RodneyS Posted January 19, 2012 Share Posted January 19, 2012 I ran some January/February numbers, 1950-2011, for average temperatures, precipitation, and snowfall at Reagan National Airport, broken down by La Niña years (21, according to my count), El Niño years (19), and neutral years (22), and what I found puzzles me. Here are the respective results: La Niña: January: 36.2 degrees, 2.61 inches, 5.2 inches February: 39.1 degrees, 2.71 inches, 3.7 inches El Niño: January: 35.3 degrees, 3.14 inches, 7.3 inches February: 36.7 degrees, 2.73 inches, 9.8 inches Neutral: January: 35.9 degrees, 2.63 inches, 5.0 inches February: 39.0 degrees, 2.58 inches, 7.9 inches The La Niña numbers make sense to me, as February temperatures are almost three degrees warmer than in January, with about the same amount of precipitation in each month -- therefore, it is logical that snow would be reduced. However, the El Niño numbers seem illogical, as February temperatures are 1.4 degrees warmer than in January with significantly less precipitation in February. So, why then is there significantly more snow in February in El Niño years? Finally, the neutral years seem to make the least sense of all. While February temperatures are more than three degrees warmer than in January and precipitation is slightly less in February than in January, somehow these conditions also produce significantly more snow in February. What am I missing? (or did I simply mess up the calculations? ) Link to comment Share on other sites More sharing options...
Deck Pic Posted January 19, 2012 Share Posted January 19, 2012 Climo is 3 degrees warmer in Feb than Jan so Feb in Ninos are colder with respect to the norm and Feb in ninos are known for a reverse temp gradient which usually implies blocking and a strong STJ, split flow....the warmer air is probably coming in spikes and on sunny days when climo/sun angle are a big deal....average high is 50 for the last week of the month Link to comment Share on other sites More sharing options...
BethesdaWX Posted January 19, 2012 Share Posted January 19, 2012 La Nina climo favors a -PNA in February and an unfavorable storm track, opposite for El Nino. I don't think we're going to be following climo this go around though. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 19, 2012 Share Posted January 19, 2012 What am I missing? RodneyS, Try computing the median figures from the same data and see what you get. A cluster of extreme data can skew the means. Link to comment Share on other sites More sharing options...
RodneyS Posted January 19, 2012 Author Share Posted January 19, 2012 RodneyS, Try computing the median figures from the same data and see what you get. A cluster of extreme data can skew the means. Okay, will do when I get home this evening. Also, I would like to run the numbers back to the beginning of the official snow record in DC (1884-85). Is there a consensus as to what years were La Niña, El Niño, and neutral prior to 1950? If so, could someone identify those or post a link? Thanks. Link to comment Share on other sites More sharing options...
RodneyS Posted January 20, 2012 Author Share Posted January 20, 2012 RodneyS, Try computing the median figures from the same data and see what you get. A cluster of extreme data can skew the means. Here are the medians: La Niña: January: 35.4 degrees, 2.41 inches, 2.8 inches February: 37.1 degrees, 2.54 inches, 2.2 inches El Niño: January: 35.3 degrees, 2.78 inches, 5.5 inches February: 37.0 degrees, 2.52 inches, 5.9 inches Neutral: January: 35.7 degrees, 2.61 inches, 4.0 inches February: 38.5 degrees, 2.39 inches, 5.2 inches So, the figures are not as extreme, but they still point in the same direction; i.e., there is more snow in February than in January in El Niño and neutral years, despite higher temperatures and lesser precipitation in February; whereas there is less snow in February in La Niña years, consistent with higher February than January temperatures and similar precipitation in the two months. Link to comment Share on other sites More sharing options...
RodneyS Posted January 21, 2012 Author Share Posted January 21, 2012 What am I missing? (or did I simply mess up the calculations? ) It turns out that I did mess up the snow calculations, based on Excel treating the word "Trace" in a column as a blank field rather than as a zero. So, here are the corrected snow numbers (bolded), with temperatures and precipitation figures shown for context: Means La Niña: January: 36.2 degrees, 2.61 inches, 5.2 inches February: 39.1 degrees, 2.71 inches, 3.0 inches El Niño: January: 35.3 degrees, 3.14 inches, 6.2 inches February: 36.7 degrees, 2.73 inches, 8.3 inches Neutral: January: 35.9 degrees, 2.63 inches, 4.3 inches February: 39.0 degrees, 2.58 inches, 5.7 inches Medians La Niña: January: 35.4 degrees, 2.41 inches, 2.8 inches February: 37.1 degrees, 2.54 inches, 1.6 inches El Niño: January: 35.3 degrees, 2.78 inches, 4.0 inches February: 37.0 degrees, 2.52 inches, 5.2 inches Neutral: January: 35.7 degrees, 2.61 inches, 3.1 inches February: 38.5 degrees, 2.39 inches, 3.6 inches Link to comment Share on other sites More sharing options...
RodneyS Posted January 21, 2012 Author Share Posted January 21, 2012 A couple of additional typos to correct (in bold). Now that I finally have what I believe are the correct mean/median 1950-2011 temperature, precipitation, and snowfall figures for DCA, January/February snowfall still seems contradictory for the Niño and neutral years. Specifically, in both of those situations, mean and median temperatures are higher and mean and median precipitation is lower in February than in January, but that combination results in more mean and median snowfall in February. Perhaps it's just an aberration -- I'll try and gather some pre-1950 data. Means La Niña: January: 36.2 degrees, 2.61 inches, 5.2 inches February: 39.1 degrees, 2.71 inches, 3.0 inches El Niño: January: 35.3 degrees, 3.14 inches, 6.2 inches February: 36.7 degrees, 2.73 inches, 8.3 inches Neutral: January: 35.9 degrees, 2.63 inches, 4.3 inches February: 39.0 degrees, 2.55 inches, 5.7 inches Medians La Niña: January: 35.4 degrees, 2.41 inches, 2.8 inches February: 39.1 degrees, 2.54 inches, 1.6 inches El Niño: January: 35.3 degrees, 2.78 inches, 4.0 inches February: 37.0 degrees, 2.52 inches, 5.2 inches Neutral: January: 35.7 degrees, 2.61 inches, 3.1 inches February: 38.5 degrees, 2.39 inches, 3.6 inches Link to comment Share on other sites More sharing options...
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