Thursday, September 07, 2017

Animating a Hurricane Forecast

Hurricane picturesIt's hurricane season in Florida, and with the impending threat of hurricane Irma, people are fixated on the forecasts.

One idea I always had around these times was to create my own hurricane tracker, but what I want to track is how much the forecast deviates from the actual path. This content is hard to find. I don't think any weather service would be happy to share how their forecasts were off. In fact, even if the forecast is correct, at the end of the day people don't seem to care much. But I am curious to see if forecasts are mostly accurate or what they missed.

The most straightforward way to get a feel for how a forecast changes over time is to download a 3-day forecast picture every few hours, since usually the picture has a fixed URL. Downloading it by hand is easy except when it's 3 am. Not only that, but it's more fun to automate something.

To do this I used the online service IFTTT which stands for "if this then that" and created a new applet for Dropbox. How did they take the name applet is a mystery to me; I thought the name applets were only for Java, but given their lack of popularity maybe the name is fitting for something else.

Setting up the applet creation is extremely easy. The service links your online accounts in order to activate actions. The one I set up uses a datetime tool that triggers an action to download a URL resource to Dropbox, in this case, a fixed forecast image from NOAA that gets updated periodically.

The service worked like a charm and in a few hours I had my first batch of forecast photos. I ended up with a lot of repeats since the weather updates happen at a slower rate than my downloads.

I used the GIMP tool to put together all the images and turn them into an animated GIF. I found some useful instructions online. The final product moves really fast but you can appreciate how the cone of the forecast changes slightly.

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