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Tropical Storm Olaf Forecast Discussion Number 4
2021-09-08 16:40:59| National Hurricane Center (East Pacific)
Issued at 900 AM MDT Wed Sep 08 2021 000 WTPZ45 KNHC 081440 TCDEP5 Tropical Storm Olaf Discussion Number 4 NWS National Hurricane Center Miami FL EP152021 900 AM MDT Wed Sep 08 2021 The depression has strengthened into Tropical Storm Olaf this morning. A well-defined curved band now wraps over 50 percent around the center of the cyclone, with cloud tops to -80 degrees C. The initial intensity has been raised to 35 kt for this advisory based on the latest TAFB Dvorak intensity estimate and the UW-CIMSS ADT. Olaf is forecast to remain over warm waters and in a moist environment for the next 36 hours or so. The only inhibiting factor to strengthening in the short term could be a slight increase in vertical wind shear beginning tonight. In a couple of days, the cyclone is forecast to begin moving over cooler waters and into a drier, much more stable atmospheric environment that favors rapid weakening. These unfavorable conditions should cause Olaf to degenerate into a remnant low this weekend. The latest NHC intensity forecast was decreased only slightly from the previous one, and is in good agreement with the IVCN intensity consensus. Although the NHC forecast no longer explicitly shows Olaf becoming a hurricane, this could still occur Thursday or Thursday night. The storm is now moving northwestward at 6 kt, to the southwest of a mid-level ridge building over northern Mexico. This northwestward motion should continue for a couple of days with a gradual increase in forward speed. By Friday night, Olaf is expected to turn west-northwestward as it weakens, and by Saturday a westward motion is forecast as the cyclone becomes shallow and steered by the surrounding low-level flow. The latest NHC track forecast is little changed from the previous one, and lies near the various multi-model consensus tracks. It should be noted that the model solutions that depict a stronger cyclone favor a track slightly more to the north than the NHC forecast, closer to the southern Baja peninsula, while the weaker model solutions lie to the south of the NHC forecast track. Key Messages: 1. Olaf is forecast to strengthen to near hurricane intensity while it passes to the southwest of southern portions of Baja California Sur Thursday and Friday, and tropical storm conditions are possible in these areas. Interests there should continue to monitor the progress of Olaf. 2. Heavy rains associated with Olaf are possible across southern portions of Baja California Sur Thursday through Friday. This will pose a threat of flash flooding and mudslides. FORECAST POSITIONS AND MAX WINDS INIT 08/1500Z 18.9N 107.5W 35 KT 40 MPH 12H 09/0000Z 19.6N 108.0W 45 KT 50 MPH 24H 09/1200Z 20.6N 109.0W 55 KT 65 MPH 36H 10/0000Z 21.7N 110.5W 60 KT 70 MPH 48H 10/1200Z 22.9N 112.2W 55 KT 65 MPH 60H 11/0000Z 23.5N 113.9W 45 KT 50 MPH 72H 11/1200Z 23.8N 115.4W 35 KT 40 MPH 96H 12/1200Z 23.7N 118.0W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 13/1200Z 23.0N 120.7W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Latto
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