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Hurricane Humberto Discussion Number  27
NWS National Hurricane Center Miami FL       AL092019
500 AM AST Thu Sep 19 2019

Flight-level and surface wind observations reported by Air Force
Reserve Hurricane Hunter aircraft exiting Humberto a couple of hours
ago indicated that the maximum sustained winds have increased to 110
kt.  However, weakening is expected to commence soon.

Humberto's extratropical transition continues as a high amplitude PV
tongue, noted in the GOES-16 water vapor imagery, and associated dry
air, digs into the backside of the cyclone.  The large-scale models,
as well as the FSU Cyclone Phase Evolution forecast, indicate that
the process will be completed in less than 36 hours.  Afterward,
gradual weakening is expected until the extratropical low is
absorbed by another larger low pressure system, moving out of
Atlantic Canada, by the end of the forecast period.  The NHC
intensity forecast is basically an update of the previous forecast
and is based on a blend of the global models beyond the 36 hour
period.

The initial motion is estimated to be northeastward, or 045/19 kt.
Humberto is forecast to turn north-northeastward as the cyclone
completes its extratropical transition, followed by a turn
back toward the east-northeast within the strong deep-layer
mid-latitude westerlies.  The NHC forecast is nudged a little to the
left of the previous advisory between the 36 and 72 hour periods,
and is close to the NOAA HFIP HCCA consensus model.

Key Messages:

1. Storm surge and dangerous breaking waves, while diminishing,
could cause coastal flooding today along the coast of Bermuda.

2. Swells will continue to affect the northwestern Bahamas and the
southeastern coast of the United States from east-central Florida to
North Carolina during the next couple of days, creating life-
threatening surf and rip current conditions.


FORECAST POSITIONS AND MAX WINDS

INIT  19/0900Z 35.2N  62.2W  110 KT 125 MPH
 12H  19/1800Z 37.4N  60.0W   95 KT 110 MPH
 24H  20/0600Z 39.9N  58.9W   75 KT  85 MPH
 36H  20/1800Z 41.8N  57.4W   60 KT  70 MPH...POST-TROP/EXTRATROP
 48H  21/0600Z 43.2N  53.4W   50 KT  60 MPH...POST-TROP/EXTRATROP
 72H  22/0600Z 46.3N  36.4W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  23/0600Z...DISSIPATED

$$
Forecaster Roberts

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