The weather Grinch that stole Christmas

What a storm! When teaching weather, I frequently take the Socratic approach by asking questions. The most profound question I ask…if the surface winds are from the east, which way is the low-pressure system moving? Most of the time, I either get silence or the wrong answer. I must admit it is a loaded question, a sort of, which came first, the chicken or the egg question. If this question appeared on a Transport Canada or FAA exam, it might go like this:

If the winds are easterly (blowing from the east), which way is the surface low pressure system expected to track?

1. It doesn’t matter. Your weather App will figure it out.

2. It will move westward because of the easterly winds.

3. It will move north, southeast or west depending on Mother Nature.

4. Surface winds do not dictate the motion nor intensity of the surface low. The upper air pattern, usually derived from the 500 hPa chart, determines the motion and if it will intensify or decay.

Hint, pick the longest answer.

I compared the surface analysis that captured the “Christmas Grinch Storm” on Christmas eve with the upper air 500 hPA (hectopascal) (or millibar) (18,000 feet) chart on Christmas day. There is an upper low directly above, thus steering the surface low. The surface low will not move until the upper low moves. It’s why it’s been blowing a gale in most of Ontario for the last 2.5 days. Having said that, with the low stacked vertically from the surface upward, it means a slow meteorological death.

2 responses to “The weather Grinch that stole Christmas”

  1. Why do present day charts still look like they were made by the meteorologist from the 1920s?
    Love the blog.


    1. You make an excellent point! Environment Canada needs to update their products. For example, all of their analysis charts are abbreviated as “anal.” With computers, it’s no longer necessary to have such abbreviations. Thanks for the comment.


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