ZCZC MIATCDEP4 ALL TTAA00 KNHC DDHHMM TROPICAL STORM SIMON DISCUSSION NUMBER 8 NWS NATIONAL HURRICANE CENTER MIAMI FL EP192014 800 AM PDT FRI OCT 03 2014 First-light visible imagery and a 1205 UTC SSMI/S overpass indicate that Simon has become a little better organized. The storm has a central dense overcast with outer bands present in all quadrants, and the microwave data shows a mid-level eyewall forming near or over the low-level center. However, the cloud pattern continues to show some signs of easterly shear. Satellite intensity estimates are 55 kt from TAFB and SAB, and recent CIMSS ADT, AMSU, and SATCON estimates are 50-55 kt. The initial intensity is thus increased to 50 kt. The initial motion is now 285/8. Simon should move generally west-northwestward for the next 36 hours or so as it is steered by the subtropical ridge to the north and northeast. After that time, the track guidance becomes very divergent. The GFS, GFS ensemble mean, and UKMET forecast Simon to recurve through a break in the ridge near 115W and move inland over Baja California and northwestern Mexico. The ECMWF and the NAVGEM show Simon moving much farther west, with a northward turn delayed until the cyclone is west of 120W. Given the magnitude of the disagreement, the official forecast will follow the trend of the previous forecast in showing a slow northward to northeastward motion from 72-120 hours. The new forecast track is and update of the previous track and similar to, but slower than, the Florida State Superensemble. Simon will be moving over warmer water with SSTs near 28-29C during the next 24-36 hours while the deep-layer vertical shear is expected to be light. This should allow continued strengthening until the cyclone encounters cooler waters in 36-48 hours. The new intensity forecast is similar to the previous forecast and is in best agreement with the SHIPS model. There are two major sources of uncertainty in the intensity forecast. The first is that rapid intensification is still a possibility during the next 24 hours or so, although the probabilities shown in the SHIPS Rapid Intensification Index are slowly decreasing. Second, how much cool water Simon will encounter is dependent on the track. The GFS track would keep the storm over relatively warm water, while the ECMWF/ NAVGEM track would take it over much cooler water. FORECAST POSITIONS AND MAX WINDS INIT 03/1500Z 18.6N 109.8W 50 KT 60 MPH 12H 04/0000Z 19.1N 111.4W 55 KT 65 MPH 24H 04/1200Z 19.6N 113.3W 65 KT 75 MPH 36H 05/0000Z 20.5N 115.0W 75 KT 85 MPH 48H 05/1200Z 21.5N 116.1W 75 KT 85 MPH 72H 06/1200Z 23.0N 116.5W 60 KT 70 MPH 96H 07/1200Z 24.5N 116.0W 50 KT 60 MPH 120H 08/1200Z 25.5N 115.0W 35 KT 40 MPH $$ Forecaster Beven NNNN