With a strong El Niño underway in the tropical Pacific and unfavorable formation conditions in the Atlantic, the outlook for a well-below average Atlantic hurricane season is still on target, researchers say.
In fact, this year's conditions "should combine to produce one of the quietest Atlantic hurricane seasons since 1950," according to a report from Colorado State University researchers in the third update to their initial April prediction.
In addition to the named tropical storms that have already formed -- Ana, Bill and Claudette -- five more are predicted for the rest of the season, which runs from June 1 to Nov. 1. Two are expected to become hurricanes, with one predicted to reach major strength as Category 3, 4 or 5, according to the school's Tropical Meteorology Project. That's compared with the average of 12 named storms, 6.5 hurricanes, two of them major.
Still, the lead author of the report, Phil Klotzbach, points out that even storms that form in a quiet year can and do pack a punch. He cited Hurricane Agnes in 1972 and Hurricane Bob in 1991 that occurred in overall quiet seasons, but that went on to have significant impacts in New York State.
Among the key factors leading to this year's expectations are cooler than normal Atlantic sea surface temperatures, stronger-than-normal vertical wind shear and the strong El Niño "that is now firmly entrenched," the report said. El Niño, a climate pattern that affects weather worldwide, "is characterized by unusually warm temperatures" in the tropical Pacific, according to the National Oceanic and Atmospheric Administration.
While the outlook is a "best estimate," said Klotzbach, a research scientist, "historical data indicate fewer storms form in these conditions."
The outlook is based on study of 60 years of historical data, with oceanic and atmospheric conditions at this point similar to those leading into five seasons with below-normal activity -- 1965, 1972, 1982, 1987 and 1997, the report said.
Earlier in the spring, researchers at Stony Brook University, where a new prediction model has been developed for New York State, and NOAA's Climate Prediction Center, made calls for below-average activity this year. The Climate Prediction Center's update is scheduled for Thursday.