While we are bracing for a week or more of colder than normal weather in our area, a low pressure system in the eastern Atlantic south of the Azores is showing some potential to become a tropical or subtropical cyclone.
Showers and thunderstorms have wrapped around the center, and if this pattern holds up, the National Hurricane Center may start issuing advisories. NHC gives this a 20 percent chance of becoming a tropical or subtropical cyclone. Working against tropical development of this low is cooler water and forecast increasing wind shear later Thursday.
The low center is about 300 miles south of the Azores Islands and is moving slowly towards the north. It is a large system and winds are already near tropical storm (gale) strength in the Azores. When I was flying weather in the U.S. Navy in the early 1970s, we frequently went to the Azores during the winter months. The only runway on the island runs north to south, and strong easterly cross winds caused by a low south of the islands made landings very challenging!
The low will move slowly north through Sunday and then become absorbed in a strong cold front approaching from the west. By Tuesday, its remnants will be moving rapidly across Iceland in the far north Atlantic.
December tropical cyclones are quite rare.
Since 1851 there have only been 14 tropical or subtropical storms in December, about half in the Caribbean and about half in the central and eastern Atlantic.
Seven of the December storms reached category 1 hurricane intensity.