ZCZC MIATCDEP3 ALL TTAA00 KNHC DDHHMM HURRICANE JIMENA DISCUSSION NUMBER 10 NWS NATIONAL HURRICANE CENTER MIAMI FL EP132015 800 PM PDT FRI AUG 28 2015 Jimena is rapidly intensifying. Conventional satellite imagery shows that the hurricane's well-defined eye has warmed and contracted since the last advisory. Its central dense overcast, consisting of very cold cloud top temperatures, has also become increasingly more symmetric. Aside from Jimena's core features, outer bands surrounding the cyclone have also increased and become better defined. Dvorak classifications were T5.5/102 kt from TAFB and SAB at 0000 UTC and the latest UW-CIMSS ADT value is 6.2/120 kt. A blend of these data are used to arrive at an intensity estimate of 110 kt, making Jimena the fourth major hurricane of the season. The initial motion estimate is 275/10, although the cyclone appears to have recently experienced a southward trochoidal wobble. Directly underneath a subtropical ridge to the north, Jimena should maintain a general westward course for the next 12 to 24 hours. After that time, Jimena's heading should become west-northwestward as it nears a break in this ridge around 140W, created by a mid-level trough extending southwestward from California. A significant decrease in forward speed is likely after 96 hours when the cyclone reaches the weakness around 140W. The track guidance is tightly clustered through 3 days and is only slightly divergent after that time, with the multi-model consensus trending southward during the last 24 hours from days 3 to 5. The new track forecast has been nudged slightly southward in the short term and a little bit more in the extended range, following the trend in the guidance. The rapid intensification phase that Jimena is undergoing is likely to continue in the short term while it encounters relatively light shear and moves over anomalously high oceanic heat content. These very conducive large-scale factors for intensification suggest that Jimena should reach a peak intensity of near category 5 strength in about 24 hours or so. The hurricane could remain around its peak intensity through 48 hours, even though SHIPS model output shows some drying of the lower to middle troposphere along Jimena's track. However, it should be noted that intense hurricanes such as Jimena frequently experience eyewall replacements that can cause fluctuations in intensity, and their occurrence and evolution are nearly impossible to predict. After about 2 days, a slow decay is forecast since oceanic and atmospheric conditions will only gradually become less conducive. Jimena's continued strenghtening has required an upward adjustment of the intensity forecast in the short term, and the new forecast is in excellent agreement with the statistical guidance as well as the FSU Superensemble output. The new forecast then trends toward the multi-model consensus from days 3 to 5. FORECAST POSITIONS AND MAX WINDS INIT 29/0300Z 12.3N 124.2W 110 KT 125 MPH 12H 29/1200Z 12.5N 125.5W 125 KT 145 MPH 24H 30/0000Z 13.0N 127.4W 135 KT 155 MPH 36H 30/1200Z 13.9N 129.5W 130 KT 150 MPH 48H 31/0000Z 14.9N 131.9W 125 KT 145 MPH 72H 01/0000Z 16.3N 136.6W 115 KT 130 MPH 96H 02/0000Z 17.3N 139.8W 100 KT 115 MPH 120H 03/0000Z 18.0N 141.7W 85 KT 100 MPH $$ Forecaster Kimberlain NNNN