You hear this a lot in Chicago.  “We are having a cold snap because there is a low-pressure system over the Midwest and a high-pressure system to the North.  This causes windy conditions which brings cold air down from Canada.”

This sounds better than just saying “it’s cold today” but I can’t tell if it really is saying anything more than that.  First of all, as I have said before the following two statements are equivalent, at least empirically:

  1. The air is colder than usual
  2. The air was blown here from some place colder than here.

So telling me that the air came from Canada isn’t telling me much more than I already knew, it’s cold.  But the extra bit here seems tautological at an even deeper level because these two statements:

  1. The air is blowing from down Canada
  2. There is high pressure in the North and low pressure here

appear to be literally the same thing.  Why else would the air move from position A to position B if it were not due to pressure imbalances?

Is meteorology really just like finance?  (“Stocks fell today because of bearish investors”)  Or is there a non-circular way of explaining my frozen toes that just doesn’t fit into a 30 second weather report?

(drawing: glooming from

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