ZCZC MIATCDEP2 ALL TTAA00 KNHC DDHHMM Hurricane Fernanda Discussion Number 6 NWS National Hurricane Center Miami FL EP072023 500 PM HST Sun Aug 13 2023 Fernanda continues to rapidly intensify this evening. Since the prior advisory, the eye signature on visible satellite has become much more distinct as infrared cold cloud tops between -65 to -75 C have grown and encircled the eye. The last few microwave passes indicate quickly improving structure, with a 2331 UTC GMI pass showing a thick closed eyewall on the 89 and 37 GHz channels. Satellite intensity estimates have responded by rapidly increasing, with subjective estimates at 0000 UTC from TAFB and SAB between 77- to 90-kt, and objective estimates covering a similar range. Given the improvement of Fernanda's structure on satellite since that time, the initial intensity is set near the top of those estimates at 90 kt this advisory. The hurricane continues to move generally westward to west-northwestward at 280/8 kt. As mentioned previously, the hurricane has been moving rather slowly over the last 24 hours due to a weak mid-level ridge that has been eroded some by a cutoff low located further north near the California coast. However, the ridging north of Fernanda should gradually build back in as this cutoff low retrogrades off to the northwest. The net effect of this change should lead to the hurricane gradually accelerating over the next several days. As Fernanda becomes more vertically shallow towards the end of the forecast, it should also turn more westward. The official track forecast is quite similar to the prior one, but just a little faster, favoring a blend of the latest HCCA and TVCE consensus aids. Given the most recent microwave imagery showing Fernanda developing a well-defined single closed eyewall, the hurricane seems poised to continue rapidly intensifying. Vertical wind shear is forecast to remain under 5 kt and sea-surface temperatures (SSTs) remaining near 29 C for the next day or so. In fact, SHIPS-RII shows a 67 percent chance of another 30 kt increase in intensity over the next 24 hours, and the latest NHC intensity forecast now shows Fernanda becoming a powerful Category 4 hurricane in the next day or so. Thereafter, Fernanda will move into an increasingly dry and stable environment, as SSTs rapidly drop off along the forecast track. These negative factors should lead to initially gradual, and then more rapid weakening towards the second half of the forecast period. The latest NHC intensity forecast is above most of the guidance over the next 24 hours, in light of its continued rapid intensification, but falls back closer to the HCCA and IVCN intensity aids between days 2-4. Both the GFS and ECMWF models suggest the cyclone will become devoid of organized convection by 120 hours, and the latest intensity forecast now shows the system becoming a remnant low by that time. FORECAST POSITIONS AND MAX WINDS INIT 14/0300Z 15.6N 117.2W 90 KT 105 MPH 12H 14/1200Z 15.8N 118.3W 105 KT 120 MPH 24H 15/0000Z 16.3N 119.8W 115 KT 130 MPH 36H 15/1200Z 16.9N 121.6W 105 KT 120 MPH 48H 16/0000Z 17.2N 123.8W 95 KT 110 MPH 60H 16/1200Z 17.3N 126.3W 75 KT 85 MPH 72H 17/0000Z 17.4N 129.0W 65 KT 75 MPH 96H 18/0000Z 17.7N 134.6W 40 KT 45 MPH 120H 19/0000Z 18.0N 140.5W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Papin NNNN