Olaf (2009)

A tropical depression formed about 475 nautical miles west-southwest of the southern tip of Baja California on October 1, 2009, after a tropical wave moved from the Atlantic into the eastern Pacific. The system strengthened to Tropical Storm Olaf the same day and tracked generally northward around the western edge of a ridge over northern Mexico. Olaf reached its peak intensity late on October 1 and into October 2, then turned sharply east and weakened over cooler water and increasing wind shear. It became a remnant low by 1200 UTC October 3 and the remnants moved ashore over southern Baja California before dissipating on October 4.

Olaf did not make any tropical-storm-force landfalls while it was an organized tropical cyclone. After degenerating to a remnant low, the circulation moved ashore over the southern Baja California peninsula early on October 4. The report lists the system as a remnant low at landfall; when it was closest to land earlier, it had already weakened from its peak tropical-storm intensity.

The storm’s maximum sustained winds were 40 knots (about 46 mph), and its minimum central pressure at peak was estimated at 996 millibars. That peak corresponds to a weak tropical storm (below hurricane strength).

Storm-related water effects included localized coastal flooding and heavy rains. The highest reported rainfall in Baja California was 75.2 mm (about 3.0 inches) at Ciudad Constitución; in Sinaloa the maximum was 132.5 mm (about 5.2 inches) at El Carrizo. Flooding was reported in the cities of La Paz and Comondú. Two ships — the Happy Rover and the Nikkei Dragon — reported near-tropical-storm-force winds and shipboard pressures around 1003–1005 mb.

No deaths were reported in the National Hurricane Center’s report. Impacts were mainly heavy rain, localized flooding, and associated disruption in parts of northwestern Mexico and southern Baja California, with La Paz and Comondú specifically noted for flooding and Ciudad Constitución and El Carrizo among the locations with the largest rainfall totals.

Noteworthy aspects included that Olaf was a short-lived, relatively weak tropical storm that degenerated before significant coastal landfall. The system’s development was preceded by a long-tracked tropical wave, and forecasters issued genesis probabilities only 12 hours before formation despite earlier mention in tropical outlooks. Official track forecasts had larger-than-normal errors because Olaf moved northward and then made an unexpected sharp eastward turn; however, official intensity forecasts were largely accurate and better than many guidance models.