Ask HN: Looks like the app store search algorithm changed

I religiously track my app's ranking in the App Store for my key search terms and it looks like there has been a major tweak today. My app that usually ranks around 60 for a search, has dropped down to 126, and my less popular app has moved from 250 up to 127 for the same keyword.

Is anyone noticing the change? Have you determined any of the underlying reasons?