The Lawrenceville Weather Blog today offers some great insight into why it's so blasted cold around here.

According to Jon Richards, it has to do with something called the Arctic Isolation. His source on this is the Weather Service's own Climate Prediction Center, which recently became offering online charts of this. (Shown.)

The chart is pretty easy to read. When the arrows are pointing up, it's going to be warm, and when the arrows are pointed down, it's going to be cold.

The lower chart here is a forecast going 14 days out, and it does not look good.

Jon explains:

The Arctic Oscillation tracks the relationship between air pressure in the Arctic and the middle latitudes (around 45 degrees North). Useful for measuring and predicting winter weather, when it's in a positive phase, high pressure in the south and low pressure in the north tend to bring warm, dry weather to the central and southern US, while when it's in a negative phase, the jet stream moves south, and we get colder, wetter weather.

The Arctic Oscillation is one of several relationships between pressures or temperatures called Teleconnections that can be useful in measuring and predicting weather.

As you can see, the AO has been in its negative phase since late November, just as the weather started to turn colder than normal here in Georgia. So far in December, we're running about 5.4 degrees cooler than normal, on average, with only two days of above average temperatures. The normal temperatures for the beginning of the month are a high of 58 and a low of 39, and at the end of the month, a high of 51 and a low of 32. The normal average temperature is 44.5 for the entire month, to date, the average is 40.5 degrees.

Bundle up.