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Tropical Storm Humberto Forecast Discussion


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000
WTNT44 KNHC 150856
TCDAT4

Tropical Storm Humberto Discussion Number  11
NWS National Hurricane Center Miami FL       AL092019
500 AM EDT Sun Sep 15 2019

Since reconnaissance aircraft departed the storm after midnight, the
overall cloud pattern of Humberto has not changed appreciably.  Both
the earlier aircraft data and a blend of the most recent subjective
satellite intensity estimates from SAB and TAFB still support an
initial intensity of 50 kt.  While there is significant banding
evident over the northern and eastern portions of the circulation,
the cyclone has not be able to maintain convection over the center,
likely due to some mid-level dry air that has wrapped around the
southwestern and southern part of the system.  As Humberto moves
slowly northward today, it will be over warm water and generally
within low vertical wind shear.  This should allow for
strengthening, and the NHC foreast continues to calls for Humberto
to become a hurricane later today or tonight.  Additional
strengthening is likely after that time when the storm recurves and
remains within favorable environmental conditions.  Late in the
period, Humberto is forecast to interact with an approaching
mid-latitude trough, and increasing shear ahead of that system is
likely to cause weakening.  This interaction should also begin
Humberto's transition to an extratropical cyclone.  The updated NHC
intensity forecast is essentially unchanged from the previous
advisory and is in best agreement with the HFIP corrected consensus
model.

Humberto continues to be steered north-northwestward at about 6 kt
by a mid-level ridge over the western Atlantic.  The tropical storm
should turn northward and slow down later today as a weakness
develops in the ridge.  On Monday, a broad trough over the the
northeastern United States is expected to turn Humberto
northeastward, and then east-northeastward away from the United
States.  The dynamical models remain in good agreement on the
overall track forecast scenario but there are some differences in
the forward speed of Humberto after the east-northeastward turn.
The latest NHC track is similar to, but a little slower than, the
previous advisory.  The new track forecast is closest to the
multi-model consensus to account for the forward speed differences
among the guidance.

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  15/0900Z 28.3N  77.7W   50 KT  60 MPH
 12H  15/1800Z 29.0N  77.9W   60 KT  70 MPH
 24H  16/0600Z 29.6N  77.6W   65 KT  75 MPH
 36H  16/1800Z 30.1N  76.7W   70 KT  80 MPH
 48H  17/0600Z 30.5N  75.3W   75 KT  85 MPH
 72H  18/0600Z 31.3N  71.2W   90 KT 105 MPH
 96H  19/0600Z 33.5N  64.5W   95 KT 110 MPH
120H  20/0600Z 38.0N  58.0W   70 KT  80 MPH

$$
Forecaster Brown