National Hurricane Center reviews Otis. Here's why they say it was rare
SACRAMENTO - It's only been one day since Hurricane Otis made landfall near Acapulco, Mexico, killing 27 people. Forecasters are now studying how quickly it strengthened from a tropical storm to a massive Category 5 hurricane.
Hurricane Otis slammed into Acapulco early Wednesday with 165 miles-per-hour winds, but 24 hours prior, the storm looked very different to forecasters at the National Hurricane Center.
"It's something we've seen, but it's pretty rare. It doesn't happen very often," Daniel Brown, a senior hurricane specialist at the National Hurricane Center, said.
Otis rapidly intensified from a Tropical Storm to a Category 5 Hurricane in the eastern Pacific in a 12-hour window.
"Between Monday evening and Tuesday morning, this system did a lot of developing, and then it just continued all the way up through landfall," Brown said. "It's something we've seen before. It's pretty rare for a storm to strengthen this rapidly, but it has occurred a few times."
Brown said that although in the Atlantic, hurricanes Harvey, Ian and Ida are all examples of rapidly intensifying storms. But Otis did it just a bit faster.
"We define rapid strengthening as about 35 miles per hour increase in wind speed over 24 hours. This one really did about two to three times that amount in that 24-hour period," Brown said.
Above-average sea surface temperatures and a low wind shear helped Otis grow to its massive size.
"It's not unusual for those waters to be pretty warm there off the southern coast of Mexico for this time of the year and wind shear decreased in that final day which allowed the storm to get a better structure. Once that it had that structure over those warm waters then it rapidly strengthened really almost all the way up to the time it made landfall," Brown said.
Brown said now more work is being done to improve forecasting rapid strengthening as recent storms start to take this path.
"Just in the last maybe 5-7 years, we have seen some progress in that area being able to forecast rapid strengthening however we still have a long ways to go and this case did unfortunately illustrate that," Brown said. "Sometimes we see the conditions are there but still, it's difficult to be able to forecast the magnitude of what will happen."
Otis was hurricane number three to make landfall this October along Mexico's Pacific coast.
Brown said usually at the beginning of hurricane season and toward the end, the better the chances are of landfalling storms.
"Oftentimes the later periods of the year in which we get more land threats. Earlier in the year, the waters aren't usually quite as warm as most of those are tropical storms or low-end hurricane threats," Brown said.
The Eastern Pacific has an average of 15 named storms and eight hurricanes a year. Hurricane season is still open until November 30.
"Hurricane season isn't over. If you live in a hurricane-prone area, this is the reason why we want folks to have those supplies already on hand so they can take these quick actions and be ready if there is a threat and that threat ramps up quite quickly," Brown said.