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Tropical Storm Xavier Forecast Discussion Number 5
2018-11-03 21:40:28| National Hurricane Center (East Pacific)
Issued at 300 PM MDT Sat Nov 03 2018 000 WTPZ45 KNHC 032040 TCDEP5 Tropical Storm Xavier Discussion Number 5 NWS National Hurricane Center Miami FL EP252018 300 PM MDT Sat Nov 03 2018 Xavier continues to show a sheared cloud pattern in conventional satellite imagery this afternoon, with the low-level center located near or just southwest of the main convective mass. The various subjective and objective satellite intensity estimates are near 45 kt, and recent scatterometer data also indicate winds near 45 kt. Thus, the initial intensity remains at that value. Analyses from CIMSS and from the SHIPS model indicate that Xavier is still in an environment of 20-25 kt of southwesterly vertical shear. There is little change in the intensity forecast philosophy from the last advisory. During the next 12-24 h, the dynamical models suggest that an upper-level trough located to the north and west of Xavier should provide upper-level divergence over the cyclone. This could allow some additional strengthening despite the ongoing shear. After that time, the trough is forecast to dissipate, leaving the tropical storm in an area of upper-level convergence, moderate to strong shear, and a dry surrounding air that should cause it to weaken. Based on this evolution, the intensity forecast calls for a little more strengthening early in the forecast, followed by gradual weakening through the remainder of the forecast period. As in the previous forecast, Xavier is expected to degenerate to a remnant low in about 96 h. The forecast again follows the overall trend of the intensity guidance and lies near the upper edge of the guidance through 48 h. The initial motion is now 060/8. As mentioned previously, Xavier should turn northeastward and then northward during the next 24 h toward a weakness in the subtropical ridge created by the aforementioned trough. As Xavier weakens and becomes a shallow system, the cyclone should turn toward the west-northwest and west as it is steered by the low-level flow to the south of the subtropical ridge. All of the dynamical models follow this scenario except for the UKMET, which shows a much more northward motion toward the southern Gulf of California. The new forecast track will follow the model consensus in showing the westward motion, and the new NHC forecast track is similar to the previous track. FORECAST POSITIONS AND MAX WINDS INIT 03/2100Z 15.6N 106.1W 45 KT 50 MPH 12H 04/0600Z 16.1N 105.7W 50 KT 60 MPH 24H 04/1800Z 16.9N 105.7W 50 KT 60 MPH 36H 05/0600Z 17.3N 106.1W 45 KT 50 MPH 48H 05/1800Z 17.5N 106.8W 40 KT 45 MPH 72H 06/1800Z 18.0N 109.5W 30 KT 35 MPH 96H 07/1800Z 18.0N 112.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 08/1800Z 18.5N 114.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Beven
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