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Hurricane Hector Discussion Number  48
NWS Central Pacific Hurricane Center Honolulu HI   EP102018
1100 PM HST Sat Aug 11 2018
 
The satellite presentation of Hector has degraded significantly
from the previous advisory, as the system is getting hammered by
around 30 knots of south-southwesterly shear as indicated by the
latest UW-CIMSS shear analysis. This has resulted in rapid weakening
of the system this evening. The latest subjective Dvorak intensity 
estimates were 5.0 (90 knots) from PHFO and JTWC, while SAB came in 
with 4.5 (77 knots). Meanwhile the Advanced Dvorak Technique from
UW-CIMSS was 5.2 (95 knots). Given the current satellite
presentation of the system, the initial intensity is set on the
lower side of the estimates at 80 knots. The poor satellite
presentation is making it very difficult to locate the center of
Hector, but an 0516Z SSMIS pass was helpful in determining its
location. The initial motion is set at 315/13 knots. 

The latest model guidance remains tightly clustered through 72 
hours, with increasing spread by 96 hours and a considerable amount 
of spread by 120 hours. Hector is expected to track off to the 
northwest tonight and Sunday on the eastern periphery of an upper 
level low to the west of the International Date Line. The system is 
expected to make a turn more westerly Sunday night and continue on 
this course through Wednesday as an upper level ridge builds north 
of the system. A turn toward the northwest and eventually north is 
then expected by Thursday and Friday as Hector rounds the southwest 
periphery of the upper level ridge. Given the latest guidance
trends and the current northwesterly motion of the system, the
official forecast track was nudged slightly north of the previous
advisory through 48 hours, which is very close to the model
consensus. Beyond 48 hours, the forecast track is very close to the
model consensus and GFEX tracks, which is also close to the track
from the previous advisory. 

The intensity forecast calls for fairly rapid weakening of Hector
over the next 24 hours as the system will be in a very hostile
environment under 20 to 30 knots of southwesterly shear. The shear
is forecast to decrease beyond 24 hours, but the system will likely
have weakened considerably by this time and will be moving over
marginal sea surface temperatures between 79 and 81 degrees
Fahrenheit. There is quite a bit of spread in the intensity guidance
beyond 24 hours, with the HWRF continuing to show rapid weakening of
Hector through 36 hours while the intensity in the consensus
guidance levels off. The dynamical models then show an increase in
intensity between 48 hours and 96 hours, while the consensus
guidance remains pretty much steady state. The official forecast
will show continued rapid weakening through 24 hours, then show a
leveling off in the intensity from 36 to 72 hours with gradual
weakening beyond 72 hours.

Given the close approach Hector is expected to make to the 
Northwestern Hawaiian Islands on Sunday and Monday, a Tropical
Storm Watch remains posted for the area from Lisianski Island to
Pearl and Hermes Atoll, as well as fore Midway and Kure Atolls.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  12/0900Z 22.1N 172.9W   80 KT  90 MPH
 12H  12/1800Z 23.4N 174.8W   75 KT  85 MPH
 24H  13/0600Z 24.9N 177.4W   65 KT  75 MPH
 36H  13/1800Z 26.0N 179.7E   60 KT  70 MPH
 48H  14/0600Z 26.8N 176.8E   60 KT  70 MPH
 72H  15/0600Z 28.6N 170.4E   60 KT  70 MPH
 96H  16/0600Z 31.1N 165.1E   55 KT  65 MPH
120H  17/0600Z 34.3N 162.4E   50 KT  60 MPH
 
$$
Forecaster Jelsema
 
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