eli5 Why cant tropical storms form over land when it’s really humid outside?

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I understand that tropical storms need moist warm air to form but on a really hot humid day wouldn’t the moist air already be over the land?Like when humidity is 80%+ over land, why couldn’t the tropical storm just use that humidity to form?

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2 Answers

Anonymous 0 Comments

Tropical storms aren’t just wide, they’re also tall. They’re drawing that humid air 50,000 feet up and using this powerful updraft/downdraft loop to fuel the cyclone.

Once you suck up all the humid air over land and replace it with cold air from 50,000 feet the power source is gone, you don’t have an infinite reservoir of warm water to continuously replenish it so these storms rapidly lose power once they run into a continent.

Smaller systems can definitely use the heat and humidity over a bunch of cropland to fuel some nasty thunderstorms, but they can only do this for a few hours instead of three weeks.

Anonymous 0 Comments

Evaporating water from oceans provides a lot of the energy in play. When a storm goes over land, it is cut off from the water supply. It is why storms that cross over Florida lose strength, and then begin to regain strength after getting out over water again.