Jerry Likely To Become Hurricane Friday

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.

To explain subtropical storms, we need to start by explaining the two different storm types with which subtropical storms share some characteristics.

Type 1: Tropical Storms, or more broadly, tropical cyclones, are low-pressure systems fueled solely by heat energy released when water vapor 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.

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With low wind shear and moist air, these tropical storms can intensify into hurricanes. The National Hurricane Center issues forecasts for each of these tropical cyclones once they become at least tropical depressions or require watches or warnings.

Type 2: Extratropical Lows: However, an extratropical or non-tropical low derives its energy from contrasts between cold and warm air.

They always have at least one front — cold, warm or occluded — attached to them. You can see an example in the map below.

They can occur both over the ocean and land, and they are responsible for most of the precipitation that falls over land areas in the middle latitudes. They take the shape of winter storms, powerful storms marching in from the Pacific Ocean, coastal storms along the East Coast or even just a low driving a strong cold front out of Canada with relatively little precipitation.

An extratropical storm's core is cold, and its strongest winds are typically quite far from its center.

The Strange Brew Of A Subtropical Storm

An interesting thing happens when an extratropical or non-tropical low begins to warm up.

This can happen when the low slows down, tracks over ocean water just warm enough — usually at least 70 degrees — and thunderstorms begin to percolate closer to the low-pressure center.

If winds aloft aren't too strong to blow away the low-pressure center but instead help ventilate the storm, encouraging rising air and thunderstorms, the core of the low-pressure circulation will warm, first in the lower levels.

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

It's now deriving some of its energy from warmer ocean water, like a tropical storm, but also some energy from the lingering temperature contrast that originally spawned it as an extratropical storm.

Subtropical cyclones are typically associated with upper-level lows and have colder temperatures aloft, whereas tropical cyclones are completely warm-core, and upper-level high-pressure systems overhead help facilitate their intensification.

Why subtropical storms matter: The NHC issues advisories and forecasts for subtropical depressions and storms. They are assigned a number or name, just like a tropical depression or storm.

Strictly speaking, subtropical storms cannot directly intensify into hurricanes. But there is a path to doing so.

If the subtropical storm remains over warm water, thunderstorms can build close enough to the center of circulation, and latent heat given off from the thunderstorms can warm the air enough to create a fully tropical storm.

Once that happens, further intensification into a hurricane becomes possible.

Even if they don't eventually become tropical storms or hurricanes, they can still produce soaking rain, strong winds and rough surf.

Mature subtropical cyclones often have a large, cloud-free center with thunderstorms and rainbands displaced some distance away.

Maximum sustained winds are also much farther from the center, while the strongest winds in a tropical storm are close to the center.

Subtropical storms can also generate swells that can reach the coast, producing high surf and rip currents.

Here's how often they happen: Subtropical storms were not officially recognized until the beginning of the satellite era, and they weren't named until 2002.

(MORE: The History of Atlantic Subtropical Storms)

They don't occur every hurricane season. When they do, it's typically early or late in the season, when colder upper-level lows and former extratropical lows in more southern latitudes are more common.

For example, in October 2025, a frontal low began to shed its frontal features as convection began to brew in the center of the storm. Late on Oct. 9, 2025, a satellite-based radar detected that convective clouds around the center had cooled while the direct center of the system had a distinct warm spot, which earned the system the name “Subtropical Storm Karen.”

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.