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Hurricane Hector Discussion Number 38

Wiki-Hurricanes Forecast Center

5:00 AM HST Thu Aug 9 2018

Hector has shirveled up slightly on satellite imagery during the overnight, with cloud tops warming and the eye becoming less distinct. The culprit appears to have either been an eyewall replacement cycle faintly noted on GMI microwave imagery from 0951Z or a possible passive intrusion of some dry air as implicated by water vapor imagery showing a thinning of moisture content in the storm's western semicircle. Subjective satellite intensity estimates remain at a consensus T6.0/115kt from all three primary satellite estimating agencies, though SAB estimated a final score of T5.0/90kt. UW-CIMSS ADT current intensity estimates are at T5.7/107kt. Given the partial structure of an inner eyewall as observed in microwave data, the intensity for Hector has been lowered slightly to 110 kt, and Hector remains a powerful hurricane.

Hector is tracking steadily towards the west-northwest, and is expected to gradually turn more towards the northwest with time as the western periphery of the steering subtropical ridge north of Hawaii is sharpened meridionally by a nearby tropical upper-tropospheric trough. An upper-leve low should detach from the trough as it moves away, with the ridge reconnecting with another ridge over the western Pacific to fill the pressure vacuum left behind by the trough. Hector is forecast to move between these features, secruing the northwest trajectory through the next five days.

For the time being, the nearby TUTT cell and Hector are oriented in a manner such that the upper-level wind flow is aiding divergent flow over the hurricane. Beginning tomorrow, Hector's close proximity to the upper-level low will bring it in an unfavorable shearing flow that would more harmful than helpful. Indeed, SHIPS diagnostic outputs show as high as 30 kt unfavorable shear on Sunday which would most likely disrupt Hector's persistent core significantly. Statistical guidance generally weakens Hector from here on out at a fairly linear rate due to worsening conditions. The late-morning hours and afternoon today are likely to be the last opportunity Hector has to reintensify before shear worsens, with sea surface temperatures falling to unfavorable levels in around four days. Slight strengthening is depicted today before an extending weakening trend leaves Hector a tropical storm as it moves through the West Pacific basin.

MAXIMUM WINDS FORECAST

INIT 10/1500Z 110 KT 125 MPH

12H 11/0000Z 115 KT 130 MPH

24H 11/1200Z 110 KT 125 MPH

36H 12/0000Z 105 KT 120 MPH

48H 12/1200Z 85 KT 100 MPH

72H 13/1200Z 70 KT 80 MPH

96H 14/1200Z 55 KT 65 MPH...WEST PACIFIC

120H 15/1200Z 40 KT 45 MPH...WEST PACIFIC