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Hurricane Hector Discussion Number 19

Wiki-Hurricanes Forecast Center

8:00 AM PDT Sun Aug 5 2018

Hector continues to cruise along westward with not much change in strength, with infrared satellite images showing a strong central dense overcast with intermittent banding features in the northern semicircle. Cirrus is flowing radially outward in all quadrants with no clear signs of inhibition, signifying favorable upper-level winds. A microwave pass from 0931Z showed that the eywall was open to the south, and hinted at the possibility of another eyewall replacement cycle. However, the supposed secondary eyewall is not currently solidifed. Both SAB and TAFB estimated final T-values of T5.5/102kt, with UW-CIMSS indicating T6.0/110kt. With good agreement between these estimates, the intensity for Hector is maintained at 110 kt.

No changes to the track forecast for Hector as the same west-northwest curve is anticipated today, though the degree to which this slant occurs depends on the weakness of the subtropical ridge north of Hector. General consensus between the ensemble members of the EPS delay this turn until tomorrow, while most other stiatistical gudiance initiates the turn slowly today. A westerly course should resume by around 96 hours after which ridging rebuilds near Hawaii. Ensemble guidance has sharpened on a track 50-150 miles south of Hawaii's Big Island some time Wednesday afternoon or evening, which should keep the worst effects offshore. However, rough surf is highly likely for the Hawaiian Islands, and some areas of Big Island, particularly elevated regions, could see gale-force winds and higher gusts. A landfall cannot be ruled out this time, but has become less probable as the forecast has become more clear.

Hector has done well in an area of marginal moisture as observed on water vapor, and despite several changes in its core structure the past day or so it has managed for the most part to avoid significant intrusions of dry air thanks to a low shear environment. Such conditions are typically supportive of intensity maintenance, which Hector has demonstrated. There remains a decent probability of intensification in the next two days, but afterwards the environment dries sufficiently enough where it could be difficult for Hector to reap much from the ocean waters despite favorable upper-level winds. From then on, Hector will most be depending on its own core to maintain its intensity, and likely weaken slowly over time. At the end of the forecast run, once Hector has moved past is closest approach with the Hawaiian Islands, warming sea surface temperatures and a favorable divergent flow aloft kicked up by a nearby trough could allow Hector to reintensify. No significant changes introduced in this advisory's intensity forecast.

An NOAA Gulfstream-IV aircraft is expected to take off this afternoon to sample upper-air conditions around Hector, which may clarify conditions observed in model guidance for both track and intensity parameters.

FORECAST POSITIONS AND MAX WINDS

INIT 05/1500Z 110 KT 125 MPH

12H 06/0000Z 115 KT 130 MPH

24H 06/1200Z 120 KT 140 MPH

36H 07/0000Z 115 KT 130 MPH

48H 07/1200Z 110 KT 125 MPH

72H 08/1200Z 95 KT 110 MPH...NEARING HAWAII

96H 09/1200Z 85 KT 100 MPH...LEAVING HAWAII

120H 10/1200Z 90 KT 105 MPH