[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 202053
TCDAT5

Hurricane Jerry Discussion Number  14
NWS National Hurricane Center Miami FL       AL102019
500 PM AST Fri Sep 20 2019

Satellite images indicate that deep convection has re-developed
near and northeast of the center, with a new rainband also present
in the southwest quadrant.  Overall the degradation in satellite
seen this morning has stopped, and that trend basically matches the
last aircraft data from several hours ago.  The initial wind speed
is set to 70 kt on this advisory, and another Air Force Reserve
Hurricane Hunter aircraft is scheduled to investigate the hurricane
tonight.

Jerry has been moving a little faster today, west-northwestward at
16 kt, perhaps due to the system becoming a little shallower and
feeling the faster low-level flow. There are no significant track
changes to the NHC forecast this afternoon. The hurricane's motion
should gradually bend to the right and slow down during the next few
days while the cyclone is steered around the western flank of a
weakening subtropical ridge. At longer range, a mid-latitude trough
will likely turn the hurricane northward and northeastward, but how
quickly that occurs is an open question. The guidance spread has
only increased this afternoon, although the model consensus hasn't
changed much, so the NHC forecast will hold the course on this
advisory.

Northwesterly shear is forecast to persist near Jerry for the next
day or so, and further weakening is expected.  While the shear might
not change much by late this weekend, a combination of very warm
water and a more moist mid-level environment could sustain the
cyclone and even allow some strengthening afterward. The long-range
intensity forecast depends on the mid-latitude trough and whether it
is a trough that tends to shear the cyclone, or whether it gives
Jerry a baroclinic kick to increase the winds. I'm hesitant to
change anything at this point given the huge track spread, so the
latest intensity forecast is basically an update of the previous
one, near or slightly above the model consensus.

Key Messages:

1. Although the core of Jerry is expected to move north of the
northern Leeward Islands, heavy rainfall and flash floods are
possible there tonight.


FORECAST POSITIONS AND MAX WINDS

INIT  20/2100Z 19.6N  62.0W   70 KT  80 MPH
 12H  21/0600Z 20.5N  63.9W   65 KT  75 MPH
 24H  21/1800Z 21.8N  65.9W   60 KT  70 MPH
 36H  22/0600Z 23.2N  67.5W   60 KT  70 MPH
 48H  22/1800Z 24.5N  68.6W   65 KT  75 MPH
 72H  23/1800Z 27.0N  68.9W   65 KT  75 MPH
 96H  24/1800Z 30.0N  67.5W   65 KT  75 MPH
120H  25/1800Z 33.5N  63.5W   65 KT  75 MPH

$$
Forecaster Blake
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