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Hurricane NORMAN

Hurricane Norman Discussion Number  33...COR
NWS Central Pacific Hurricane Center Honolulu HI   EP162018
1100 PM HST Tue Sep 04 2018
Norman's large distinct eye surrounded by cold cloud tops have
persisted for several hours now. In addition, the overall outflow
pattern is indicative of a stronger tropical cyclone compared with
12 hours ago. An AMSU microwave pass from 0635z, which was provided
by FNMOC/NRL, also confirmed that the eyewall is closed in all
quadrants. As a result, all of the satellite fix agencies (SAB,
JTWC, and PHFO) provided subjective Dvorak current intensity
estimates of 4.5/77 kt. In addition, the latest UW-CIMSS estimate
was 4.8/85 kt. Based on the vastly improved appearance of Norman,
and a blend of these intensity estimates, we have increased the
intensity to 80 kt for this advisory.
Norman continues to move westward, or 270 deg, at 10 kt. It is 
being steered by a deep subtropical ridge located to the north and
northeast. The NOAA Gulfstream IV aircraft completed a mission to
sample the environment around Norman earlier this afternoon. Their
primary target was this ridge and the weakness that is developing
west of the ridge. As a result, most of the track forecast guidance
had these data available for initialization of the models at 0000z.
The latest model guidance shows little spread through the next 36
hours, which likely is a result of the strength of the ridge.
However, starting around 48 to 72 hours, the spread increases. this
is likely due to the way the different models forecast the weakening
of the western flank of the ridge due to an upper-level trough
digging down into the region north of Hawaii. This weakening of the
ridge is expected to cause Norman to slow its forward motion and
gradually turn toward the west-northwest on Wednesday. This will
likely be followed by a turn toward the northwest from Wednesday
night into this weekend. The latest forecast track has been nudged
slightly left of the previous forecast, and remains near the middle
of the guidance envelope through the next 2 days. Even though the
guidance spread increases during days 3 through 5, all of the models
support the general northwestward motion persisting. The official
forecast is also very close to the TVCE, HCCA and GFEX consensus
model guidance.
Norman is expected to remain a hurricane for the next couple of
days. The latest CIRA ocean heat content (OHC) analysis appears to
support additional intensification during the next 12 hours or so.
In addition, vertical wind shear is around 10 kt based on the
latest UW-CIMSS estimate. By late Wednesday night, all guidance is
in good agreement that Norman will start to weaken under the effects
of increasing southwesterly vertical wind shear, cooler SSTs, and 
drier environmental conditions. This weakening will likely persist
through day 5, when Norman is forecast to become a remnant low. The
intensity forecast follows similar trends of the prior advisory, and
favors the latest ICON.
INIT  05/0900Z 19.6N 146.6W   80 KT  90 MPH
 12H  05/1800Z 19.8N 147.9W   85 KT 100 MPH
 24H  06/0600Z 20.4N 149.4W   85 KT 100 MPH
 36H  06/1800Z 21.3N 150.5W   75 KT  85 MPH
 48H  07/0600Z 22.5N 151.4W   70 KT  80 MPH
 72H  08/0600Z 25.2N 153.4W   50 KT  60 MPH
 96H  09/0600Z 27.5N 155.0W   30 KT  35 MPH
120H  10/0600Z 29.5N 156.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
Forecaster Houston