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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.
Depsite a wider than normal spread in the along- and cross-track
guidance, most guidcance has been consistent from run-to-run, and
there is little change in the track forecast philosophy. 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 days 3 and 4. 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.  
 
 
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
 
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