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Tropical Storm Priscilla Forecast Discussion Number 2
2019-10-20 16:40:29| National Hurricane Center (East Pacific)
Issued at 1000 AM CDT Sun Oct 20 2019 000 WTPZ44 KNHC 201440 TCDEP4 Tropical Storm Priscilla Discussion Number 2 NWS National Hurricane Center Miami FL EP192019 1000 AM CDT Sun Oct 20 2019 Deep convection, with some overshooting cloud tops to -90 deg C, has continued to develop and expand since the previous advisory. Most of the convective cloud mass has been displaced into the western semicircle due to modest easterly to southeasterly vertical wind shear. However, the cold cloud canopy has expanded eastward over the center during the past couple of hours, suggesting that the cyclone is becoming better organized and has also strengthened. The initial intensity of 35 kt is based on earlier scatterometer wind data that showed 32-33 kt in the southwestern quadrant, along with the much- improved satellite signature since the time of the ASCAT passes. The 35-kt intensity is also supported by recent satellite intensity estimates of T2.5/35 kt and T2.3/33 kt from TAFB and UW-CIMSS ADT, respectively. Thus, the cyclone was upgraded to Tropical Storm Priscilla at 1200 UTC. Priscilla is moving a little west of due north or 355/6 kt. The small cyclone is expected to move generally northward around the western extent of a deep-layer ridge that is oriented east-to-west across the Bay of Campeche and south-central Mexico. This slow motion should bring the center of Priscilla inland over southwestern Mexico late this afternoon or early evening. The latest NHC model guidance is tightly packed around the previous advisory track, so no significant changes to the previous track forecast were required. Priscilla will be moving over SSTs in excess of 29 deg C and into an upper-level environment of gradually decreasing shear, so some additional slight strengthening will be possible before landfall occurs in about 12 hours. However, the peak intensity likely will not be much higher than 40 kt. After moving inland, Priscilla will rapidly weaken and dissipate due to the rugged mountainous terrain of southwestern Mexico. The primary threat with Tropical Storm Priscilla will be heavy rainfall, along with the potential for flash flooding and mudslides, over portions of southwestern Mexico during the next day or two. FORECAST POSITIONS AND MAX WINDS INIT 20/1500Z 18.1N 104.0W 35 KT 40 MPH 12H 21/0000Z 19.0N 104.2W 35 KT 40 MPH...NEAR MEXICAN COAST 24H 21/1200Z 19.7N 104.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 36H 22/0000Z...DISSIPATED INLAND $$ Forecaster Stewart
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