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Hurricane Hector Discussion Number 14

Wiki-Hurricanes Forecast Center

8:00 PM PDT Fri Aug 3 2018

Hector has rapidly intensified since the previous advisory. Infrared animations show a dramatic expansion of cloud tops cooler than -70C, and the eye has rapidly warmed to around 5C. This has resulted in satellite intensity estimates of T5.5/102kt from SAB and TAFB, while raw values from UW-CIMSS ADT have climbed to T6.1/117kt. It is worth pointing out that Hector is an extremely small hurricane; given that Dvorak is keenly sensitive to the width of convection, there is a good chance it is running too low in this case. It is also worth noting that a series of microwave passes between 22z and 0z shows that Hector is well into the process of an eyewall replacement cycle, which is reflected in a break in the deepest convection to the north in the most recent satellite frame. This may portend that Hector maximum winds are running below instantaneous Dvorak estimates, especially if the inner eyewall has already begun to erode and give way to the secondary feature. All told, the initial intensity is raised to a comfortable 110kt.

The environment Hector finds itself in is optimal to intensification, with wind shear around 5kt and mid-level relative humidity values around 60 percent. Ocean temperatures are fluctuating on either side of 27C, which suggests that Hector may not become an upper-end tropical cyclone; waters are certainly warm enough for continued intensification, however. The story with model guidance is mostly unchanged from past advisories, with the GFS, ECMWF, HWRF, and HMON indicating pressure falls for the next 48 to 72 hours, to varying degrees. The LGEM and SHIPS, meanwhile, remain sensitive to the marginal ocean temperatures, predicting slight strengthening over the next six hours before a steady decline thereafter. We still expect a drier environment around day 4 to promote some weakening, although guidance suggests this may be short-lived, with maintenance or even intensification possible just outside the day 5 window.

Hector continues its steady westward march this evening, a trajectory that should continue for the next 48 hours. By day 3, a slight erosion of the subtropical ridge to the storm's north should promote a turn toward the west-northwest. A redevelopment of the high pressure should force Hector back due west by day 5, a solution that may keep the brunt of the hurricane south of the Hawaiian Islands. Still, it is too early to say this with high confidence, and a direct impact on Hawaii still cannot be ruled out at this time.

FORECAST POSITIONS AND MAX WINDS

INIT 03/2100Z 110 KT 125 MPH

12H 04/0600Z 110 KT 125 MPH

24H 04/1800Z 115 KT 130 MPH

36H 05/0600Z 120 KT 140 MPH

48H 05/1800Z 120 KT 140 MPH

72H 06/1800Z 110 KT 125 MPH

96H 07/1800Z 95 KT 110 MPH

120H 08/1800Z 85 KT 100 MPH