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Hurricane Hector Forecast Discussion Number 19
2018-08-05 10:51:16| National Hurricane Center (East Pacific)
Issued at 200 AM PDT Sun Aug 05 2018 218 WTPZ45 KNHC 050851 TCDEP5 Hurricane Hector Discussion Number 19 NWS National Hurricane Center Miami FL EP102018 200 AM PDT Sun Aug 05 2018 Hector has maintained a well-defined, 10-nmi-diameter eye inside a gradually shrinking central dense overcast. Satellite intensity estimates at 0600Z from TAFB and SAB supported an intensity of 102 kt, while UW-CIMSS ADT raw estimates have been near 100 kt. However, more recent infrared satellite images indicate intensity estimates just below 115 kt, so the advisory intensity of 110 kt is based on a blend of the available estimates with more weight placed on recent IR trends. The initial motion remains 275/10 kt. A large, deep-layer ridge to the north of Hector is expected to steer the hurricane westward for the next 24 h or so, followed by a modest poleward 'stair-step' in the track through 72 h due to a dissipating frontal trough pushing southward and becoming stationary northeast of the Hawaiian Islands, which should weaken the low-level ridge. After that time, however, the surface trough is forecast to weaken, allowing the ridge to build back across the Islands, forcing Hector back onto a more westerly course on days 4 and 5. More weakening of the ridge in 48-72 hours has resulted in yet another northward shift in the guidance envelope, with the HWRF and HMON models bringing Hector within 60 nmi of the Big Island on day 4. The new NHC forecast track has been shifted slightly northward as a result, but lies just a tad south of the consensus models out of respect for the reliable ECMWF model, which is the southernmost of all of the global and regional models. Outer banding features have become less evident since the previous advisory, and with Hector moving into an increasingly drier airmass, the chances of Hector evolving into an annular hurricane are increasing in the longer term. Although the hurricane will be embedded within a light vertical wind shear environment, marginal SSTs and a much drier airmass characterized by mid-level humidity values less than 40 percent are expected to produce a slow weakening trend throughout the forecast period. The official intensity forecast is a little lower than the previous advisory, and closely follows the intensity consensus models HCCA, FSSE, and IVCN, which all show steady weakening. While the official forecast track continues to lie south of the Hawaiian Islands, it is too soon to determine what kind of impacts might occur in the state, since track errors can be large at long time ranges. This remains a good time for everyone in the Hawaiian Islands to ensure they have their hurricane plan in place. For additional information on any potential local impacts from Hector in Hawaii, please refer to products issued by the NWS Weather Forecast Office in Honolulu at http://www.prh.noaa.gov/hnl . FORECAST POSITIONS AND MAX WINDS INIT 05/0900Z 14.4N 135.7W 110 KT 125 MPH 12H 05/1800Z 14.6N 137.5W 110 KT 125 MPH 24H 06/0600Z 15.0N 139.9W 105 KT 120 MPH 36H 06/1800Z 15.6N 142.7W 105 KT 120 MPH 48H 07/0600Z 16.2N 145.6W 100 KT 115 MPH 72H 08/0600Z 16.9N 151.8W 95 KT 110 MPH 96H 09/0600Z 17.2N 157.4W 90 KT 105 MPH 120H 10/0600Z 17.7N 162.6W 85 KT 100 MPH $$ Forecaster Stewart
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