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Hurricane NORMAN

Hurricane Norman Discussion Number  37
NWS Central Pacific Hurricane Center Honolulu HI   EP162018
1100 PM HST Wed Sep 05 2018
Cold convective cloud tops persist within the inner core of Norman,
but the eye has started to become cloud-filled as the system begins
to feel the effects of increasing wind shear. Subjective Dvorak
current intensity estimates ranged from 5.0/90 kt at SAB to 5.5/102
kt out of HFO and JTWC, while CIMSS ADT came in with a higher
estimate of 107 kt. Given the steady state nature of the satellite
presentation through most of today, the intensity will be held at
105 kt for this advisory.

The long-awaited turn toward the northwest is underway, with the
initial motion set at west-northwest (295 degrees) at 7 kt. Norman
will gradually turn toward the northwest on Thursday as the
hurricane heads toward a weakness in the deep ridge centered far to
the northeast. The northwestward motion will persist through the
weekend as Norman interacts with a mid- to upper-level trough
sitting to the northwest. The track forecast is essentially an
update of the prior advisory through 48 hours and was nudged
slightly west of the prior advisory afterward. The track forecast
is nearest to TVCE, FSSE, and HCCA and is down the middle of the
guidance envelope, which is tightly clustered through 48 hours then
spreads considerably thereafter. None of the reliable guidance
suggests direct impacts from Norman on the main Hawaiian Islands.
However, as the tropical cyclone will be in our general vicinity for
the next couple of days, people should continue to monitor the
progress of this system.

Although Norman has been maintaining intensity, weakening will
commence shortly. As Norman approaches a weakness in the deep ridge,
it is encountering increasing southwesterly vertical wind shear that
is being produced by the mid- to upper-level trough parked to the
northwest. This wind shear will steadily increase through Saturday
and remain in place through the next five days. In addition, SSTs
will begin to cool late Thursday. The combined effect will be
steady weakening, which will likely render Norman a post-tropical
remnant low on late Sunday or Monday. The rate of weakening has been
accelerated slightly compared to the prior advisory, but the
intensity forecast remains on the higher side of a tightly clustered
guidance envelope of both the dynamical and statistical models.
INIT  06/0900Z 20.3N 149.8W  105 KT 120 MPH
 12H  06/1800Z 20.9N 150.8W   95 KT 110 MPH
 24H  07/0600Z 21.9N 151.8W   85 KT 100 MPH
 36H  07/1800Z 22.9N 152.9W   70 KT  80 MPH
 48H  08/0600Z 24.0N 154.1W   55 KT  65 MPH
 72H  09/0600Z 26.2N 156.6W   35 KT  40 MPH
 96H  10/0600Z 28.0N 158.4W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  11/0600Z 30.0N 161.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
Forecaster Wroe