Using the Wolfram Language

The National Weather Service provides detailed satellite images from a number of its satellites operated by the NOAA. When there is a serious weather event, like hurricane Ida, they train one of their satellites on that event to track it during its lifetime. This post shows how you can use the Wolfram Language to turn these images into a single video. This video gives an interesting insight into the evolution of Ida, from a small tropical depression, to a major hurricane, to a major rainmaker in the north-east of the United States:

The images used to generate the video shown above are stored on a NOAA web server. The following code sets the base URL for these NOAA images:

base = ""

This web page has a lot of hyperlinks to specific images at different sizes (250×250, 500×500, 1000×1000, and 2000×2000):

To get the image links from this page we import the page with the Wolfram Language as an XMLObject:

xml = Import[base, "XMLObject"];

Using this xml object we can use Cases and Select to extract the images we are interested in (in this case we want the 2000 x 2000 pixel images):

files = Select[
XMLElement["a", {_, "href" -> href_}, _] :> href,

The files variable is a list with all the image files we’re interested in.

Next we use CreateDirectory to create a directory to store the downloaded images:


Using URLDownload we can download the images to the local hard drive:

downloads = URLDownload[
URLBuild[{base, #}],
FileNameJoin[{"ida-images", #}]
] & /@ files;

The downloads variable is a list to all the local image files.

Using SlideShowVideo, we can now create a video from the list of images. We give each image a display time of 0.3 seconds, or three images per second:

video = SlideShowVideo[downloads -> 0.3]

The generated video is stored as a file on the local computer and is ready for upload to YouTube:

So what can we learn now that we have this video and can play back the whole event? The thing that struck me was how early the National Weather Service was able to detect this tropical depression and that it would turn into a hurricane. They pointed one of their satellites and focused on this depression very early on: three days before landfall.

I find the early sequence of images, up to the…

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