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Tropical Storm Marty Forecast Discussion Number 1
2021-08-23 10:37:13| National Hurricane Center (East Pacific)
Issued at 300 AM MDT Mon Aug 23 2021 000 WTPZ43 KNHC 230837 TCDEP3 Tropical Storm Marty Discussion Number 1 NWS National Hurricane Center Miami FL EP132021 300 AM MDT Mon Aug 23 2021 Recent scatterometer wind data indicate that the circulation associated with the low pressure area located a couple of hundred miles south-southwest of the southern tip of the Baja California peninsula has become better defined. In addition, convective activity has persisted and expanded over the western portion of the circulation overnight, resulting in Dvorak T-numbers of 1.5 and 2.0 from SAB and TAFB, respectively. Both ASCAT-A and B instruments revealed 30 to 35 kt winds over the western portion of the circulation and based on these data, advisories are being initiated on Tropical Storm Marty, the thirteenth named-storm of the 2021 eastern Pacific hurricane season. Marty is moving westward at about 13 kt. A strong mid-tropospheric ridge that extends from the south-central United States westward across northern Mexico and the eastern Pacific is forecast to steer Marty westward over the next couple of days. After that time, the cyclone is forecast to weaken and become vertically shallow. This should cause it to turn toward the west-southwest as it steered by the low-level trade wind flow. The dynamical model guidance is in excellent agreement, and the NHC track is near the middle of the tightly clustered model envelope. Although the tropical storm is currently located over warm waters, it is within an area of moderate northeasterly shear. In addition, it is likely to ingest drier and more stable air located to the northwest of the system over the next couple of days. As a result, only slight strengthening is indicated in the official forecast. By 36 hours, Marty is forecast to cross the 26C isotherm and gradual weakening is anticipated after that time. Less favorable thermodynamic conditions should result in the system becoming a remnant low in 60 to 72 hours, if not sooner. The NHC intensity forecast is in good agreement with the HCCA and IVCN consensus aids. FORECAST POSITIONS AND MAX WINDS INIT 23/0900Z 20.0N 111.0W 35 KT 40 MPH 12H 23/1800Z 20.3N 113.2W 40 KT 45 MPH 24H 24/0600Z 20.4N 116.0W 40 KT 45 MPH 36H 24/1800Z 20.2N 118.4W 35 KT 40 MPH 48H 25/0600Z 20.1N 120.4W 30 KT 35 MPH 60H 25/1800Z 20.0N 122.3W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 26/0600Z 19.8N 124.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 27/0600Z 19.0N 129.2W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 28/0600Z...DISSIPATED $$ Forecaster Brown
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