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El Nino is back but the question remains as to what its effects will be on the U.S. climate and more specifically Oklahoma weather over the next few months. However, if the current event continues strengthening as models project, climate data suggests Oklahoma could be in for a wet winter.
El Nino occurs when warmer than average sea surface temperatures are seen throughout the equatorial waters in the Eastern Pacific. Once the sea surface temperatures reach anomalies of +.5 C, for at least five months, the condition is classified as El Nino. The name El Nino means "little boy" in Spanish, and refers to the Christ child as the event's normal peak happens around Christmas. In the past, El Nino has had varied effects on Oklahoma weather according to the strength of the warming that occurred.
Historically, if the event has been weak, it has produced little impact on Oklahoma's weather. But, if the event reached moderate or strong levels, the impact on Oklahoma's weather has been significant. Based on a 100 year average from 1895-1996, winter precipitation has increased substantially over Oklahoma during moderate to strong El Ninos. According to the Climate Prediction Center, during these moderate events, the period from November through March brings precipitation increases from 125 to as high as 170 percent of normal over Oklahoma. This equates on average to about a 2-4 inch increase in precipitation over the winter season. However with strong events, the impacts have been even greater.
The two strongest El Ninos recorded in the last century occurred during the winters of 1982-83 and 1997-98 (pictured above). During these stronger events in which SST anomalies reached +2.5C, Oklahoma saw precipitation increase to anywhere from 4-7 inches above normal.
The Climate Prediction Center's latest report released on 18 Oct. reported that sea surface temperature anomalies were running about +.8C to +1.2C in all the El Nino regions which would rank the current phase as weak. Based on September model runs however, the current El Nino is expected to intensify over the coming months. Most models predict that there will be a moderate El Nino event this year, but with current SSTs in the high range of what the models forecasted for this point of the season, the area bears watching for further development.
For more information on Oklahoma weather, we recommend the following local links:
Story is ©
Steve Irwin, 2006
