El Niño September update - KCTV5

El Niño September update

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In the latest forecast discussion, the Climate Prediction Center (CPC) says a majority of computer models "favor a weak El Niño" developing before the end of the year. The CPC says "the chance of El Niño is at 60-65% during the Northern Hemisphere fall and winter."

This could be good news for Arizona. When El Niño coincides with winter months, Arizona generally has a wetter than average winter. The winter storm track drops farther south than average allowing storms to dump more rain and snow on the state than is typical of an Arizona winter. However with a weak El Niño in the forecast the a wet winter could still elude the state. 

El Niño and La Niña refer to the sea surface temperature (SST) of the eastern equatorial Pacific Ocean, off the coast of central America. The temperature of the water in this area can influence weather across the world, including right here in Arizona. El Niño is when the SSTs are warmer than average versus La Niña, which is when SSTs are cooler than average. The below image from National Climate Data Center shows how El Niño influences weather during the cool and warm months in the Northern Hemisphere.   

The below image shows the latest El Niño forecast from the CPC. The '0.0' line indicates average SST. The colored lines represent different computer models that forecast El Niño and La Niña trends. The thicker yellow line is the average of all the model data.  The letters at the bottom represent the months. For example, 'JAS' represents June, July, and September. In the forecast, you can see that the yellow line is trending slowly upward through the rest of summer and into fall. Once the line goes above '0.5', an El Niño is in the forecast. The current observations show the SSTs are hovering around this threshold.  

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