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Hurricane Hector Discussion Number 24

Wiki-Hurricanes Forecast Center

2:00 PM PDT Mon Aug 6 2018

A US Air Force reconnaissance C-130 investigating Hector this afternoon found winds supportive of raising the hurricane to a 130 kt Category 4 intensity. Maximum flight level winds at the 700 hPa level were 142 kt in the northwest quadrant, with peak estimated surface winds of 137 kt from the stepped-frequency microwave radiometer instrument onboard the aircraft. Dropsonde data verified these approximations and lends confidence to the current intensity estimate. It could be argued that the northeastern quadrant presented stronger winds, though as an annular tropical cyclone it is anticipated that winds would be radially symmetric about the eye. The reconaissance data indicates that satellite intensity estimates have done well in determining the storm's strength from afar. Hector has maintained a fairly steady appearance throughout the day, with various pulsations of cloud top temperatures around the central dense overcast and an eye that has trended warmer, indicative of some strengthening since this morning. Various eyewall mesocyclones are also evident in high-resolution imagery within the eye. The infrared configuration of the hurricane remains annular and should remain that way as new convective growth in convection-free locations is not favored at this time.

Hector's motion has been slightly north of west, and the storm has thus moved north of 15°N. This motion is anticipated for the next day or, gradually dampening to a more straightforward westerly path which is expected to continue to the end of the forecast window. Some motion to the west-southwest could take place if the ridge now centered 300 mi north of Hawaii tilts enough to push Hector slightly southward. Models are tightly clustered over the next five days, so this is a high confidence track forecast.

A track 150 miles south of Hawaii as currently anticipated steers Hector clear of the most unfavorable effects of downsloping winds from Hawaii's Big Island. Sea surface temperatures, though marginal, can support a hurricane of considerable intensity through the entire forecast window. However, lapse rates do decrease to more unfavorable values in about two days, which could prevent cold convective tops from appearing with as much frequency as they do now. Model guidance generally sees some gradual tapering off of Hector's intensity, but given the storm's annular state, Hector could remain a powerful storm for the entirety of the next five days. Conditions become more favorable at day 4 and day 5 southwest of Hawaii, and thus reintensification is depicted during that time.

FORECAST POSITIONS AND MAX WINDS

INIT 06/2100Z 130 KT 150 MPH

12H 07/0600Z 125 KT 145 MPH

24H 07/1800Z 115 KT 130 MPH

36H 08/0600Z 105 KT 120 MPH

48H 08/1800Z 95 KT 110 MPH

72H 09/1800Z 95 KT 110 MPH

96H 10/1800Z 100 KT 115 MPH

120H 11/1800Z 105 KT 120 MPH