Snowfall Forecasting -- The Difficulty & The Hatred - abc27 WHTM

Snowfall Forecasting -- The Difficulty & The Hatred

Posted: Updated:

March 19, 2013

The winter is officially almost over -- tomorrow is the first day of Spring after all. This is despite the fact that it will continue to feel like winter perhaps until the end of March. Once again, Central PA was spared from a really bad winter. We did have some snow the week between Christmas and New Year's Day and a few mixed events in January and February. Now it seems Mother Nature wants to keep brushing us with winter as most folks are ready to move on. All-in-all, however, it was another fairly unremarkable year for our viewing area.

March seems to have brought with it some very difficult storms to forecast. There was the storm a couple weeks ago that didn't bring any snow to certain regions in the viewing area (although many others saw their fair share), and there was also a little snow this past Saturday and then yesterday too. Each storm brought with it some challenging elements. This, of course, is no consolation to the vocal minority who whine, complain, and troll the Internet with hatred and vitriol on those rare occasions (yes, I said rare, and actually mean it!) when a forecast goes bust. Why all the venom? Why is it so hard to predict snowfall in some storms? Let's try and answer these questions. This article is written, obviously, for the fair-minded folks among us and not the ones that spew their venom all over Facebook and Twitter who probably stopped reading after the title.

When forecasting snowfall amounts, we look at computer guidance. There are several different models that we use to forecast. Forget about the fact that sometimes these models offer wildly different solutions to the same problem. Even if all the models agreed on the basic track and structure of the storm (which they often don't -- further complicating matters -- like two weeks ago by the way), they still do not tell us anything about snowfall amounts. The models predict liquid precipitation. In other words, when we forecast snowfall, we are looking at the liquid equivalent of what the snow would be if it fell as rainfall. Now, predicting rainfall amounts is just as difficult as forecasting snowfall amounts. However, most of the time, unless it's in a flooding situation, we are not going to waste everybody's time by giving out rainfall amount forecasts. Why? Because whether we get 2 tenths, 4 tenths, or even 1 inch of rain -- it usually doesn't matter to people and doesn't affect them.

Imagine if meteorologists were required, or felt obligated to give such amounts every time it rained. It is more than likely that the forecasted amounts would be off by several tenths of an inch or more. Most folks would realize this and not care. Thackara said it would rain 3 tenths overnight and it rained 7 tenths. Who cares? It rained -- the forecast was correct! Yes -- it did in fact rain -- but the forecast wasn't dead on. It rained more that I thought it would. More often than not, however, the inaccurate rainfall amounts go unnoticed. If we gave rain amounts every time it was going to rain, it would almost be a guarantee that the actual amounts wouldn't line up exactly with what was forecasted. Compare this with snowfall forecasting. Each and every time it is expected to snow -- it is essential for meteorologists to predict how many inches will fall.

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Let's break down the numbers by a few hypothetical examples. Stay with me here! On average (and this isn't always the case -- again complicating matters), one inch of rainfall is equivalent to about 10 inches of snow. This means that one inch of snow is 1 tenth of an inch of water. Let's say our meteorologists predict 6 inches of snow and instead only 2 inches actually falls from the sky. Most people would wonder -- where's all this snow these guys said was coming? Well -- that would be comparable to missing a rainfall forecast by 4 tenths of an inch -- follow me? Not a concern when it's all rain. Who would notice 4 tenths of an inch of water? But look out when it's all snow baby! Now the trolls come out from under the bridge with the usual comments we hear all too often: "You blew it", "I only got 2 inches and you said 6 -- a total failure!", "I would love to have a job where I could be 50% right and still get paid", "How much do these guys make anyway?", "Fry these weathermen -- they haven't been right all winter!" Believe it or not, we've heard this same song and dance on many occasions. Some comments I can't post here -- by the way. Yikes! And this for missing the forecast by 4 tenths of an inch!

Compare this to the other way around -- similar to last night where we got more snow in some spots than what we forecasted. We said up to 2 inches and mainly on grassy areas. Well, some folks got 4-5 inches and the roads did get slick during the evening commute. Again, in certain backyards we missed the forecast by 3 tenths of an inch and now it becomes a "shocker of a snowfall". It can be very frustrating to hear news people and viewers alike vent their hatred and put their own spin on what happened. In last night's case -- it's like we didn't predict a flake! Or, in the case two weeks ago, we predicted higher numbers and some folks missed out completely. In that situation, many people failed to realize that half our viewing area did get plenty of snow. Would you rather we said nothing and not prepare you for what we truly believe COULD happen? It's enough to drive any meteorologist insane -- which probably happened to me a long time ago. Those of you that watch my morning forecasts probably concur.

There is no easy way to combat this. Most fair-minded individuals understand and are forgiving when the forecast doesn't exactly pan out. They understand that we are only talking about a few tenths of an inch of liquid falling from up above. The computer models can only be so accurate -- even with all the new technology we use. We could get around this troublesome area of forecasting by simply not giving snowfall amounts and saying things like "small" storm or "plowable" snow -- but let's get real. We live in a society of entitlement. WE WANT INCHES! WE WANT INCHES! This is also part of the problem. Even when we give those snow forecasts -- some viewers want to know how many inches will fall IN THEIR BACKYARD. They want to know the minute, no excuse me, the SECOND when the snow will start and end. Anything less in their eyes is a failure of the utmost degree! "Where did these guys go to school anyway?"

Well -- because of this demand -- we will give you your snow forecast in inches time and time again. But bear in mind that along with those accurate forecasts (and yes, we were more accurate this winter than we weren't) there will come the busts and the misses and the ridicule and venom from frustrated and angry viewers that don't have anything better to do with their time. Something to keep in mind too -- if we really were only right 50% of the time -- I wouldn't be writing this column because I wouldn't have a job. But keep on thinking that and keep on forgetting about the days when the forecast is accurate. Instead, focus on the ones we miss by 5 or 6 tenths of an inch of liquid in your backyard.

While I focused this article mainly on liquid equivalent and snow forecasting, there are many other factors that can mess up a forecast of inches. If the snow is moving into dry air with low dewpoints, the start time may be later than forecasted and that could help limit accumulation. If the famous rain/snow line in the upper atmosphere splits our viewing region in half (as is often the case around here) snow forecasts could bust because warm air invades at the upper levels and quickly changes the precipitation to rain. This is very hard to pinpoint. Also, I mentioned above that the average ratio for snow to rain is 10:1 -- but that isn't always the case. If the snow is falling in a slightly warmer environment, the ratio may be 6:1. If a clipper system moves through with lots of cold air in place -- the ratios could be as high as 20:1 -- this means that if only 5 tenths of an inch of water fall from the sky -- some backyards could get 10 inches of snow!! Plus, no matter how much we explain the uncertainties and the bust potential and the scientific reasoning during our forecasts -- some people still don't get it! And some of you thought this job was a piece of cake right?

The one other item for me to address in this column is the fact that all meteorologists tend to get "lumped together" in this day and age. We here at abc27 take our jobs very seriously and aren't about to "hype" a potential storm to get ratings. We, in fact, hate hype. When other national weather organizations (and some local ones for that matter) start saying things like "major storm on the way for next week" or "blizzard possible for the east coast in the next 7 days" -- we just roll our eyes. You won't hear us talking about a snowstorm more than 3 days or so in advance. Why? It's simple -- all the uncertainties explained above. No solid meteorologist in their right mind would claim to know what will happen with a snow event days in advance -- don't believe them if they do! There are so many ways to get weather information in our present age. Some of these national organizations write headlines to grab page-views or get people talking about their name. It's a joke. We want to be as accurate as possible and not lead to any hype or mis-information. We get so frustrated here when people start asking us about "snow coming next week" when in reality one model showed the smallest sign of a big snow and some national weather organizations start calling for a major storm to hit Pennsylvania. Plus, after nothing happens, and we call for nothing -- we still get lumped together with other organizations saying we hyped a blizzard! My advice -- be careful who you listen to and weed out the hype on your own. You're smarter than that -- I know it!

Thanks to the viewers who stuck with me to the end of this piece. For those of you that wanted to read and to learn -- thank you. For those of you that want to remain ignorant about how we forecast (throwing darts aside) then I can't help you. There will always be busts when it comes to forecasting exact amounts of snowfall -- it's the nature of the beast. With those busts will always come the negativity and the hatred from those people who will never fully understand or grasp the difficulties and the adversities that go along with forecasting how much rain or snow will fall each and every time precipitation is in the forecast. The vocal minority can grow deafening at times -- especially in the era of Facebook and Twitter. We do appreciate all of our viewers and understand this too: nobody feels worse when we miss a forecast than us. Thanks for sticking with us -- we'll keep trying our best and hopefully you have a better understanding of what we go through when putting our forecasts together. If you don't, and think you can do better, as some people have written me -- see you at 2:45AM tomorrow morning -- I'll have the coffee ready!

-Meteorologist Brett Thackara

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