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TROPICAL STORM NORA DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP182015
800 AM PDT SAT OCT 10 2015

The satellite appearance of Nora has improved slightly during the
past several hours with deeper convection near the center and
increased banding features in the northwestward quadrant.  The
initial intensity is raised to 40 kt as a compromise between the
TAFB and SAB satellite estimates.

Further strengthening seems likely over the next couple of days
while Nora remains in a low shear, warm water environment.  The
models, however, generally show a lower peak intensity with Nora,
perhaps due to drier air in the mid-levels, so the new forecast will
reflect this trend.  The most notable change to the forecast
is at day 3 and beyond when the global models are predicting the
vertical wind shear to increase earlier and be much stronger than
predicted yesterday for the cyclone. Intensity guidance is notably
lower during that period, with only the GFDL showing hurricane
strength. The latest NHC prediction is similar to the previous one
through 48 hours, then is reduced afterward by about 10 kt. That's
about the largest change I feel comfortable making at long range due
to continuity concerns, but most of the historically reliable
guidance is still below my new forecast.

Nora is moving westward at roughly 12 kt.  The cyclone should move
to the west or west-northwest for the next couple of days while it
is steered by a ridge over the east-central Pacific.  This
ridge is forecast to weaken during that time, which should result in
Nora slowing down and gradually gaining latitude.  A mid-latitude
trough should help the ridge break down in a few days and turn Nora
northward, although there remains some spread in the guidance when
Nora will recurve. The GFS and HWRF models have joined the ECMWF
model in predicting a weaker Nora, which results in a delayed
northward turn. The official forecast is similar to the previous one
through 72 hours, then is shifted westward at long range in
accordance with the new guidance.



FORECAST POSITIONS AND MAX WINDS

INIT  10/1500Z 11.7N 137.2W   40 KT  45 MPH
 12H  11/0000Z 11.9N 139.0W   45 KT  50 MPH
 24H  11/1200Z 12.1N 140.9W   50 KT  60 MPH
 36H  12/0000Z 12.3N 142.5W   60 KT  70 MPH
 48H  12/1200Z 12.6N 143.7W   65 KT  75 MPH
 72H  13/1200Z 13.6N 145.3W   65 KT  75 MPH
 96H  14/1200Z 15.9N 145.4W   55 KT  65 MPH
120H  15/1200Z 18.0N 144.5W   45 KT  50 MPH

$$
Forecaster Blake

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