This is a scary new paradigm in the tropics. And we all need to worry.
Hurricane Otis struck very near Acapulco, Mexico, on Tuesday night as a monster 165 mile-per-hour category 5 cyclone. On Monday night, about 24-hours before landfall, the National Hurricane Center (NHC) was predicting it would do so as 70 mile-per-hour tropical storm.
With the energy content (and destructive potential) of the wind increasing with the cube of the windspeed, that means that Otis reached Mexico with 13 times more destructive potential than what had been expected! Even when the hurricane warning was issued at 4 a.m. local time on Tuesday, the hurricane center was still forecasting just an ordinary category 1 hurricane to reach Mexico’s Pacific coast. For a region of Mexico that had never experienced anything stronger than a category 1, getting hit by a cat-5 with little to no warning has led to severe consequences.
I want to be clear that this is not an article about the skill of the National Hurricane Center. The collection of experts at their offices in Miami is the best in the hemisphere at analyzing and forecasting tropical cyclones. In recent years, I’ve seen them become less hesitant to forecast rapid intensification of hurricanes‚ as they correctly did for hurricanes Idalia and Lee in the Atlantic this year.
In the case of Otis, the hurricane center first noted in its Sunday advisories that the waters were “very warm.” While the statement was certainly correct, that characterization of the sea surface temperatures could be a candidate for the understatement of the year. Water temperatures across the world’s oceans aren’t just very warm. They’re record-hot. In the Pacific, short-term climatic variations like el Niño have a lot to do with the elevated surface temperatures. The phenomenon is causing readings 3 degrees Celsius warmer than average in the equatorial Pacific. Closer to the Mexican coast near Acapulco, the water was above 31 °C (88 °F) on the eve of Hurricane Otis. Generally, tropical storms only need the water to be 27 °C or warmer to support strengthening, so the hot pool of water near Mexico was premium fuel for Otis. [Continue reading…]