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A Review: What Is A Subtropical System Again?
September 20, 2023 at 07:30 AM EDT
By WeatherBug's Christopher Smith
With the start of hurricane season approaching, it’s not uncommon to hear the term “subtropical”. Let’s look at what defines a subtropical cyclone and how they form.
Most subtropical cyclones start out as a low pressure or extratropical cyclone with a cold core, meaning the air at the core of the cyclone is cold. These extratropical systems strengthen based on interactions between cold and warm air and the progression of fronts.
If an extratropical cyclone moves over waters of at least 70 degrees Fahrenheit, the cyclone will begin to have thunderstorm development. Over time, the cyclone condenses evaporated water vapor from the warm ocean waters below, releasing latent heat. Latent heat will help warm the core of the cyclone, making it more tropical in nature.
Unique to subtropical cyclones is the common cloud-free area surrounding the center of circulation. The intense thunderstorms associated with the cyclone are usually over 100 miles away from the center. Unlike tropical cyclones, not as much precipitation is associated with subtropical ones due to the large area of dry air.
A subtropical cyclone only turns tropical if it moves over even warmer water, usually at least 80 degrees Fahrenheit, leading to a warm core with intense thunderstorms near the center.
Subtropical cyclones and tropical cyclones both can be impactful wind events and are both named by the National Hurricane Center. Just last year, one named system remained purely subtropical, Alpha, and impacted Portugal.
Listen for the term ‘subtropical’ in the coming days a system develops off the Southeast coast.
Source: weather.gov
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Story Image: Subtropical Storm Ana on April 20, 2003 (Wikimedia Commons/NOAA’s National Climatic Data Center).
Most subtropical cyclones start out as a low pressure or extratropical cyclone with a cold core, meaning the air at the core of the cyclone is cold. These extratropical systems strengthen based on interactions between cold and warm air and the progression of fronts.
If an extratropical cyclone moves over waters of at least 70 degrees Fahrenheit, the cyclone will begin to have thunderstorm development. Over time, the cyclone condenses evaporated water vapor from the warm ocean waters below, releasing latent heat. Latent heat will help warm the core of the cyclone, making it more tropical in nature.
Unique to subtropical cyclones is the common cloud-free area surrounding the center of circulation. The intense thunderstorms associated with the cyclone are usually over 100 miles away from the center. Unlike tropical cyclones, not as much precipitation is associated with subtropical ones due to the large area of dry air.
A subtropical cyclone only turns tropical if it moves over even warmer water, usually at least 80 degrees Fahrenheit, leading to a warm core with intense thunderstorms near the center.
Subtropical cyclones and tropical cyclones both can be impactful wind events and are both named by the National Hurricane Center. Just last year, one named system remained purely subtropical, Alpha, and impacted Portugal.
Listen for the term ‘subtropical’ in the coming days a system develops off the Southeast coast.
Source: weather.gov
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Story Image: Subtropical Storm Ana on April 20, 2003 (Wikimedia Commons/NOAA’s National Climatic Data Center).