Why Hurricanes Like Dorian Stall

This is hurricane Dorian on September 1st, 2019 and Here it is more than 24 hours later still pummeling those same islands you see Hurricane Dorian. It’s stalled right there in its path In fact at times it was crawling across the Bahamas at just one point six kilometers per hour That’s slower than the average person walks So what causes hurricanes like Dorian to stall and why does it matter? First of all, Dorian is not the first hurricane to stall not even close actually in 2018 for example hurricane Florence spent more than 50 hours within one small region of North Carolina and the year before Harvey, lingered over the houston area for more than two days straight, but in every case Hurricanes, that stall are really bad news Because the longer they linger the more rain they unload and the more damage they deal Harvey for example dropped more than sixty inches of rain in some parts of Texas and it cost the country an estimated 125 billion dollars Dorian on the other hand dropped more than 36 inches of rain in some regions and is expected to have a multi-billion dollar price tag as well So then why – hurricane stall in the first place think of a hurricane like a cork bobbing in a stream although it produces Its own wind and spin it actually travels. Thanks to larger wind patterns Which carry it along those wind patterns themselves evolve and change and sometimes The winds that guide to hurricanes collapse endures what you might think of as a stagnation point. That’s Tim Hall I’m a senior scientist at NASA’s Goddard Institute for Space Studies in New York And he says that at these stagnation points a hurricane has nowhere to go So it just sits there Dropping rain until another wind system picks it up and pushes it along and that’s exactly what happened in the Bahamas When Dorian arrived a pressure system nearby called the North Atlantic subtropical ridge started to weaken and That caused winds that were carrying the hurricane to essentially stopped blowing and it will definitely happen again in fact those stagnation events They’re actually becoming more common and as a result, so are hurricanes that stall according to Hall’s research there were 66 hurricanes that stalled in the North Atlantic between 1944 and 2017 and nearly half occurred in the last third of that time frame Which helps explain another trend the average speed of hurricanes in a given year is declining in fact compared to the mid 20th century Hurricanes today are moving on average about 17% slower Scientists still aren’t sure why but we’ve got some suspects and the suspects are that in a warming climate climate model simulations show both in the future and in the past several decades a reduction in the overall tropical wind patterns and Unfortunately a stalled hurricane isn’t the only consequence of climate change It’s also been shown to worsen storm surge increased rainfall and produce more intense storms So while Dorian is of course devastating, it’s likely just one of many hurricanes like it still to come You