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Tropical Storm Hector Discussion Number  51
NWS Central Pacific Hurricane Center Honolulu HI   EP102018
500 PM HST Sun Aug 12 2018
 
Hector continues to weaken this afternoon due to south-southwesterly
shear of around 10 kt over the system as analyzed by the latest
UW-CIMSS shear analysis. The low level circulation center in
visible satellite imagery remains on the south side of the
deepest convection.  The latest subjective Dvorak intensity
estimates were 3.5 (55 knots) from PHFO, SAB, and JTWC. The
satellite presentation clearly shows that slow weakening is ongoing,
but given the persistent deep convection near the low level
circulation center and necessary spin down time needed
as these systems weaken, will only lower the initial intensity to
60 knots with this advisory. The initial motion is set at 300/15
knots.
 
The latest model guidance remains tightly clustered through 72
hours, with the spread in the track guidance increasing at 96 and
120 hours. Hector is expected to continue on a west-northwest track
tonight 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 to a more westerly direction on Monday, 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 Wednesday night through Friday as Hector rounds the
southwest periphery of the upper level ridge. The new official
forecast track is very close to the consensus guidance as well as
the track from the previous advisory.
 
The intensity forecast calls for slow weakening of Hector over
the next 12 to 24 hours as the system will remain in southwesterly
shear of 10 to 15 kt. The shear is forecast to decrease beyond 24
hours, but the system will likely have weakened by this time and
will be moving over cooler sea surface temperatures. The intensity
guidance is in fairly good agreement through 36 hours, so confidence
during this portion of the forecast is fairly good. Most of the
intensity guidance levels off during the 36 through 48 hour time
frame while SHIPS guidance and AVNI indicating some strengthening. 
This seems rather aggressive given the state the hurricane is in at
the moment. As a result, the official intensity forecast calls for
slow weakening through Monday afternoon. Beyond 24 hours the
forecast intensity has been held steady through 48 hours, with slow
weakening expected at the end of the forecast period due to
increasing shear and cooler sea surface temperatures. Hector is
forecast to transition over to an extratropical system in about 96
hours.
 
Probabilities for tropical storm force winds reaching the
Northwestern Hawaiian Islands have decreased since the previous
advisory. A Tropical Storm Watch remains in effect for Kure Atoll
and Midway Atoll. The Tropical Storm Watch has been discontinued for
the waters between Midway Atoll and Pearl and Hermes Atoll. If
Hector remains on its forecast track to the west-northwest, the
Tropical Storm Watches currently in effect may be canceled later
tonight.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  13/0300Z 24.6N 177.0W   60 KT  70 MPH
 12H  13/1200Z 25.6N 179.3W   55 KT  65 MPH
 24H  14/0000Z 26.7N 177.6E   50 KT  60 MPH
 36H  14/1200Z 27.8N 174.5E   50 KT  60 MPH
 48H  15/0000Z 28.8N 171.4E   50 KT  60 MPH
 72H  16/0000Z 31.5N 165.8E   45 KT  50 MPH
 96H  17/0000Z 35.1N 162.7E   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  18/0000Z 39.8N 162.8E   35 KT  40 MPH...POST-TROP/EXTRATROP
 
$$
Forecaster Burke
 
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