863 
 WTPA45 PHFO 311508
 TCDCP5
 
 HURRICANE MADELINE DISCUSSION NUMBER  21
 NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP142016
 500 AM HST WED AUG 31 2016
  
 After a period of rapid intensification that ended early Tuesday,
 Madeline has been rapidly weakening since Tuesday afternoon,
 primarily due to increased vertical wind shear. Latest satellite
 images show that the cyclone's structure has degraded significantly,
 with the center estimated to be on the southwest side of the cold
 cloud tops. The subjective Dvorak current intensity estimates ranged
 from 4.0/65 kt to 5.0/90 kt, while data-T values ranged from 3.0/45
 kt to 4.0/65 kt. Based on a blend of this data, and the aircraft
 data from earlier in the night, the initial intensity for this
 advisory has been lowered to 70 kt. 
 
 While low cloud lines seen in a 1129Z VIIRS day night image hinted
 that the low-level center of Madeline was becoming partially
 exposed, a timely 1126Z GPM pass confirmed this. Using this
 position, the initial motion vector for this advisory is 260/12 kt,
 which represents a slight acceleration from previous advisories.
 Despite a wider than normal spread in the along- and cross-track
 guidance, most guidance has been consistent from run-to-run, and
 there is little change in the track forecast philosophy presented 
 over the past couple of days. A mid-level ridge to the north and 
 northwest of the cyclone will impart a motion just south of due 
 west over the next 24 to 36 hours. After this time, the ridge is 
 expected to move east, and a weakened Madeline is expected to move 
 toward the west or west-northwest in the low- to mid-level trade 
 wind flow. On the forecast track, the center of Madeline will pass 
 dangerously close to the Big Island (Hawaii County) later today. 
 The updated track forecast is very close to the previous and close 
 to the TVCN multi-model consensus.
  
 Vertical wind shear provided by a high-level trough to the north and
 northwest of the cyclone is expected to lead steady weakening
 through the forecast period, even as Madeline moves over
 increasingly warmer water. While the updated intensity forecast is
 more aggressive in weakening Madeline than the previous forecast, it
 lies on the higher end of the intensity guidance through day 2, and
 is close to SHIPS by day 3. While SHIPS and HWRF indicate 
 strengthening at the end of the forecast period, ECMWF guidance
 indicates dissipation by day 3 while the GFS indicates degeneration
 to a remnant low on days 4 and 5. The official forecast favors
 these solutions, and now indicates degeneration to a remnant low 
 by day 5.  
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  31/1500Z 18.9N 153.1W   70 KT  80 MPH
  12H  01/0000Z 18.5N 154.8W   65 KT  75 MPH
  24H  01/1200Z 18.2N 156.9W   55 KT  65 MPH
  36H  02/0000Z 17.9N 159.1W   45 KT  50 MPH
  48H  02/1200Z 17.9N 161.7W   40 KT  45 MPH
  72H  03/1200Z 18.0N 166.3W   35 KT  40 MPH
  96H  04/1200Z 18.5N 171.0W   30 KT  35 MPH
 120H  05/1200Z 19.6N 175.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
  
 $$
 Forecaster Birchard