New Drought Risk Atlas gives real context to extreme weather

 

Maybe it’s the grey creeping into my hair, or the lines around my eyes. For whatever reason, whenever the weather gets a little bit weird — maybe it doesn’t snow in December or gets really sunny in January — people ask me if it’s “normal for these parts.” No, I’m not a climate scientist or a meteorologist or even a television weather man, though sometimes I wish I were. It’s just that I’ve lived in the same region for most of my 40-some years, and my age is starting to show, so folks figure I must have a pretty good sense of what the weather’s supposed to be like around here.

In response, I typically regale my interrogator with a story of an applicable extreme weather event from my past. If it’s a dry winter, I tell him about that Christmas Eve in ’89 when we played volleyball at the family gathering instead of going sledding. If it’s especially snowy, I might recount the time, while on a mid-December backpacking trip in Utah’s canyon country, that two friends and I got buried by a sudden storm, requiring an epic trek out. If spring refuses to blossom until May, I’ll tell him about the Memorial Day blizzard of ’96 that forced hundreds of hypothermic bike racers to abandon their steeds mid-ride in exchange for a seat in a heated bus.

The Drought Risk Atlas provides great graphs of precipitation -- aggregated by week, month or year -- for the entire period of record of particular climate stations. Source: Drought Risk Atlas.

Usually my tales are enough to make the questioner forget his initial query, thus obscuring the fact that I didn’t even get close to answering that query. Which is a good thing. Because if you were to ask me if the remainder of that volleyball-on-Christmas winter was extraordinarily dry or warm, I would have no clue. Did that late May snowstorm follow an intensely snowy winter? No idea.

Now you can find out what “normal” weather might look like for your area, without having to listen to me blather on about ill-conceived adventures of my youth. That’s thanks to the National Drought Mitigation Center’s new Drought Risk Atlas, a Web-based clearinghouse of historic climate and drought data. While much of the information in the virtual Atlas was available to the public in various places and forms before, this tool is far easier to use, and provides a wealth of information in one quick stop.

The Atlas has its weaknesses. Precipitation and temperature data are only available to the end of 2012 for most stations, so in order to compare current conditions to historic ones, you’ll need to go elsewhere to find current data. The drought monitor tab, on the other hand, goes all the way up to the current month, but it only goes back to 2000, so the historic context is mostly missing. And some of the data are configured oddly. When aggregating by year, for example, precipitation data labelled 1/1/2012 are actually for the year 2012 (1/1/2012 - 12/31/2013).

Still, the Atlas is far better than the human mind — or at least mine — when it comes to processing weather objectively over an entire season. My experience has been that even the most observant folks, even those with a photographic memory of discrete weather events, can’t accurately look back and sum up the weather of an entire season, let alone determine what is “normal” or “average.” Our perception of the weather is simply too subjective, and our memories too faulty, to do so.

While precipitation amounts fluctuate wildly from year to year, making a "normal" hard to find, average maximum temperatures are more steady. Note the uptick in temperatures in recent years at the Fort Lewis station in SW Colo. Source: Drought Risk Atlas.

And that’s where the Risk Atlas comes in. Surely the biggest beneficiaries of the new tool will be those whose job it is to keep an eye on climactic conditions, like water managers or farmers. But it will also be helpful for journalists, particularly those who like to call every dry spell “unprecedented,” simply because it’s damned dry. Now, with a few clicks of the mouse, they can back that statement up, in the unlikely event that it’s true. As for those who like to refer to the latest extreme weather as “the new normal,” they may not get much help from the Risk Atlas; a quick look reveals that, when it comes to weather, there really is no “normal.”

By looking at data for the Ft. Lewis station here in Southwestern Colorado, I can quickly find proof, for example, that 2012 was nearly unprecedented in its dryness here, but that things were worse in 1956. But 2012’s drought was intensified by its heat, with an average maximum temperature more than three degrees higher than in 1956, meaning that the SPEI, or Standardized Precipitation-Evapotranspiration Index (another data set in the Atlas) was far lower for 2012 than 1956. That makes 2012 a pretty nasty year.

The Atlas also offers insight into single, extreme weather events and the disasters they breed, like big floods. Around here, the old, old-timers talk about the flood of 1970, which turned the glacially-carved valley into a massive reservoir, washed out miles of railroad tracks in the upper Animas River Gorge, wrecked structures along streams in Durango and, miles downstream, caused the San Juan River in Bluff to shoot up to 35,000 cubic feet per second, approximately 50 times what it had been a few days earlier. I had often heard — or maybe just assumed — that it had been a particularly soggy summer leading up to the flood. Turns out it wasn’t. Even the month of the flood wasn’t outrageously rainy; August of 1971 and October of 1972, when there were no floods of note, were wetter. The great flood of 1970 was the result, essentially, of one, single downpour that came out of the blue. Emergency management folks and San Juan River runners take heed.

Best for me, though, is that the Atlas is an easy way to find some context for my weather stories. That volleyball-playing holiday was not a dream. In fact, there was no precipitation around here at all whatsoever in November and December of that year, making it virtually unprecedented in itself. Now if they’d just put the Risk Atlas onto a mobile app, I could surreptitiously take a gander next time someone asks me if the weather’s normal or not. Maybe then, I could give them a real answer.

Jonathan Thompson is a senior editor at High Country News. He tweets @jonnypeace.