Winter 2011-12 Review

The astronomical spring will begin on March 20, 2012, but the meteorological spring already started this past March 1^st.  Now that winter is over in a meteorological point of view (meteorological winter is Dec-Feb), I will take a look at how it compares with average and with this past 2010-11 winter.

Winter 2011-12

This winter was very unusual to say the least.  The average high for the winter months is 32.3°F but this winter was 39.5°F, which is 7.2°F above average.  Looking at each month:

December average high was 41.5°F (7.4°F above average)
January average high was 37.8°F (7.8°F above average)
February average high was 39.3°F (6.4°F above average)

Breaking it down even further, out of the 91 days of the 2011-12 winter:

66 of the days were above average (72.5%)
-17 days were 1-4 degrees above average (18.7%)
-29 days were 5-9 degrees above average (31.9%)
-20 days were 10+ degrees above average (22.0%)

Out of the 25 days that were not above average:
-11 days were exactly average (12.1%)
-14 days were below average (15.4%)

This winter was the warmest that I can remember.  I do not yet know where it ranks historically for Detroit winter’s but I am sure it has to be in the top 5 warmest, probably top 3 warmest.

Winter 2010-11

So how does this compare to last winter?  The two winters couldn’t be any more opposite. 

2010-11 winter average high was 30.1°F (9.4°F cooler than this winter)
-December 2010 was 30.6°F (10.9°F cooler than this December)
-January 2011 was 27.7°F (10.1°F cooler than this January)
-February 2011 was 32.1°F (7.2°F cooler than this February)

The 2010-11winter had 90 days, and 59 of the 90 days were below average (65.6%).

Snow Comparison

Considering that it was much warmer than average this winter, it should come as no surprise that there was less snow than average as well.  So far there has been 25.8 inches of snow at the Detroit Airport in Romulus Michigan, where official records are kept for the Detroit area.  The average for our area is 39.3 inches, so we are currently 13.5 inches below normal.  This can change considering it could still snow in March and into April.  As I just mentioned, the 25.8 inches is from the Detroit Airport.  Locations further east (specifically Macomb County), received much less snow.  I do not know for sure, but I would guess my area received about half of the 25.8 inches, maybe even less.

Last winter we received 69.1 total inches!  Last season’s total snow was 29.8 inches above average and an amazing 43.3 inches more than what we have received this year.  That is nearly 4 feet more snow!

So with snow totals so low this winter, one might think that we were below average with liquid precipitation (rain/snow/sleet/freezing rain), but that is not the case.  In fact, we had more liquid precipitation this winter with 7.70 inches than we did last winter with 6.41 inches.  So even though we had nearly 4 feet less of snow this winter compared to last winter, we received much more rain than average for a typical winter season which gave us more liquid precipitation.  Basically, since it was so warm this winter, most of the systems that moved through our region that would have normally gave us snow instead gave us rain.

Seasonal Forecasts

Meteorologists use a combination of weather patterns, weather models, and historical data to create seasonal forecasts.  The seasonal forecasts are used by many groups including the government, private businesses, and weather enthusiasts.  Creating a seasonal forecast is no easy task, and this past winter is a great example of that.  The image below represents highlights of Accuweather’s 2011-12 winter seasonal forecast.   Just by looking at this image, it is easy to say that their winter forecast was a major bust for most of the US.  For example, Accuweather predicted that the Midwest would experience a harsh winter with cold temperatures and a lot of snow.  In reality, the Midwest had a very warm winter with very little snow.  Their forecast was also a bust for most of the Plains, the North East, and the Central US. 

 Image represents highlights of Accuweather's 2011-12 winter prediction.  Courtesy of Accuweather.

I could be wrong but I have a feeling that Accuweather put too much weight into the similarities in global patterns that were present this winter that also occurred last winter when it was cold and snowy.  Last winter was a La Nina winter and the forecast was for this winter to be one as well.  La Nina winters favor a wetter winter for Michigan, and if the temperatures are cold enough, that translates to a lot of snow.  As I have mentioned in a previous post, the problem with this is there are other weather patterns that need to be considered as well such as the North Atlantic Oscillation and Arctic Oscillation.  Last winter, these oscillations were strongly negative which allows cold Arctic air to spill into the eastern half of the US, but this winter they remained positive which kept the cold air to our north.  The oscillations are significant to our winter weather but unfortunately meteorologists currently do not know enough about these oscillations to forecast their seasonal trends.  At the present time, meteorologists can only accurately forecasted the NAO and AO about two weeks into the future.   I suspect that Accuweather did not anticipate a drastic change in the oscillations from last winter to this winter which ultimately really screwed up their winter seasonal forecast.  There are some things in life that the more you know, the more you realize you don’t know…and weather is one of them.

If anyone is interested in seasonal forecasts, I would recommend using the NWS Climate Prediction Center website.  Their three month seasonal forecasts can be found here.  I like to use their seasonal forecasts for two reasons.  The first reason is that they are not interested in being flashy by making big predictions to draw attention.  Instead they are interested in being accurate.  The second reason is that they use probabilities instead of making predictions with specific wording (example is Accuweather saying “Worst of Winter Cold & Snowy”).