[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 160847
TCDAT4

Hurricane Humberto Discussion Number  15
NWS National Hurricane Center Miami FL       AL092019
500 AM EDT Mon Sep 16 2019

The satellite presentation of the hurricane has continued to
improve overnight, with the center embedded within a fairly
symmetric area of cold cloud tops.  Although no eye is evident in
conventional satellite imagery, a ragged eye could be seen in
long-range NWS Doppler radar data from Melbourne, Florida early
in the night.  Satellite intensity estimates from TAFB, SAB, and
UW/CIMSS all support an intensity of 75 kt, and that is used as the
initial wind speed for this advisory.  An Air Force Reserve
Hurricane Hunter aircraft is scheduled to investigate Humberto this
morning, and should provide a better assessment of the storm's
strength.

Humberto is likely to continue intensifying during the next day or
so while it moves over the warm waters of the Gulf stream and the
shear is not expected to be prohibitive.  The updated NHC forecast
depicts a faster rate of strengthening over the first 36 hours
than before, and is at the upper end of the guidance through that
time.  By 48 hours, increasing westerly shear should slow the
intensification process, but baroclinic forcing caused by a
mid-latitude trough is likely to help the cyclone remain strong
until it begins its extratropical transition later in the period.

Humberto is moving northeastward or 050/3 kt. The hurricane is
forecast to move slowly east-northeastward during the next 24
hours, around the northwestern portion of a subtropical ridge.
After that time, Humberto should continue on an east-northeastward
heading, but at a slightly faster forward speed as a broad trough
becomes established over the western Atlantic.  Later in the period,
a strong shortwave trough is forecast to dig southward which should
cause Humberto to lift northeastward.  The track guidance is in good
agreement through 72 hours, and the confidence in that portion of
the forecast is quite high.  After that time, the forecast
confidence decreases quite a bit as the model spread becomes
unusually large.  This is the due to differs in how Humberto
interacts with the aforementioned trough.  The GFS and HWRF shows
Humberto getting caught by the trough as it cuts-off over the
western Atlantic, while the ECMWF and UKMET show a more progressive
solution, and take Humberto northeastward over the north Atlantic
ahead of the trough. Given the model spread of more than 1000 n mi
at day 5, the NHC track foreast remains close to the multi-model
consensus, but confidence in the 4- and 5-day forecast is rather
low.

Large swells from Humberto will affect portions of the northwestern
Bahamas and southeastern United States coast during the next few
days.  These swells are expected to produce dangerous surf
conditions and life-threatening rip currents.  See products issued
by your local weather office for additional information.


FORECAST POSITIONS AND MAX WINDS

INIT  16/0900Z 29.7N  77.3W   75 KT  85 MPH
 12H  16/1800Z 30.0N  76.6W   85 KT 100 MPH
 24H  17/0600Z 30.3N  75.4W   90 KT 105 MPH
 36H  17/1800Z 30.6N  73.9W   95 KT 110 MPH
 48H  18/0600Z 31.0N  72.0W   95 KT 110 MPH
 72H  19/0600Z 33.0N  66.5W   95 KT 110 MPH
 96H  20/0600Z 37.0N  62.0W   75 KT  85 MPH
120H  21/0600Z 40.0N  58.5W   55 KT  65 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown
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