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To contradict Shakespeare, 2012 was not the winter of discontent — it may go down as the year without a winter at all in many parts of the country, and you can blame — or praise — the jet stream, says a Texas A&M University climate expert.
John Nielsen-Gammon, professor atmospheric sciences who also serves as state climatologist, says upper level dynamics this year were unusual and the resulting change in the jet stream — a river of air that influences weather patterns — is the likely culprit.
“The jet stream follows a different average course each year, and the end results this time were warmer temperatures,” he explains.
“This is a La Nina year (when water temperatures in the central Pacific Ocean are lower than normal), but the atmosphere did not respond to La Nina in the normal way,” adds the Texas A&M professor who has studied weather patterns for years. Nielsen-Gammon points to another, less well-known factor, the North Atlantic Oscillation, as an important cause of the unusual weather.
“The jet stream in the North Atlantic often gets locked into either a southern route or a northern route,” Nielsen-Gammon explains. “The last two winters, it was the southern route. This year, it was the northern route, bringing the central and eastern United States warm air masses as the air traveled from south to north.”
One key question might be: Does this mean we should expect another warmer- than- normal summer?
“Not necessarily,” Nielsen-Gammon reports.
“Right now, the Climate Prediction Center’s outlooks show a tendency towards a warmer than usual summer across much of the United States, but a lot depends on the rain between now and then. More rain would mean cooler weather because the moisture keeps temperatures lower. We should know more about the summer outlook in the next few weeks. Certainly March has already had some very warm temperatures all over the country.”
Last week, more than 1,700 records were set for high temperatures from coast to coast, with many cities, such as Chicago, Boston and Washington, D.C., posting readings almost 20 degrees above normal.
“The good news locally is that rains in central and eastern Texas have eased the drought situation considerably, and lakes and reservoirs and filling back up,” the Texas A&M researcher reports. “More and more of the state is getting out of extreme drought status. But there are still large parts of west and southTexas that are very dry.”
The bad news is that the warmer weather means many people are suffering from allergies sooner than ever because pollen from plants and trees is out sooner, and there is more of it, he adds. Also, the warmer weather could mean more insects in the weeks to come.
“But I think it’s worth all that just to get to experience the beauty of Texas wildflowers,” says Nielsen-Gammon.
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