Next Storm Too Close to Call After A Wonderful Start to February
February 01, 2012 7:52 PM
What a way to start February… temperatures 15-25 degrees above average and close to record highs for the third straight day. The snow that coated the ground in most areas has almost completely disappeared as you can see in the visible satellite image on your left. But here’s the catch…. There could be more on the way. But I want to stress the word, COULD. There is no doubt that there will be a significant storm that develops in the center part of the country by the end of the week, the problem is deciphering exactly where it is going to go. In some cases this proves to be far more difficult then others and in this case, could be one of the hardest.
When we talk about storm systems developing in the center part of the country, many are straight forward; a wave rolls into the west coast, drops a bunch of rain or snow, breaks up a bit going through the Rockies, and then re-develops in the western plains and begins trecking northeast. Now that’s a classic textbook set up of how these storms are supposed to work. Unfortunately, as many of you probably know, most things in life are not exactly textbook scenarios. In this particular case, the wave entering the pacific northwest falls apart as it makes landfall (which you can see on your right), the upper level energy continues southeast until a new surface low pressure develops somewhere on the eastern side of the Rockies, but as soon as this low develops, it gets cutoff from the steering current in the atmosphere and will likely meander anywhere it wants to (you can see that in the picture on your left). This scenario proves to be especially difficult in forecasting where this thing is going to end up. As an example, picture a freight train; the train is the storm and the track is the steering current in the atmosphere. So if that train were moving at say 20 mph and you suddenly take that track away, the train could really go anywhere. In many cases the train will just keep moving in the same general direction under its own inertia, but what if it hits a hill? Or an obstruction like a few massive boulders or trees? With that in mind, who knows where it will go.
So let me show you what we are dealing with at the moment. Here is a look at a couple forecasting models that came out early on Wednesday that show snow totals through Saturday evening:
Now, look at the same two forecasting models, but these are newer and came out Wednesday evening.
You can see now why this is so difficult because the forecast models not only continuously move the heavy band of snow to different locations, but show significantly different snow amounts in each consecutive run. Now granted, these computer models will have subtle differences every time it computes (we call that a model run) and newer model “run” comes out every 6 hours.
If that doesn’t convince you that someone in the Midwest will get a significant amount of snow, how about this? The Hydrological Prediction Center issues their own forecasts for precipitation across the country for both rain and snow. They do issue their forecasts a little differently though showing the probability of receiving a specific amount of precipitation, in this case, snowfall. So here is the probability of the U. S. receiving 4 or more inches of snow from Thursday evening through Saturday evening.
Now here is the same probability map, but the amount of snow has increased to at least a foot of snow.
Notice that many portions of Nebraska and northeast Colorado have really good chances of seeing more then a foot of snow. Meanwhile, our southern counties have decent chances to see 4 inches of snow, or maybe even a little more. Now these probabilities really emphasize how much we need to watch this because if this storm moves just 50 or so miles to the north, many areas south of I-90 could be dealing with a bunch of snow.
Now that I have told you how unsure we are of the forecast, let me show you that we will be able to fine-tune this forecast through the next 24 hours. The computer forecasting models use data and current conditions from weather observing stations around the world to plot their forecast. In the United States, there are hundreds of these observing stations for the computer models to get data from so they can be as accurate as possible. All of those colored dots you see in the picture below are most of the offical observing stations in the U.S. But much like a human, the more data you have, the more accurate your decision. Well, as you know, our weather comes from the west, AKA the Pacific Ocean. These storms will form in the Pacific and then roll into the U.S. But, as you can imagine, there are very few weather observing stations in the pacific. In fact, only a few dozen sites are located on buoys throughout the HUGE Pacific Ocean. This makes long range forecast (more then 3 days) extremely difficult because the forecasting models receive very little data from these storms. But once they impact North America and the storm begins rolling over these weather-observing stations, the computer models have more data to analyze and therefore are more accurate. Because of this, we expect the forecasting models to drastically improve over the next 24 hours, thanks to this storm making landfall in the U.S. midday Wednesday. So stay tuned to the forecast, because the next 24 hours will really tell us a lot!