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HURRICANE OLAF DISCUSSION NUMBER  15
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP192015
800 AM PDT SUN OCT 18 2015

The could pattern of Olaf features a CDO with a primary convective
band extending into the southern and western semicircles. A 0726Z
GPM image showed a well-defined low- and mid-level eye, and the
initial intensity has been nudged upward to 70 kt, a little above
the latest Dvorak estimates from TAFB and SAB. Further strengthening
appears likely for the next couple of days while the hurricane moves
over warm waters and through a generally low-shear environment. The
SHIPS RI index continues to suggest that rapid intensification is
possible, with a 47 percent chance of a 25-kt increase in the next
24 hours. The new NHC intensity forecast is similar to the previous
one and is along the upper edge of the guidance, closest to the LGEM
forecast. By 72 hours, the cyclone will be moving over somewhat
cooler waters with a slight increase in shear, which should result
in slow weakening late in the period.

Olaf continues to move quickly westward, with an initial motion
estimate of 275/10. The track forecast reasoning remains unchanged,
with Olaf expected to gradually turn poleward during the forecast
period as the subtropical ridge initially to the northwest of Olaf
lifts northward and weakens. The track model guidance is in good
agreement on this scenario, but continues to trend toward a more
gradual northward turn. The new NHC track forecast has been adjusted
a little to the left of the previous one and is close to the latest
multi-model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT  18/1500Z  9.5N 133.2W   70 KT  80 MPH
 12H  19/0000Z  9.7N 134.5W   80 KT  90 MPH
 24H  19/1200Z 10.2N 136.3W   90 KT 105 MPH
 36H  20/0000Z 10.8N 138.0W  100 KT 115 MPH
 48H  20/1200Z 11.6N 139.5W  110 KT 125 MPH
 72H  21/1200Z 13.5N 142.4W  105 KT 120 MPH
 96H  22/1200Z 15.5N 143.9W   95 KT 110 MPH
120H  23/1200Z 17.8N 144.1W   85 KT 100 MPH

$$
Forecaster Brennan

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