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HURRICANE OLAF DISCUSSION NUMBER  19
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP192015
800 AM PDT MON OCT 19 2015

A small eye is now apparent in infrared imagery, and the coverage
and symmetry of the cold cloud tops has improved during the past few
hours. The initial intensity is set to 100 kt based on the latest
Dvorak classification of T5.5/102 kt from SAB, making Olaf the 6th
major hurricane in the eastern North Pacific this year. This is the
farthest south that a major hurricane has formed in the basin since
reliable records began in 1971.

Further strengthening appears likely in the next day or so, and in
fact the SHIPS RI index shows a 44 percent chance of a 25-kt
increase in the next 24 hours. The NHC intensity forecast has been
adjusted upward to account for the observed strengthening, and shows
a peak of 125 kt in 24 hours. Little change in intensity is then
shown through 48 hours, however, there could be fluctuations in
intensity due to eyewall cycles during this time that are not
represented in the forecast. Later in the period, gradual weakening
should begin as Olaf moves over slightly cooler waters into a
somewhat drier environment. The new NHC forecast is above the
guidance in the first 24 hours and close to the latest SHIPS model
prediction thereafter.

Olaf continues to move westward, with an initial motion of 280/12.
This continues a trend of a motion that has been a little faster and
to the left of much of the guidance and the NHC forecast. While the
track forecast reasoning has not changed, with Olaf expected to
gradually turn northward through the forecast period as the ridge to
the north erodes, the guidance envelope has continued to shift
westward this cycle. In fact, the multi-model consensus has shifted
westward by about 2 degrees compared to 24 hours ago at days 4 and
5. The new NHC track forecast has been adjusted to the left this
cycle by 60 to 90 n mi at days 2 through 5. The NHC track is now on
the left side of the guidance envelope and closer to the UKMET
model, which has been the best performing track model so far for
Olaf.

FORECAST POSITIONS AND MAX WINDS

INIT  19/1500Z  9.9N 137.7W  100 KT 115 MPH
 12H  20/0000Z 10.2N 139.1W  115 KT 130 MPH
 24H  20/1200Z 10.8N 140.8W  125 KT 145 MPH
 36H  21/0000Z 11.4N 142.4W  120 KT 140 MPH
 48H  21/1200Z 12.2N 144.0W  120 KT 140 MPH
 72H  22/1200Z 14.0N 146.0W  110 KT 125 MPH
 96H  23/1200Z 16.7N 146.9W  100 KT 115 MPH
120H  24/1200Z 19.5N 147.5W   85 KT 100 MPH

$$
Forecaster Brennan

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