ORLANDO, Fla. – The storm that impacted Florida Dec. 16 had the feel of a low-end tropical storm.
So why wasn’t this system highlighted by the National Hurricane Center and why didn’t it get a name?
The simple answer is, meteorologically this storm isn’t tropical in nature. Storms are only named if they are tropical.
Extra-tropical cyclones, like the one coming to Florida for the weekend can bring similar impacts to tropical storms and even hurricanes, but they are built completely different.
Tropical cyclones, in this part of the world knows as tropical depressions, tropical storms, and hurricanes have a warm core.
They get their strength from warm ocean water in similar atmospheric pressure situations. These are known meteorologically as a barotropic lows.
The system that set newly daily rainfall records and broke the lowest pressure ever recorded for December in Central Florida was known as an extra-tropical cyclone. Extra-tropical cyclones have fronts attached to them and have a cold core.
These are a result of upper-level lows that originate in mid-latitudes, northern U.S. and Canada. They strengthen from differences in temperature and pressure in the atmosphere. Meteorologically known as baroclinic lows.
The storm came together from several distinct pieces that originated from the Gulf of Mexico all the way into southern Canada.
Piece 1 and 2, near the Canadian Border phased or came together to make a bigger trough, upper-level low across the Southern Plains or Mississippi River Valley before moving into the Deep South.
It then met up with piece 3 near the Northeast Gulf of Mexico.
Long story short, the strengthening of the storm was due to the trough moving into the Deep South increasing temperature differences in the atmosphere. There are also fronts attached to this storm making it extra-tropical and not tropical.
Even though impacts to us may be similar to that of a tropical storm, meteorologically it is very different.
Storms are only named if they are tropical in nature.