The user interface for the app has two components. A weather radar map and a sliding timeline bar graph at the bottom of the page. When you first launch the app it finds your location via the GPS chip in your phone. It then pulls up a weather radar map with your location centered on the map. Along the bottom of the map the bar graph shows a time line along the horizontal axis in 10 minute intervals for the next hour. If there is any precipitation occurring currently or that will occur in the next hour the graph shows a yellow curve whose height along the vertical axis represents the intensity of the rain. You can move a slider along the graph to move forward or backwards in time. As you move forward or backward in time the radar plot changes to show what it looked like or will look like at that point in time. Below the graph is a grey status bar with a readout of the current temperature and whether it is raining at this minute. At the other end of this grey bar is a prediction of whether it will be raining one hour from now. The space in between is used for status updates. The first day I had the app I was racing to get home before some severe thunderstorms arrived. As I pulled into my driveway it was just starting to spritz and Dark Sky said “It should be starting to rain”. So far it has been highly accurate: When it says it will start raining in 5 minutes, you can pretty much bet on it plus or minus a minute or so. It is 8:00 AM as I write this. Flicking the grey bar to the right shows rain predictions for the Next 3 hours, This Afternoon, This Evening and Overnight. These predictions aren’t meant to be as accurate as those for the next hour. The app authors say under certain worst case conditions the accuracy might be closer to 15 minutes, but still that ain’t too shabby.
I mentioned the weather radar map earlier. It has several features unique to Dark Sky. The first feature is it the weather radar image of the precipitation is cleaner and more accurate than traditional doppler radar images. The app’s authors spent a great deal of time working on algorithms to help clean up the clutter found in most radar images. What you are left with gives you a more accurate view of where the precipitation is. Doppler radar stations in the US take their images in 5 minute intervals. This sometimes results in a jerky appearance when the images are strung together and set into motion. Sometimes this herky jerky motion makes it hard for someone (particularly a novice) to tell the actual direction of the storm. Once again the app’s authors have created algorithms to allow them to create the in-between frames, thus giving you a smooth animation unlike any you’ve seen before. I mentioned earlier you can scrub backwards through the time line. The radar image will move backwards through time as well and goes back farther than the traditional doppler radar feeds in other weather apps. The apps authors also track the accuracy of their predictions and interpolated Doppler radar images and tweak their programs to insure even greater accuracy in the future.
Dark Sky is a universal app that is customized for both the iPad and the iPhone or iPod +. So far I’ve used it mostly on my iPad, but think how handy it would be to have an app that will accurately predict precipitation for the next hour when you’re out and about. On the smaller screen of the iPhone the radar takes up the entire screen and the bar graph and prediction data get their own screen. I’ve had Dark Skies on my iPad 3 for over a month now and it has been amazingly accurate within it’s one hour time window. Right now the app is available in the US only and it is only available at this time for iOS devices. There are Kickstarter projects online to raise funding to create an Android version as well as versions for other countries besides the US. The cost is $3.99 and is worth every penny.