ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM 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 NNNN