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Hurricane Hector Discussion Number 41

Wiki-Hurricanes Forecast Center

5:00 AM HST Sat Aug 11 2018

The structure of Hurricane Hector is gradually declining as it tracks towards the northwest. The once prominent eye has, for the first time in a very long time, disappeared, and although it made a brief return this morning, it is likely that we won't see a traditional hurricane eye from this point forward. Enhanced infrared imagery does show a slight warm spot embedded in a central dense overcast with rainbands spreading outward north of the center of circulation, with little activity south of the core convection. Microwave data this morning does not indicate too much more than the infrared wavelengths aside from confirming that the strongest activity in the eyewall is concentrated towards the north of a shrinking microwave eye. UW-CIMSS ADT seems to be having an issue with data downlink, so its latest values have been ignored. Both SAB and PGTW estimated a T6.0/115kt current intensity, while PHFO showed T5.5/102kt. In keeping with the lagged nature of weakening storms, the intensity of Hector has been reduced to 105 kt, despite lower Category 2 raw estimates.

Hector is tracking towards the northwest into an accelerated northwest flow crafted by both a subtropical ridge to its northeast and a trough to its northwest. In around two days, a mid-level low should detach from the trough and lose some latitude, bringing Hector within its fetch and causing it to curve towards the west. Hector is expected to cross the International Date Line in around 48 to 72 hours. Towards the end of the forecast window, Hector could begin curving towards the northwest in response to an approaching trough.

Hector is being battered by strong deep-layer wind shear of 15-30 kt, though the storm's convective activity and direction of the shear have reduced the impacts of such shear relative to what would typically expected at such a magnitude. However, the unfavorable winds have already done a number on the major hurricane's core and will continue to do so for at least the next two days or so due to the upper-level low. Sea surface temperatures are expected to remain favorable today, and perhaps rise to around 28°C before falling to marginal values in three days and unfavorable values in four. The combination of these conditions are expected to weaken Hector through the end of the forecast window, though due to lessened shear in the latter part of the forecast, the weakening phase may slow. The HWRF, HMON, and GFS all show a strengthening window in three to four days which could potentially raise Hector back to a typhoon, but I'm not really buying into this scenario given that the HWRF appears to show an erroneous band of 28-30°C surface tempeartures coincident with the reintensification. Still, conditions stablize just enough to allow for the slightest strengthening in around 48-96 hours, amidst an overall weakening.

MAXIMUM WINDS FORECAST

INIT 11/1500Z 105 KT 120 MPH

12H 12/0000Z 95 KT 120 MPH

24H 12/1200Z 80 KT 100 MPH

36H 13/0000Z 70 KT 80 MPH

48H 13/1200Z 60 KT 70 MPH

72H 14/1200Z 60 KT 70 MPH...WEST PACIFIC

96H 15/1200Z 55 KT 65 MPH...WEST PACIFIC

120H 16/1200Z 45 KT 50 MPH...WEST PACIFIC