Updated Oct 11, 2018 - Science

How Hurricane Michael got so strong, so quickly

Data: National Hurricane Center; Chart: Harry Stevens/Axios

Hurricane Michael intensified at an extraordinarily rapid pace, growing from a tropical storm on Sunday to a borderline Category 5 storm featuring one of the lowest air pressure readings ever observed in a landfalling hurricane in the U.S. by Wednesday.

Why it matters: Hurricane Michael is occurring just days after the United Nations released a major report on climate change, concluding that potentially irreversible and major consequences, including extreme weather events, will grow far worse much earlier than previously thought.

Details: Hurricane Michael faced an array of obstacles when it first became a hurricane off the western end of Cuba on Sunday night.

  • One key impediment on its power was wind shear, which threatened to topple its thunderstorms over as they attempted to encircle the storm center.
  • There was also some dry air that got sucked into the storm, disrupting it for a time.
  • But in a matter of a few hours on Tuesday night, Michael transformed from a potent storm into a nightmare scenario, and just kept getting worse.
  • The likely cause is the fact that the rest of the ingredients needed for rapid intensification were there — plenty of unusually warm water, moist air, and an upper level wind pattern over the northeast Gulf of Mexico that was particularly conducive to evacuating the air the storm vaulted upwards, like venting the exhaust from a giant engine.
  • Still, the pace of intensification that Hurricane Michael went through is startling, with the winds jumping from 110 mph to 155 mph in 24 hours, and the air pressure dropping 46 millibars during that period.

The big picture: Studies have shown that storms may be undergoing rapid intensification — during which the maximum sustained winds in a storm increase by at least 35 miles per hour in 24 hours, more frequently in parts of the North Atlantic Ocean Basin, and that this may be due to human-caused global warming.

  • A hurricane's main source of fuel, in the form of heat and moisture, is the ocean, and water temperatures have been increasing as the world warms.
  • Sea surface temperatures in the Gulf of Mexico this week were between 1.5°C to 4°C, 2.7°F to 7.2°F above average for this time of year.

However, one study on trends in rapidly intensifying storms did not find statistically significant trends taking place in the Gulf of Mexico, where Hurricane Michael formed.

Another study, however, found that as the globe continues to warm, with most of the heat being absorbed by the world's oceans, rapidly intensifying hurricanes will occur more frequently. Also, new research published this month found that warming ocean waters will yield more hurricanes that rapidly intensify.

Between the lines: Experienced meteorologists expressed shock on social media at how quickly the hurricane ramped up and how it kept strengthening through landfall.

  • Each hurricane has what's known as its potential intensity, as defined by the difference between sea surface temperatures and temperatures in the upper atmosphere. The bigger the difference, the stronger the potential storm.
  • As sea surface temperatures continue to warm, it's thought that the potential intensity of some storms will increase.

"The Gulf of Mexico is very warm. It's quite a bit a bit warmer than the long-term October average," said James Kossin, a NOAA meteorologist, regarding Hurricane Michael.

"This makes the hurricane "speed limit" in the Gulf high right now. Michael was sitting in wind shear for awhile, which was keeping it from reaching that speed limit. Then the shear relaxed and Michael was able to intensity, rapidly in this case, to its speed limit."
— James Kosin, NOAA's National Centers for Environmental Information

What we're watching: Scientists will conduct research on this storm to make sure that the official forecasts anticipate such rapid intensification rates, rather than being caught off guard. After all, as recently as Monday, the forecast for Hurricane Michael was for it to come ashore as a Category 3 storm.

Then that ratcheted steadily upwards, but the storm always seemed to be a step ahead of forecasters — a dynamic that can have deadly consequences if people aren't taking action on land to evacuate ahead of it.

Go deeper: Our full Hurricane Michael coverage...

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