[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 201457
TCDAT5

Hurricane Jerry Discussion Number  13
NWS National Hurricane Center Miami FL       AL102019
1100 AM AST Fri Sep 20 2019

Data from both NOAA and Air Force Reserve Hurricane Hunter aircraft
indicate that Jerry is weakening quickly, and radar images from NOAA
show no sign of the eyewall reported on the last mission. Maximum
flight-level winds on the mission were about 78 kt, with SFMR values
near 70 kt, and the central pressure has risen about 10 mb
overnight.  These observations also agree with the latest satellite
imagery that shows a less organized cyclone, with the center on the
far northwestern edge of a distorted central dense overcast. A blend
of all these data gives an initial wind speed estimate of 75 kt.

Jerry is moving about the same as before, west-northwestward at
15 kt.  The hurricane should gradually bend to the right and slow
down during the next few days while the cyclone is steered
around the western periphery of a weakening subtropical ridge.  The
guidance is tightly packed on the forecast through Monday, and
little change was made to the previous NHC prediction.  At longer
range, a mid-latitude trough interaction should turn the hurricane
northward and northeastward, but the models are really struggling on
how quickly this occurs. While yesterday much of the guidance had
Jerry accelerating ahead of the trough, today's models have slowed
everything down as the trough looks like it could weaken before
fully recurving the cyclone.  The new track forecast is considerably
slower than the last one beyond 72 hours, about as much as
continuity allows, and later forecasts could slow Jerry down even
more.

Northwesterly shear is forecast to persist near Jerry for the next
day or two, and some weakening is expected.  The intensity forecast
is reduced from the previous one, and could be a bit too high in
the short term given recent trends.  In a few days, the
aforementioned trough interaction is anticipated, but it is next to
impossible to know at this lead time whether the trough will weaken
or strengthen the cyclone, so no forecast change is made.  It is a
little tempting to raise the intensity by the end, given the recent
weaker mid-latitude trough in the models, but there's just too much
track uncertainty to mess with the intensity forecast at this time.


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 today.


FORECAST POSITIONS AND MAX WINDS

INIT  20/1500Z 18.8N  60.3W   75 KT  85 MPH
 12H  21/0000Z 19.6N  62.4W   70 KT  80 MPH
 24H  21/1200Z 20.9N  64.7W   65 KT  75 MPH
 36H  22/0000Z 22.3N  66.6W   60 KT  70 MPH
 48H  22/1200Z 23.6N  68.0W   60 KT  70 MPH
 72H  23/1200Z 26.5N  69.0W   65 KT  75 MPH
 96H  24/1200Z 29.0N  67.5W   65 KT  75 MPH
120H  25/1200Z 33.0N  64.0W   65 KT  75 MPH

$$
Forecaster Blake
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