Climate change is making monster hurricanes harder to forecast

Gulf of Mexico temperatures compared to average in °C (Tropical Tidbits via WashPost)

If it seemed liked the rapid intensification of Hurricane Laura into a Category 4 storm caught forecasters by surprise, that’s because it did.

Projected storm surge totals just about doubled between Tuesday and Wednesday.

What’s driving that rapid intensification? Thanks to global warming, Laura is moving over Gulf of Mexico waters that are “exceptionally warm.” The Washington Post reports, “Virtually the entire Gulf is above average or well above average in terms of temperature” (see graphic).

And because of this fast warming-fueled intensification, Mann explained “once again the people in the storms path may not have enough lead time to prepare for what will landfall as a Category 4 monster.”

Laura’s rapid development into a major hurricane points to the fact that global warming is not only making hurricanes more dangerous through stronger winds, higher storm surge, and much more precipitation; it also has begun to make them harder to forecast.

The northern Gulf of Mexico is a hotspot

Flickr / eutrophication&hypoxia

These keeps happening. Back in September 2018, the Weather Channel ran a story on the unexpectedly rapid intensification of Florence into a Category 4 hurricane, whose headline read in part, “We didn’t expect it to get so strong so soon.”

In 2017, Harvey spun up from a tropical depression to a Category 4 superstorm in two days, while that same year, Maria intensified explosively in one day from a Category 1 storm to Category 5 superstorm.

What’s going on?

Hurricanes draw their ferocious power from warm ocean waters. One of the ways hurricanes are weakened is the upwelling of colder, deeper water due to the hurricane’s own violent churning action.

But if the deeper water is also warm, it doesn’t weaken the hurricane and often continues to intensify it. As human-caused global warming continues decade after decade, not only do sea-surface temperatures rise, but the warming penetrates deeper into the ocean.

“Storms are intensifying at a much more rapid pace than they used to 25 years back,” explained the author of a 2012 study on hurricane intensification trends. “They are getting stronger more quickly and also [to a] higher category. The intensity as well as the rate of intensity is increasing.”

A 2015 study on the impact of sea-surface temperatures on the intensity of hurricanes in the North Atlantic found “intensification increases by 16 percent for every 1°C increase in mean SST.” And a 2016 study warned that “the vast majority (79 percent) of major storms” are rapid intensification storms,” and “the most intense storms” are those that undergo rapid intensification.

Warming-driven rapid intensification leads to super-hurricanes

NASA / Johnson

As climatologist and hurricane expert Greg Holland explained in 2017, “globally, the proportion of Cat 4 and 5 hurricanes has increased from ~20 percent of all hurricanes to around 40 percent due to climate change over the past 60 years.”

Bottom line: We are going to keep seeing more and more difficult-to-forecast super-hurricanes in the coming years and decades — until we get serious about slashing carbon pollution and stopping global warming.