ZCZC MIATCDEP4 ALL
TTAA00 KNHC DDHHMM

HURRICANE OLAF DISCUSSION NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP192015
200 AM PDT SUN OCT 18 2015

Olaf has intensified overnight.  Satellite images show that
convection has deepened with a sizable area of -90C cloud tops near
the center, along with an eye occasionally appearing on the
night-visible channel.  Microwave data also show that the eye has
become better defined, and the feature has even become more distinct
in the lower resolution AMSU data.  With the appearance of the eye
in conventional satellite data and the increase in convection near
the center, the initial wind speed is set to 65 kt, near the Dvorak
estimate from SAB. It is also worth noting that ASCAT data show that
Olaf has also grown in size significantly from yesterday, and this
is reflected in the larger initial and forecast wind radii.

Olaf should continue to intensify during the next couple of days
with favorable environmental conditions of low shear, warm water and
high mid-level moisture in the forecast. Rapid intensification is a
distinct possibility, with the SHIPS-RI index showing about a 40
percent chance of a 30-kt increase in the next 24 hours.  The
intensity forecast will bring Olaf up to major hurricane strength in
36 hours, in line with the highest guidance from the LGEM model and
the Florida State Superensemble. In a few days, some southerly shear
and dry air entrainment is possible, which could lead to Olaf
beginning a weakening trend.  Little change was made to the long
range intensity forecast, close to a blend of the previous NHC
prediction and the intensity consensus.

ASCAT and satellite data were very helpful in determining an
initial motion of 275/8.  A motion to the west and then west-
northwest is expected for the next two days or so while the cyclone
moves on the south side of the subtropical ridge.  After that time,
a mid- to upper-level trough passing north of the Hawaiian Islands
is forecast to cause a break in the ridge, allowing Olaf to turn
northwestward by 96 hours and northward by 120 hours.  Although
guidance is in general agreement on the large-scale pattern, the
timing of the northward turn is in some question, especially since
Olaf has been struggling to gain latitude.  Overall, the guidance
has generally been showing a later turn, with the ECMWF/UKMET models
having a weaker trough and less of a ridge breakdown.  The NHC track
forecast is shifted west toward the latest consensus aids, although
it still lies east of the model consensus.

At 9.4N, Olaf is the lowest-latitude hurricane formation in the
eastern Pacific dataset.  Reliable records in the basin go back to
about 1971.


FORECAST POSITIONS AND MAX WINDS

INIT  18/0900Z  9.4N 131.9W   65 KT  75 MPH
 12H  18/1800Z  9.6N 133.2W   75 KT  85 MPH
 24H  19/0600Z 10.0N 135.1W   90 KT 105 MPH
 36H  19/1800Z 10.6N 136.9W  100 KT 115 MPH
 48H  20/0600Z 11.3N 138.6W  110 KT 125 MPH
 72H  21/0600Z 13.3N 141.7W  105 KT 120 MPH
 96H  22/0600Z 15.0N 143.5W   95 KT 110 MPH
120H  23/0600Z 17.5N 143.5W   80 KT  90 MPH

$$
Forecaster Blake

NNNN