"Nightmare Scenario": Otis Stuns Forecasters, Rapidly Strengthens and Strikes Acapulco as a Category 5 Hurricane

Otis strengthened unexpectedly from a tropical storm to a Category 5 hurricane in the 24 hours leading up to landfall in Mexico on Wednesday

Enhanced satellite of Category 5 Hurricane Otis at 12:20 AM ET Wednesday, October 25, 2023, two hours before making landfall near Acapulco with 165 mph winds. Credit: NOAA

Only 24 hours before it hit, Tropical Storm Otis was forecast to come ashore along Mexico’s Pacific coast as a Category 1 hurricane. Instead, the storm rapidly strengthened 110 mph in 24 hours – a rate exceeded only once (Hurricane Patricia in 2015) by any observed Pacific or Atlantic hurricane – striking near Acapulco around 2:25 AM ET Wednesday as a catastrophic Category 5 hurricane with estimated winds of 165 mph, the strongest hurricane on record to hit Mexico from the Pacific side.

Category 5 Hurricane Otis nearing landfall in southern Mexico shortly after midnight on Wednesday. Credit: TropicalTidbits.com

The stunning rate of strengthening – so fast by late Tuesday that satellite estimates couldn’t keep pace – was poorly forecast by all major hurricane models, with virtually none predicting more than a borderline Category 1 hurricane before landfall in Mexico.

Early intensity guidance from Tuesday morning for then-Tropical Storm Otis. None of the most widely used intensity models predicted Otis to become more than a low-end Category 1 hurricane at landfall. The National Hurricane Center forecast in black (OFCI) was the most bullish of the forecasts at the time, but still only carried a borderline hurricane at landfall. Credit: Clark Evans/ University of Wisconsin-Milwaukee

Such unforeseen rapid intensification – from a tropical storm to a Category 5 hurricane on approach to land – underscores what’s long been viewed as a hurricane forecaster’s worst nightmare. The National Hurricane Center characterized the situation as a “nightmare scenario” for southern Mexico – including the Acapulco metropolitan area, home to over 1 million people – noting “no other hurricanes on record even close to this intensity for this part of Mexico.” The few hurricanes on record to pass near Acapulco never exceeded Category 1 status – Pauline in October 1997, Bridget in June 1971, and an unnamed hurricane in June 1951. Otis was an unprecedented landfall for this stretch of coastline.

Tropical cyclone tracks near southern Mexico, centered on Acapulco, with the track of Category 5 Hurricane Otis in bold black. No other hurricane close to the intensity of Otis has passed near Acapulco going back at least 75 years.

Otis comes only two weeks after Category 4 Hurricane Lidia came ashore 40 miles south of Puerto Vallarta, Mexico, with 140 mph winds upon rapidly strengthening from a 75-mph hurricane in the 24 hours leading up to landfall. So far in 2023, the northeast Pacific has recorded 8 Category 3 or stronger hurricanes – nearly double the average – including five Category 4 hurricanes and two Category 5 hurricanes in the basin’s most active hurricane season since 2018.

Otis will quickly weaken inland over the mountains of Mexico but heavy rains will continue to produce flash flooding and the possibility of mudslides in areas of high terrain through Thursday.

Tammy restrengthens over the open Atlantic, forecast to become a large and powerful extratropical storm this week

Tammy is making a run at Category 3 strength this morning over the open waters of the western Atlantic, outrunning forecast expectations. The hurricane is expected to merge with a cold front by tomorrow and transition into a much larger hurricane-strength extratropical storm.

Tammy will gradually weaken into the weekend as it bends back toward the west or even west-southwest. Interests in Bermuda will want to continue to monitor the progress of Tammy and its extratropical spinoff. Though forecast uncertainty remains high, the storm system could pose a threat to Bermuda over the weekend.

Probability of Tammy’s center or its remnants passing within 100 miles of a given location. Major global model tracks are shown, with the American GFS in green and the European model in red. Interests in Bermuda should continue to monitor the progress of Tammy or its still strong extratropical spinoff for the weekend. Though there’s a low chance Tammy’s remnants could dive southwestward by next week, in such a scenario, it would likely be a much weaker non-tropical system and isn’t a concern for Florida or the U.S. at this time. Credit: Tomer Burg/University of Oklahoma

As we’ve discussed in newsletters this week, though Tammy’s remnants could dip southwestward, it would likely remain weak in such a scenario and isn’t a current concern for Florida or the mainland U.S.