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Hurricane Hector Discussion Number 32

Wiki-Hurricanes Forecast Center

5:00 PM HST Wed Aug 8 2018

According to microwave and radar from the PHWA site in South Shore, Hawaii, Hector is currently undergoing an eyewall replacement cycle, which in addition to shear assessed in the previous advisory appears to be the culprit for a degradation in satellite appearance throughout the day today. The secondary eyewall spans nearly 35 nautical miles across while the old eyewall, now a partial fragment in orbit about the secondary, spans about 12 nautical miles across. Cloud top fragmentation due to this process is evident on enhanced infrared imagery and evidence of a moat between the eyewalls is somewhat clear on visible imagery, but nonetheless the system remains well organized as a whole, with good outflow especially in the northern semicircle. SAB gave a final constrained value of T5.5/102kt with UW-CIMSS ADT in good agreement at T5.7/107kt. Thus, even despite the eyewall replacement cycle, we are not too far along in the process to diminish winds because of it, and thus the intensity remains at 105 kt.

A westerly track continues for Hector along the southern periphery of a mid-level subtropical ridge centered north of the Hawaiian Islands. A curve towards the northwest is anticipated beginning in around two days, accentuated by a shortwave trough that is increasing the poleward potential on the westward flanks of the aforementioned ridge. The primary players in the steering regime may change past five days, but out to 120 hours a gradual west-northwest to northwest heading is anticipated once the turn initiates. Given that the secondary eyewall in the ongoing eyewall replacement is roughly three times larger than the primary eyewall, it appears that this new eyewall replacement cycle will take a bit longer than previous eyewall replacement cycles in Hector's history, which took only a matter of hours. Thus, Hector's intensity as a result of this process should be subdued for a bit longer than what we've seen previously, compounded by some southwesterly shear from a nearby monsoonal equatorward trough. A tapering of shear and warming waters in around two days should allow for some gains in inetnsity before a nearby upper-level disturbance generates more shear near Hector in around four days, bringing about a new weakening phase.

MAXIMUM WINDS FORECAST

INIT 09/0300Z 105 KT 120 MPH

12H 09/1200Z 100 KT 115 MPH

24H 10/0000Z 95 KT 110 MPH

36H 10/1200Z 100 KT 115 MPH

48H 11/0000Z 105 KT 120 MPH

72H 12/0000Z 110 KT 125 MPH

96H 13/0000Z 95 KT 110 MPH

120H 14/0000Z 80 KT 90 MPH...WEST PACIFIC