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Hurricane Hector Discussion Number  45
NWS Central Pacific Hurricane Center Honolulu HI   EP102018
500 AM HST Sat Aug 11 2018
 
Hector's ragged and cloud-filled eye is surrounded by a nearly solid
ring of very cold cloud tops, but the overall structure of the
cyclone is diminishing. Outflow has become increasingly restricted
in the southern semicircle as Hector moves closer to southerly shear
associated with a developing low aloft to the west-northwest.
Subjective Dvorak current intensity estimates from HFO/SAB/PGTW
ranged from 5.5/105 kt to 6.0/115 kt, while Final-T numbers were as
low as 4.5/77 kt. Based on a blend of these values, and the
assumption that a weakening of a cyclone's wind field will lag the
satellite presentation, the initial intensity for this advisory is
maintained at 105 kt.

The initial motion estimate for this advisory is 300/10 kt. The 
steering environment is characterized by a mid-level ridge to the 
northeast and a mid- to upper-level low to the northwest. As the 
ridge remains stationary and the low becomes better developed, a
slight turn toward the northwest is expected in the short term, with
an increase in forward speed. By Monday, the ridge will build to the
north of Hector, inducing a slight turn toward the west that will
persist until the end of the forecast period, at which time Hector
is expected to make a turn back toward the northwest. The updated
forecast track was once again nudged to the left of the previous
forecast and lies close to HWFI/TVCN guidance. Note that FSSE
guidance appears to have problems with the International Date Line
that is causing errors with the tracker. 

A fairly rapid rate of weakening is expected over the next 36 hours 
as south to southwesterly shear increases to near 30 kt, with a
slower rate of weakening expected thereafter as shear relaxes. After
24 hours, SSTs along the forecast track will steadily decrease from
the current 28C, but are still expected to be near 26C on day 3, and
near 25C on day 5. With weaker shear beyond 36 hours, SHIPS
indicates little change in intensity, keeping Hector a minimal
hurricane through day 5. The HWRF indicates the upcoming shear
increase will weaken Hector to a minimal tropical storm within 48
hours before it re-intensifies on days 4 and 5. The official
forecast is close to the previous forecast and closely follows the
IVCN consensus, with increased guidance spread in the later forecast
periods leading to decreased confidence. 

Given the close approach 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. Interests on 
Midway and Kure Atolls should monitor continue to monitor the 
progress of Hector.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  11/1500Z 19.3N 170.1W  105 KT 120 MPH
 12H  12/0000Z 20.5N 171.6W   90 KT 105 MPH
 24H  12/1200Z 22.2N 174.0W   80 KT  90 MPH
 36H  13/0000Z 23.7N 176.6W   70 KT  80 MPH
 48H  13/1200Z 24.8N 179.3W   65 KT  75 MPH
 72H  14/1200Z 26.6N 174.9E   60 KT  70 MPH
 96H  15/1200Z 29.0N 169.0E   55 KT  65 MPH
120H  16/1200Z 32.0N 164.0E   50 KT  60 MPH
 
$$
Forecaster Birchard
 
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