ZCZC HFOTCDCP4 ALL TTAA00 PHFO DDHHMM Tropical Storm Norman Discussion Number 45 NWS Central Pacific Hurricane Center Honolulu HI EP162018 1100 PM HST Fri Sep 07 2018 The exposed low-level circulation center (LLCC) of Norman remains clearly evident in infrared and fog product satellite imagery this evening, with diminishing deep convection confined only to the northeast quadrant in a strongly sheared pattern. The subjective Dvorak current intensity estimate came in at 3.5/55 kt from PHFO, while JTWC estimated 3.0 or 45-50 kt using the subtropical method. Objective intensity estimates are lower, with CIMSS SATCON showing 44 kt, and CIMSS ADT 2.8/41 kt. Recent satellite images since the 06Z synoptic time also show the remaining deep convection becoming increasingly separated from the LLCC. Out of respect for the stronger winds found around midday today by the 53rd Weather Reconnaissance Squadron aircraft penetration as well as the 2001Z ASCAT pass, will lower the initial intensity for this advisory only slightly to 55 kt. The initial motion estimate for this advisory is 335/8 kt. Norman continues to move to the north-northwest between a deep-layer ridge centered to the east, and a longwave trough to the northwest. The latest track guidance has shifted a bit more to the right, in better agreement with the motion of Norman during the past 18 hours or so, and shows the cyclone continuing on a north-northwest to northward course during the next 2 to 3 days. The new track forecast lies close to the consensus HCCA and TVCE objective aids, and was shifted only slightly to the right from the previous forecast. The CIMSS vertical wind shear estimate for this advisory is 230/56 kt, and is supported by recent GOES satellite-derived upper-level wind retrievals. Very strong wind shear of 45-55 kt will persist over Norman for the next 36 hours, with some decrease possible thereafter. However, the system is forecast to be moving over cool SSTs below 25C by that time. The combined effects of the shear and increasingly cool water should cause Norman to steadily weaken to a remnant low by 72 hours, then dissipate by day 5. It is worth noting that the GFS and ECMWF models maintain Norman as a stronger system, possibly transitioning toward extratropical after 72 hours, while the hurricane dynamical and statistical models show more rapid weakening. The official intensity forecast compromises between these extremes, and delays dissipation as compared to the statistical guidance, but does not keep Norman as strong as the GFS/EC and does not show extratropical transition. If the recent loss of deep convection near the LLCC persists, Norman could become post-tropical considerable sooner than indicated in this forecast. FORECAST POSITIONS AND MAX WINDS INIT 08/0900Z 25.6N 153.6W 55 KT 65 MPH 12H 08/1800Z 26.8N 154.0W 50 KT 60 MPH 24H 09/0600Z 28.6N 154.3W 45 KT 50 MPH 36H 09/1800Z 30.3N 154.3W 40 KT 45 MPH 48H 10/0600Z 32.3N 154.0W 35 KT 40 MPH 72H 11/0600Z 34.5N 154.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 12/0600Z 35.5N 156.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 13/0600Z...DISSIPATED $$ Forecaster Jacobson NNNN
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