WINTER FORECAST 2012-2013
By Chief Meteorologist Gary Lezak
November 19, 2012
Another unique weather pattern has set up across the Northern Hemisphere and this winter forecast is based on the early analysis that we have just completed. This weather pattern, that we will be experiencing for the next year, is a complex puzzle and we have a weather forecast formula as you can see on this first graphic:
Knowledge of Lezak’s Recurring Cycle (the LRC) and many other variables will help us make accurate weather forecasts from day 1 to almost a year ahead of time. The Arctic Oscillation, which will be discussed below, is one factor that has potentially been huge during the past three winters. The El Niño Southern Oscillation, or ENSO, is another factor that has been shown to influence the overall weather pattern. And, there are many other factors such as the North Atlantic Oscillation, the PNA, and the MJO. We learn more every year and we are expecting our weather forecasts to become more accurate in the years ahead of us.
Let’s begin this winter forecast discussion by explaining what we know about the LRC. We believe the weather pattern is cycling with a somewhat regular period of days. And, there are major features within this cycling pattern that return, on schedule. If you know the cycle length and the major features within the cycling pattern, then the accuracy in these weather forecasts improves. We learn more as we go through the rest of autumn into the early part of winter. The cycle length is currently still being identified, but we now know where the main features are located that will be factors in how we experience weather at the surface. These features will be discussed below.
The LRC (Lezak’s Recurring Cycle)
- A unique weather pattern sets up and evolves every year between the end of July into the first half of November. The most important weeks of this developing pattern are between October 1st and November 10th when the major features set up and show themselves across the westerly belt of the Northern Hemisphere.
- Long term long-wave troughs and ridges become established and are the predominant features that will exist and return on schedule through the next winter, spring, and into the first half of summer.
- The pattern is always cycling, but a new cycle length becomes established. Identifying this cycle length is challenging, but it usually is firmed up by the end of the calendar year.
Three main long term long-wave troughs have shown up during the critical developing period. We are calling these “the hot spots” for storm systems to intensify in during the next few months before summer settles and this pattern breaks down in late July. The most likely spot for the most intense winter storm systems this winter will be located near the northeast into New England coast and extending into the immediate inland areas. A second hot spot has shown up from Minnesota into the western Great Lakes states and extending south into eastern Kentucky and West Virginia. A third long term long-wave trough or hot spot has affected the Pacific Northwest at times already. We will show examples below.
Arctic Oscillation (AO)
The Arctic Oscillation (AO) is one of our key factors in the Winter Forecast Formula. When the AO index is positive, like it was last winter, Arctic air is likely going to be held north across Canada with a farther north jet stream across North America. Last winter had a strongly positive AO and the United States ended up having a very mild winter. The previous two winters had deeply negative AO index values. And, those two winters (2009-2010 & 2010-2011) were cold and very snowy across the United States even though the weather patterns were quite different.
If the AO goes negative, then Arctic air is much more likely to plunge south into the United States. The jet stream would be forced farther south and become energized. This stronger jet stream can lead to major winter storm systems. Again, if the AO does go negative, the hot spots would likely shift farther south and lead to a more southern track of winter storm systems during this phase of the Arctic Oscillation, as you can see on the map to the right. The hot spots would likely shift south during the negative phase of the AO. You can click on these two maps for a larger view.
The Climate Prediction Center keeps track of the AO index and has a graphic that indicates where the ensemble members of the GFS are forecasting the AO to go. Let’s look at the AO index and forecast from November 18th:
Last year the AO index was high positive, but there has been a trend into negative territory as you can see above. Most of this past month of November has had a positive AO. In October a strong trend towards a negative AO occurred as the new LRC was setting up. And, the forecasts right now are for a dip back into the negative during the next two weeks. This oscillation also shows a cycling pattern and we are expecting it to go deeper into the negative at times this winter, something that did not happen last winter when record warm temperatures were set across the United States. It will have to be a harsher winter just based on what we believe will happen with the AO.
The ENSO (El Niño Southern Oscillation) index has been slightly positive or really near neutral. It appears that we are going to have a neutral year for the ENSO index. To be an El Niño there has to be a five month stretch where the three month average is +.5°C and so far we haven’t had one three month average at that level or higher this season. This is still an influence on the weather pattern, but it is obviously going to be different every year and it is another factor that is considered into the LRC Winter Forecast Formula. There are other indices that are likely factors as well, but we will leave those out in this discussion.
We are about to look at the main features of this year’s pattern. We are expecting the AO to go into the negative much more than last winter, but perhaps not as low as the two previous cold and snowy winters. The AO, ENSO, and other factors may be deciding factors or influences on how the LRC sets up each year, but there may be something else entirely going on that has yet to be identified in the field of meteorology. We believe we have identified something and we call it the LRC. Let’s take a look:
Main Features #1 & #2 of this year’s LRC
I am sure we all remember Hurricane Sandy. A long term long-wave trough became strongly established during October and the conditions became favorable for Sandy to be pulled into the New Jersey shore and affect the east coast big time.
The AO index graphic, above, shows that there was close to a negative two AO while Sandy was approaching the east coast. This indicates a strong likelihood of blocking forming over Greenland aloft, and sure enough a big upper high developed just as Sandy was moving north off the east coast and this blocking upper level high helped Sandy slam into the Jersey shore. Sandy was a small scale feature compared to the strong jet stream diving east southeast over the Mississippi River Valley. (You can click on either of these two maps for a larger view)
A main feature of this year’s LRC showed itself very well and Sandy got absorbed into a much bigger upper level low that formed over the northeastern United States on October 30th. You can see the blocking upper high, which was a strong sign of the negative AO during October. that actually lead to some below average temperatures across the United States in October in many spots. This is one main feature that will return often this winter and into next spring. It is what we call a long term long-wave trough.
When the trough was digging west of the Great Lakes you can see another strong feature of this year’s LRC weather pattern, the Upper Midwest & Great Lakes long term long-wave trough:
Ten days before the part of the pattern that helped guide Hurricane Sandy into Superstorm Sandy and slammed it into the east coast, there was another deep system that is a strong indication of another part of the pattern that will return often this winter and into the spring. This map, above, shows the 500 mb flow on October 18, 2012. If you save the October 28th map and this October 18th map to your computer and then overlay them you will clearly see that the trough and upper low just west of the Great Lakes line up almost perfectly clearly showing this main feature that will return many times in the next year.
Main Feature #3 of this year’s LRC
Just nine days after Superstorm Sandy blasted the east coast and the Jersey shore another major storm dropped into the Midwest and New England/Northeast long term long-wave trough. Again, look at the Arctic Oscillation index graphic above. You will see that the AO went positive by this first week of November and there was suddenly no blocking upper high, and yet this storm still dropped into the same spot and looks somewhat similar to what happened just nine days earlier and this time it was a snowstorm that affected New York City and adjacent areas just inland. This shows how strong this long term long-wave likely is, with it returning with an AO+ and an AO- index.
There is also another strong feature on this map that was digging down the west coast. This is feature #3 of this year’s LRC:
A rather strong and deep upper low formed near the west coast on November 9th. This part of the pattern has not been as dominant as the other features in the LRC, but it is there and will return. We will have to pay close attention to this part of the pattern, especially if it returns during an AO negative phase. This version occurred during the November AO positive phase. When this trough returns, the Pacific Northwest will get blasted by some strong storm systems, and if the AO goes negative while this storm is cycling through the LRC, then the storm will likely be much farther south and affect not just California big time, but also set up a potential winter storm in the plains states and Rocky Mountains. This will likely not happen often, but it likely will happen once or twice this winter which will bring precipitation to areas that will likely be quite dry this winter season.
Precipitation and Temperature Seasonal Forecasts
The Great Lakes and New England/Northeast long term long-wave troughs will likely return often enough to produce above average rain and snow from the Great Lakes south into the Carolina’s and into New England. The most likely spot for below average precipitation will extend from the desert southwest into the plains. This is not good for some of the drought stricken region and we are concerned for the Winter Wheat crop that needs some moisture. Hopefully the AO will go negative while a storm is swinging into the western states and this region could have a few wet storm systems.
Most of the nation is likely to have near to above average temperatures this winter and into next spring. The most likely spot we have picked out to have below average temperatures will be near the middle of the two long term long-wave troughs from Michigan south into northern Kentucky.
Kansas City Forecast Discussion
Kansas City is in a position to have a harsher winter than last year, but only a few winter storms. We are located south of the upper Midwest and Great Lakes hot spot with the long term long-wave trough located north to northeast of Missouri (look at the hot spots map near the top of this winter forecast). When the Arctic Oscillation goes into the negative phase, and we believe it will a few times, then we will have a good chance of some winter storm activity.
Kansas City Region Winter Forecast Specifics
- Temperatures will be near to above average from December through March
- Precipitation will be below average. Kansas City averages around 6 1/2 inches of melted down precipitation (rain and melted down snow).
- Expect below average snowfall (Kansas City averages around 20 inches of snow per winter season)
- We are forecasting one 5″ snowstorm, one 3″ snowstorm, and a few smaller events
- We are forecasting one ice storm, most likely a weak to moderate one
- Our forecast total snowfall for the region will be between 10 and 20 inches
- The snowfall forecast for Kansas City is 14″ which is more the three times as much snow as last winter
This weather pattern continues to evolve. According to the LRC, we believe that it will become established with a cycle length identified in the coming weeks. When we learn a bit more about this cycling pattern and can pin down exactly what the Arctic Oscillation, the North Atlantic Oscillation (NAO), ENSO, and other factors, we will be able to improve on the accuracy of this forecast and get a bit more specific as to when storm systems are likely to hit your area. Look for an update to this forecast in a few weeks.
KSHB 41 Action News Chief Meteorologist