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HURRICANE OLAF DISCUSSION NUMBER  20
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP192015
200 PM PDT MON OCT 19 2015

Olaf has continued to rapidly intensify today. The hurricane has a
classical appearance on satellite imagery with a small, clear eye
surrounded by a CDO with cloud tops of -70C to -80C. Dvorak
estimates from TAFB and SAB and UW-CIMSS were T6.0/115 kt, and these
are the basis for the initial intensity. Olaf has strengthened 45 kt
in the last 24 hours, and some additional strengthening is still
possible in the next day or two. However, there could also be
fluctuations in intensity due to eyewall replacement cycles that are
not accounted for here. The new NHC forecast shows a peak of 125 kt
at 12 h to 36 h and then a slow decay as the cyclone begins to move
over slightly cooler SSTs and into a drier environment later in the
period. The official forecast is above the intensity consensus and
close to the FSU Superensemble.

The initial motion estimate is 275/10, as Olaf continues to move
westward to the south of a mid-level ridge centered near 30N/140W.
This ridge will gradually weaken as a trough advances over the
north-central Pacific, and this will allow Olaf to finally begin
gaining some latitude as it gradually turns northwestward and then
northward during the forecast period. The UKMET model still is on
the left side of the guidance envelope for the first 48 hours, but
has shifted toward a sharper northward turn after that time. This
puts the GFS and ECMWF now on the left side of the guidance
envelope. Overall, the new NHC track forecast is an update of the
previous one and is still left of the consensus. The official
forecast is between the UKMET and the rest of the guidance in the
first 48 hours, and then lies along the left side of the track model
envelope at days 3 through 5.

FORECAST POSITIONS AND MAX WINDS

INIT  19/2100Z 10.0N 138.7W  115 KT 130 MPH
 12H  20/0600Z 10.3N 140.1W  125 KT 145 MPH
 24H  20/1800Z 10.9N 141.6W  125 KT 145 MPH
 36H  21/0600Z 11.7N 143.1W  125 KT 145 MPH
 48H  21/1800Z 12.6N 144.4W  120 KT 140 MPH
 72H  22/1800Z 14.7N 146.1W  110 KT 125 MPH
 96H  23/1800Z 17.7N 147.0W  100 KT 115 MPH
120H  24/1800Z 20.0N 147.0W   85 KT 100 MPH

$$
Forecaster Brennan

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