Hurricane GONZALO

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HURRICANE GONZALO DISCUSSION NUMBER  18
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL082014
500 PM AST THU OCT 16 2014

Recent microwave data indicate that Gonzalo has a concentric
eyewall structure, with a small open inner ring of convection
surrounded by a larger closed ring.  The satellite presentation has
not changed appreciably since this morning, and the CI estimate from
the UW-CIMSS ADT supports maintaining the initial intensity at 125
kt.  An Air Force reconnaissance aircraft is scheduled to
investigate Gonzalo later this evening and should give us a better
handle on the hurricane's current intensity.

Light westerly shear has been affecting Gonzalo, but it hasn't been
enough to disrupt the hurricane's structure.  Vertical shear is
forecast to increase slightly during the next 12-24 hours, and then
increase substantially after 48 hours.  Also, sea surface
temperatures along Gonzalo's forecast path are expected to be at
least 26C for the next 48 hours.  Therefore, only gradual weakening
is anticipated during the next couple of days while Gonzalo moves
near Bermuda.  More rapid weakening should occur after 48 hours
once Gonzalo moves north of the Gulf Stream and is affected by
40-50 kt of westerly shear.  The NHC intensity forecast closely
follows the intensity consensus ICON, and no significant changes
were required to the previous forecast.  The global models indicate
that Gonzalo will likely become extratropical by 72 hours, and that
is now indicated in the NHC forecast.

Gonzalo has turned north-northeastward and begun to accelerate with
an initial motion estimate of 015/8 kt.  The hurricane is entering
the flow ahead of a deep-layer trough located over the eastern
United States, and this pattern is expected to cause Gonzalo to
accelerate further toward the north-northeast during the next 48
hours.  After 48 hours, the cyclone is forecast to turn
northeastward and east-northeastward over the north Atlantic.  The
track guidance is tightly clustered for much of the forecast
period.  However, the new models are again a little slower than the
previous forecast, and they have shifted northwestward between 48-72
hours.  The updated NHC track forecast has also been shifted
northwestward during that time toward the TVCA model consensus.

Significant coastal flooding on Bermuda is likely if Gonzalo
continues on the current NHC forecast track.  Although specific
amounts cannot be forecast for Gonzalo, Hurricane Fabian produced an
estimated 10 feet of storm surge when it moved over Bermuda as a
major hurricane in 2003, and similar values could occur with
Gonzalo.

FORECAST POSITIONS AND MAX WINDS

INIT  16/2100Z 27.1N  68.2W  125 KT 145 MPH
 12H  17/0600Z 28.7N  67.3W  120 KT 140 MPH
 24H  17/1800Z 31.1N  65.9W  110 KT 125 MPH
 36H  18/0600Z 34.3N  64.0W  100 KT 115 MPH
 48H  18/1800Z 39.0N  60.8W   95 KT 110 MPH
 72H  19/1800Z 50.5N  46.0W   65 KT  75 MPH...POST-TROP/EXTRATROP
 96H  20/1800Z 55.0N  21.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  21/1800Z...DISSIPATED

$$
Forecaster Berg

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