Hurricane Hector Update 5am, 8-7-2018

A Tropical Storm Watch is in effect for…
* Hawaii County

A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area within 48 hours.

Interests elsewhere in the Hawaiian Islands should monitor the
progress of Hector.

DISCUSSION AND OUTLOOK
———————-
At 500 AM HST (1500 UTC), the center of Hurricane Hector was located
near latitude 16.1 North, longitude 147.8 West. Hector is moving
toward the west near 16 mph (26 km/h). This general motion is
expected to continue through Thursday. On the forecast track, Hector
is expected to pass roughly 165 miles south of the Big Island of
Hawaii on Wednesday.

Maximum sustained winds are near 130 mph (215 km/h) with higher
gusts. Hector is a category 4 hurricane on the Saffir-Simpson
Hurricane Wind Scale. Some weakening is forecast during the
next 48 hours.

Hurricane-force winds extend outward up to 30 miles (45 km) from the
center and tropical-storm-force winds extend outward up to 90 miles
(150 km).

The estimated minimum central pressure is 947 mb (27.97 inches).

HAZARDS AFFECTING LAND
———————-
SURF: Swells generated by Hector are expected to reach southeast
and east facing shores of the Big Island and eastern Maui late
today, likely becoming large and dangerous by late tonight and
Wednesday.

WIND: Tropical storm force winds are possible across Hawaii
County late tonight and Wednesday.

500 AM HST Tue Aug 07 2018

The satellite presentation of Hector has degraded slightly since
the previous advisory, with cooling temperatures noted within the
slowly shrinking eye of the hurricane. Aircraft reconnaissance data
from the mission flown between 06Z and 12Z by the Air Force Reserve
53rd Weather Reconnaissance Squadron indicated that Hector was
weakening, confirming what was being seen in satellite imagery. The
last report from the overnight mission measured a surface wind of
107 knots in the northwest eye wall around 1030Z, on their way back
to Honolulu. The various 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 6.2 (120 knots). The initial intensity was weighted
equally between the various satellite estimates and the
observational data from the aircraft, taking into account that the
aircraft could have very easily under sampled the strongest winds
within the hurricane. As a result, the initial intensity with this
advisory is set at 115 knots with a motion remaining locked in at
280/14 knots.

The latest model guidance remains tightly clustered and brings
Hector just north of due west today. A building subtropical ridge
to the north of the Hawaiian Islands should then steer Hector
nearly due westward tonight 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 lies virtually on top of the previous
track and is very close to the model consensus. The forecast track
brings the center of Hector roughly 165 miles south of the
Big Island as a strong category 2 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 on Saturday.
There are a couple factors that should lead to some gradual
weakening over the next couple of 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 west of the Hawaiian Islands Thursday through
Saturday. Additionally, very dry mid-level air will continue to
surround the storm through the forecast period, and this is should
lead to gradual weakening of the system over the next couple days.
The intensity of Hector is then expected to level off and perhaps
increase slightly by the 72 and 96 hour forecast points Thursday
through Friday as it encounters the higher SSTs. Some weakening
should then ensue on 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 downward today through Wednesday night, then is nearly the
same as the previous forecast from Thursday through Saturday. This
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 better performers recently.

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