It is that time of the year again where many weather forecasters release their forecast on the upcoming winter pattern across the United States. If you can recall from last year, everyone got the forecast wrong. In fact, temperatures were supposed to be average with equal chances for precipitation across our area. Instead, we mainly saw warmer than average temperatures. In my post from last year, I predicted a colder November or December with a quick warmup by February/March of 2012. Generally, I was correct regarding a warmer pattern for the end of winter. However, I legitimately thought we had a shot of seeing snow.
If you want to read my winter outlook, you’ll have to skip to the bottom of this post. Otherwise, you can read about the science of how I am forecasting our upcoming winter below.
If you buy into Accuweather’s winter forecast, they believe the Southeast will see below average temperatures and better shots at precipitation and snow. (See images below)
|Image Credit: Accuweather|
|Accuweather’s winter forecast for 2012-2013|
This year, I am focusing on weather and climate trends and how they have affected our weather so far. Here are a few things I have been analyzing recently:
1) ENSO remains neutral
The El Niño Southern Oscillation, also called the ENSO, pretty much looks at the water temperatures off the central and equatorial Pacific Ocean. When these temperatures are cooler than average, we are considered to be in a La Niña. When these temperatures are above average, then we are in an El Niño. As of today, we are in netural conditions, and this phase is expected to continue throughout the winter. Originally, the forecast was for a weak El Niño to develop this winter, and it would provide the Southeast greater opportunities for seeing an increase in moisture and cooler conditions. However, in a La Niña phase, we typically see drier and slightly warmer winters. Since we are in neutral territory, the outlook shows equal chances of seeing a mix of wet/dry conditions.
Note: A lot of these meteorological terms are referenced as “oscillations”. What is an oscillation? An oscillation is a repetitive variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states.
Positive Phase Negative Phase
The Pacific Decadal Oscillation (PDO) is like a long lived El Niño like pattern where it involves the Pacific Basin and the North American climate. PDO goes through two phases in where the ocean temperature anomalies in the northeast and tropical Pacific Ocean: a cold and warm phase. If you want to learn more about the PDO, you can click here. To summarize it, the PDO is in a cold phase, which could be a contributing factor of seeing more of a winter this year. Granted, there are other important factors to look at besides this one.
3) AO (Arctic Oscillation)
Positive Phase Negative Phase
The Arctic Oscillation or the AO can play a role on our weather during the winter months. According to NOAA, The oscillation exhibits a “negative phase” with relatively high pressure over the polar region and low pressure at midlatitudes (about 45 degrees North), and a “positive phase” in which the pattern is reversed. In the positive phase, higher pressure at midlatitudes drives ocean storms farther north, and changes in the circulation pattern bring wetter weather to Alaska, Scotland and Scandinavia, as well as drier conditions to the western United States and the Mediterranean. In the positive phase, frigid winter air does not extend as far into the middle of North America as it would during the negative phase of the oscillation. This keeps much of the United States east of the Rocky Mountains warmer than normal, but leaves Greenland and Newfoundland colder than usual. Weather patterns in the negative phase are in general “opposite” to those of the positive phase, as illustrated above.
Take a look at the Arctic Oscillation and the phase it has been and what it could be for December:
As you can see above, the AO is expected to be negative for the end of November and early part of December. If this pattern continues, that will tend to be a positive sign for you winter lover fans.
The North Atlantic Oscillation is probably one of the most important factors for our upcoming winter. Like the other oscillations, it also has a negative and positive phase. In a negative phase, it reflects above-normal heights and pressure across the high latitudes of the North Atlantic and below-normal heights and pressure over the central North Atlantic, the eastern United States and western Europe. In other words, negative phases are more conducive for troughs and colder air to spill into the eastern United States. The huge cold blast and winter storm of early January 2011 in north Georgia was brought upon when the NAO dropped negative. In fact, after looking at past winter events, they typically occurred when the NAO was negative. Last winter, this feature stayed positive, which translated into a warmer than average winter. NAO is unpredictable and can change back and forth week after week. However, if you look at the graphic below, you can see that the NAO has been trending more negative recently than positive, which is a good sign for the future weather pattern.
In the above graphic, do you see how the NAO dipped below 0 during the month of October? Can you recall October being cooler than average? Well, it was. In fact, the United States overall experienced a slightly below average October. The NAO played a huge role into that. If you look at the red spaghetti lines towards the end of November and early December, you can see the NAO is trending neutral to mostly negative values. If this occurs, than December could bring in cooler temperatures and possibly shots at a few systems pushing into our area giving us opportunities for rain.
As of now, December will start off cold as we will see large troughs digging into the Southeast. Temperatures could easily be ten degrees below average. The pattern is opposite of last December, so that is a good sign for those who love winter weather.
I think January will provide us a roller coaster ride with cold surges, a few warm ups, and possibly a threat or two for storm systems to affect us and possibly give us snow. Of course, many things typically change, but I expect January to be much cooler than January 2012.
By the end of winter, I expect us to begin warming up pretty quick, and I honestly think the heart of winter will occur in December and January. Sure, we’ll see waves of cooler air during the February and March months, but overall, I expect to see above average temperatures.
Of course, long range forecasts are always up in the air. I could be completely wrong, or I could be right. You have to look at the overall pattern to see how it will set up and whether or not it will affect us down the road. I have a theory that our seasons are developing about a month early. Fall arrived a little earlier than expected this year, and so did our spring and summer. With that said, winter will be here for December and January, and I fully expect a transition to spring and warmer temperatures to occur earlier than usual in February and March.
If you have any questions, let me know via the blog, twitter, facebook, or Google +. Overall, the trend looks positive for more snow and cold weather across the United States (besides the SW portion of the U.S.) this winter.
Text and sources cited via NOAA/NWS/NCDC/CPC/HPC