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Tropical Storm Marty Forecast Discussion Number 4
2021-08-24 04:36:26| National Hurricane Center (East Pacific)
Issued at 800 PM PDT Mon Aug 23 2021 000 WTPZ43 KNHC 240236 TCDEP3 Tropical Storm Marty Discussion Number 4 NWS National Hurricane Center Miami FL EP132021 800 PM PDT Mon Aug 23 2021 Northeasterly vertical wind shear continues to disrupt the organization of Marty. The limited shower activity associated with the cyclone remains displaced to the southwest of its exposed low-level center. Despite its poor satellite appearance for much of the day, earlier scatterometer data showed 35 to 40-kt winds in the sheared cyclone. The latest objective satellite estimates and subjective Dvorak classifications support an intensity of 35 kt. However, the initial intensity for this advisory is conservatively held at 40 kt, with hopes that new scatterometer data become available overnight to better reassess Marty's intensity. Marty is moving westward, or 270/15 kt. The subtropical ridge to the north of Marty will continue to steer the cyclone generally westward over the next couple days. Then, the weakening cyclone is forecast to turn west-southwestward during the latter part of the week within the low-level trade wind flow. The latest NHC track forecast is adjusted just a bit south of the previous one, near the middle of the guidance envelope and close to the multi-model consensus aids. Despite the modest wind shear values diagnosed from the SHIPS guidance, Marty is clearly struggling to maintain organized convection. Furthermore, Marty only has a brief window over sufficiently warm SSTs before it crosses the 26 deg C isotherm on Tuesday and moves into a drier, more stable airmass. Therefore, gradual weakening is expected to begin on Tuesday and continue through the rest of the week. In fact, the latest global model simulated satellite imagery suggests Marty could struggle to generate any organized convection beyond tonight's convective maximum period. The latest NHC intensity forecast is essentially unchanged. Marty is forecast to weaken to a depression by early Wednesday, degenerate into a remnant low by Wednesday night, and dissipate late this week. But, it is possible these changes could occur even sooner than forecast if Marty's convective structure does not improve soon. FORECAST POSITIONS AND MAX WINDS INIT 24/0300Z 20.7N 115.8W 40 KT 45 MPH 12H 24/1200Z 20.7N 117.8W 35 KT 40 MPH 24H 25/0000Z 20.7N 119.9W 35 KT 40 MPH 36H 25/1200Z 20.7N 121.8W 30 KT 35 MPH 48H 26/0000Z 20.7N 123.9W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 26/1200Z 20.5N 126.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 27/0000Z 20.1N 128.5W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 28/0000Z 18.7N 133.1W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 29/0000Z...DISSIPATED $$ Forecaster Reinhart/Pasch
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