an erratic autumn: a recap

With just 10 days left in 'meteorological autumn' (Winter beings December 1, for weather nerds, anyways), the temperature today is forecast to rebound to a very pleasant (and sunny!!) 50ºF, which is actually 5º above the average for November 20. That, however, won't make up for the very cold November we've been having (the mean temperature is running about 5º below average for the first 19 days of the month). 

Before our very cold November, September and October were extremely warm. Does anyone remember when it was above 90ºF for seven days in a row in late September?? And when the high temperature was 77º on October 21. In fact, on the night of October 21 I went out wearing a summer dress and the temperature never dipped below 60º. Here is a graph showing the mean daily temperature (the average of both the high and the low temperature) compared against the climatological "normals" for autumn:

You can see the flip from an above-normal patter prior to October 22 and a below-normal pattern since. Beginning a few days ago, the pattern has stabilized closer to normal (hence the high of 50 today, yay!)

If we just look at this as a departure from the normal, we get this graph, and the flip from hot to cold becomes very apparent:

And when we place autumn in context with the rest of 2017 we notice that our rapid descent into winter beginning October 23 is very unusual to the rest of the year:

 In fact, on average, November 2017 in Chicago has been as cold as February 2017 (which is normally about 15º colder than November; February was astronomically warm this year) which is unreal !!

The good and bad news: 

This erratic pattern is forecast to continue with temperatures plunging into the 30s on Tuesday only to rebound back into the 50s on Friday. There are signs, however, from the longer-range climate models, that December temperatures will be well above normal 😎:

Mika ToscaComment