Sunday, March 18, 2012

Winter Was Warm, But March Is %#!@^

Winter was the fourth warmest on record for the U.S. according to the National Climatic Data Center (NCDC).  Here winter is defined as the months of December through February, also known as meteorological winter.  The map below shows that most of the warm weather was east of the Rockies with near normal conditions in the West.

Statewide rank of winter temperatures for 2011-2012.  Image Credit: NOAA/NCDC.

Enter March.  This supposed to be a time of change, a transition from winter to spring.  However, this month has simply been a continuation of the trends in winter and more so.  It has been unseasonably warm over all, but the west coast of the U.S.  In fact, temperatures have been averaging more than 10 degrees F above normal in the Midwest.

Mean temperature anomalies for the U.S. for March 1-16, 2012.  Image Credit: NOAA/CPC.

The weather pattern during the middle of the month led to a rare event from the Climate Prediction Center (CPC).  They issued a 6-10 day outlook with a 90% chance of above normal temperatures for parts of the Midwest.  The forecast was issued on March 13.

The 6-10 day outlook issued on March 13 from CPC.
To understand how extraordinary this is you need to look at the probability lines used by CPC (see image below).  In the forecast above the 90% probability means that there is a 6.7% chance of near normal conditions with a 3.3% of below normal which is probability line number 17.

The probability lines for the forecast maps used by CPC.

The CPC explains the probabilities this way:

The probabilities of all three categories are implied on the map, and sum to 100%. The forecast probabilities given on the map generally fall far short of complete confidence (100%) in any single category. When the probability of the above (A) or below (B) category is greater than 33.33% by some amount, the probability of the opposite category declines by that amount, while the probability of the middle category remains at 33.33%. In the event that the "N" category is greater than 33.33%, the probabilities of both the "A" and "B" categories is each reduced by 1/2 the amount that the "N" category exceeds 33.33%. When the probability of "A", or "B" reaches 63.33% or higher, the odds of the opposite category reach a minimum allowed value of 3.33%, while the odds of the middle category are allowed to drop below 33.33%.

So what does the rest of the month look like.  Temperatures will continue to be above normal for much of the country east of the Rockies.  The latest 6-10 day outlook issued Sunday, March 18, is below.

The lastest 6-10 day outlook issued Sunday, March 18 by CPC.  This is for the period March 24-28, 2012.

Notice that it continues to be unbelievably warm.  It is interesting to note that at last check record high temperatures were beating record low temperatures by a ratio of 14:1.  Hope this is not a sign of summer.