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Hurricane Hector Discussion Number  12
NWS National Hurricane Center Miami FL       EP102018
800 AM PDT Fri Aug 03 2018

The satellite presentation of Hector has degraded over the past
several hours, with only occasional hints of an eye in the latest
imagery.  More notably, an AMSR2 microwave pass at 0945Z shows a
secondary eyewall structure beginning, with a ring of convection
noted at about a 30 n mi radius.  All these data indicate that
Hector has weakened, so the initial wind speed is conservatively
reduced to 80 kt, near or just above the latest Dvorak estimates.

The current northeasterly shear is forecast to abate by the
numerical models during the next 12 hours, which would normally lead
to a restrengthening of Hector.  However, the secondary eyewall
formation throws a wrinkle into the forecast, since that process
usually takes longer than that amount of time.  As a compromise,
gradual intensification is shown starting tomorrow, with a small
uptick on Sunday as Hector reaches warmer waters in a light-shear
environment. The HWRF and HMON still show Hector becoming a major
hurricane, so it is too soon to abandon that forecast.   The new
forecast is a blend of the latest corrected-consensus guidance and
the previous forecast, resulting in about a 10-kt reduction from the
last NHC prediction.  Slow weakening is shown at the end of the
forecast due to cooler SSTs and potential entrainment of drier
mid-level air.

The initial motion remains 270/10 kt.   A large subtropical
ridge should steer the hurricane westward for the next couple of
days, then a weakness in the ridge develops, which should cause a
more west-northwestward track.  The model guidance suite is a little
slower than yesterday, about 1 or 2 kt overall.  While that doesn't
sound like much, over the course of a forecast that could change
the final cyclone position by a few degrees, so it is meaningful.
In this particular case, a slower solution turns Hector to
the west-northwest earlier in the forecast, since the hurricane
feels the developing weakness to the north-northeast sooner.  The
new NHC track forecast follows the trend of the model consensus and
is adjusted slightly to the north.


FORECAST POSITIONS AND MAX WINDS

INIT  03/1500Z 14.1N 128.8W   80 KT  90 MPH
 12H  04/0000Z 14.2N 130.4W   80 KT  90 MPH
 24H  04/1200Z 14.2N 132.4W   85 KT 100 MPH
 36H  05/0000Z 14.1N 134.5W   90 KT 105 MPH
 48H  05/1200Z 14.2N 136.6W  100 KT 115 MPH
 72H  06/1200Z 15.1N 141.4W  100 KT 115 MPH
 96H  07/1200Z 16.3N 146.7W   90 KT 105 MPH
120H  08/1200Z 17.0N 152.0W   85 KT 100 MPH

$$
Forecaster Blake

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