where did the Saturday night aurora go?

It is really nice to see that the scientists were wrong, and it wasn’t “just me”. It is very validating. Reposting from the NOAA SWPC Facebook page, here is an explanation of what happened to the CME that was predicted to hit earth (resulting in the predicted aurora Saturday night). I could not locate this statement on their website.

What happened; where did the 21 November CME go? These are questions you may be asking. We are asking, too. [Note: long post.]We had been expecting two distinct CMEs to arrive – a weak one on the 23rd followed by a more robust event (from 21 Nov) on the 24th. What we experienced was a fairly weak transient passage on 23 November followed by nothing spectacular.

The question forecasters wrestled with recently was: has CME #2 already passed, or is it still on its way? Yesterday we decided to err on the side of caution. We assumed the second CME hadn’t arrived and continued to forecast the impact. As time wore on, however, it began to look less and less likely that CME #2 was coming.Much can happen to a plasma blob as it travels from the Sun to the Earth. Sometimes the evolution is captured well by numerical models. Sometimes, it isn’t. What eventually arrives at earth can be so modified that the characteristic CME signatures are obliterated. Then it sneaks by.

This is an example of a forecast gone awry. Good forecasters and researchers use these events to learn and improve, and the science moves forward.