands Friday, although it is
too soon to determine if there will be any direct impacts in the
islands. Interests there should ensure they have their hurricane
plan in place and monitor the progress of this system.


FORECAST POSITIONS AND MAX WINDS

INIT  18/0900Z 14.1N  47.7W   40 KT  45 MPH
 12H  18/1800Z 14.8N  49.4W   45 KT  50 MPH
 24H  19/0600Z 15.7N  52.0W   55 KT  65 MPH
 36H  19/1800Z 16.8N  54.9W   60 KT  70 MPH
 48H  20/0600Z 17.9N  57.9W   65 KT  75 MPH
 72H  21/0600Z 20.2N  64.2W   65 KT  75 MPH
 96H  22/0600Z 22.8N  68.6W   65 KT  75 MPH
120H  23/0600Z 25.6N  70.2W   65 KT  75 MPH

$$
Forecaster Roberts

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