Otis was a tropical storm, not forecast to become even a category one hurricane until 24 hours before landfall and wasn’t forecast to become a major hurricane until less than 12 hours beforehand. It became the most powerful hurricane to hit Mexico on recorded history.
The issue with Otis wasn’t that the track was way off like in most problem forecasts with tropical systems but that the intensity was WAY off the mark. Otis blew up from a tropical storm to a Category 5 hurricane in just 12 hours. It’s maximum wind speeds increased 115 mph in less than 24 hours. We call this ‘rapid intensification.’
Hurricane Otis ranks number one in the eastern Pacific for rapid intensification now. Surface water temperatures this month were as much as 4 degrees (F) above normal. That’s a lot of extra energy. The actual water temperatures were near 90 degrees.
(Above: surface water temperature anomalies (deg C) through October 2023)
Warm water holds a huge amount of energy and is key to these rapid intensification events. Climate change is pushing global oceans above and beyond normal, packing tons of extra energy for storms, both tropical and extratropical. We can measure the oceans in terms of temperature but also total heat content- both of which have been majorly on the rise. In fact the rate of increase has even increased multiple times to what the rate of increase had been 40 years ago.
The change in ocean heat content of just 10 zettajoules from 2021 to 2022 alone is enough to power the entire global electricity bill… 100 times!
All this extra, increasing heat might make one wonder: are hurricanes increasing more rapidly more often? The answer is yes and it’s expected to become worse.
In the Atlantic, we have good data on increasing rapid intensification events in recent decades:
The percentage of major hurricanes, those that are category 3 or higher, in the Atlantic have increased since 1980 from about 15 to 20% of hurricanes to now nearly 40% of hurricanes.
As the ocean absorbs more heat, it will have more energy and we can expect rapid intensification events to continue to be more likely. MIT hurricane scientist Kerry Emanuel published a paper that stated extreme rapid intensification events could be up to 20 times more likely by the end of the current century! In regards to Otis, he stated that the rapid event Mexico just experienced was essentially ‘non existent in the 20th century climate.’ That probability is increasing though in our warming climate.
The climate models paint a complicated picture for future hurricane seasons. We may not necessarily see more hurricanes, but we’ll see more major hurricanes and more rapid intensification events. This looks like ‘flattening the curve’ in the chart below.
In our historic climate, we saw the highest number of storms in the middle, at a tropical storm or weak category 1 or 2 hurricane level (black line). In a warming climate the spread widens to include more storms at more intense levels.
Let’s say hurricane season is a dangerous pin ball machine game in the Gulf of Mexico or Florida, where you have to board up occasionally. You won’t necessarily have to do that more often now and in the future but you will have to prepare for more severe storms that will have more devastating and catastrophic consequences.
To top it off, these predictions are just for winds in the hurricane. At the same time, as we warm our oceans and atmosphere the air is holding more water vapor so we’re already measuring increases in the flooding rains tropical systems bring as well. Current and future hurricanes will be more and more disastrous for life and property.
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