Happy Valentines Day NBC Action Weather bloggers,
A big warm up is likely early Thursday before the last in a long series of Arctic fronts blasts in on Valentines Day. It may jump briefly into the 50s on Thursday and then drop into the 20s by the evening rush hour with a few snow flurries.
We must, suddenly, watch the weekend storm. The Canadian model and GFS model came out with the storm moving into our viewing area Saturday and Saturday night. And, I thought we may get a little break, maybe not. More on this later today.
It is time to go into what the pattern has been doing and what we can expect in the future.
THE WEATHER PATTERN & THE LRC (February 13, 2008)
The weather pattern, that setup from October into early November, continues to cycle. We have had a lot of discussion on the NBC Action Weather Blog with some very productive dialogue about the LRC, the length of the cycle, and other various parts of this fascinating weather pattern that keep repeating. I would like to thank Scott, Notes in the Margin, Pvt Murphy, and many others for your insight, ideas, and constructive criticism. This communication only helps us focus in on the weather pattern and we continue to learn more. I am convinced that the LRC is a major discovery in meteorology. It is just my theory (you can read much more about it in previous blog entries, look on January 2nd), and I will continue to share it with you and use it as it has provided our weather team with a huge forecasting advantage. The LRC helps snow removal companies to decide whether they need to stock up on salt. It helps in long range forecasting for the grain and energy commodity futures. And, it helps our weather team as it is just another tool we use to bring Kansas City the most accurate forecast.
We noticed that the weather pattern was repeating in early December. This is about the time we can see the cycle every year, but it takes until around January 1st before we gain confidence. Remember, every year is unique, and there can be no denying this again. Just look at what has been happening. Madison, Wisconsin is up to nearly 80 inches of snow already. A few weeks ago, our first guess on the cycle length was 54 days, and although this was a guess based on how we saw the weather pattern repeating, we are now convinced that it is closer to 50 days. Some aspects of the pattern seem to have repeated every 46 to 49 days, while other storm systems, troughs, and ridges have returned closer to the original 54 day idea, but not longer than this cycle length. So, when you see our long range forecast it is going to be using this 50 day cycle length.
Before we get to the forecast, let's look at this year's LRC and weather pattern. We believe the weather pattern is cycling every 50 days or so, give or take a few days. It isn't exact. If it was, then there would be no discussion, no debate, and the fun would be taken out of weather forecasting. But, it is close, amazingly close! The bigger features will often return throughout the pattern. "Long term" longwave troughs and ridges become established and the weather pattern will return to these positions right on schedule through the cycle. One "long term" longwave trough is likely located between central Missouri and Chicago, IL. When the flow is deamplified the trough is disguised eastward a bit (as you can see below). But, when it is amplified the trough sharpens up into it's real position extending from western Lake Superior to just west of St. Louis, MO. It is this strong feature that is the biggest reason why there have been near record snowfalls over Wisconsin, located just east of the trough position.
The above map is the mean 500 mb flow when the pattern is more deamplified. There is one "long term" longwave trough a bit east of its more amplified position, and in this lower amplified part of the pattern there is another weaker "long term" longwave trough west and southwest of Kansas City. This allows for some storm systems to move through the west coast and then deepen into the plains and this has allowed for some of our spring like severe weather set ups during these winter months. And, this has provided our local region with some wet storm systems this season.
This next map below, shows what happens to the pattern when it amplifies. Remember this is where I believe the "long term" longwave troughs are located. Storm systems will intensify as they move into the trough position and then weaken as they move out of it. In this more amplified part of the cycle, which has happened a lot this season, the southern storm systems track farther south and just clip our viewing area.
So, I have established where we believe the "long term" longwave troughs are located. But, other features will form in places that the pattern doesn't support very well. A perfect example is on the map below. Twice this season the flow super amplified and a big "cold generating" ridge formed across the eastern Pacific poking all the way up into the North Pole. This happened on November 30th. We then used the LRC to forecast this part of the pattern returning in mid to late January and weeks ahead of time only NBC Action News forecasted the cold outbreak that lasted around 10 days. Other forecasts had called for a warm January into February. This year we took a different approach at an attempt to show you that it would not just be a coincidence. In the blog (January 2nd), and on the air, we made a long range forecast for the next 50 days and clearly showed what the pattern would look like later in January. The pattern developed almost exactly as we had forecast.
Below, is the pattern that formed twice already this season. But, this huge ridge is not in a mean "long term" longwave ridge position. So, this is why it breaks down so fast. If the amplified pattern would just last a little bit longer then the Arctic air masses that formed would have become even colder with much stronger surface high pressure.
The map below is what happens to the pattern just days after that big ridge forms. So, once that big ridge forms, amazingly it will break down and strong storm systems will then move across the nation. Kansas City will experience the series of storm systems that has now happened 3 times (October, December, and late January and early February).
These next two maps show the pattern from November 30, 2007 and January 20, 2008. This is 50 days apart. So, expect this to return around March 10th. It will not be a coincidence.
So, now how can we use this knowledge to make a long range forecast. We believe that we are in around a 50 day cycle. It could be 51, 54, or even 46 days in between some of our significant features. The big features will be returning and very close to right on their scheduled dates. And, remember this pattern will continue through the summer. And, the exact same weather conditions will not repeat in the exact same spots as before. We can still look forward and make an accurate prediction of when storm systems are most likely going to occur. And, not just any storm, but the ones unique to this season. They will look the same as previous storm systems, they will intensify and weaken similarly to what happened the last few times through the cycles, and we will be able to use this information as the storm systems approach. The computer models will make errors and we will be able to tell if they have the right or wrong solutions.
LONG RANGE FORECAST February 15th - March 31st
Kansas City averages around 5.5" of snow between now and early April. With the pattern we are in right now I think there will be well above the average number of chances for snow, some wet storm systems, likely our first severe thunderstorms (unless it stays cold), another cold outbreak, more hard freezes, and it is just going to be a bit on the wild side as winter battles spring and winter will win out a few more times before spring takes over. It is very likely going to be a wild ride!
One last thing before the forecast. We had a series of storm systems as the pattern was born in October, then they repeated in December, and again in late January as we had predicted. In October the series of storm systems were spread out over 14 days from October 13th - October 26th. In December the series spanned 15 days from December 1st through December 15th. And, it was a a 13 day spread from January 25th through February 6th. We expect this series of storm systems to repeat during the second half of March. Between now and then there should be no lack of storm systems as the pattern across Canada could get blocked up. We must watch Canada closely. If a block forms, then we will have some major winter storms.
The Forecast:
February 15-22:
This is just the next 8 days, so it is already on our 7 day. We expect the Pacific flow to break through the west coast, but it could be quite active if the jet stream stays south of us. The Arctic air will retreat early next week. We expect one, perhaps a second storm system around the 21st, right now the first one may just miss us to the south, but it could suddenly turn north as the flow amplifies around the 16th. The pattern stays active with the warm ups still in question.
February 23-March 4:
Two storm systems, one of which will likely produce severe thunderstorms near or just south of our region, and it should be a rather wet storm. The Arctic air may be lurking near by, and there may still be a strong winter component to these storm systems.
March 5-13:
Cold air again builds in Canada. One significant storm with two other fast moving systems will affect Kansas City. Arctic air will threaten a move south.
March 14-31st:
The series of four storm systems returns during the second half of March. Arctic air will likely make a surge south into Texas. There will be reinforcing shots of very cold air and one of the four storms will be very wet. There will likely be a blizzard and massive winter storm very close to us between March 21st and March 28th.
That last statement is pretty strong. It is sort of our signature storm system and a test of a very long range forecast and the LRC!
We expect some very hard freezes in late March. Looking ahead to April I think that our average last freeze date of around April 9th may be about right. There will be a threat of a light late freeze towards the end of April as the cold part of the pattern returns again, but by this time we may just avoid the killing freeze we had last year.
I hope you have enjoyed reading this today. We will spend some time getting to all of your questions during the morning on Thursday. A strong front will be approaching. Watch NBC Action News for details. And, Friday night at 10 PM I will be talking about the new CASA radar system.
And, if that storm system forming over the southwest takes a more northward trend on the models, then we will update the blog. As I stated near the beginning, the trend for the storm to move farther north has started.
Gary