15th Named Atlantic Storm of Season May Be Forming

(Oct. 5) -- An area of low pressure in the western Atlantic is showing signs of becoming more organized this afternoon and may become the 15th named storm of the season.

It would be Tropical Storm Otto, and initial indications are that the storm will not be a direct threat to the United States.

Upper-level conditions in the vicinity of the low pressure system, centered about 140 miles to the north of San Juan, Puerto Rico, are becoming more conducive for tropical development. National Hurricane Center meteorologists are giving the low-pressure system an 80 percent chance of developing into an organized tropical cyclone (tropical depression or tropical storm) by midday Thursday.

No official forecast track will be issued by U.S. government forecasters until the system is upgraded. The system is expected to drift northwestward for the next couple of days and then, according to most computer models, take a northeastward turn into the Atlantic.

While the system will produce heavy thunderstorms -- and the potential for flooding -- in Puerto Rico, the Virgin Islands and Leeward Islands over the next couple of days, this track would prevent the storm from having a direct effect on the continental United States.


(Image courtesy of NOAA)

Forecasters note that the storm could be assigned the moniker of Subtropical Storm Otto instead of the standard Tropical Storm Otto. A subtropical storm is one that has the intensity of a tropical storm -- a sustained wind of at least 39 mph but less than 74 mph -- but has some weather characteristics of a nontropical type of storm. Such a storm is often referred to as a hybrid storm since it combines energy from two types of weather systems, tropical and nontropical.

The potential storm is in a region where tropical development is most common during October: near the Caribbean and along the Eastern Seaboard of the United States.

A large area of thunderstorms farther to the east, about 900 miles to the east of the Lesser Antilles, is not expected to develop into a tropical system. Even though sea-surface temperatures are warm, the interaction of the disturbance with an upper-level storm system will prevent intensification.

The season, regardless of what happens with the current system, has already had more storms than is typical for an entire season. The average number of named storms is 11, and the updated National Hurricane Center forecast is for 14 to 20 named storms before the season ends Nov. 30.