WINTER FORECAST 2011-2012
Another unique weather pattern has set up and the pieces to this LRC (Lezak’s Recurring Cycle) puzzle are still falling into place. La Niña will likely affect the weather pattern as well. We will go over the main features as I see them this year and we will begin with introducing you to the LRC:
Lezak’s Recurring Cycle (The LRC)
- A unique weather pattern sets up every year between October 1st and November 10th
- The weather pattern cycles, repeats, and continues through winter, spring and into summer. Identifying the cycle length helps tremendously when making long range weather predictions
- “Long term” long-wave troughs and ridges become established and also repeat at regular times within the cycle. These dominant repeating features are a clue to where storm systems will reach peak strength, and where they will be their weakest
- There is a pattern! It isn’t just one long-wave trough, storm system, or ridge. It is a sequence of troughs and ridges that are cycling across the Northern Hemisphere and we use our forecasting experience to piece together the LRC puzzle
Analysis of this year’s LRC
Let’s begin this discussion with La Niña, the cooling of the tropical Pacific Ocean, as it has been strengthening in recent weeks. Last year became a moderately strong La Niña and we could see some of the influences. But, every year is different. The strength of this year’s La Niña is still undetermined and the weather pattern has set up differently than last year as described by the LRC. Last year there was an historic drought inTexas andOklahoma, but we see this weather pattern setting up into one that should bring some relief to these drought stricken areas. La Niña didn’t create the drought. It was the weather pattern that prevented storm systems from producing precipitation over this region. We see some good potential forTexas andOklahoma to be closer to average on precipitation which may keep the drought going, but bringing some relief as even average rainfall would be much more than they received last year. There is a secondary long term long-wave trough that will swing wet disturbances farther south affecting Texas and Oklahoma at times this winter and into early summer.
The Arctic Oscillation(AO) is a an index that describes blocking in the Northern Hemisphere. When it is in the negative phase cold air drops much farther south than normal, and when it is in the positive phase colder air is held up across Canada. The past two years have had near record negative phases of the AO, and as a result we had some cold and snowy winters across theUnited States. So far this season there has been no indication that this will happen again. The index has been staying close to neutral the past few weeks, but it is something that we will be paying close attention to. If it goes into the negative again, then this weather pattern will be energized. If it goes into the positive then more zonal flow will result in a lack of Arctic air. I just don’t know where this is going yet, so stay tuned.
Here are the main features that will likely affect the weather pattern this winter:
Dominant feature #1: Great Lakes to Mississippi River Valley Long term long-wave trough:
The strongest long term long-wave trough in North America evolved over the Great Lakes south into the Mississippi River Valley. It first showed up late in the second week of October as you can see on the October 13th 500 mb chart to the left. Why do we consider this example as good evidence of the long-wave trough position? It is because it was backed up and followed up by two more examples during the next three weeks. You can take this map and overlay it on top of this next map and they are almost perfectly aligned, yet six days apart. Here is the next map showing a deeper version of this trough on October 19th:
You can click on either of these maps for a larger view. On October 19th a deep upper low formed over southern Illinois as the trough deepened into the dominant feature #1. This storm system will likely develop in each cycle of this years LRC. It will vary in strength, but likely from into a major storm as it digs over the Missouri River Valley into the Mississippi River Valley. Remember the concept of the LRC. These troughs evolve and set-up during the critical October 1st through November 10th period. There were other examples as well during these critical 41 days. This strong long term long-wave trough set up October 13th, 19th, and again on the 31st. When this trough intensifies and gains amplitude it will affect some of the larger population centers with major winter storms this up coming winter season.
Dominant Feature #2: I am going to call this next feature a secondary long term long-wave trough as it has not occurred as often as the dominant feature #1, but it has repeated several times by mid November and is likely centered near Colorado.
This secondary long-wave trough developed just as the new weather pattern was evolving in early October. It has also repeated a couple of times since it’s evolution and this map shows the October 8thversion of the trough. It is this mean trough that will likely bring some drought relief to the excessively dry areas across the southern plains. This trough, as it swings out into the plains and heads into the Great Lakes dominant trough #1 position, will create the conditions for some major winter storms and the likely development of a couple of moderate to severe ice storms. One of these ice storms is likely in the Kansas City viewing area.
The flow aloft will split, get blocked up, and have high and low amplitude phases. These are very difficult to predict using the LRC. But, when these variances happen there will be some interesting storm systems to track. The following two maps show our initial thoughts on temperature and precipitation anomalies across the United States:
Winter Temperature Forecast
A cold winter is most likely from the Mississippi River Valley northeast intois the most likely spot to have a warmer than average winter. Everyone else should be close to average as we bounce between dominant feature 1 and secondary feature 2. A warmer than average winter is expected across the deep south.
Winter Precipitation Forecast
We are forecasting an active weather pattern across North America this winter with strong and wet storm systems, most frequently over the Great Lakes states. The most likely spot for a drier winter is the deep south from Texas to Florida hugging the Gulf of Mexico. Very strong Pacific storm systems will blast into the western states at times deepening into the long-term long wave troughs. We will learn a lot more about how storm systems will track, intensify, weaken, and strengthen in the next few weeks.
For Kansas City, we are expecting more rain than in recent winters. The past two winters have had mostly dry and fluffy snowstorms with very little of the precipitation coming in other forms. This year we expect rain, freezing rain, and sleet to cut into what could be higher totals. And, we are forecasting above average precipitation and near average temperatures:
Average snowfall amounts vary from north to south. Maryville, MO has an average seasonal snowfall of around 26 inches of snow, while Clinton, MO averages closer to 15 inches of snow. Kansas City’s average is close to 20 inches and we are forecasting just above this number:
Let us know if you have any questions or comments and we will answer them during the day Tuesday. The weather pattern is about to strengthen. Remember the jet stream reaches peak strength late in January and this energy influx into the weather pattern will be significant in the next two months. The exciting winter ride is about to begin. Will it match the past two winters?