Why Atlantic tropical updates look a tad stormier

One reason the early hurricane-season forecasts for the Atlantic Basin were on the gentler side was the potential for an El Nino warning in the tropical Pacific.

When the waters out that way become warmer than normal, they interact with the atmosphere in such a way as to generate upper-level winds from the west that can rip apart tropical disturbances before they mutate into hurricanes.

Sea surface temperatures in the Pacific have been flirting with the El Nino threshold, about a degree Fahrenheit above normal.

But various models favor "neutral" temperatures, near the averages, through the peak of the hurricane season, according to an update Friday from the U.N.'s World Meteorological Organization.

That's a big reason why the updated outlooks have bumped up the forecast numbers. With Cindy, already three named storms — those with winds of at least 39 mph — have formed in the Basin, something that usually doesn't happen until Aug. 13.

A study of more than 70 hurricane seasons by researchers Chris Landsea and Roger Pielke Jr. documented el Nino's mitigating influences on Atlantic tropical-storm seasons.

They found that in the 22 El Nino-influenced seasons, the numbers of storms causing at least $1 billion worth of damage occurred far less frequently than in other years. The study adjusted for inflation and levels of building.

Not that El Nino acts alone. The atmosphere is a chaotic, messy place, with any number of variable affecting seasons, including Atlantic, Gulf, and Caribbean sea-surface temperatures, and dry air bounding off the African coast.

And not that El Nino makes the East Coast bullet-proof. This year marks the 45^th anniversary of Agnes, one of the most-destructive storms on record.

That year, 1972, was an El Nino year.