This month, we’re going to look at something that happens every winter. And I’m not talking about snow, shoveling, or snowball fights. While those are fun, I’m talking about…posting GFS, NAM and other model imagery of forecast snowfall on social media.
Now, you’re thinking: I’m violating copyright laws by doing that, aren’t I? Actually, if you post still shots or even animations of an event online, it can be very instructive. Posting our satellite, radar and upper air images and animations of an event, along with a good explanation, is something I like to see! Go ahead and do that, with credit to AllisonHouse for the imagery.
But… problems occur when model data is posted without any interpretation. It becomes a real problem… especially in life-threatening, or life-altering situations, when the model (NOT data!) is only going to get it right out of, more than anything, luck. And more often than not, beyond 48 hours, it frequently blows the forecast.
Now: I’m not talking about posting an upper level map of a hurricane’s 850 MB winds posted 12 hours before landfall, with an explanation of what the map is about, and that those winds are aloft. No, you know what I’m talking about:
I’m talking about posting GFS and European model output of snowfall totals of a potential storm system 3 days in advance or more. Without context, without explanation, or even worse: “look what this storm is going to do to (insert area in question)!”.
But why? Isn’t the European model the greatest thing since sliced bread? And since the GFS got upgraded early in 2015, didn’t it nail the big ones so far this year? Isn’t it now doing the strut down the road to the Model Hall of Fame?
Not really. You see: 3, and especially 4 days out and more…those systems, more than likely, are somewhere out in the Pacific Ocean. And all that is there are usually two things for the models to use, to try to figure out what is happening: satellite data, which is of coarse or low resolution, and…ship reports.
That’s like blindfolding someone and walking them to a zoo, and then having them feel an animal, and have them try to guess what it is, and how old it is, with one touch in one area of the animal!
Which is why it is remarkable that the models do as well as they do. Sure: I’ve seen the success stories where a model, 7 days in advance, predicted that storm X was going to produce a swath of heavy snow across part of the country. And it did just that…but was many miles off where the model said it would be. And even if you are only 20 miles off, it can mean the difference between 4″ of snow, and 12″. That’s the difference between everything shutting down, and a somewhat slower commute into work. What that does is when you post that model image without understanding its limitations, is this: it quickly ruins your credibility, it scares people unnecessarily, and more than likely, the amounts and the path of the heavy snow will be wrong…many times, horribly wrong. And that causes a lot of unnecessary and sometimes very serious problems.
Don’t get me wrong: this extends into the spring, summer, and fall as well. The HRRR model, which you can see via AllisonHouse Maps and GRearth, are of such high resolution that they will resolve a supercell, or rotating thunderstorms, right down to the “hook echo”, like it’s on radar. If you post one of those maps with a supercell over town X, without an explanation, non-weather weenies may think that will hit THEM, when the model is merely suggesting a *general area* for the development of storms, and the model “thinks” that supercells are *possible*.
It doesn’t stop there. Model precipitation totals in the spring, summer and fall are often wildly exaggerated due to a phenomenon called “convective feedback”, where the model mishandles the amount of warm, moist air once thunderstorms develop. Usually seen on days 2 and beyond, but it can be seen even in the first 12 hours: when this happens, the model causes predicted rainfall areas and rainfall rates to go bonkers…without a corresponding and appropriate loss of overall instability, reducing the amount of time a storm spends in one area, or the intensity of the precipitation. The result is wildly over inflated precipitation “bullseyes”, where rainfall amounts are way higher than what one would expect, given the amount of instability and moisture available. As a result, people thinking this would bust a drought they are in would be disappointed, and those in areas where everything is saturated or where flooding is already occurring could be freaked out. And believe me, I have seen that happen many times.
So what, then? Should I never post any model graphics? Of course not. But, if you do, you need to do it wisely. Here’s some guidelines I have learned over the years to help you to do just that:
1. Any graphic you post on Facebook could be shared by others, and frequently, the explanation gets erased as the graphic is shared. That actually happened to me, and I got rightfully yelled at for posting a model snowfall graphic on there. Although Facebook has gotten better about it, they now only show the top 160 characters or so of what you share, and then the rest you have to click through to see the description. Some people won’t do that, or don’t know how, and that causes problems. And yes, it IS your problem when that happens. Scaring people with dangerous weather possibilities is NEVER a good thing to do.
2. European model forecast snowfall graphics are not legal to post publicly on social media! I don’t care if you get it from Accu-Weather, WSI, WeatherBell…or if you got it from someone else. It’s not legal…period! And the ECMWF folks are now taking a dim view of Americans sharing it online, and are starting to come after some people. This is why that data is not found in a lot of places: it’s very expensive, and it’s for personal use only.
3. All other models: don’t post them on social media unless you are 48 hours out or less, and you have reasons why the model is right, or wrong, using sound scientific reasoning. DO NOT say, to the effect, “you’re all in big trouble in this area” or even “well, this model is out to lunch, LOL!” UNLESS you have valid scientific reasoning to support such a claim.
4. IF YOU MUST post about model data showing 12″ of snow for you 7 days out, post it on a private weather forum, along with the questions and concerns that you have. Post the questions (but not the graphic itself) to the National Weather Service social media sites. They’ll get back to you…though it may take a bit, as they have many duties that they must perform. Hang in there, and be patient!
But…I want to warn my neighbors! That’s great! Share current NWS graphics/website links instead, or current data/radar images from AllisonHouse (but tell people what TIME this is occurring; weather information gets dated very quickly!). One of the things we’re learning about in the meteorology world is that one of the best ways to share forecast uncertainty to the public is via the web. You know what: I bet your neighbor or friends would like to know that the NWS is forecasting 8″-12″ of snow, starting tomorrow evening, but the forecast confidence isn’t good. Or maybe it is good. Either way, share their graphics and link to their website. That builds YOUR credibility, and that of the NWS as well.
AllisonHouse is always to be used in conjunction with information, alerts and discussions supplied by the National Weather Service. If you don’t know of an atmospheric phenomena you see on radar, satellite, or a METAR/mesonet site, and it’s happening right now, do ask on the NWS or your favorite social media pages. But, again, putting our forecast snowfall forecasts from the GFS model and saying “SNOWMG!!!” on your Facebook page? You’ll just cause trouble, rather than inform and help your readers.
What we at AllisonHouse want to do is take the weather data and information we receive, put it in your hands in an organized and very helpful way, help you interpret the information as easily as possible, and then make sound decisions from it. If posting one of our graphics (or someone else’s) doesn’t fall into that genre, you may cause unnecessary angst or concern, and bad decision making by people you care for, or even don’t know! Remember: information is not power; the wisdom to use it well is. And we hope by this post, you can be responsible and help others understand what’s heading their way…without causing undue concern and alarm.