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Hurricane Olaf Forecast Discussion Number 9
2021-09-09 22:46:16| National Hurricane Center (East Pacific)
Issued at 300 PM MDT Thu Sep 09 2021 000 WTPZ45 KNHC 092046 TCDEP5 Hurricane Olaf Discussion Number 9 NWS National Hurricane Center Miami FL EP152021 300 PM MDT Thu Sep 09 2021 Olaf is quickly strengthening. An eye is now apparent in visible and satellite imagery. For most of the morning and early afternoon, a large and very symmetric eyewall was also apparent in radar data from Cabo San Lucas. Dvorak intensity estimates at 1800 UTC were 4.5/77 kt from both TAFB and SAB at 1800 UTC, and estimates from the U-W CIMSS ADT have increased to 80 kt since then. The initial intensity has been set at 80 kt, in close agreement with all available estimates. Olaf has moved consistently to the right of the forecast track for the past 12 hours, and the NHC track forecast has been shifted in that direction again. Olaf is now forecast to move very near or over southern Baja California Sur tonight. Regardless of the hurricane's exact track, it is very likely that a portions of southern Baja California Sur will get direct impacts from the eyewall of Olaf tonight. A large ridge centered over the southwestern U.S. is still expected to cause Olaf to make a slight turn toward the northwest tonight or early Friday. The hurricane should then make a westward turn by early Saturday as it weakens and the ridge extends westward. Despite the recent adjustments required to the NHC forecast, this forecast is still generally supported by all of the typically-reliable track guidance. By around 60 h, Olaf will likely have lost all of its deep convection and become a shallow post-tropical low, steered primarily southwestward by low-level flow. The environment should support additional intensification during the next 12 h as Olaf approaches the Baja California peninsula, so any fluctuations in intensity will likely be driven by internal dynamics at this point. The appearance of Olaf's eyewall in radar imagery has degraded a little during the past couple of hours, but it is possible this is due to attenuation of the radar signal and not fully representative of the hurricane's structure. Regardless, Olaf should begin to weaken once it interacts with land or moves inland. By late Friday, the rate of weakening is forecast to increase due to a combination of continued land interactions and cool sea surface temperatures. Olaf should quickly weaken over the weekend as it continues to move over cold water, and it will likely become a post-tropical cyclone on Sunday. The NHC intensity forecast is above the consensus at 12 h to allow for additional short-term strengthening, but follows the consensus closely at 36 h and beyond. Key Messages: 1. Olaf is forecast to move very near or over the southern portion of Baja California Sur tonight and Friday. Hurricane conditions are expected to begin within the southern portion of the hurricane warning area tonight and will spread northward through Friday. 2. Heavy rains associated with Olaf are expected across portions of southern Baja California Sur through Friday. This will pose a threat of significant and life-threatening flash flooding and mudslides. FORECAST POSITIONS AND MAX WINDS INIT 09/2100Z 22.2N 108.9W 80 KT 90 MPH 12H 10/0600Z 23.1N 110.0W 85 KT 100 MPH...INLAND 24H 10/1800Z 24.2N 111.5W 70 KT 80 MPH...OVER WATER 36H 11/0600Z 24.6N 112.9W 60 KT 70 MPH 48H 11/1800Z 24.5N 114.1W 50 KT 60 MPH 60H 12/0600Z 23.9N 115.3W 40 KT 45 MPH...POST-TROPICAL 72H 12/1800Z 23.2N 116.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 96H 13/1800Z 22.0N 119.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 14/1800Z 21.5N 122.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster D. Zelinsky
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