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Posted at 10:45 AM ET, 04/14/2011

Grading our 2010-2011 Winter Outlook


Though we are still in a time of highly variable weather as is typical of April, we can safely put winter weather behind us.  As such, and as it is custom here at Capital Weather Gang, it is time to grade our 2010-11 Winter Outlook.  Our outlook was broken down into two main facets, temperatures and snowfall. 

Here’s a summary in table format of what we predicted versus what actually happened:

 PredictedActual
December Temps -1 to -2 deg-4.9 deg
January Temps+1 to +2 deg-1.3 deg
February Temps+2 to +3 deg+3.6 deg
Overall Temps0 to +1 deg-0.9 deg
National Snow14"10.1"
Dulles Snow19"12.6"
BWI Snow21"14.4"

Now, let’s take a more detailed look at how we did with temperatures.

Our temperature outlook was provided in two parts.  A breakdown of the individual months and an overall temperature forecast for the whole winter.  Our performance was good, but not great, on both. 

In our monthly assessment, we forecast December to be 1 to 2 degrees below normal, January 1 to 2 degrees above normal, and February to be 2 to 3 degrees above normal. 

We were correct in predicting December to be colder than normal and the coldest winter month relative to normal, but we underdid the cold.  It ended up being almost 5 degrees below normal and our 3rd coldest December in over 40 years.  January was a miss for us as it ended up 1.3 degrees below normal.  However, as we predicted slightly above and it ended up slightly below, it was not a complete bust. But still a miss.  February was our best month as it finished 3.6 degrees above normal which was just outside our range of +2 to +3, so not a bullseye, but very good nonetheless.

Overall, for the December through February period, we called for temperatures to be normal to 1 degree (or slightly) above normal.  Winter ended up finishing 0.9 degrees (or slightly) below normal.  So we were incorrect in our assessment that winter would lean slightly toward warmer than normal, but did not miss by much. 

While there are multiple ways to look at it, it really was the severely cold December that kept winter as a whole on the slightly colder side of normal versus the slightly warmer side.  As we suggested was possible in our outlook, the negative North Atlantic Oscillation really performed in December and January and kept us cold.

I would grade the temperature aspect of our outlook a B-/C+.  On the positive side, we correctly predicted the coldest to warmest months with respect to normal with December the coldest, February the warmest and January in the middle, and we almost nailed the warm February.  This was mitigated by a slight miss on the really cold December, and what I would consider a worse miss on January.  Overall, while we were on the wrong side of normal, winter temperatures finished close enough to normal that our assessment was a decent one, if not great.

Our snowfall prediction, like our temperature one, was good at best, but certainly not great.  We got the easy prediction right.  It did not snow as much as the 2009-10 winter.  But we still overdid amounts.  Generally, around 70 percent of what we predicted fell across DC metro.

At DCA (Reagan National), we predicted 14” of snowfall, or slightly below normal.  10.1” fell for the season.  At IAD, we also predicted a slightly below normal 19”, but only 12.6” fell.  At BWI, we predicted an around normal 21” and 14.4” was the seasonal total. 

The problem was not the number of events.  We actually had 12 discrete snow events, or 3 more than last season’s epic winter.  It was that these events were generally moisture starved and thus usually resulted in just dustings up to an inch or two. 

We only had one sizable event.  The heavy, wet, crippling snow of January 26th in which a general 5-9” fell across the region in a very short time. In order to get to our predicted number, we really needed one other decent 4-8” event across the region and we never got it.  Our best chance was likely the 12/26 event that seemed to hit everybody on the East Coast except for our region.  Some of you might recall that we were under winter storm warnings that never came to fruition.  That near miss among several others is of some consolation, but we still fell somewhat short.  Despite the sharply negative NAO in December and January, La Nina still asserted itself, as we suggested, with resultant storm tracks that either cut to our west or left us without ample moisture even when cold air was in place.

In a region where we have such a wide range of what can fall over a season, our predicted numbers really weren’t that bad.  Normal to slightly below normal predicted snowfall in actuality ended up being somewhat below normal.  I would lean toward a snowfall grade of C+, but I think the miss by less than 4” at DCA merits a B/B-, so overall a B-/C+ for snow

Overall, we grade our outlook a B-/C+.  It was a decent, better-than-average outlook with some high points, and we believe it provided value heading into winter.  But there were enough things wrong with it, that while it borders on good, we think falls just a hair short.  Let us know what you think.

By  |  10:45 AM ET, 04/14/2011

Categories:  Capital Weather Gang, Winter Storms, Local Climate, Latest

 
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