Here is the clip of the meteorite crashing into the mountain that I plan to use in my film. I drew the frames in Paint Tool SAI and imported them into Pencil to animate them.

It took me a few attempts to get the meteorite to look convincing. Here are some of my first tries:

The first attempt I used too many frames and didn't take enough care to align them properly. The second was better but still too many frames to make it look real. The final version I only used 5 frames of the meteor in the sky as opposed to the 20ish i used in the first version.

If I have time I would like to do something with the lighting in this scene to make it a little less static, maybe i can try animating the clouds/mist too.

Here are some of the clips I used as references: