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Tropical Storm SIMON Forecast Discussion Number 5
2014-10-02 23:00:20| National Hurricane Center (East Pacific)
Issued at 200 PM PDT THU OCT 02 2014 000 WTPZ44 KNHC 022100 TCDEP4 TROPICAL STORM SIMON DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL EP192014 200 PM PDT THU OCT 02 2014 The center of Simon has either re-formed or has made a large wobble during the past few hours, as a TRMM overpass at 1827 UTC suggests the center is well southwest of the position seen in earlier SSM/IS overpasses. This requires a southward adjustment of the initial position. The new advisory position is still north of the TRMM position, and an additional adjustment may be required later if no subsequent northward wobble occurs. The initial intensity is increased to 45 kt based on satellite intensity estimates from TAFB and SAB, along with CIMSS ADT and CIRA AMSU estimates. The initial motion is a rather uncertain 280/8. For the next day or so, mid-level ridging to the north and northeast of the cyclone should steer Simon generally westward to west-northwestward. From 24-72 hours, the cyclone should turn more northward as it approaches the western end of the ridge. The guidance continues to show significant divergence after that. The GFS, GFDL, and HWRF, show a northeastward turn between 72-120 hours and bring Simon close to Baja California in 96-120 hours. On the other hand, the the ECMWF and UKMET show a generally northwestward motion that keeps the center well away from land. The track forecast compromises between these extremes by showing a slow northward motion by 120 hours. The new forecast is shifted to the south and west of the previous forecast based on current trends, and it is in best overall agreement with the Florida State Superensemble. Simon is forecast to remain in a light vertical wind shear environment and over sea surface temperatures of 28-29C for the next 48 hours, which should allow at least steady strengthening. After that, movement over cooler water should cause weakening. The new intensity forecast is increased over the previous forecast in best overall agreement with the SHIPS model, and it lies near the upper edge of the intensity guidance. An alternative forecast scenario is that rapid intensification begins in the next 12-24 hours, with Simon becoming significantly stronger than forecast. This scenario is supported by above average probabilities in the Rapid Intensification Index of the SHIPS model, and by the TRMM data, which suggests Simon is developing a small inner core. FORECAST POSITIONS AND MAX WINDS INIT 02/2100Z 18.3N 108.0W 45 KT 50 MPH 12H 03/0600Z 18.6N 109.2W 50 KT 60 MPH 24H 03/1800Z 19.0N 111.0W 60 KT 70 MPH 36H 04/0600Z 19.7N 112.6W 70 KT 80 MPH 48H 04/1800Z 20.7N 114.1W 75 KT 85 MPH 72H 05/1800Z 22.5N 115.5W 70 KT 80 MPH 96H 06/1800Z 24.0N 116.0W 60 KT 70 MPH 120H 07/1800Z 25.0N 116.0W 45 KT 50 MPH $$ Forecaster Beven
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