WORLD
La Nina`s exit leaves climate forecasts in limbo
Baku, July 4 (AZERTAC). Some recent news reports have attributed the nation`s record snowfall, killer tornadoes, and devastating floods phenomenon to an extreme "La Niña," a band of cold water stretching across the Pacific Ocean with global repercussions for climate and weather."La Niña was strong in December," says NASA climatologist Bill Patzert. "But back in January it pulled a disappearing act and left us with nothing - La Nada - to constrain the jet stream. Like an unruly teenager, the jet stream took advantage of the newfound freedom--and the results were disastrous."
Natures Mistakes or Misunderstood? Where the Rarest Breeds are found La Niña and El Niño are opposite extremes of a great Pacific oscillation. Every 2 to 7 years, surface waters across the equatorial Pacific warm up (El Niño) and then they cool down again (La Niña). Each condition has its own distinct effects on weather.
The winter of 2010 began with La Niña conditions taking hold. A "normal" La Niña would have pushed the jet stream northward, pushing cold arctic air (one of the ingredients of severe weather) away from the lower US. But this La Niña petered out quickly, and no El Niño rose up to replace it. The jet stream was free to misbehave.
According to Russell Schneider, Director of the NOAA-NWS Storm Prediction Center, explains: "First, very strong winds out of the south carrying warm, moist air from the Gulf of Mexico met cold jet stream winds racing in from the west. Stacking these two air masses on top of each other created the degree of instability that fuels intense thunderstorms."
Extreme contrasts in wind speeds and directions of the upper and lower atmosphere transformed ordinary thunderstorms into long-lived rotating supercells capable of producing violent tornadoes.
In agreement with Patzert, he notes that the very strong and active jet stream across the lower US in April "may have been related to the weakening La Niña conditions observed over the tropical Pacific."
And of course there`s this million dollar question: "Does any research point to climate change as a cause of this wild weather?"