What's the difference between a tropical and a subtropical storm?

Alberto runs hot and cold, making him subtropical


MIAMI – Alberto is a Subtropical Storm. So what does that mean?

There are two main types of storm systems, and their classification has to do with where they get their energy.

Cold Core

These are common through most of the U.S., and we see more of them in the winter in Florida. These are the systems that bring us those nice cool-downs in January, with brisk nights and comfortable afternoons. We feel it when they go by. These are low-pressure systems that get their fuel from the difference in temperatures between air masses. The boundary between the warm and cold air is called a front. When an upper level system passes over this boundary, the air over the front will want to rise, and a low pressure forms. 

  • These can produce rain, snow, and even severe weather outbreaks 
  • Their centers are the coldest parts, and the winds get stronger the higher in the atmosphere you go

Warm Core/Tropical

These are the types of lows that bring tropical storms and hurricanes. Warm core lows originate over the waters of the tropics, and they get their energy from the heat of the warm ocean. The warm ocean air rises, condensing into clouds and showers. Even more heat is released when these clouds form. Since warm air rises, a low develops. Eventually, a large thunderstorm complex develops. After enough time, the rotation of the earth causes the storms to rotate around a center, and a tropical cyclone forms. 

  • These do not have fronts
  • Their centers are the warmest parts, and the winds get weaker with height

Subtropical Storms/Alberto

Simply, these are a hybrid of both. They may originate over warm subtropical waters, but there may also be some difference in temperatures. Thus, they get their energy from both sources.

It is important to note that storms may transition from one type to another over the course of its lifetime. It is common for tropical cyclones to end their life as Cold Core Lows, for example.

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