Tuesday, April 16, 2013

Just How BIG have this April's "Ups and Downs" been so far?...

Cleveland Skyline
The dramatic "ups and downs" in recent weeks have caused many to draw the conclusion that this pattern must be something very unique even for spring. Andre has a great blog on his website about how our memory is very selective. We tend to put more weight on recent events or events that are important to us without taking a look at the "big picture" and the data. I've also written extensively about our cognitive biases in how they shape how we perceive the weather (behavioral meteorology) HERE and the human condition pertaining to weather HERE. Our cognitive dissonance couldn't be more apparent in how we view this recent 14 days weather pattern, i.e. One day at 80 then 30s with drizzle and sleet, etc

So how does this April so far compare to the last few years comparing day-to-day HIGH temperatures drops and rises compared to the normal high of the day?  Here are the largest "drops and rises" compared to the daily normal over the 25 Aprils through the first two weeks. For example, if the high was 80 (normal for that date was 60 for a +20 degree difference) and the next day, the high was 45 (normal was 61 for a -16 degree difference), the final difference over the 24 hour period was -36 degrees! These are the numbers I used in the graph below.

Don't be intimidated by this chart. There a lot of numbers here. First, I BOLDFACED the instances of day-to-day positive change (WARMER) of more than 10 degrees. Second, I underlined instances where the temperature change was more than 10 degrees for back-to-back days.  Frankly, I couldn't figure out a good way of illustrating this so the raw data will have to do for now.

Here are some of my notable conclusions:

Recently, 2011 had some VERY big "ups and downs". During one stretch in 2011, temperatures dropped 31 degrees in 24 hours then rose 13 degrees the following day!

April 2010 had an instance where temperatures dropped 20 degrees and then rose 22 degrees the following day.

April 2007 had a 12 degree jump then a 17 degree drop followed by ANOTHER 35 degree drop.

April 1995 from a Sunday to Friday saw a 20 degree jump, a 17 degree drop, a 12 degree drop, 22 degree jump then finally a 19 degree drop!


The bottom line is that historically, April is known for wild swings in temperature and weather. We just don't want to believe it because what's happening NOW is usually perceived as more significant than what happened in the past.

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