Today we have a special guest post from my friend, Lauren McCarthy, who is a meteorologist based out of Plymouth, NH. Lauren has loved meteorology for as long as I have known her. I learned so much about the weather I see every day on the news from reading this! You can find her on #ScienceTwitter at: @wx_lem
The way that scientists communicate their research can be just as important as how they conduct their research. When it comes time for a scientist to step outside the realm of their field to talk about their findings, some may find themselves toeing the line between over-simplifying their work and fully getting their point across. The level of clarity and comprehensiveness achieved when communicating scientific findings will ultimately determine how the results impact those that are listening. As meteorologists, myself and others in my field consistently make it a priority to improve how we communicate. This is relevant not only for research, but for operational weather forecasting as well.
I’m excited to write this piece for Sara’s #science blog because I think it’s the perfect platform to address some common misconceptions non-meteorologists may have about meteorology and forecasting. My idea for this topic stemmed off of a few articles by Dr. Marshall Shepherd in Forbes magazine. Dr. Shepherd is a Professor of Atmospheric Science at the University of Georgia and is a former president of the American Meteorological Society (AMS). He is a really admirable scientist, writer, and communicator. I’ve included a couple of his articles as references for some of the info I’m sharing below.
The first forecasting concept that I think could use some additional explanation relates to something that can often make or break your day: rain.
1.) What does a chance of rain actually mean?
Probability is a common way to express uncertainty in the forecast. However, at the end of the day, it ultimately rains or it doesn’t. For example, here is a sample 2-day forecast for Plymouth, NH from the National Weather Service (NWS) office in Gray, Maine (https://forecast.weather.gov/MapClick.php?CityName=Plymouth&state=NH&site=GYX&lat=43.7386&lon=-71.6983#.XL5EfTBKjb1):
You’ll notice that there’s a 60% chance of rain on Wednesday for the Plymouth area. In other words, the probability of precipitation, or PoP, is 60%. This value reflects both the confidence (C) the forecaster has that rain showers will occur somewhere in the Plymouth area, as well as the percentage of the forecast area (A) that will receive measurable precipitation, should precipitation occur (NWS, 2019; Shepherd, 2019). Those two values are multiplied together to get PoP: C x A
There are several opportunities for a misunderstanding here. Not everyone in the forecast area could observe rain, and even if they do, it may not be measureable. A brief, light drizzle may not end up being measureable (needs to accumulate to more than 0.01”), but it still technically “rained”. Keep in mind, that even though a forecast calling for a 60% chance of rain makes rain seem relatively more likely, there’s still a chance that it won’t happen. Because meteorologists need to produce a forecast for a relatively large area, and different amounts of precipitation can occur within that area, it makes sense to use probabilities to communicate the chance of rain. Strange Planet (https://www.instagram.com/p/BwhIJYdlv5M/) really sums up this dilemma perfectly:
2) What are all these watches, advisories, and warnings?
The above terms are three ways NWS offices go about assessing “risk to life and property” within their forecasting zone (NWS, 2019). These terms can apply to several different types of weather phenomena, including winter weather, thunderstorms, tornados, floods, high winds, and more. Each of the three categories essentially tells us how imminent weather-related damages to life and property are. Using winter storms as an example:
- WATCHES indicate that the atmospheric/environmental ingredients necessary to produce a winter storm are present, but there is still uncertainty regarding the details of the storm (which areas will be impacted, when the storm will move in, or if the storm will happen at all)
- ADVISORIES indicate that a winter storm has become imminent, weather conditions can create inconveniences for things like travel, and caution needs to be taken to avoid damage to life and property
- WARNINGS indicate that a winter storm has become imminent, and weather-related damages to life and property are likely
The NWS Central Illinois Office (https://www.weather.gov/ilx/wwa_social) page presents a great graphic that breaks these differences down further. Broadcast Meteorologist Brad Panovich also explained watch vs. warnings in terms of cupcakes (https://twitter.com/wxbrad/status/985565693826478080), because who doesn’t like cake:
3) “How does it feel to have a job where you can be wrong half the time and get paid?”
First of all, RUDE. Second of all, despite the fact that meteorologists have historically been criticized for being wrong, recent analyses of forecast skill (with real numbers and forecast verifications) have shown that forecast error has decreased steadily over the past 40+ years. Take temperature forecasts, for example:
Image courtesy of the Weather Prediction Center (WPC) (obtained from https://www.e-education.psu.edu/meteo3/node/2285)
The graph above shows that maximum temperature forecasts are, yes, becoming more accurate than they used to be. For example, the red line represents the maximum temperature forecast made three days in advance. In the 1970s, this forecast used to be about 6°F off from the actual observed temperature, but can now be predicted within about 3°F. Currently, 1-day forecast error for maximum temperature is as low as 2-2.5°F. It’s still not perfect, but it’s pretty good for predicting the future on a “complex fluid on a rotating planet with oceans, mountains, and varying heat distribution changes” (Shepherd, 2019).
I hope that this assortment of meteorology- and forecasting-related topics were helpful and informative! Improving the way that forecasts are communicated and consumed will ultimately help citizens, private companies, and government organizations alike make decisions based on the weather and will on the whole create a more scientifically-literate society.
Thanks for reading!
References
National Weather Service (NWS) Central Illinois, 2019: What is the Difference Between a Winter Storm Watch, Warning, and Advisory? Accessed 22 April 2019, https://www.weather.gov/ilx/wwa_social.
National Weather Service (NWS) Peachtree City, GA, 2019: What is the Meaning of PoP? Accessed 22 April 2019, https://www.weather.gov/ffc/pop.
Shepherd, M., 2019: How Meteorologists Compare to Other Professions that Predict the Future, accessed 22 April 2019, https://www.forbes.com/sites/marshallshepherd/2019/04/02/how-meteorologists-compare-to-other-professions-that-predict-the-future/#4f9e23975698.
Shepherd, M., 2019: The Top 7 Most Unreasonable Expectations About Weather Forecasts, accessed 22 April 2019,
Dr. Sara LoTemplio, PhD 