La Nina conditions to thank for our wet and cold winter

For nearly a decade Idaho has been in the throes of drought conditions plaguing local farmers and residents with water woes every summer.

Last summer, many communities including Kuna were forced to shut-off irrigation earlier than usual in response to low water levels. Despite last summer’s water troubles, current snow levels look promising, with the snow pack in southeast and southwest Idaho ranging from 80 to 90 percent of normal. In central and northern Idaho many basins are above normal including the Salmon, Payette and Weiser basins.

In February 2007 NASA’s Jet Propulsion Laboratory reported La Nina conditions as shown by satellite pictures taken by the Jason altimetric satellite. La Nina has come to fruition, causing Idaho’s promising snow pack.

El Nino and La Nina are essentially opposite cooling and warming patterns (see satellite images left) that originate in the Pacific Ocean and effect weather patterns all over the world, especially impacting the weather patterns in the western United States.

According to the National Oceanic and Atmospheric Administration in a “normal” year, the trade winds blow westward and push warm surface water near Australia and New Guinea. During an El Nino event, the trade winds weaken and warm, nutrient-poor water occupies the entire tropical Pacific Ocean. Heavy rains that are tied to the warm water move into the central Pacific Ocean and cause drought in Indonesia and Australia.

According to the NOAA, during a La Nina event, the trade winds are stronger and cold, nutrient-rich water occupies much of the tropical Pacific Ocean. Most of the precipitation occurs in the western tropical Pacific Ocean, so rain is abundant over Indonesia. Typical La Nina winter weather patterns include very cool, wet conditions in the Pacific Northwest, and unusually dry conditions in the Southwest and Southeast. The NOAA reports that since 1975, La Ninas have been only half as frequent as El Ninos. Further, a La Nina episode may, but does not always, follow an El Nino. La Nina conditions often peak in January, and current conditions appear to have followed that same pattern this past month.

While La Nina is bad news for Idaho’s neighbors to the south–it has proven to be just what Idaho needs in order to negate the effects of the persistent drought conditions Idaho has experienced the last several years.

It remains to be seen how long the current La Nina will last–according to the NOAA, conditions could go on for another month or another year.