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Hurricane Hector Discussion Number  19
NWS National Hurricane Center Miami FL       EP102018
200 AM PDT Sun Aug 05 2018

Hector has maintained a well-defined, 10-nmi-diameter eye inside a
gradually shrinking central dense overcast. Satellite intensity
estimates at 0600Z from TAFB and SAB supported an intensity of 102
kt, while UW-CIMSS ADT raw estimates have been near 100 kt. However,
more recent infrared satellite images indicate intensity estimates
just below 115 kt, so the advisory intensity of 110 kt is based on
a blend of the available estimates with more weight placed on
recent IR trends.

The initial motion remains 275/10 kt. A large, deep-layer ridge to
the north of Hector is expected to steer the hurricane westward for
the next 24 h or so, followed by a modest poleward 'stair-step' in
the track through 72 h due to a dissipating frontal trough pushing
southward and becoming stationary northeast of the Hawaiian Islands,
which should weaken the low-level ridge.  After that time, however,
the surface trough is forecast to weaken, allowing the ridge to
build back across the Islands, forcing Hector back onto a more
westerly course on days 4 and 5. More weakening of the ridge in
48-72 hours has resulted in yet another northward shift in the
guidance envelope, with the HWRF and HMON models bringing Hector
within 60 nmi of the Big Island on day 4. The new NHC forecast track
has been shifted slightly northward as a result, but lies just a tad
south of the consensus models out of respect for the reliable ECMWF
model, which is the southernmost of all of the global and regional
models.

Outer banding features have become less evident since the previous
advisory, and with Hector moving into an increasingly drier airmass,
the chances of Hector evolving into an annular hurricane are
increasing in the longer term. Although the hurricane will be
embedded within a light vertical wind shear environment, marginal
SSTs and a much drier airmass characterized by mid-level humidity
values less than 40 percent are expected to produce a slow weakening
trend throughout the forecast period. The official intensity
forecast is a little lower than the previous advisory, and closely
follows the intensity consensus models HCCA, FSSE, and IVCN, which
all show steady weakening.

While the official forecast track continues to lie south of the
Hawaiian Islands, it is too soon to determine what kind of impacts
might occur in the state, since track errors can be large at long
time ranges.  This remains a good time for everyone in the Hawaiian
Islands to ensure they have their hurricane plan in place.  For
additional information on any potential local impacts from Hector in
Hawaii, please refer to products issued by the NWS Weather Forecast
Office in Honolulu at http://www.prh.noaa.gov/hnl .


FORECAST POSITIONS AND MAX WINDS

INIT  05/0900Z 14.4N 135.7W  110 KT 125 MPH
 12H  05/1800Z 14.6N 137.5W  110 KT 125 MPH
 24H  06/0600Z 15.0N 139.9W  105 KT 120 MPH
 36H  06/1800Z 15.6N 142.7W  105 KT 120 MPH
 48H  07/0600Z 16.2N 145.6W  100 KT 115 MPH
 72H  08/0600Z 16.9N 151.8W   95 KT 110 MPH
 96H  09/0600Z 17.2N 157.4W   90 KT 105 MPH
120H  10/0600Z 17.7N 162.6W   85 KT 100 MPH

$$
Forecaster Stewart

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