Some Perspective on Record Weather Events

Record weather events in the United States from 8/13/12 to 8/20/12. In total, there are 1756 record weather events in this period, 1732 of which are displayed on this map.  (I’m guessing the remaining records are in Alaska and Hawai’i.)

As a meteorologist and lover of social media, I see a lot of news regarding the weather on a daily basis.  I follow numerous weather-related Twitter handles that pass along little tidbits of information throughout the day.  Honestly, I ignore most of it as it doesn’t pertain to my life and/or I don’t find it very interesting.  One category of tweets I am starting to ignore more and more is the record weather event.  Nearly every day I’ll see that a record high or low was set somewhere in America.  (ZOMG!! RECORD HIGH IN TRUTH OR CONSEQUENCES!!!  IT’S THE TRUTH!!!  AND SWEATING IS THE CONSEQUENCE!!)  Every once in a while, I run across a map like the one seen above.  Usually it contains only one side of the spectrum – either record warmth or record cold.  (You can tailor the map to only show one side at the web site where it’s designed.)  When you don’t bother to filter the map, you end up with something like that seen above.

What can you glean from this image?  This past week was warm in the west and southwest.  It was cold in the Plains and Midwest.  It rained in the Deep South up through the Ohio River Valley and into New England.

BUT, BUT… RECORDS!!!!

Please stop and think about it for a second.  There are a lot of factors suggesting you shouldn’t be all that excited for a daily record weather event.

Age of the Station

How old is this station that’s reporting a record?  Let’s look at one record set yesterday as an example.  From the Little Rock, AR NWS…

A RECORD LOW TEMPERATURE OF 61 DEGREES WAS SET AT JACKSONVILLE/LITTLE ROCK AFB YESTERDAY. THIS BREAKS THE OLD RECORD OF 63 SET IN 1991.

This location is titled “North Little Rock” by the NWS office.  The station’s record period goes back to 1975 – only 38 years.  In other words, yesterday’s low temperature was competing with only 37 other low temperatures for the record low.  Meanwhile, the Little Rock station at Adams Field goes back to 1875.  So, that station has an extra 100 years worth of daily temperature and precipitation data.  The record low for yesterday at Adams Field is 61 degrees, set in 1949.  This station only dropped to 65 degrees yesterday.

Furthermore, consider the age of any station – even those close to 150 years old – with respect to the age of the planet (4.5 billion years), the time since the last major extinction (65 million years), or just the age of modern human beings (10,000 years).  Now, 150 years doesn’t seem like a long enough time to get really excited about a record low or high, does it?

A Station is a Single Point

Most of the daily rainfall records set during the late Spring to early Fall months are a result of a convective storm passing over the reporting station.  These storms are usually quite small when compared to something like a hurricane or snowstorm.  Thus, the odds of the heaviest rain passing over the station aren’t really good on any day.  When it does, it will almost certainly set a daily record unless that same date in some year past had an event stronger storm pass right over the station.

Even so, what is the value in saying there has been a daily rainfall (or snowfall) record?  So this station never had this much precipitation on this date in any previous (recorded) year?  OK.  Why is that important?  I can see where setting a monthly or annual record for precipitation (either on the low or high end) is relevant.  It can help alleviate (or cause) a drought and it can help forecasters prepare the public for potential floods if the soil moisture content is high.  But a daily record? I don’t see the point other than putting a pretty green dot on the image at the top.

Station Siting Issues

Two main issues arise with the siting of weather stations around the US: 1) they have moved and 2) they don’t meet the standards required for proper siting.  The latter issue has been tackled by others, most notably Anthony Watts and his supporters around the country.  I’ll leave you to sift through that as you see fit.

The first issue I identified is most common in the older stations that arose in the late 19th century.  As cities expanded, the main reporting stations often moved out of the way, normally finding themselves at airports once those were established in every major city.  In many cases, the data associated with the station moved along with it, which compromised the data.  There have been adjustments made to these data in an effort to smooth out the differences between station sites, but it’s not a perfect solution.

I’m not trying to say a daily record is meaningless (well, when it comes to precipitation, that’s exactly what I’m saying).  I’m simply trying to put them in perspective.  The weather we experience today has been experienced by living things on this planet for at least millions of years – it only started to be recorded systematically very recently.  Is a daily record noteworthy?  Yes, it is worth noting.  I’m just not sure it’s worth getting excited about.

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