Today was another cool and gray February day. Although we miss out on the extreme cold and snow that’s been hitting D.C. this winter, we have managed to have a few borderline cold days in Houston. Temperatures in the 30s aren’t really worth complaining about, but when it goes from 80 to 35 in the span of 36 hours you can’t help but notice.
As far as late February days go, the previous Sunday was pretty good. It was warm — around 80 degress Fahrenheit — though cloudy and humid with a few sprinkles here and there. A trip to the zoo almost coaxed some showers along, but no significant rain fell that afternoon. But I’ve been around Texas weather long enough to know that something special was in store for us. The geography of the Great Plains and Gulf Coast, with the Rocky Mountains to the west and the Gulf of Mexico to the southeast, can bring “interesting” weather patterns. In this case, something known as a blue norther’. (The internet tells me it’s also called a Texas norther’, but I’ve never heard that in 30+ years of living in the state.)
A blue norther’ is really nothing more than a strong cold front. The weather ahead of the front tends to be a bit warmer than normal because of changes in atmospheric pressure (increasing atmospheric pressure warms the air) and because wind patterns in the plains allow for more warming ahead of the front. Cold fronts tend to move faster than warm fronts, so these systems move in and can drop temperatures quickly. Virtually anyone who has lived in this part of the world for any span of time will have a story about leaving the house in a lightweight clothing only to be surprised by the mercury dropping 20+ degrees in an hour. It’s happened to me before, which is why I’m suspicious anytime it gets above 75 between November and March.
But why is it called blue? At first you might think that its because that’s the color your shorts-wearing legs turn after your 80 degree picnic turned into a 40 degree mad dash to the indoors. But the reason has to do with the clouds. The dark clouds that form along the edge of the frontal boundary take on a dark, ominous blue appearance. On the flat-as-a-pancake landscape of the plains, this helps serve as a warning so you have time to put on some damn pants and maybe grab a jacket.
For more, here’s a story from The Weather Channel all about blue northers: