No, it’s not Chris Farley in a unitard…but NOAA scientists announced today that El Nino has returned. First..what really is El Nino? El Nino is the periodic warming of the central and eastern tropical Pacific waters, which occurs on average every two to five years. That’s it…that’s the definition of El Nino. There is nothing in the definition which states it WILL change global climate in a certain way. However, scientists are confident that El Nino does influence global weather, ocean conditions and marine fisheries. That influence can vary from one El Nino to the next.
Let’s look at a few pictures which will help describe El Nino.
On the left is the signs of a very strong El Nino. The white band represents equatorial pacific waters that were as high as 5 degrees celsius above normal. On the right, is a weaker, but still impressive El Nino event.
Here is another depiction of an El Nino event. Notice the red band off the west coast of South America.
So what could El Nino mean for Oklahoma? It could mean a cooler and wetter period during the cool months. In general, the El Nino event has to be significant for it to impact Oklahoma’s weather.
The General effects El Nino has on the United States climate (top). Notice how the effects of La Nina (bottom) are almost completely opposite.
Our friends at the Oklahoma Climatological Survey studied 20 previous El Niño episodes from 1950-2005 and tracked the corresponding October-March precipitation totals in an effort to detail the warm pacific water’s effects on Oklahoma’s climate. Of the 20 El Niño episodes, four were considered “strong”, while the remaining 16 events were broken down into eight of both “moderate” and “weak” classifications.
The influence of the four strong events was easily seen, with above average
rainfall in all areas of the state. In fact, the wettest October-March since
1951 occurred in east central Oklahoma with the strong El Niño of 1998, along with the 2nd wettest such period in the southeast. This follows typical El Niño influences in which the southeastern United States receives above average moisture. The effect extends westward into southeastern Oklahoma during a strong event, and can actually extend farther west to benefit the entire state.
Moderate El Niño events appear to influence the weather differently across the state. Western Oklahoma has in increased chance of above average rainfall in the case of a moderate event, while the results for eastern and central Oklahoma are nondescript. Of the eight moderate events tracked, north central and west central Oklahoma had above average rainfall in six of those instances,while the Panhandle, southwest, and south central areas observed above average precipitation five times.
The prospects for drought relief become bleak during weak events. All areas of the state experienced below average precipitation during weak El Niños. Of the eight weak events tracked, all regions were below average at least five times. South central Oklahoma fared the worst with seven below-average periods.
History shows us that El Nino could bring us some cooler and wetter weather by the end of the year. But the strength of this year’s El Nino will probably be the determining factor whether it will have any influence over our climate. So how strong will El Nino 2009 be?…that is still up in the air…or out in the ocean.