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Tropical Storm Olaf Forecast Discussion Number 13
2021-09-10 22:45:35| National Hurricane Center (East Pacific)
Issued at 300 PM MDT Fri Sep 10 2021 000 WTPZ45 KNHC 102045 TCDEP5 Tropical Storm Olaf Discussion Number 13 NWS National Hurricane Center Miami FL EP152021 300 PM MDT Fri Sep 10 2021 The low-level center of Olaf is completely exposed in visible satellite imagery this afternoon. The system has been devoid of organized convection since around 1200 UTC, and Olaf is at risk of losing its status as a tropical cyclone overnight if it is unable to generate new convection within the next 12 h. Despite its lack of convection, a weather station at Puerto Cortes measured sustained tropical-storm-force winds several hours ago as the center of Olaf passed very near the observation site, and it has more recently reported several tropical-storm-force gusts. The initial intensity is lowered to 40 kt for this advisory based on the aforementioned surface observations and T2.5/35 kt Dvorak classifications from TAFB and SAB. Olaf has rapidly weakened today, and this weakening trend is expected to continue during the next couple of days. The cyclone will be moving over sub-26 deg C sea-surface temperatures and into a drier, more stable environment that should largely suppress new convective development. Model simulated satellite imagery from the GFS and ECMWF indicate that Olaf will struggle to produce any new convection by tomorrow, and the intensity guidance consensus favors continued weakening as the vortex spins down. The official NHC intensity forecast shows Olaf becoming a 25-kt remnant low by 24 h. The remnant low is forecast to linger around for several days after, but remain weak as it moves over the open waters of the eastern Pacific. The tropical storm has begun moving more westward away from Baja California Sur, and its initial motion is estimated to be west-northwest (295 degrees) at 9 kt. A mid-level ridge building to the north of Olaf should steer the cyclone westward tonight into Saturday. By late Saturday, the shallow cyclone will begin moving southwestward as it is steered around a low-level ridge to its northwest. The official NHC track forecast lies near the middle of the guidance envelope, closest to the multi-model consensus aids. Key Messages: 1. Olaf is moving away from the Baja California peninsula, and lingering tropical storm conditions along portions of the southwestern coast of Baja California Sur are forecast to diminish this evening. 2. Heavy rains associated with Olaf are expected across portions of southern Baja California Sur through tonight. This rainfall may trigger life-threatening flash flooding and mudslides. FORECAST POSITIONS AND MAX WINDS INIT 10/2100Z 24.6N 112.7W 40 KT 45 MPH 12H 11/0600Z 24.8N 113.6W 35 KT 40 MPH 24H 11/1800Z 24.7N 114.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 36H 12/0600Z 24.2N 115.8W 25 KT 30 MPH...POST-TROP/REMNT LOW 48H 12/1800Z 23.3N 117.0W 20 KT 25 MPH...POST-TROP/REMNT LOW 60H 13/0600Z 22.3N 118.3W 20 KT 25 MPH...POST-TROP/REMNT LOW 72H 13/1800Z 21.4N 119.7W 20 KT 25 MPH...POST-TROP/REMNT LOW 96H 14/1800Z 20.8N 121.7W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 15/1800Z 20.5N 123.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Reinhart
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