Hurricanes Might Invade Inland More Than In The Past

Tropical Storm Alberto came ashore in the Florida Panhandle
in June, 2018.  It was still a tropical depression when
it was over northwestern Indiana a few days later, as this
satellite photo shows. Recent research shows that tropical
storms and hurricanes are not dissipating as fast as they
once did after making landfall.

 We're mercifully nearing the end of the record breaking 2020 hurricane season. 

One more tropical storm has formed, named Iota in the Caribbean Se.  This would be the 30th tropical storm or hurricane in the Atlantic Basin his year. That's a record for the most in a single year. 

Iota is very bad news. It's forecast to grow into a major hurricane and probably strike Nicaragua and Honduras. This is the same area slammed by powerful Hurricane Eta in late October, causing multiple deaths and widespread destruction. 

After this year, we probably, hopefully won't have to worry about so many tropical storms or hurricanes in a single season any time soon.

But new research that came out in the past week gives us more hurricane bad news.  Hurricanes are dissipating more slowly once they hit land than they did decades ago.

Tropical storms and hurricanes thrive on very warm sea water.  Once they move over land, that source of nourishment dries up or these storms, so they ultimately weaken and dissipate after they come ashore. 

Usually, this process is pretty quick, all things considered.  Which is why a hurricane that makes it ashore in, say, Texas, won't make it anywhere close to someplace in Minnesota, aside from having transitioned to a non-tropical rain storm once it gets that far north.

This rapid weakening in  tropical storms and hurricanes is a good thing. Though remnant former hurricanes can still cause damaging floods as far inland as places like Minnesota on rare occasions, at least you don't have to worry about destructive winds way inland. 

But that is changing somewhat.  Many hurricanes seem to be holding on to their destructive winds longer than they used to. Also, they dump more rain inland, causing more flooding than there otherwise would be.

From a report by the BBC:

"'We show that hurricanes decay at a slower rate in a warmer climate,' said Prof. Pinaki Chakraborty from the Okinawa Institute for Science and Technology in Japan, who led the study 

For North Atlantic land falling hurricanes, the timescale of decay has almost doubled over the past 50 years."

Back in the 1960s, hurricanes tended to lose 75 percent of their intensity in the first day after landfall. Now, that figure is closer to 50 percent, says the BBC.

Since a hurricane usually keeps moving forward after it hits land, one that weakens more slowly can spread its destruction further inland from the coast since the storm hold together better nowadays.

The problem seems to be, sigh, climate change. 

If the oceans are warmer, hurricanes can pull more moisture from the sea. Also, warmer air holds more moisture than chillier conditions. Remember that sea water is a hurricane's fuel.  A warmer climate means a hurricane can suck up more moisture from the ocean and carry it with it.  This added moisture is like a fuel tank the hurricane carries with it inland, allowing it to stay stronger longer. 

The air mass that was waiting for the hurricane inland would tend to be warmer than it was decades ago.  Which means that air holds more moisture than it did a generation or two ago.  That added humidity could also slow an inland hurricane's decay. 

By the way, it's the added moisture in the warmer air, not the toastier air itself that's the problem.  Chakraborty's team ran simulations in which they increased the air temperature for hurricanes but left out the added humidity.  In those simulations, hurricanes wouldn't be much different than they were back when Elvis Presley ruled the pop charts. 

It's hard to tease out, but we in Vermont might be starting to see the effects of these inland storms.  We suffered through the immense flooding from Tropical Storm Irene in 2011.  This past summer, Isaias was still a tropical storm as it moved inland through central Vermont. Luckily, Isaias wasn't a big disaster, just causing quite a few power outages and fallen trees in eastern Vermont. 

Vermont has always been prone to the effects of tropical storms and hurricanes heading north toward New England, but episodes like Irene and Isaias might becoming more common locally. 

All in all, this is another reason, among zillions, to detest climate change.