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Hurricane Hector Discussion Number 7

Wiki-Hurricanes Forecast Center

2:00 AM PDT Thu Aug 2 2018

Somewhat unexpectedly, Hector has rapidly intensified into a hurricane this morning. Infrared satellite animations show that the compact central dense overcast evident this afternoon has expanded and become more symmetric. Microwave images from as soon as 23z showed little evidence of an inner core; however, a series of passes between 2z and 4z showed the rapid materialization of an eyewall. Hints of an eye have been visible on infrared imagery for the past several frames, despite core convection colder than -80C. Final satellite estimates were T3.4/53kt from UW-CIMSS and T3.5/55kt from both SAB and TAFB. However, raw estimates from UW-CIMSS have increased to T3.9/63kt, and the PT value from SAB was T4.0/65kt. Given the latter values, as well as the rapid improvement in presentation on satellite, the initial intensity is set to 65kt.

HWRF is performing miles ahead of any other model, suggesting many runs ago that Hector would quickly intensify into a hurricane this morning. That being said, the HWRF continues to show noticeable weakening of the storm over the next 24 to 36 hours, with the minimum pressure rising from 981mb to 990mb. The GFS and its parallel also show slight pressure rises during that time period. The culprit, as has been advertised in previous advisories, appears to be the interjection of 15-20kt of northeasterly wind shear and dry air. This shear is observable as high-level cirrus impinges on Hector's core, though clearly it has not begun to make an impact yet. Given how well the HWRF has been performing so far, my updated forecast does indicate slight weakening over the next day. Thereafter, however, wind shear should decrease below 5kt while the environment remains adequately moist and sea surface temperatures adequately warm. This should lead to steady, if not rapid, intensification of the system during the days two to four time frame, and Hector is now expected to become a major hurricane as it enters the Central Pacific. By day five, some dry air entrainment and marginal ocean temperatures may cause the storm to level off in intensity.

Hector continues to move west around 11kt, steered by subtropical ridging to its north. This ridge should only intensify over the next few days, directing Hector on a west-southwest course on days two through four. A turn back toward the west is expected by day five. It is too soon to determine how close Hector may come to the Hawaiian Islands outside the forecast period, and what impacts may occur as a result.

FORECAST POSITIONS AND MAX WINDS

INIT 02/0900Z 65 KT 75 MPH

12H 02/1800Z 60 KT 70 MPH

24H 03/0600Z 55 KT 65 MPH

36H 03/1800Z 65 KT 75 MPH

48H 04/0600Z 80 KT 90 MPH

72H 05/0600Z 95 KT 110 MPH

96H 06/0600Z 105 KT 125 MPH

120H 07/0600Z 105 KT 125 MPH

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