[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 192033
TCDAT4

Hurricane Humberto Discussion Number  29
NWS National Hurricane Center Miami FL       AL092019
500 PM AST Thu Sep 19 2019

Humberto is almost a post-tropical cyclone.  Satellite images show
a well-defined cold and warm front, but they do not appear to be
fully connected to the center of circulation yet.  In addition, the
cyclone is still producing an area of deep convection to
the northwest of the exposed low-level center.  ASCAT data from
earlier today indicated that the wind field of Humberto is very
large with tropical-storm-force winds extending up to 330 n mi from
the center and hurricane-force winds extending out to 70 n mi from
the center. The initial intensity is lowered a little to 90 kt for
this advisory.

The cyclone is anticipated to become fully extratropical soon,
within the next 6 to 12 hours.   Although weakening is forecast,
Humberto is expected to be a large and powerful extratropical
cyclone for a couple of days before it is absorbed by another
extratropical low over the north Atlantic.  The NHC intensity
forecast generally follows the guidance of the GFS model, which
typically handles extratropical lows better than the tropical
cyclone intensity guidance.

Humberto is moving northeastward at 21 kt.  A slight turn to the
left and a decrease in forward speed are expected during the next
12 to 24 hours as the cyclone rotates around the east and north
sides of a mid- to upper-level low to its west.  After that time, a
faster east-northeast or east motion is expected when the cyclone
becomes embedded in the mid-latitude westerlies.  The NHC track
forecast is largely an update of the previous one and near the
various consensus aids.

Key Messages:

1. Large swells will continue to affect Bermuda, the northwestern
Bahamas, and the east coast of the United States from east-central
Florida to the Mid-Atlantic States during the next couple of days.
These swells could create life-threatening surf and rip current
conditions.


FORECAST POSITIONS AND MAX WINDS

INIT  19/2100Z 38.5N  58.7W   90 KT 105 MPH
 12H  20/0600Z 40.4N  57.5W   75 KT  85 MPH...POST-TROP/EXTRATROP
 24H  20/1800Z 42.8N  55.5W   60 KT  70 MPH...POST-TROP/EXTRATROP
 36H  21/0600Z 44.6N  51.2W   55 KT  65 MPH...POST-TROP/EXTRATROP
 48H  21/1800Z 45.6N  44.6W   50 KT  60 MPH...POST-TROP/EXTRATROP
 72H  22/1800Z...DISSIPATED

$$
Forecaster Cangialosi
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