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Hurricane Norman Discussion Number  35
NWS Central Pacific Hurricane Center Honolulu HI   EP162018
1100 AM HST Wed Sep 05 2018
 
Norman continues to exhibit a ragged eye this morning. Cirrus
outflow is somewhat restricted on the western semicircle, but a 1626
UTC WINDSAT pass shows the core of Norman remains quite
well-developed, with the most intense convection on the north and
east sides of the eyewall. Subjective intensity estimates were
unanimous at 5.5. However, UW-CIMSS ADT and the latest SATCON
objective estimates were slightly higher. The current intensity was
maintained at 100 kt for this advisory, although this may be a bit
conservative. 

After losing a little latitude overnight, Norman appears to have 
assumed a nearly due west motion once agin over the past several
hours, or about 270/7. A weak trough in the middle and upper levels
of the atmosphere is located several hundred miles to the north of
the main Hawaiian Islands. This trough is expected to sharpen over
the next 24 to 36 hours, and impart a gradual northwest turn on
Norman. The consensus tracks changed little this cycle, thus only a
minor westward tweak was made to the official forecast for the first
36 hours. In the 36 to 48 hour time frame, the consensus guidance as
well as the HMON and HWRF actually shifted slightly to the right, in
better agreement with the previous official forecast, so the current
forecast exhibits little change from 48 hours and beyond, and lies
near the middle of the guidance envelope. The NOAA G-IV is currently
flying another data-gathering mission to help better determine the
synoptic environment around Norman. 

The UW-CIMSS shear analysis shows that Norman is currently being
affected by 15 to 20 knots of southwesterly shear. The tropical
cyclone is also over marginal SSTs of 26.5 to 27C. After 48 hours,
cooler sub-26C water lies along the forecast track and significantly
stronger shear is ahead. Little change in intensity is anticipated
until the stronger shear begins to impact the core of Norman in 12
to 24 hours, then weakening should commence. The intensity forecast
is on the high side of the guidance spread for the first 36 hours,
then weakens Norman at a rate near the middle of the guidance spread
afterwards, and not quite as fast as the GFS- or ECMWF-based SHIPS
indicates. 

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/2100Z 19.6N 148.4W  100 KT 115 MPH
 12H  06/0600Z 19.8N 149.6W  100 KT 115 MPH
 24H  06/1800Z 20.8N 150.8W   90 KT 105 MPH
 36H  07/0600Z 21.8N 151.8W   80 KT  90 MPH
 48H  07/1800Z 22.9N 152.7W   65 KT  75 MPH
 72H  08/1800Z 25.3N 154.8W   40 KT  45 MPH
 96H  09/1800Z 27.2N 156.8W   30 KT  35 MPH
120H  10/1800Z 29.1N 158.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster R Ballard
 
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