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 432 
 WTPA44 PHFO 081440
 TCDCP4
  
 Tropical Storm Norman Discussion Number  46
 NWS Central Pacific Hurricane Center Honolulu HI   EP162018
 500 AM HST Sat Sep 08 2018
  
 Deep convection near the exposed low-level circulation center
 (LLCC) of Norman dissipated around 07Z last evening, and has not 
 returned as of advisory time, with only a small area of convection
 present about 90 nm north of the center. The LLCC has remained
 clearly visible in infrared and fog product satellite imagery during
 the night. The subjective Dvorak current intensity estimate came in
 at 3.0/45 kt from PHFO, while JTWC estimated 3.0 or 45-50 kt using
 the subtropical method. The latest objective estimates remain lower,
 with CIMSS SATCON showing 43 kt, and CIMSS ADT 2.3/32 kt. The
 overnight ASCAT pass missed Norman, but a 0648Z ScatSat pass found
 winds of 40 kt in the northeast quadrant. The initial intensity is
 lowered to 50 kt for this advisory, reflecting an assumed gradual
 spindown from the stronger winds measured by the 53rd Weather
 Reconnaissance Squadron aircraft on Friday, and this may be
 generous.
 
 Norman appears to have turned more to the northwest during the
 night, likely in response to the loss of deep convection, and the
 initial motion estimate for this advisory is 320/8 kt. All of the
 reliable guidance insists that the current northwest motion is
 temporary, and that Norman will quickly resume a north-northwest
 motion today, becoming almost due north thereafter, as it moves
 between a deep-layer ridge centered to the east and a cutoff low
 to the west. The guidance envelope did not shift much from the 
 previous advisory. The new track forecast is on the left side
 of the reliable guidance for the first 24 hours due to the current
 motion, then near the previous forecast and the consensus HCCA and
 TVCE aids thereafter. 
 
 The CIMSS vertical wind shear estimate for this advisory is 235/52
 kt, and very strong southwest vertical wind shear of 45 to 55 kt is
 expected to persist over Norman for the next 36 hours or so, with
 some decrease possible thereafter. However, the system is forecast
 to be moving over cool SSTs below 25C by that time. Also, the SHIPS
 and experimental ECMWF-based SHIPS guidance now both categorize
 Norman as extratropical in 24 hours. This seems plausible given the
 asymmetric wind field observed by the ScatSat pass, the fact that
 the system already is acquiring a rather subtropical appearance, and
 Norman's increasingly shallow warm core as depicted by the FSU
 phase-space diagrams. The new intensity forecast continues to weaken
 Norman, and makes it a post-tropical gale center in 36 hours. If
 Norman does not regain deep convection near the LLCC soon, it will
 likely be declared post-tropical considerably sooner than shown in
 this forecast.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  08/1500Z 26.0N 154.4W   50 KT  60 MPH
  12H  09/0000Z 27.4N 154.8W   45 KT  50 MPH
  24H  09/1200Z 29.1N 154.9W   40 KT  45 MPH
  36H  10/0000Z 31.2N 154.7W   40 KT  45 MPH...POST-TROPICAL
  48H  10/1200Z 32.9N 154.5W   35 KT  40 MPH...POST-TROPICAL
  72H  11/1200Z 34.5N 155.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
  96H  12/1200Z 35.5N 156.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 120H  13/1200Z...DISSIPATED
  
 $$
 Forecaster Jacobson
  
 
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