Hercules has not yet departed, and winter storm Ion (pronounced EYE-on) is here. The Weather Channel, which names the storms and has priority in forecasting their effects, is predicting up to a foot of snow in a band from Missouri to Michigan.
Here at Decoded Science, we expect less snow, not more than six inches, except in narrow lake-effect bands where the wind comes off the water.
All forecasters agree that Ion will usher in the coldest air of the millennium — and in some places the coldest air ever — along with fierce winds. As a result, the National Weather Service has issued a blizzard warning for Montana and North Dakota.
Winter Storm Ion: The Arctic Express
Normally, the jet stream courses from west to east, dipping here and there, but generally locking the coldest air in northern Canada and Alaska. Once in a while, however, the gates open, and the cold air streams south into the continental United States. That is what will happen in the wake of Ion. Low temperature records are likely to be set in the upper midwest and northern plains, and records could be set as far south as Memphis and Atlanta.
The Weather Pattern of the Last Two Months
For some time now, the jet stream has been unusually vigorous, with a dip (trough) over the center of the United States. A vigorous jet stream is correlated with a strong temperature gradient (change in temperature) near the ground, and this is a high potential energy state. The warm air wants to rise and the cold air wants to sink to create a lower potential energy state. When this happens, warm, rising air produces precipitation. The recent string of storms is no surprise. With the passing of Ion, the pattern appears to be about to change.
Next Week: The New Pattern
Late next week, the jet stream will weaken, according to the computer-model forecasts. A trough will still be in evidence over the Rockies, but it will not be pronounced. The supply of arctic air willl be cut off and the temperature gradient will relax. Conditions are still favorable for some stormy activity, but it will be modest in comparison with that associated with Gemini, Hercules, and their friends.
As Ion Passes: Time For Summer?
This does not mean anyone should put away his winter coat and get out the water skis. Winter is a stubborn thing; it lasts until spring every year. The weather tends to be persistent, and patterns tend to be re-established. On the other hand, there are feedback mechanisms that tend to even things out. This push of arctic air far to the south will require the northern latitudes to replenish their supply of frigid air. The best decoded guess is that there will be a relatively warm spell for nearly a month, then a struggle between competing types of jets stream patterns that could go either way. But that’s just a guess – with the weather, no one knows for sure.