La Nina Developing, What Does This Mean for ND?

La Nin and the Pacific Decadal Oscillation?
El Nino and La Nina represent both the positive and negative phases of El Nino Southern Oscialltion (ENSO) across the Pacific Ocean, occurnig on average every three to five years. La Nina conditions in the eastern Pacific are characterized by cooler than normal seas surface temperatures, where as, El Nino is characterized by warmer than normal seas surface temperatures. Such changes in seas surface temperatures drive large scale atmospheric processes that can affect our weather in North Dakota.
Current Observed Sea Surface Temperatures
Current Forecast Sea Surface Temperatures
Shown above are the observed and forecast seas surface temperature anomolies across the eastern Pacific. Note in the observed seas surface temperatures (above left) the trend towards negative anomolies, or cooler than normal sea surface temperatures, denoted by the blue coloring from late may into late July. In order for an event to classified as a La Nina, the anomoly must average -0.5 Celsius or lower over three months. The forecast (above right), indicates continued cooling across the eastern Pacific into the fall and winter of 2010-2011, indicative of a possible La NIna. Each line in the graph (above right) represents a possible forecast of seas surface temperatures for the remainder of this summer and into the coming winter. While most forecasts show continued cooling and a possible La Nina, there are differences in the strength of cooling, repsented by the spread in lines on the graph. This is a result of forecast uncertainty and model limitations. Therefore, it can be stated that while most model forecast suggest La Nina is possible this coming fall and winter, the strength and duration of this possible event are yet to be determined.
What Does This Mean for Western and Central ND Weather?


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