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Why the tropics are suddenly active, when June systems are extremely rare

Satellite image of Bret and a second complex in the open Atlantic.

JACKSONVILLE, Fla. – The tropics in the Atlantic have become very active.

Tropical Storm Bret formed Monday evening and a second system is becoming likely to develop by midweek.

But it’s not just active. It’s historically active in a region where June systems are extremely rare.

The MDR

The area where Bret and the second complex are located is in the open Atlantic.

This region is called the Main Development Region, or MDR.

The Main Development Region rarely produces tropical systems in June.

Systems that develop in the MDR are often the result of tropical waves floating off the coast of Africa and organizing further.

The majority of tropical storms and hurricanes form in the MDR during a hurricane season.

Forecasters normally look at the MDR for development in the months of August, September and October.

Activity is June is almost unheard of.

The odd atmospheric conditions

Two key things are coming together to allow development in the MDR this early.

Water temperatures in the area are well above average, giving fuel to any system that attempts to organize.

Very warm water temps in the MDR are allowing tropical waves to organize.

The other major factor is the lack of dry air in place.

Normally in June, large plumes of Saharan dust are moving across the MDR and open Atlantic.

While the dust is there, it is significantly weaker than average and is placed just north of the two systems.

The historic nature

If two systems develop in the MDR this week, it will be the first time in recorded history in the month of June.

If Bret becomes a hurricane, it would be only the third hurricane ever recorded in the MDR in June.

The last hurricane was Elsa back in 2021.

While tropical systems have formed in June, seeing a complex in the MDR in rare. And seeing two systems simultaneously would be historic in nature.


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