La Nina Has Returned

The latest ENSO discussion issued by the Climate Prediction Center shows that La Nina conditions have strengthened and suggests that we are likely going to see a double-dip La Nina this winter.

Below average sea-surface temperatures now extend across much of the eastern and central tropical Pacific, consistent with La Nina conditions.

Source: CPC

About half of the models used to predict the ENSO cycle call for La Nina to strengthen during the fall and winter.

Source: CPC

One model, the NCEP climate forecast system (NCEP CFSv2) calls for a fairly strong La Nina to develop, although this is an outlier.

Based on the model guidance and an analysis of this and past events, the Climate Prediction Center concludes that "a weak or moderate strength La Nina is most likely during the Northern Hemisphere winter.

It should be noted, however, that this does not necessarily mean a repeat of the 2010/11 winter, for reasons we have discussed in a previous post.  The dice are merely slightly loaded for above average snow in the Pacific Northwest and below average in the far southwest, as indicated in the CPC precipitation outlook for Jan-Mar.

Source: CPC

Wasatch skiers should note that we sit in an area where there is an equal chance of above or below normal precipitation.  In other words, we don't really know how good this ski season will be in Utah relative to average.