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Hurricane Hector Discussion Number  35
NWS Central Pacific Hurricane Center Honolulu HI   EP102018
500 PM HST Wed Aug 08 2018
 
Hector continues to have the satellite appearance of a strong
hurricane, with cold cloud tops surrounding a well-developed eye,
while radar reflectivity data highlight a concentric eyewall
structure typically seen in intense hurricanes. Subjective
satellite-based intensity estimates range from 102 kt to 115 kt,
while ADT from UW-CIMSS is near 100 kt. Hurricane Hunters from the
53rd Weather Reconnaissance Squadron completed their final mission
into Hector this morning, and sampled peak flight-level winds near
106 kt. With little overall change in satellite appearance since the
aircraft departed, the initial intensity for this advisory is
maintained at 100 kt.
 
The initial motion for this advisory is 275/14 kt as a mid-level
ridge north of the cyclone continues to support a westward
trajectory to the south of the main Hawaiian islands. The ridge will
move little through Thursday, and the high-confidence short-term
track forecast keeps Hector moving steadily west. Hector is expected
to gradually turn toward the west-northwest in 36-48 hours as it
reaches the southwestern periphery of the ridge, with a more decided
turn toward the northwest expected after 72 hours. The updated track
forecast lies close to the previous forecast and a tightly-packed
guidance envelope through day 3. Increased guidance spread on days 4
and 5 arises due to differences in the forecast strength and
position of the ridge, and a developing low aloft to the northwest
of Hector. With the previous forecast track near the middle of the
guidance envelope, and close to the high-performing TVCN consensus,
little change was made.
 
Rather unusual to witness concentric eyewalls from a land-based
Hawaii radar as has occurred with Hector today. While interesting
from a science viewpoint, this adds some complexity to the short-
term intensity and wind field forecast, as an eyewall replacement
cycle (ERC) could soon follow. This process would lead to a
temporary weakening of the cyclone, and some changes in the wind
field. With uncertainty surrounding the timing and eventuality of
any ERC, the intensity forecast anticipates little overall change
over the next couple of days as Hector remains in a light shear
environment with SSTs near 27C. Increasing southwesterly shear in
the later forecast periods and decreasing SSTs toward day 5 will
likely lead to weakening. The official forecast is close to SHIPS
guidance, and follows trends indicated by FSSE and IVCN, but is not
as aggressive in indicating weakening. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0300Z 16.7N 156.8W  100 KT 115 MPH
 12H  09/1200Z 16.7N 159.0W   95 KT 110 MPH
 24H  10/0000Z 16.9N 161.8W   95 KT 110 MPH
 36H  10/1200Z 17.3N 164.6W   95 KT 110 MPH
 48H  11/0000Z 18.1N 167.4W   90 KT 105 MPH
 72H  12/0000Z 20.3N 172.5W   90 KT 105 MPH
 96H  13/0000Z 23.0N 177.0W   80 KT  90 MPH
120H  14/0000Z 26.0N 178.0E   70 KT  80 MPH
 
$$
Forecaster Birchard
 
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