Fall and Winter Outlook, or Here Comes El Nino!

Summary of Summer 2009

It has been a warm and dry summer for much of the Western United States including Eastern Utah and Western Colorado. The monsoon season, the sub-tropical moisture that bubbles up from the south in the summer, has been very weak so far this season. Grand Junction and Vernal have registered above normal monthly temperatures for July, August, and mid-September. As of September 19, Grand Junction was 0.60 inch behind normal, and Vernal was a whopping 2.41 inches drier than normal.

Mid June to Mid September Percent of Normal Precipitation. Brown color represents below normal.Mid June to Mid September departure of Temperature from Normal. Yellow and Brown colors are above normal.


El Nino!

Climatologists look to the state of the oceans for seasonal outlooks. Since May 2009, the sea surface temperatures in the Equatorial Eastern Pacific have been above normal.  This is typically called an El Nino event. Local studies for Eastern Utah and Western Colorado indicate El Nino fall seasons tend to be wetter than normal, while El Nino winters tend to be drier than normal.

Sea Surface Temperature Anomaly Forecasts. The warm red color west of Peru indicates El Nino conditions are forecast to persist through the winter.


October and October-November-December Outlooks from the Climate Prediction Center 

Temperature Outllooks (left) and Precipitation Outlooks (right for October (top) and Oct-Nov-Dec (bottom)

There are increased chances that temperatures will be above normal this fall season. And there is an increased chance of above normal precipitation for October. This fits well with local study results.

Outlook for the Winter Season from the Climate Prediction Center

Temperature Outlook for December-January-February. The brown colors indicate an increased probability of a warmer than normal winterPrecipitation Outlook for December-January-February. The area of "EC" indicates no skill.

El Nino winters tend to produce closed Low Pressure Systems that track through the Four-Corners region, and then lift onto the Plains. This tends to produce potentially heavy precipitation along the Front Range, and perhaps the San Juan mountains of Southwest Colorado. Overall though, local studies show a tendency towards lower precipitation than normal for December and January.

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