The factors behind the peak of hurricane season

A Moment of Science

There’s no denying that this hurricane season is already extremely active, but it’s just getting started as we approach the peak of tropical activity.  

This peak between late August through early October is due to a number of meteorological factors.

  • Less vertical wind shear that can rip apart fledgling storms.
  • More tropical waves, often the origin for many tropical systems, move off the western coast of Africa.
  • Dry dusty air from the Sahara becomes less prevalent and no longer widely suppresses development.
  • Finally, water temperatures in the tropical Atlantic are at their warmest during this time.

Let’s focus on that last factor.

Water is the source of a hurricane’s power. The warmer the water is, the more energy a hurricane can tap into. Sea surface temperatures have to be nearly 80 degrees or warmer for tropical systems to form and in September temperatures average around 85 degrees, the warmest they’ll be throughout the year. That may seem wrong as September brings “slightly” cooler weather for us alongside the start of fall. The thing is, we’re accustomed to ambient, or air temperatures. Water takes much longer to heat up! 

Let’s make a cup of tea to explain it further.

You fill up the kettle. You crank up the stove, and you wait. The metal that makes up the kettle gets hot quickly while the water takes time. This is called an object’s heat capacity. It describes the amount of heat needed to raise the temperature by 1 degree. Some materials, like metal, have a very low heat capacity. It doesn’t take that much for it to get hot! Water, on the other hand, has a high heat capacity. It has to absorb a lot of heat to warm it up!  Air’s heat capacity falls in the middle, not nearly as low as most metals, but several times smaller than air!

Now imagine this kettle is millions times larger, the size of the Atlantic, and your heat source is not the stovetop, but the sun! 

Historically 85 percent of major hurricane activity occurs after August 20th.

While we’ve been baking in the heat since May, the Atlantic has lagged behind. Absorbing the sun’s warmth all summer, slowly heating up into the 80s. This warm bathwater will allow for hurricanes to become much stronger.

Water temperatures will begin to cool alongside an increase in vertical wind shear by November, bringing an end to hurricane season that I’m sure all of us can’t wait for. 

Storm Team 2 Meteorologist David Dickson

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