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Subtropical Systems: Weather's Hybrid

April 4, 2021
By WeatherBug Meteorologists, Andrew Rosenthal
Hurricanes and tropical storms form throughout the summer and fall months in the Atlantic, each one gaining a well-organized circular shape. However, a storm, like Subtropical Storm Melissa, will occasionally come along that forms a bit differently.
 
These systems, known as subtropical storms and depressions, are actually a hybrid between tropical storms or depressions and an area of low pressure like we see with cold fronts. There are a few key differences between lows and hurricanes.

Subtropical storms or depressions begin in the tropics, but cold or dry air impedes its development, pushing the clouds well away from the storm`s center. As the storm is of tropical origins, Subtropical storms or depression are capable of releasing copious amounts of rainfall on an area, similar to a hurricane. 

Often, when a subtropical storm or depression interacts with warm tropical waters such as those in the Gulf Stream, the storm`s organization will complete, allowing the system to reach full tropical status.

Historically, subtropical storms or depression are not well documented.  The National Hurricane Center has only included these storms in the hurricane-name list since 2004. Instead, meteorologists were left to create their own names for these hybrids as they approached a given area. One example of a subtropical storm is the "Perfect Storm" of 1991, which brought tropical rain to eastern New England as it moved near the coast.