Fall is here and before you know it, we will be talking about the S word… snow. As we head into the end of September, places across the Upper-Midwest region will likely see some flakes within the next month (per climatology)! As we inch closer and closer to the winter season, here are a few things we have been asked about and what meteorologists want you to know!
Why app/automated predictions for a single, pinpoint location aren’t the most accurate or reliable
Technology has allowed for major advancements in almost every aspect of our life, making information and data easier to access. Weather forecasts are no exception. Cell phones have only added additional convenience. We now have more power in our hands than was on Apollo 11 that went to the moon! Weather apps and programs from all different companies and developers can bring us the latest forecast for our exact location at the touch of our fingertips or the click of a mouse. While this is convenient, it’s not always the most accurate-but why?
Before I explain why, let me ask you this: Have you ever logged onto your weather app at 7 am and saw that it was forecasting 7.38” of snow, just to log in again at 10 am to see it changed to forecasting 3.27”? This is something we call a yo-yo forecast. So, why does this occur? Most weather apps rely on a single forecast model (GFS, HRRR, NAM 3km, etc.) to generate a pinpoint forecast for your given location, so as new model data comes in, a new forecast is generated. While theoretically this is great, models simply are not powerful enough, and in turn, are not accurate enough to generate perfectly accurate forecasts for a single given point. These forecasts can become especially bad if a given model is performing poorly. For example, the NAM 3km is doing well, but the bad news is, your free app or automated forecast is using the GFS which is doing very poorly. This means you’re going to get a bad forecast regardless.
WEATHER MODEL VERIFICATION SCORES
This is why the human element in meteorology is so important! Meteorologists can look over many models and other pieces of data and use their expertise to help generate a much more accurate, reliable, and trustworthy forecast. And while we may not be able to tell you exactly how much snow will fall behind the shed in your backyard, we can give you a much better idea of what to expect for your area and convey the threats in association with those conditions, all without the yo-yo forecast!
Why some forecasts have more uncertainty than others.
Weather is very dynamic; things are occurring in the environment all around us, and small changes to those elements can have a significant impact on the forecast. In the winter, small shifts of the area of low pressure, frontal boundary placement, amount of moisture, or even how much afternoon sun there is can greatly impact the overall forecast!
When the temperature is 32° F, every 1” of rain/QPF equates to 10” of snow, but when the temperatures drop to 27°F, 1” of rain equates to 15” of snow! This means for every 0.10” of rain/QPF there is 1.5” of snow, so any very minor changes in the amount of moisture can have very dramatic impacts on snowfall amounts. This is just one example of how small changes in environmental conditions can have big impacts to forecasts.
While weather forecasts can and do change, and are rarely perfect, a good meteorologist should convey uncertainties in their forecasts. What are the caveats, what could the top end accumulation be and what could be the low end? How could this change the impacts? These are all examples of information that should be conveyed during times of hazardous weather!
What do the precipitation percentages actually mean?
40% rain, 70% storms, 30% snow- what do all the percentages and probabilities mean?! This may be one of the biggest misconceptions in meteorology and weather forecasting of all time, and it’s our fault as meteorologists!
Many people think when meteorologists talk about precipitation percentages we are talking about probability, I mean, we almost always use probability. However, in this case we are not! When we talk about percentage of precipitation, it actually has to do with the coverage!
For example, let’s say you live in Illinois, and I am forecasting for the I-80 area up to the state line (approx. northern ¼ of the state). If the forecast says there’s a 40% chance of rain, that means rain will occur over 40% of that area and 60% will be dry! It’s not a 40% chance for any given location. I think this is a bad and outdated way to convey precipitation forecasts, especially with all the graphics we now have, which is why for our clients the only place we show precipitation percentage is in the 7-day outlooks!
Why forecasts that seem overhyped usually turn out to be
Weather hype seems to be all the rage these days, especially in the world of social media where it’s all about clicks. No matter if it’s posting a single model run showing 28” of snow, the GFS at 248 hours showing a major hurricane, or posting as a time traveler on TikTok saying there’s an EF-6 tornado coming, it’s all the same.
While it’s obvious some of these things are a little more outlandish than the others, it’s still important to realize, if a forecast seems a bit extreme, in many cases it is! One thing I have learned as a meteorologist and as a storm chaser, is that forecasts often fall in the middle of the worst case and best-case scenario.
Why having a certified, degreed meteorologist is important for accurate information
This ties very well with the previous discussion. Most meteorologists who hold degrees, certifications, seals, etc. strive to bring you accurate information. Are there some out there that don’t? Sure. But as a degreed meteorologist we have learned the actual science behind the forecasts and can recognize things someone else may miss and we want to use this knowledge to bring you the best forecast we can!
Many of us have either taken forecasting classes in college or interned under someone who taught us how to forecast, then over the years have worked on our craft and honed-in on our abilities. I’m not saying there aren’t good, non-degreed weather forecasters out there- I know plenty of them! However, when it comes to making decisions regarding hazardous weather, I would choose to trust someone who has dedicated years to understanding it.
Why do forecasts vary from source to source?
I have often received the question “You are forecasting X to happen, but this other meteorologist is forecasting Y, why are your forecasts different?” Obviously, I can never speak for another meteorologist, but I am always happy to explain why I am forecasting one thing or another!
Overall, weather forecasting is something that is open to interpretation, I like to say “meteorology is the science, but forecasting is more of an art.” Some meteorologists may put more trust in a certain model than the next meteorologist does, so that is more of an influence of their forecast. One person could think they have a better understanding of how forecasts usually trend or verify in a certain area, or perhaps they just have a gut instinct! All of these factors can cause forecasts to vary from person to person.
Most of the time, forecasts will tend to be relatively close from source to source, varying only slightly. However, there are times where forecasts are dramatically different than others and that’s ok too… at times. If this is something that happens consistently and the forecasts are not accurate, it may be time to find another source!
While we know there are many other questions out there in regards to meteorology and forecasting, we hope this article helps answer some of them and you can use this information to become better prepared this Winter! If you have any questions you would like us to talk about in later articles please let us know!
Thermodynamic Solutions (“TDS Weather”) provides professional weather consulting services to a variety of industries including: professional and minor league sports, snow removal and landscaping, golf courses and turf management, colleges and universities, and hospital networks. With nearly two decades of living and forecasting in the Ohio Valley region, our meteorologists provide custom, reliable forecasts that help clients SAVE and MAKE money in their daily operations. Our services include commercial and agricultural forecasting in the short and long ranges, lightning alerts and on-site hazardous weather monitoring, 24/7 on-call decision support services, forensic weather reporting, and more! For weather consulting inquiries, please contact us at info@tdsweather.com. We also provide public weather information multiple times daily on our social media outlets- make sure you’re following us on Facebook, Twitter, and Instagram @tdswx, and TikTok @tdsweather!