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Hurricane Norman Discussion Number  40
NWS Central Pacific Hurricane Center Honolulu HI   EP162018
500 PM HST Thu Sep 06 2018
 
Norman started to look quite messy this afternoon as 35 to 40
kt of southwesterly shear rips apart the core of the hurricane.
Deep convection is now an amorphous blob around the low level
circulation center. Fortuitous 2343 UTC AMSR2 and 0021 UTC SSMI
passes were very helpful in confirming the center location. The
degrading satellite presentation yields lower confidence in the
satellite intensity estimates. The initial intensity of 85 kt was
based on 5.0 from PHFO and SAB, 4.5 from JTWC, and reasonable
agreement with the most recent CIMSS SATCON estimate.

The initial motion estimate remains 315/8, and there is little 
change to the forecast philosophy from the previous package. The 
track guidance remains tightly clustered along a northwest motion 
for the next 48 hours as Norman heads toward a trough in the middle 
and upper levels of the atmosphere. As it does so, Norman will 
continue to encounter strong wind shear, which lends increasing
uncertainty to the remainder of the forecast track. The ECMWF
continues to take Norman or its remnants farther north, to the east
of a large low expected to develop over the northwest Pacific. The
GFS model has shifted slightly northward with this cycle, somewhat
closer to the consensus guidance, which was already very close to
our previous forecast track. Thus, only a slight northward
adjustment was made to the official forecast track beyond 48 hours.

Norman will continue to experience very strong shear over the next 
48 to 72 hours. This should continue to weaken the tropical cyclone 
rather rapidly, particularly in light of the cooler sea surface 
temperatures ahead. Norman is expected to become a remnant low in 4 
to 5 days, but this could happen sooner. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/0300Z 22.0N 151.6W   85 KT 100 MPH
 12H  07/1200Z 22.8N 152.5W   70 KT  80 MPH
 24H  08/0000Z 23.8N 153.6W   55 KT  65 MPH
 36H  08/1200Z 24.9N 154.7W   45 KT  50 MPH
 48H  09/0000Z 26.0N 155.7W   35 KT  40 MPH
 72H  10/0000Z 28.0N 157.0W   30 KT  35 MPH
 96H  11/0000Z 30.0N 158.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  12/0000Z 32.0N 160.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster R Ballard
 
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