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Atlantic system could become subtropical storm Owen


Hurricane season officially ended last week but the Atlantic Ocean doesn’t own a calendar. The possibility has emerged of a named December subtropical storm over its open waters — the first in nine years.

Hurricane season was tamer than expected and horrific all at once

A large low-pressure area about 1,600 miles east of Miami and 750 miles to the north of the Leeward Islands of the Caribbean is currently meandering over open waters. The National Hurricane Center indicates it has a 40 percent chance to become a subtropical depression or storm in the next five days.

Subtropical systems contain a mix of mid-latitude and tropical characteristics, but can earn a name if they have a defined center of circulation and winds of at least 39 mph. If this system is named, it will be drawn from the list of storms from the 2022 Atlantic hurricane season. The next name on the list is Owen, following Nicole, which slammed into the east coast of Florida on Nov. 9.

The system being monitored is moving eastward at 6 mph. The Ocean Prediction Center has issued a storm warning for waters within several hundred miles of the system. It said winds of 23 to 35 mph (20 to 30 knots) and seas of eight to 13 feet were ongoing in a large area around its center of low pressure.

The Prediction Center calls for the storm to intensify over the next 48 hours. On Wednesday morning, it anticipates its pressure to fall from 1005 millibars to 984 millibars while hosting winds of 46 to 57 mph (40 to 50 knots) and seas of 20 to 27 feet.

Compared to tropical storms, subtropical storms tend to have a larger wind field and are typically less symmetrical. Subtropical storms may transition to fully tropical systems if they sit over warm water and aren’t disrupted by hostile high altitude winds; Nicole pulled this off before striking Florida.

This particular system has little time to get better organized and will not benefit from warmer waters. Instead, it will stay over water just marginally warm enough to support a tropical system for the next few days.

By Friday, it is “expected to move over cooler waters, ending its chances of becoming a subtropical cyclone,” the Hurricane Center wrote.

While it is unusual to deal with tropical storminess this late in the calendar, this is not a first.

According to NOAA’s historical hurricane data, the last storm to become subtropical in December was an unnamed system around this time in December 2013. That storm was not named due to uncertainty about how long it would last, although it briefly attempted to take on tropical characteristics.

Before 2013, the most recent December tropical cyclone was Olga in 2007, which was initially subtropical. During the hyperactive season of 2005, a storm named Epsilon became a hurricane while spinning over the central Atlantic in early December.

It’s also not impossible to see a tropical cyclone in the heart of winter or into early spring. In 2016, Alex became a hurricane in mid-January over the open ocean.