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Hurricane Humberto Forecast Discussion


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718 
WTNT44 KNHC 162051
TCDAT4

Hurricane Humberto Discussion Number  17
NWS National Hurricane Center Miami FL       AL092019
500 PM EDT Mon Sep 16 2019

A NOAA Hurricane Hunter aircraft investigating Humberto this
afternoon found peak 850-mb flight-level winds of 78 kt in the
western quadrant, along with SFMR surface winds of 71-72 kt, which
is an increase in the winds in this part of storm since the earlier
Air Force Reserve reconnaissance flight. The NOAA aircraft also
measured a central pressure of 972 mb, down 4 mb from the previous
flight. A combination of subjective and objective satellite
intensity estimates of 90 kt and the aircraft data support an
initial intensity of 80 kt.

The initial motion estimate remains east-northeastward or 070/06 kt.
Humberto made a wobble to the north during the past few hours, but
has now wobbled toward the east, which is an indication that the
hurricane's inner core is continuing to consolidate and contract.
That being said, the latest model guidance is in even better
agreement with and more convergent about the previous forecast
track.  Thus no significant changed were required through 72 hours.
Thereafter, the models are also now in better agreement that
Humberto will not slow down as much as previously expected, and the
hurricane is forecast to gradually lift out and accelerate to the
northeast on days 4 and 5 when Humberto is well to the northeast of
Bermuda.  No significant track changes were made to the previous
advisory track through 48 hours, with the track having been nudged
southward slightly on days 3-5 in agreement with the consensus
models TVCN, NOAA-HCCA, and FSSE.

Humberto has continued to strengthen at a rate of 20 kt per 24
hours, and I see no physical reasons why this trend should not
continue for another 24-36 hours. By 48 hours and beyond, the
hurricane will be entering the right-rear quadrant of a strong
upper-level jet maximum that could briefly impart some additional
baroclinic forcing on the cyclone, helping it to maintain its
intensity or at least slow down the weakening process. By day 3 and
beyond, however, the wind shear becomes prohibitively hostile at
more than 50 kt, which should cause the central deep convection to
erode, resulting in significant weakening. On day 5, extratropical
transition over the colder north Atlantic waters is forecast to
begin as Humberto interacts and possibly merges with a strong cold
front.

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

FORECAST POSITIONS AND MAX WINDS

INIT  16/2100Z 30.2N  75.9W   80 KT  90 MPH
 12H  17/0600Z 30.4N  74.9W   90 KT 105 MPH
 24H  17/1800Z 30.8N  73.3W   95 KT 110 MPH
 36H  18/0600Z 31.2N  71.3W  100 KT 115 MPH
 48H  18/1800Z 32.0N  68.7W   95 KT 110 MPH
 72H  19/1800Z 36.0N  61.3W   85 KT 100 MPH
 96H  20/1800Z 40.1N  59.0W   70 KT  80 MPH
120H  21/1800Z 41.7N  54.0W   60 KT  70 MPH...POST-TROP/EXTRATROP

$$
Forecaster Stewart