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Tropical Storm Olaf Forecast Discussion Number 5
2021-09-08 22:47:14| National Hurricane Center (East Pacific)
Issued at 300 PM MDT Wed Sep 08 2021 000 WTPZ45 KNHC 082047 TCDEP5 Tropical Storm Olaf Discussion Number 5 NWS National Hurricane Center Miami FL EP152021 300 PM MDT Wed Sep 08 2021 Olaf's appearance has remained steady today and the storm is characterized by a large curved band that encompasses much of the circulation. There is good outflow in all quadrants, indicative of a low-shear environment. An earlier ASCAT pass sampled peak winds of 37 kt, and this data along with a blend of the latest Dvorak T-numbers from TAFB and SAB indicate that the initial intensity is around 40 kt. The storm is forecast to remain over warm waters and in a moist environment for the next 36 hours. Therefore, additional strengthening is likely during that time period. In a couple of days, the cyclone is forecast to begin moving over cooler waters, and into a drier and a much more stable atmospheric environment. This should result in rapid weakening, and Olaf is expected to become a remnant low this weekend. The latest NHC intensity forecast is little changed from the previous one, and continues to be in good agreement with the IVCN intensity consensus aid. Although the NHC forecast does not explicitly show Olaf becoming a hurricane, this could still occur Thursday or Thursday night. Olaf continues to move slowly northwestward, or 325/5 kt. A mid-level ridge building over northern Mexico should help maintain this heading 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 when the shallow cyclone is steered by the surrounding low-level flow. The overall model guidance shifted slightly to the east through 48 hours, and thus the NHC track forecast was nudged in that direction for that time frame. Because of this track shift, probabilities of tropical storm and hurricane conditions have increased for southern portions of Baja California Sur. Therefore, the government of Mexico has issued a Hurricane Watch and a Tropical Storm Warning for portions of this area. After 48 h, the guidance has shifted a little to the south, and the NHC forecast was tweaked in that direction as well. Key Messages: 1. Olaf is forecast to strengthen to near hurricane intensity while it passes to the southwest of the southern portion of Baja California Sur Thursday and Friday. Tropical storm conditions are expected and hurricane conditions are possible across that area beginning late Thursday. Interests there should continue to monitor the progress of Olaf. 2. Heavy rains associated with Tropical Storm Olaf are possible across portions of far southern Baja California Sur Thursday through Friday. This will pose a threat of flash flooding and mudslides. FORECAST POSITIONS AND MAX WINDS INIT 08/2100Z 19.4N 107.7W 40 KT 45 MPH 12H 09/0600Z 20.2N 108.3W 50 KT 60 MPH 24H 09/1800Z 21.2N 109.4W 60 KT 70 MPH 36H 10/0600Z 22.3N 110.9W 60 KT 70 MPH 48H 10/1800Z 23.2N 112.5W 55 KT 65 MPH 60H 11/0600Z 23.5N 114.2W 45 KT 50 MPH 72H 11/1800Z 23.5N 115.5W 35 KT 40 MPH 96H 12/1800Z 23.1N 118.1W 30 KT 35 MPH...POST-TROP/REMNT LOW 120H 13/1800Z 22.4N 120.9W 25 KT 30 MPH...POST-TROP/REMNT LOW $$ Forecaster Latto
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