When was the last time we had a colder-than-normal month?

With our mild winter, incredibly warm March, and reasonably warm May coming in sequence, it seems as if it has been a long time since Madison experienced a below-normal month.

In reality, it is not that long ago – September 2011 was 2.0 degrees below normal and the six months from December 2010 through May 2011 were all below normal, though often only slightly so. The average departure over that period was only 1.16 degrees below normal. Since Oct. 1, we have averaged 8.3 degrees above normal — a remarkably warm stretch.

The current seasonal outlook for our summer from the National Centers for Environmental Prediction suggest “equal chances” for us to have a normal summer. This forecast amounts to saying that there are no clear indicators that the summer will be warmer or colder than normal.

One physical factor that has changed since we embarked upon our now eight-month warm spell is that the tropical Pacific sea-surface temperatures have returned to their normal state after having demonstrated anomalous cooling (La Nina conditions) in the eastern Pacific during our warmth.

Though such forecasts are more statistical than physical in nature (quite different from the more physical one- to five- day forecasts of the weather) such a switch from La Nina conditions to more neutral conditions often heralds a return to normal seasonal conditions for the north central United States. It appears more likely than not, however, that the southern tier of states will have a warmer-than-normal summer.

Category: Climate
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