Tropical Storm Priscilla

Tropical Storm Priscilla Track 1000 Hours October 20 2019
Tropical Storm Priscilla Track 1000 Hours October 20 2019

Tropical Storm Priscilla Satellite 0700 Hours October 20 2019Tropical Storm Priscilla – (see Yuma Sunday weather below) NWS National Hurricane Center Miami FL 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 - Tropical Storm (WSW Cuyutlán, Mexico)
 12H  21/0000Z 19.0N 104.2W   35 KT  40 MPH - Tropical Storm (WSW El Colomo, Mexico)
 24H  21/1200Z 19.7N 104.3W   20 KT  25 MPH - Low (WSW Autlán, Mexico)
 36H  22/0000Z...DISSIPATED INLAND

NWS National Hurricane Center Miami FL 400 AM CDT Sun Oct 20, 2019

Microwave, geostationary satellite, and scatterometer data indicate that the small area of low pressure located near the southwestern coast of Mexico quickly became better defined during the evening hours and deep convection has persisted and become better organized overnight. Multiple ASCAT passes revealed winds of at least 25-30 kt over the southern portion of the circulation, and based on these data, the system is being classified as a 30-kt tropical depression.

The depression is moving northward or 355/6 kt. The global models indicate that the depression will move generally northward around the western periphery of a mid-level ridge that extends over the southeastern Gulf of Mexico and eastern Mexico. This motion should bring the center of the cyclone inland over southwestern Mexico later today or early tonight. The NHC track forecast follows a blend of the GFS and ECMWF model fields.

The depression is currently located over warm waters and within an area of moderate easterly shear. In fact, the center of the depression is currently located near the eastern edge of the convective mass. Due to the shear and the very short time the system is expected to remain over water, only slight strengthening is predicted. The depression, however, could become a short-lived tropical storm later today. Once inland, the cyclone should rapidly weaken and dissipate over the high terrain of southwestern Mexico.

The primary threat with the cyclone will be heavy rainfall and the potential for flash flooding and mudslides over portions of southwestern Mexico during the next day or so.

FORECAST POSITIONS AND MAX WINDS

INIT 20/0900Z 17.5N 104.0W 30 KT 35 MPH – Tropical Depression (WNW Lázaro Cárdenas, Mexico)
12H 20/1800Z 18.3N 104.2W 35 KT 40 MPH – Tropical Storm (WSW San Juan de Alima, Mexico)
24H 21/0600Z 19.6N 104.4W 30 KT 35 MPH – Tropical Depression (WSW Autlán, Mexico)
36H 21/1800Z…DISSIPATED

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