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Tropical Storm Jerry Discussion Number   6
NWS National Hurricane Center Miami FL       AL102019
500 PM AST Wed Sep 18 2019

Jerry continues to strengthen this afternoon, as indicated by 1-min
GOES-16 satellite imagery, with a large burst of convection close
to the center.  In addition, microwave data show that the central
structure has improved, displaying a tightly wrapped band near the
center.  The initial wind speed is set to 50 kt, on the conservative
side of the intensity estimates.

The storm should become a hurricane on Thursday while it is moving
over very warm waters with light shear.  Dropsondes from the NOAA
G-IV aircraft this afternoon show that Jerry is surrounded by some
very dry air in the lower to mid-levels, and this is likely the main
limiting factor on the cyclone's strengthening rate in the near
term.  By 48 hours, almost all of the models show an increase in
northwesterly shear due to flow from an upper-level ridge, which
seems likely to cause some weakening.  At long range, Jerry is
likely to interact with a mid-latitude trough, which is notoriously
difficult to forecast.  Only small changes were made to the previous
wind speed prediction, and this advisory is close to a blend of the
various consensus aids.

The initial motion continues to be west-northwestward, or 290/13 kt.
There's no substantial change to the track forecast on this
package, with a subtropical ridge providing a well-defined steering
current.  This ridge should move Jerry along at a faster forward
speed in about the same direction for the next couple of days,
taking the center close to but north of the northern Leeward
Islands.  Afterward, a northwest to northward turn, influenced by a
weakness in the aforementioned ridge left behind by Humberto and a
new mid-latitude shortwave, is anticipated. The new forecast is very
close to the previous one and a blend of the latest ECMWF ensemble
mean and the corrected-consensus HCCA.

Key Messages:

1. Jerry is expected to become a hurricane before it moves close to
the northern Leeward Islands Friday. Although the core of Jerry is
currently expected to pass north of the islands, tropical-storm-
force winds and locally heavy rainfall are possible, and tropical
storm watches have been issued for a portion of this area.

FORECAST POSITIONS AND MAX WINDS

INIT  18/2100Z 15.0N  50.5W   50 KT  60 MPH
 12H  19/0600Z 15.7N  52.5W   60 KT  70 MPH
 24H  19/1800Z 16.7N  55.3W   70 KT  80 MPH
 36H  20/0600Z 17.8N  58.3W   70 KT  80 MPH
 48H  20/1800Z 19.1N  61.4W   65 KT  75 MPH
 72H  21/1800Z 21.5N  66.5W   60 KT  70 MPH
 96H  22/1800Z 25.2N  70.0W   60 KT  70 MPH
120H  23/1800Z 28.5N  69.5W   60 KT  70 MPH

$$
Forecaster Blake

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