A week into June and two tropical storms have drenched the U.S. South. Perhaps it would be a good time to stock up on duct tape, plywood and sandbags.
Unfortunately, using the first few weeks to predict the rest of the six-month Atlantic hurricane season is a fool’s errand.
From 1950 to 2012, the number of hurricanes was virtually the same whether storm activity started in June or not, according to Phil Klotzbach, lead author of the Colorado State University seasonal forecast.
“There is no strong correlation between what happens prior to June 30 and during the peak of the season,” agreed Bob Henson, a meteorologist and blogger with Weather Underground, who cited Klotzbach’s work.
That’s because the way storms form early on is often different from how they come together in late August to mid-October — the heart of the season.
June storms “rarely form from waves off the coast of Africa,” Klotzbach said. “They typically form from mid-latitude systems or at least have significant mid-latitude enhancement.”
Weather fronts coming off the U.S. this month can provide the push to get a tropical system started in the warm waters of the Gulf of Mexico, Caribbean Sea or just off the East Coast.
As the northern hemisphere’s summer progresses, that changes. The African easterly jet stream moves north and contributes to the creation of tropical waves: areas of disturbed weather moving west across the Atlantic that are essentially a conveyor belt of the raw material for a hurricane.
These waves travel over an ocean that has been baking under the sun throughout the summer, which provides fuel for ignition. About 60 percent of all Atlantic hurricanes and tropical storms grow from these waves, which come about every three to four days, according to the Hurricane Research Division of the National Oceanic and Atmospheric Administration.
These easterly waves also are the origin of almost 85 percent of intense, or major, hurricanes, according to research conducted by Chris Landsea, science and operations officer at the National Hurricane Center’s technology & Science Branch.
These intense hurricanes, Category 3 or stronger on the five-step Saffir-Simpson Scale, are the ones that stay etched in memory. They include Katrina, Camille and Andrew.
As for Bonnie and Colin, the pair of storms that buzzed around U.S. waters for the last 10 days, well, they will never be confused with those hurricanes, which scraped the landscape clean and killed thousands. As Colin moved closer to Florida, in fact, there were times when forecasters had trouble finding its center because it was so poorly organized.
Both were “very unimpressive,” Henson said.