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Tropical Storm Vicente Forecast Discussion Number 3
2018-10-20 04:36:33| National Hurricane Center (East Pacific)
Issued at 1000 PM CDT Fri Oct 19 2018 000 WTPZ43 KNHC 200236 TCDEP3 Tropical Storm Vicente Discussion Number 3 NWS National Hurricane Center Miami FL EP232018 1000 PM CDT Fri Oct 19 2018 Radar imagery from Guatemala has been extremely helpful in tracking the center of Vicente, especially after sunset. The low-level center of the small tropical storm appears to have accelerated northwestward during the past couple of hours, away from its rapidly decaying central dense overcast, and is now almost entirely exposed. Analysis from UW-CIMSS indicates that 10-15 knots of northwesterly shear is currently affecting Vicente, and this appears to have been enough to significantly disrupt the organization of the cyclone, probably due to its small size. The initial intensity has been held at 35 kt based on objective and subjective satellite estimates at 00Z, but given the tiny size of Vicente and its large swings in organization since early this morning, its unclear how representative these estimates are of the true maximum winds. Vicente is now moving west-northwestward, or 300/3 kt, and all of the guidance indicates that it will turn westward overnight. After that time, a Gulf of Tehuantepec gap wind event will likely cause the cyclone to turn southwestward, especially if Vicente remains weak and shallow. A few models even indicate the tropical storm could dissipate entirely as it interacts with these winds. Assuming the cyclone makes it past the Gulf of Tehuantepec intact, Vicente should turn back toward the west-northwest or northwest after about 48 h as it gets steered by the flow between a mid-level ridge over Mexico and another tropical cyclone that will likely develop off the coast of Mexico by that time. The NHC forecast has been shifted a little to the west at most forecast times, closer to the HCCA and FSSE aids, but is generally similar to the previous advisory. Due in part to the rapid decline in Vicente's organization this evening, the intensity forecast has been adjusted lower at most forecast hours for the first 48 h of the forecast, but is still generally higher than the model consensus. Most of the intensity guidance still calls for intensification, especially between 36 h and 72 h, when Vicente should be past the Gulf of Tehuantepec, and the shear should remain generally low. By the end of the forecast period, the global models indicate that Vicente will interact with a much larger tropical cyclone to its west, which should cause Vicente to weaken and possibly dissipate, though a 120 h point is still carried in this forecast for continuity purposes. Vicente should begin to slowly pull away from the coast overnight and on Saturday, however, heavy rainfall, with possible life-threatening flash flooding, is expected over portions of El Salvador, Guatemala, and southeastern Mexico during the next few days. FORECAST POSITIONS AND MAX WINDS INIT 20/0300Z 13.7N 92.5W 35 KT 40 MPH 12H 20/1200Z 13.7N 93.3W 40 KT 45 MPH 24H 21/0000Z 13.3N 94.3W 45 KT 50 MPH 36H 21/1200Z 12.5N 95.7W 45 KT 50 MPH 48H 22/0000Z 12.3N 97.4W 45 KT 50 MPH 72H 23/0000Z 13.8N 100.8W 55 KT 65 MPH 96H 24/0000Z 17.0N 104.0W 50 KT 60 MPH 120H 25/0000Z 20.5N 107.5W 40 KT 45 MPH $$ Forecaster Zelinsky
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