Weak El Niño leaves wet winter up in the air - Tucson News Now

Weak El Niño leaves wet winter up in the air

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Warmer than average sea surface temperatures in the eastern equatorial Pacific Ocean is known as El Niño.  Sea surface temperatures in this area can influence weather across the globe by shifting seasonal wind flow patterns.  Here in the Southwest an El Niño during the winter generally means wet weather.  However, the amount of rain is extremely variable.

This summer an El Niño did form in the waters off central and south America. But in the latest discussion the Climate Prediction Center (CPC) at the National Oceanic and Atmospheric Administration (NOAA) says "the Pacific basin reflects borderline ENSO-neutral/ weak El Niño conditions".   

This is not good news. If El Niño disappears, so could our hope for a wet winter. 

The CPC discussion goes on to say "Compared to the past few months, the chance is reduced for El Niño to develop during Northern Hemisphere fall/winter 2012-13 (see CPC/IRI consensus forecast). Due to the recent slowdown in the development of El Niño, it is not clear whether a fully coupled El Niño will emerge. The majority of models indicate that borderline ENSO-neutral/ weak El Niño conditions will continue, and about half suggest that El Niño could develop, but remain weak (Fig. 7). The official forecast therefore favors the continuation of borderline ENSO-neutral/ weak El Niño conditions into Northern Hemisphere winter 2012-13, with the possibility of strengthening during the next few months."

The below colorful graphic shows all the computer model predictions for El Niño. An El Niño is named when the sea surface temperature reaches 1/2° above average. The different colored lines show all the different model predictions in three month blocks. (At the bottom, ASO means August/September/October.) Most of the models have the weak El Niño continuing through the winter with a weakening of conditions in the spring. A weak El Niño means the hopeful wet winter for drought-stricken Arizona may not become a reality. 

In the latest U.S. Drought Monitor update, Arizona is still experiencing Moderate, Severe, and Extreme drought.  Although Tucson had near-average rain totals for the monsoon, the rain totals for the year at the end of the monsoon were 2.5" below average.  That's because the start of the year started off extremely dry with less than an inch of rain January through June 15th. 

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