ZCZC HFOTCDCP4 ALL TTAA00 PHFO DDHHMM Hurricane Norman Discussion Number 41 NWS Central Pacific Hurricane Center Honolulu HI EP162018 1100 PM HST Thu Sep 06 2018 Norman's satellite presentation certainly has not improved since this afternoon, with deep convection continuing to shear northward away from the low level circulation center (LLCC). No eye is noted in infrared imagery and animation is not very helpful in locating the center. With 30 to 40 kt of vertical shear continuing across Norman and tilting its core this evening, we relied on timely 0341 UTC and 0431 UTC SSMIS imagery to track the LLCC. Subjective Dvorak current intensity estimates were 4.5/77 kt from all three analysis centers, and ADT from UW-CIMSS was 66 kt. Given the continued apparent deterioration of this system, an initial intensity of 75 kt seems reasonable for this advisory. We rebested the 0000 UTC Norman position slightly to the left and slower to more align it with later SSMIS imagery. With this adjustment, the initial motion estimate for this advisory is a more northerly 325/7 kt. Norman is moving northwestward along the western flank of a ridge and into an upper trough to its north. Track guidance is tight through 48 hours, then pretty much all over the map afterwards as each model handles a shear-decapitated Norman differently. We maintained a forecast track in the middle of the envelope, along ECMWF through 24 hours, then along TVCE consensus from 36 through 72 hours. The forecast track was tapped slightly to the right through 72 hours to account for the more northerly initial motion, with the current track almost on top of the previous one at 96 and 120 hours. Norman will continue to experience very strong shear through 72 hours. This will weaken the tropical cyclone rather rapidly, particularly in light of the cooler sea surface temperatures ahead. Norman is expected to become a remnant low in 3 days. FORECAST POSITIONS AND MAX WINDS INIT 07/0900Z 22.5N 151.7W 75 KT 85 MPH 12H 07/1800Z 23.3N 152.5W 60 KT 70 MPH 24H 08/0600Z 24.4N 153.6W 50 KT 60 MPH 36H 08/1800Z 25.5N 154.6W 40 KT 45 MPH 48H 09/0600Z 26.5N 155.4W 35 KT 40 MPH 72H 10/0600Z 28.5N 157.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 11/0600Z 30.5N 158.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 12/0600Z 32.5N 160.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Powell NNNN
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