We’ve Reached the Annual Lull in Global Tropical Cyclones, When the Northern Hemisphere Switches On

The global tropics are about to begin the big switch to a more active Northern Hemisphere as the seasons change.

Heading into early May, we are as close to the global tropics being in the "off" position as possible.

The peak for tropical activity in the Southern Hemisphere, which includes cyclones near Madagascar and Australia, occurs from about February into early April. We are now in the declining phase of activity south of the equator.

As Dr. Phil Klotzbach notes, early May is the intersection of the end of Southern Hemisphere activity and the slow percolation of activity in the Northern Hemisphere, in what is still a generally hostile environment north of the equator.

May is typically the least active time of the year for hurricanes and cyclones around the world, since heat is gradually fading in the Southern Hemisphere and the Northern Hemisphere isn't warm enough for cyclones yet.

Remember, a tropical cyclone's main "job" is to transport heat from lower latitudes to the poles in an attempt to balance incoming heat from the sun, which is strongest toward the tropics.

As the sun's heating migrates northward into the Northern Hemisphere, tropical activity also moves northward as more heat builds in the lower latitudes.

We've already seen some signs of life in the Northern Hemisphere recently, well ahead of when the calendar says hurricane season begins.

We just saw a record-early start to the Eastern Pacific hurricane season with the formation of Tropical Depression 1-E on April 25. It was hundreds of miles from any communities and never had any impacts outside of marine traffic.

There was also a short-lived area of low pressure that recently bubbled up east of the Philippines but didn't develop into a tropical cyclone.

Now, the Indian Meteorological Department is watching a festering area of clouds in the southeastern Bay of Bengal. As of April 30, this system is expected to form into the season's first depression in the North Indian Ocean.

There are no signs of activity in the Atlantic Basin yet. Hurricane season in the Atlantic begins on June 1 but has started before that date numerous times in recent years. In fact, the Atlantic's first named storm has developed prior to hurricane season in every year since 2015.

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