ZCZC HFOTCDCP4 ALL TTAA00 PHFO DDHHMM Hurricane Norman Discussion Number 34 NWS Central Pacific Hurricane Center Honolulu HI EP162018 500 AM HST Wed Sep 05 2018 Norman appears to have rapidly intensified overnight. Although the eye has become slightly less distinct during the past couple of hours, the satellite fix agencies (SAB, JTWC, and PHFO) were in unanimous agreement that the subjective Dvorak current intensity estimate was 5.5/102 kt. In addition, the most recent UW-CIMSS ADT estimate was 5.8/110 kt. Based on these estimates, we have increased the initial intensity to 100 kt for this advisory. Norman has been moving just south of due west, or 265 deg, at 10 kt. It is being steered by a deep subtropical ridge located to the north and northeast. The western edge of this ridge is forecast to erode later today as an upper-level trough digs down toward the region north of the Hawaiian Islands during the next couple of days. As a result, the forecast guidance is showing an increasing spread in the track forecasts starting in 48 hours. This is likely due to the way the different models forecast the weakening of the western flank of the ridge due to the upper-level trough. This weakening of the ridge is expected to cause Norman to slow its forward motion and gradually turn toward the west-northwest starting later today. This will likely be followed by a turn toward the northwest starting later tonight or early Thursday, and continuing into this weekend. The latest forecast track has been shifted to the left of the previous forecast, and remains close to the middle of the guidance envelope through the next 2 days. Even though the guidance spread increases during days 3 through 5, all of the models support the general northwestward motion persisting. The latest official forecast is also very close to the FSSE, TVCE, HCCA and GFEX consensus model guidance. Norman is expected to remain a hurricane for the next couple of days. The latest CIRA ocean heat content (OHC) analysis appears to support it remaining near major hurricane intensity today. Vertical wind shear has gradually increased to near 15 kt based on the latest UW-CIMSS estimate, which may be contributing to some of the degradation of the eye this morning. By tonight, most of the guidance is in good agreement that Norman will start to weaken under the effects of increasing southwesterly vertical wind shear, cooler SSTs, and drier environmental conditions. This weakening will likely persist through day 5, when Norman is forecast to become a remnant low. The intensity forecast follows similar trends of the prior advisory, and favors the latest ICON guidance. The NOAA Gulfstream IV aircraft is scheduled to conduct another mission to sample the environment around Norman later today. The valuable data collected during this mission will be used to improve the initialization of the various hurricane forecast models that we use to predict the motion and intensity of Norman later today and tonight. FORECAST POSITIONS AND MAX WINDS INIT 05/1500Z 19.5N 147.7W 100 KT 115 MPH 12H 06/0000Z 19.8N 148.9W 100 KT 115 MPH 24H 06/1200Z 20.4N 150.2W 90 KT 105 MPH 36H 07/0000Z 21.4N 151.3W 80 KT 90 MPH 48H 07/1200Z 22.6N 152.3W 70 KT 80 MPH 72H 08/1200Z 24.9N 154.3W 45 KT 50 MPH 96H 09/1200Z 27.0N 156.5W 30 KT 35 MPH 120H 10/1200Z 28.6N 158.0W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Houston NNNN
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