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Hurricane Hector Discussion Number  28
NWS Central Pacific Hurricane Center Honolulu HI   EP102018
1100 PM HST Mon Aug 06 2018

Hector remains a powerful category 4 hurricane this evening, but 
the satellite presentation has degraded slightly since the previous 
advisory, likely due to the storm feeling some of the effects of the
very dry mid-level air on the periphery of the system. Hector
continues to display a well defined 10 nautical mile wide eye,
surrounded by a ring of -65 to -75 degree Celsius cloud tops.  The
latest subjective Dvorak current intensity estimates from PHFO, SAB
and JTWC came in at 6.5 (127 knots), while the latest estimate using
the Advanced Dvorak technique from UW-CIMSS yielded 6.6 (130 knots).
In addition, the Air Force Reserves 53rd Weather Reconnaissance
Squadron measured a surface wind of 126 knots in the northwest
eye wall around 0730Z. Taking all this data into account, the
initial intensity has been lowered to 125 knots. Hector continues to
track just north of due west, with an initial motion set at 280/14
knots.
 
The latest model guidance remains tightly clustered and brings 
Hector just north of due west tonight and Tuesday. A building
subtropical ridge to the north of the Hawaiian Islands should
then steer Hector due westward Tuesday night through Thursday
night. The system should begin to bend back toward the
west-northwest or northwest Friday through Saturday as it rounds the
southwest periphery of the subtropical ridge and begins to be
influenced by an upper level trough setting up between 170W and the
International Date Line. The new official forecast track has been
nudged slightly southward and is roughly in between the previous
official forecast and the latest model consensus. The forecast
track brings the center of Hector roughly around 165 miles south of
the Big Island as a major hurricane on Wednesday, and given the
proximity of the storm to the island, the Tropical Storm Watch
remains in effect.
 
Hector will remain in a favorable low shear environment through
Friday, before west-southwesterly shear increases late Friday or
Saturday. There are a couple factors that should lead to gradual
weakening over the next few days however. The hurricane will be
traveling over marginal sea surface temperatures around 27C through
Wednesday night, before the SSTs increase slightly to around 28C to
the south and southwest of the Hawaiian Islands Thursday through
Saturday. Additionally and likely more importantly, very dry
mid-level air will surround the storm through the forecast period,
and this is expected to lead to gradual weakening of the system over
the next couple days. The intensity of Hector is then expected to
level off Thursday through Friday as it encounters the higher SSTs.
Some weakening should then ensue by Saturday as Hector begins to
feel increasing west-southwesterly shear as it approaches the upper 
trough between 170W and the Date Line. The intensity forecast has
been adjusted slightly lower than the previous forecast through 36
hours, then slightly higher between 48 and 120 hours, which is in
line with the latest trends of the statistical and dynamical
models, but with more weight given to the dynamical models which
have been performing better over the past several days.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/0900Z 15.8N 146.3W  125 KT 145 MPH
 12H  07/1800Z 16.1N 148.6W  120 KT 140 MPH
 24H  08/0600Z 16.3N 151.5W  110 KT 125 MPH
 36H  08/1800Z 16.4N 154.5W  105 KT 120 MPH
 48H  09/0600Z 16.5N 157.6W  100 KT 115 MPH
 72H  10/0600Z 16.8N 163.8W  100 KT 115 MPH
 96H  11/0600Z 18.0N 169.5W  100 KT 115 MPH
120H  12/0600Z 19.5N 173.5W   90 KT 105 MPH
 
$$
Forecaster Jelsema
 
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