ZCZC HFOTCDCP4 ALL TTAA00 PHFO DDHHMM Hurricane Norman Discussion Number 29 NWS Central Pacific Hurricane Center Honolulu HI EP162018 1100 PM HST Mon Sep 03 2018 Norman continues to weaken this evening. The final visible satellite images of the day showed a cloud-filled eye, and cloud tops have warmed further during the past several hours. Subjective Dvorak current intensity estimates came in at 4.5/77 kt from PHFO, and 4.0/65 kt from SAB/JTWC, while the latest CIMSS ADT estimate is 4.2/70 kt. A blend of these estimates supports lowering the initial intensity to 75 kt for this advisory. The hurricane has turned slightly to an almost due west track this evening, and it appears that the anticipated decrease in forward speed has begun. The initial motion estimate is 275/15 kt, which is a few knots slower than the previous advisory. Westward motion with a further decrease in forward speed is expected to continue through the next 36 hours as Norman nears the southwestern periphery of a strong subtropical ridge centered to the northeast. Thereafter, the cyclone will gradually turn to the west-northwest then to the northwest as it moves around the end of the ridge and is increasingly steered by a large deep-layered trough over the North Pacific. Most of the reliable guidance has come into better agreement with the location and timing of this turn. The consensus guidance HCCA, TVCE and FSSE are tightly packed and in good agreement with the previous official forecast through 48 hours, then shift slightly to the right thereafter. The new official forecast is very similar to the previous forecast, and generally lies very close to the consensus aids in the middle of the guidance envelope. The CIMSS initial vertical wind shear estimate was 10 kt, and SHIPS guidance shows light shear continuing for another 48 hours as Norman continues tracking around the subtropical ridge. The main issue causing weakening for the hurricane at present appears to be marginal sea surface temperatures and ocean heat content. CIRA analysis shows that Norman should move into an area of slightly more favorable OHC after about 12 more hours, and the guidance shows intensity flattening out from 12 through 48 hours. Norman may actually re-intensity a bit during that time period, but opted to keep the intensity forecast level at 70 kt for this advisory. Thereafter, a rapid increase in wind shear, a drier surrounding airmass, and progressively cooler sea surface temperatures should cause steady weakening. The new intensity forecast is similar to the previous, and in good agreement with the consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 04/0900Z 19.9N 141.7W 75 KT 85 MPH 12H 04/1800Z 20.0N 143.7W 70 KT 80 MPH 24H 05/0600Z 20.0N 145.9W 70 KT 80 MPH 36H 05/1800Z 20.3N 147.8W 70 KT 80 MPH 48H 06/0600Z 20.9N 149.2W 70 KT 80 MPH 72H 07/0600Z 23.3N 151.3W 60 KT 70 MPH 96H 08/0600Z 26.0N 153.5W 45 KT 50 MPH 120H 09/0600Z 29.0N 155.0W 30 KT 35 MPH $$ Forecaster Jacobson NNNN