Early Hurricane Forecasts: What Are They Worth?
Two unofficial early-bird predictions call for an unusually active 2011 hurricane season — but don't try to take these forecasts to the bank. They might be better this year than Punxsutawney Phil, who totally blew his prediction for an early spring, but still, a lot of meteorologists think the April forecasts are putting hard numbers on some pretty squishy science.
For the record, the Colorado State University team of William M. Gray and Philip J. Klotzbach predicts nine Atlantic Basin hurricanes, including five major hurricanes, and a 72 percent chance that at least one of the big ones will strike somewhere along the U.S. coastline sometime between June 1 and the end of November.
Accuweather.com, of State College, Penn., calls for eight hurricanes, including three big ones, and pinpoints three "higher concern areas" for a hurricane strike — the Gulf coasts of Texas and Louisiana, the Florida Peninsula, and the Carolinas.
These predictions look a lot like last year's season, which saw a record 19 "named" tropical storms, including 12 hurricanes and five major hurricanes. Last April, the Colorado State team saw a 69 percent chance of a big one making landfall along the U.S. coast. But, of course, none did — a circumstance which left a lot of people wondering what all the fuss was about.
The problem with predicting the hurricane season in early April is that a lot of the conditions that make one season different from another are not yet in place — literally, they are up in the air. Shifting from winter to summer, the atmosphere is so unstable over the Northern Hemisphere, from roughly mid-March to mid-May, that forecasters have a name for it: the "Spring Barrier."
Many of the important features of atmospheric and ocean circulation that encourage or dampen hurricane formation and steer storms along one path or another are just not there yet. Among the great unknowns is the El Niño-La Niña cycle in the equatorial Pacific Ocean. Warm El Niño conditions create powerful high-level winds over the Atlantic Ocean that rip the tops off many budding tropical storms. La Niña conditions have the opposite effect, encouraging tropical storm formation. On this side of the Spring Barrier, whether the current La Niña conditions prevail into the new hurricane season this summer is pretty much anybody's guess.
This is why the National Ocean and Atmospheric Administration's Climate Prediction Center waits until the middle of May — May 19 this year — to issue its first hurricane season outlook.
To be fair, the early-bird hurricane forecasters are serious scientists who know the limits of these prognostications as well as anybody. Gray acknowledged the problem of trying to see through the instability of spring in a recent comment to Bloomberg News. "It's a tough barrier," he said, "you don't know what is going to happen."
People who run insurance companies and other businesses begin thinking about hurricane season in the spring, and these early forecasts give them something to go on. For the rest of us living in hurricane country, the details of the seasonal forecasts probably don't matter so much. Everyone agrees that the best course of action is to be prepared for one every year.