FORT LAUDERDALE, Fla. — The first tropical depression in two months appears likely to form this week, as an unusually quiet Atlantic hurricane season shows signs of getting into higher gear.
An area of stormy weather in the central Atlantic stands a 70% chance of organizing itself into a tropical depression over the next five days, according to an update issued at 8 a.m. EDT Sunday by the National Hurricane Center. A depression is the weakest form of tropical cyclone, a rotating low-pressure system that’s classified as a depression, tropical storm or hurricane, depending on its wind speed.
The system will move northwest at 10 mph toward the islands of the northeastern Caribbean over the next few days, the hurricane center said. If it reaches tropical storm strength, which requires wind speeds of at least 39 mph, it would be named Danielle.
The system is one of four low-pressure areas being monitored for possible cyclone formation, as the Atlantic settles into the traditional peak period for the formation of storms. The most active part of hurricane season is from mid-August to the end of October, with Sept. 10 the statistical peak of the season.
The increased activity results partly from a decline of atmospheric factors that had suppressed storm formation for the past month, according to a report from AccuWeather, the private forecasting service. These storm-suppressing factors include dry air and wind shear — the changes of wind direction with altitude that can tear up storms.
“Conditions are changing in the tropical Atlantic,” said the report by AccuWeather senior meteorologist Alex Sosnowski. “In the past week, tropical disturbances, also known as tropical waves, that move westward from Africa have shown more vigor, and an area of stiff breezes, which forecasters refer to as strong wind shear, has prevented development during much of the summer has been wavering in part of the basin.
“Similarly, vast stretches of dry air over the heart of the basin are now becoming riddled by pockets of moisture, which is a necessary ingredient for tropical systems to thrive.”
A second trough of low pressure could develop over the northwestern Caribbean this week, and some slow development is possible as it moves west-northwest over the northwestern Caribbean Sea and toward Mexico’s Yucatan peninsula. As of Sunday, the National Hurricane Center has given it a 20% chance of developing in the next five days.
A third disturbance located about 600 miles east of Bermuda Sunday has been given a 10% chance of development in the five-day forecast.
A fourth area of interest is a tropical wave expected to emerge off Africa’s west coast on Monday and has been given a 20% chance of cyclone formation.
None of the systems is a threat to Florida at this time.
This could end up being just the third August since 1961 there hasn’t been a tropical storm in the Atlantic, according to AccuWeather.
There have only been three named storms so far this season — Alex, Bonnie and Colin — with the last one, Colin, dissipating on July 3, meaning this 56-day streak is the third-longest time in Atlantic hurricane season history without a named storm since 1995.
The longest dry spell since 1995 has been 61 days, from June 18 through Aug. 18 in 1999. However, that two-month run of inactivity was followed by a frenetic conclusion of the hurricane season that featured five Category 4 storms (Bret, Cindy, Floyd, Gert and Lenny) and the drenching Category 2 Irene, which achieved a rarity, with its eye passing over Miami-Dade, Broward and Palm Beach counties in mid-October. There also was a 59-day streak during the 2007 season.
Forecasters say dry air, Saharan dust and wind shear have been among the reasons there haven’t been more storms this year.
The last Atlantic hurricane was Sam, which became a hurricane Sept. 24 and maintained that status until Oct. 5 as it cut a path between the United States and Bermuda.
Of the three named storms so far this season, only Alex made its presence known in South Florida by dumping as much as 12 inches of rain in some areas.
The National Oceanic and Atmospheric Administration issued its updated hurricane season predictions earlier this month.
NOAA predicts 14 to 20 named storms and six to 10 hurricanes with three to five being major, meaning Category 3 or higher.
Hurricane season ends Nov. 30.