013 
 WTPA43 PHFO 010252
 TCDCP3
  
 Hurricane Miriam Discussion Number  24
 NWS Central Pacific Hurricane Center Honolulu HI   EP152018
 500 PM HST Fri Aug 31 2018
  
 Vertical wind shear has begun to take its toll on Miriam. The eye is
 no longer present in geostationary satellite imagery, and a
 decreasing amount of deep convection has become confined to
 the northern semicircle. Subjective Dvorak current intensity
 estimates remained at 5.0/90 kt from all fix agencies. However, the
 final T numbers were down to 4.0 or 4.5, and given the degradation
 of the satellite presentation, the initial intensity will be lowered
 to 80 kt. Also, a minor adjustment was made to the wind radii based
 on partial ASCAT passes from this morning. 
  
 The initial motion estimate is slightly east of due north (010 
 degrees) at 10 kt. Timely microwave passes (SSMI at 0014Z and SSMIS
 at 0106Z) were helpful in placing the center and determining the
 short-term motion. Through tonight, Miriam will continue to be
 steered northward by a mid to upper level trough to the northwest
 and a deep ridge to the northeast. On Saturday, Miriam will begin a
 turn toward the northwest. This will occur as the steering flow of
 the weakening system becomes increasingly influenced by the low
 level ridge that will shift to the north of Miriam. The general
 northwestward motion is expected to persist until dissipation. The
 track is essentially an update to the prior forecast and is close to
 the middle of the guidance envelope near CTCI and HCCA.
 
 Rapid weakening will occur during the next couple of days. The
 already vigorous, southwesterly vertical wind shear of 30 to 35 kt
 will increase through the next 36 to 48 hours to about 50 kt. In
 addition, SSTs, which are currently running around 26.5 C, will
 steadily decrease along the forecast track. This will cause Miriam
 to weaken to a tropical storm on Saturday and become a remnant low
 late Sunday or Monday. The intensity forecast remains in the middle
 of the guidance envelope and is close to LGEM through 36 hours,
 then remains closer to HWRF.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  01/0300Z 20.1N 141.0W   80 KT  90 MPH
  12H  01/1200Z 21.7N 141.1W   65 KT  75 MPH
  24H  02/0000Z 23.6N 142.1W   50 KT  60 MPH
  36H  02/1200Z 25.6N 143.7W   40 KT  45 MPH
  48H  03/0000Z 27.4N 145.6W   35 KT  40 MPH
  72H  04/0000Z 30.7N 149.3W   30 KT  35 MPH...POST-TROP/REMNT LOW
  96H  05/0000Z...DISSIPATED
  
 $$
 Forecaster Wroe