Forecast Confusion

Posted on | Leave a comment

  • So it has been raining in the San Francisco Bay Area. You may have heard. When a brief ray of sun broke out this afternoon, my associate Eric Fain wrote, “Weather channel says 90% of rain ALL DAY. I’m so happy it’s sunny.” I interpreted that to mean he expected it to rain all day, and so this sunshine had beat the weatherman’s* odds. The weatherman had said 90%, right? Hang on — 90% what? Is the weatherman 90% certain it will rain today? Is he saying 90% of the day will be filled with rain? Is he saying it might only rain for two minutes, but he’s 90% sure some sort of precipitation will happen? Or is he saying something crazy like “We will be receiving 90% of the storm front’s precipitation today?” I think the first explanation is what he means … and that’s when I realized I had been reading it as 90% of the day will be filled with rain. Yeah, those percentages are confusing.

    Seven day forecast icons from NOAA point forecast.

    Okay, maybe this needs some design love. I figured it was time for some conversations with people. Why do people look at weather forecasts? What are they figuring out inside their heads? A quick canvass resulted in these intentions:

    • “Whether or not I should bring a coat or hat for rain …”
    • “I want figure out what to wear, whether to bring a jacket, sweater, raincoat, or umbrella.”
    • “… to see if i need to bring an umbrella.”
    • “I try to plan for what to wear and what accessories I need. (umbrella, etc.)”
    • “It’s usually for my commute purposes.”
    • “If it’s supposed to snow, I’ll leave for work earlier and plan to leave for home earlier.”
    • “… deciding when to head to the gym–try to beat the rain and ensuing traffic.”
    • “I want to know if there will be a dry spell when I can go for a run today.”
    • “I want to decide whether I should bike to work or not today.”
    • “I look at the current temperature to figure out how many layers to wear when going for a run or a bike ride.”
    • “If an upcoming activity will be rained upon, I want to see if I should change my plans accordingly.”
    • “I might decide if I really want to go on that hike in the rain.”
    • “I’m checking to see if it’s going to be dry so I can go on a ride.”
    • “I want to know if I should plan to prune the roses today, or if I should do one of my inside projects instead.”
    • “It’s to guess at if it’s safe to go grocery shopping, or will that be a miserable experience. I look at the hourly forecast.”
    • “I want to see how hot it is expected to get the next day, so I can plan when to rack off wine.”
    • “If it’s going to rain this weekend at the Pinnacles, we won’t go climbing.”
    • “If I’m going on vacation, I’ll look up the weather there to know how to pack.”
    • “When I am getting on a plane, what to bring …”
    • “I need to figure out what to pack for a business trip.”
    • “Our basement flooded. Did I tell you how close we are to the canal?”
    • “I’m interested in how much rain has fallen in the past 24 hours.”
    • “If we are going paragliding, we look for which way the wind would blow.”
    • “… to see how close the next storm is on the radar map.”
    • “I’m a weather junkie. I want to see if there’s something exciting to look forward to.”
    • “I have weather on my iPhone in four parts of the world just to see what my friends are experiencing, for fun, to contrast with the weather in California.”

    You can see that the audience segment I contacted skews toward people who commute and go outside for exercise. If I asked people who deliver packages or paramedics or strawberry farmers, I would get some different responses in addition to those above. So let’s agree that we’re designing only for people who commute and go outside for exercise, not for the others at the moment.

    From this quick set of conversations, I can see that people are looking to see whether they will be affected by the weather during certain activities, and they may adjust the time of those activities or the things they wear to make the activity more comfortable. And they want to know how much more rain is coming, adding to the mess in their basement.

    So an icon like on the NOAA site above saying “This Afternoon 100% Rain” understandably makes people believe that they will get wet during their commute, trip to the gym, or run/hike/ride. It’s 100% certain. Imagine their consternation when they get outside and all the rain gear is unnecessary because it has finished raining. No wonder the weatherman gets a lot of complaints.

    There are a few things about the icons above that I’m not sure about. There was no easily-identifiable legend to explain things, and I didn’t contact NOAA to find out.

    • Why are the percentages part of the first read? Why are they so catchy and important-looking?
    • What is the difference between rain and showers? (Today it said rain, but it came in little 20-minute sets, and it was dry in between. I would have defined that as a shower.)
    • What does this scale of likelihood mean, exactly: Likely, Chance, Slight Chance.
    • If the percentage is the certainty of the forecast, how does it relate to the likelihood? If it is the same thing, why is it represented twice?

    It looks like the weatherman is trying to represent the data he has: how much rain we might get, and how sure he is we’ll get it. (I’m not actually sure about the former; maybe it’s just the latter, in general.) Juxtaposed to that, people I interviewed want to know how much of the day will be wet, and when those periods of wetness will occur. We all realize that the weatherman probably can’t tell us that, exactly, so we forgive them and accept less specific predictions. So, if the data we need does not exist, then let us at least clean up those confusing percentages. What if the forecast icons had a little rain gauge next to each icon that predicted how much water is expected? We can then see a little chart over the next few days of what to expect, so we can put off pruning or hiking until a more suitable day. What if we make the word placement consistent, so the type of weather expected (“Rain,” “Showers”) is always the first line under the icon, and the likelihood (“Chance,” “Slight Chance”) is the second line under the icon? It would make the set of icons easier to scan.

    Cleaned up forecast icons for the NOAA point forecast.

    Note that the rain gauge allows the weatherman to show how the intensity of precipitation may change, even though the likelihood decreases or stays the same. Notice, too, that I moved the date over to the right, just above the first icon, so that we can associate them easily. (I have to confess that a couple of years ago NOAA changed the URL for my point forecast, so my bookmark was old. For a few weeks I kept staring at the same nine icons of fog wondering when the weather would ever change. I didn’t see the “Last Update” or “Forecast Valid” lines in among all the text above the heading.)

    In the interest of clean space, and taking advantage of our super-associative brains, I thought one more design change might work. We already know that if our loved one writes us a note and double-underlines the word “important,” we had better pay attention to what the note says. We can telegraph the importance of the weather type in the same way, indicating likelihood with a double underline, or “slight chance” with a couple of question marks. I’m not sure I understand the scale the weatherman is using for likelihood, so my attempt to put it into a four-part scale may be incorrect.

    Cleaned up forecast icons for the NOAA point forecast.

    This consolidation leaves us room to layer in something else that may be important and happening at the same time, like wind or thunderstorms or tornadoes, instead of shoving it further down the page.

    I admit that these redesigns are not pretty, nor do they address one of the concerns people I talked to had, “Which hours of the day will be rainy?” I did address the concerns, “How much more rain is coming?” and “Should I put this off until a better day?” If “Showers” and “Rain” get more clearly differentiated by the weatherman, I can also address “Will there be a break in the rain for me to go for a run?” Otherwise, I tried to work within my imagined data limitations, and I tried to offer a very slight change to the format which may have a chance of getting through bureaucracy. At least it gets rid of the confusing percentages.

    * “The weatherman” is my euphemism for all the people who team up with satellites and reams of data to bring us these weather predictions. I am using the word tongue-in-cheek. There was a time in my early 20’s when I desperately wanted to work for NOAA Earth System Research Lab in Boulder, Colorado, so I got an invitation there to see what it was like there. Impressive! They have my respect.

    Leave a Reply