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TROPICAL STORM NORA DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP182015
200 PM PDT SAT OCT 10 2015

Nora is small tropical cyclone with an irregular central dense
overcast and some banding features especially northwest of the
center. Microwave data show that the inner core has improved in
organization, with a mostly closed ring noted in the 37 GHz
channel. With the increasing inner core structure, the initial wind
speed is raised to 45 kt, at the higher end of the estimates near
the Dvorak value from TAFB. The initial 34-kt wind radii were
adjusted inward based on an ASCAT-A pass from 1826Z.

Over the next couple of days, the environment near the storm is
expected to generally be favorable for strengthening, with very warm
waters and low shear anticipated.  However, some dry air aloft is
expected to temper the intensification, and only a gradual increase
in wind speed is expected at this time.  Still, with the inner core
getting better organized, a faster rate of intensification is
possible, with the SHIPS-RI index showing a 25 percent chance of a
30-kt change over the next 24 hours.  The intensity forecast will
remain close to the previous one in the first 48 hours, above most
of the guidance and closest to the GFDL and Florida State
Superensemble models.  Global models are increasing the wind shear
near Nora quite a bit in a few days and keeping it high for the
remainder of the period.  This will likely cause significant
weakening, and the NHC prediction is decreased a little bit at long
range, and is below the model consensus.

Nora continues moving westward at roughly 12 kt.  There has been no
change to the synoptic pattern with a ridge expected to gradually
weaken to the north of the tropical cyclone over the next couple of
days.  This pattern should result in Nora decelerating during that
time, while generally moving a little north of west.  Thereafter,
the storm is expected to encounter a weakness in the ridge while a
mid-latitude trough digs north of Hawaii.  These features should
turn Nora to the north and northeast, well east of the Hawaiian
Islands.  Model guidance has shifted a bit to the south and west on
this model cycle, in better agreement overall on a later northward
turn.  The NHC forecast is shifted westward through 96 hours to come
into better agreement with the consensus-based guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  10/2100Z 11.8N 138.5W   45 KT  50 MPH
 12H  11/0600Z 11.9N 140.1W   50 KT  60 MPH
 24H  11/1800Z 12.0N 141.9W   55 KT  65 MPH
 36H  12/0600Z 12.1N 143.3W   60 KT  70 MPH
 48H  12/1800Z 12.3N 144.5W   65 KT  75 MPH
 72H  13/1800Z 13.8N 146.0W   60 KT  70 MPH
 96H  14/1800Z 16.0N 145.5W   50 KT  60 MPH
120H  15/1800Z 18.0N 144.0W   40 KT  45 MPH

$$
Forecaster Blake/Brennan

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