Grading our 2013 summer outlook: A solid forecast


A child cools himself off as he plays in the fountain along the Georgetown Waterfront on the evening of September, 03, 2013. (Craig Hudson Photography)

We have now decidedly transitioned to mid-autumn weather, and there is no looking back as we slide into winter.  But let’s can take a quick look back at summer anyway,  and grade our summer outlook.

We did well this summer.  It wasn’t just unsurprisingly cooler than the previous three monsters, but measurably cooler – and we anticipated that. Let’s get down to grading.

Our temperature call for the entire summer was a bulls-eye. We predicted temperatures to be near normal to one degree above normal, and the summer finished at 0.6 degrees above normal. Can’t get better than that. That gets an A+.

On the other hand, our month to month temperature calls were mediocre.

We predicted a normal June and it finished at 1.3 degrees above normal.

Same deal in July.  We called for a normal July and we finished at 1.4 degrees above.

We predicted August to be 1 to 2 degrees above normal and it actually finished as our coolest month at 1 degree below normal. This was our worst monthly call.

When we predict temperatures, we absolutely account for urban heat island, and consider substantially elevated minimum temperatures compared to 30-year normals, especially at National Airport.  Nevertheless, overnight lows were particularly warm due to the persistently humid pattern for some of June and much of July.  But daytime highs were actually right at normal for June and July, and well below normal for August.  This gave summer the “feel” of being cooler than it actually was, and I think definitely helps to mitigate our slight misses in June and July (August was still a bad call).

Taking all of this into account, I would grade our month-to-month temperature calls as a C+ (Bs for June and July; D for August).

Our other supplemental predictions are less important in terms of grading, but we did very well on all of them: 

* Precipitation finished at 150% of normal versus our prediction of 125%.  
* With 23 90+ degree days (between June and August, meteorological summer), we fell just short of our window of 25-30.  
* Our longest heat wave was 7 days, versus our prediction of 6-8 days.  So nailed that one.  
* We correctly predicted no 100 degree days.

Overall, I think we did quite well in capturing what was in store for the summer of 2013, even if we underestimated the humid pattern of June and July, and missed the boat on the cold August.  I would give us a grade of a B+, though a B makes sense as well.  Let us know what you think.  Did we do a solid job?  Did we grade ourselves fairly?

CWG’s 2012 summer outlook (post-summer evaluation)
CWG’s 2011 Summer Outlook (post-summer evaluation)
CWG’S 2010 Summer Outlook (post-summer evaluation)
CWG’s 2009 Summer Outlook (post-summer evaluation)

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Dan Stillman · October 30, 2013

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