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Tropical Storm Norman Discussion Number  44
NWS Central Pacific Hurricane Center Honolulu HI   EP162018
500 PM HST Fri Sep 07 2018
 
The exposed low-level circulation center of Norman has been evident 
in visible satellite imagery through the day, with convection 
persisting only in the northern semicircle. Crews from the 53rd 
Weather Reconnaissance Squadron were flying aircraft from
California to Hawaii this morning, in order to prepare for future
missions into and around Hurricane Olivia. Unexpectedly, one of the
aircraft was able to briefly make a penetration into Norman. This
data indicated that Norman was likely a little stronger than
analyzed for the last advisory. Meanwhile, a 2001Z ASCAT pass
sampled Norman's eastern semicircle, and indicated winds of at least
55 kt, with wind radii somewhat larger than previously indicated.
Based primarily on the above data, the initial intensity for this
advisory will be held at 60 kt. 

The initial motion estimate for this advisory is 340/9 kt. Norman
is moving toward the north-northwest between a deep-layer ridge 
centered to the east, and a longwave trough to the northwest.
Although there are some wiggles in the forecast track, little
overall change to this pattern is expected the next couple of
days, with Norman generally moving toward the north. The updated
track forecast lies close to HCCA and TVCE, and although it was
shifted to the right again, it required less changes than the
previous two forecast cycles. 

Vertical wind shear estimated to be 40-50 kt will persist for the
next 48 hours, with some decrease thereafter. With lowering SSTs 
along the forecast track, Norman is expected to be over sub 25C
degree water when the shear eases. The combined effects will cause
Norman to weaken to a remnant low by day 3 before dissipating by
day 5. The official intensity forecast delays dissipation as
compared to the statistical guidance, and is more in line with the
dynamical model guidance.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0300Z 25.0N 153.3W   60 KT  70 MPH
 12H  08/1200Z 26.2N 153.9W   55 KT  65 MPH
 24H  09/0000Z 27.7N 154.7W   50 KT  60 MPH
 36H  09/1200Z 29.4N 154.7W   45 KT  50 MPH
 48H  10/0000Z 31.0N 154.4W   35 KT  40 MPH
 72H  11/0000Z 33.9N 154.6W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  12/0000Z 35.5N 156.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  13/0000Z...DISSIPATED
 
$$
Forecaster Birchard
 
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