A subtropical storm is different from a tropical storm, hurricane and even a nor'easter - and it can mean a lot of rain, wind and rough sea conditions for those living along the coast.

Subtropical storms in the Atlantic Basin can occur one or more times each hurricane season, and are a mix of two different, familiar storm types.

We will break down these two more common storms and explain how subtropical storms fall between them.

Type 1: Tropical Lows

Also called tropical cyclones, these are low-pressure systems fueled solely by heat energy released when water vapor that has evaporated off warm ocean water condenses into liquid. Due to all this heat, the core circulation of a tropical cyclone is warm, and its strongest winds are usually found near its center.

With low wind shear and moist air, tropical storms can intensify into hurricanes.

Type 2: Extratropical Lows

Most storms that impact a wide part of the Lower 48 are extratropical lows. Think of winter storms, lows that slam into the West Coast or storms off the coast of the East Coast.

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An extratropical or non-tropical low derives its energy from contrasts between cold and warm air to the north and south of the system. They actually have a cold center, a direct contrast to the tropical storms warm center and often have at least one front (cold, warm and/or stationary) attached to them. You can see an example in the map below.

They can occur both over the ocean and land and bring most of the precipitation that falls over land areas in the middle latitudes, and their strongest winds are quite far from the center.

The strange blend that makes a subtropical storm

When an extratropical storm experiences warmer water, it can begin to change. It begins to gain energy from two different places: the contrast of air masses and the pulling of moisture from warmer waters.

At that point, this system becomes a subtropical cyclone, exhibiting features of both tropical and non-tropical systems.

So why should you care?

The National Hurricane Center actually issues advisories and forecasts for subtropical depressions and storms. They are assigned a number or name, just like a tropical depression or storm.

These subtropical storms can still bring heavy rain, gusty winds and storm surge like a tropical system or hurricane.

Should this subtropical storm stay over warm water long enough, it can begin to transition to only using the warm ocean as its fuel source, fully becoming a tropical storm or even a hurricane.

But regardless if it becomes tropical, mature subtropical cyclones can have winds and rain some distance from the center, catching people inland off-guard.

How often they happen?

Subtropical storms were not officially recognized until the beginning of the satellite era, and they weren't named until 2002.

Subtropical storms are fairly rare, and there have only been a handful since they began to be named in 2002, though 2018 did have a whopping seven subtropical storms.

(MORE: The History of Atlantic Subtropical Storms)