Today’s post outlines the drivers at work behind the kind of winter weather we might expect this year and explores 11 different outlooks for this upcoming winter, but before getting into the winter outlooks shown here, a word of caution on these long range outlooks is needed:
Winter is a notoriously tough season to forecast. Long range climate forecasting and modeling still has a long way to go. Currently the best numerical weather prediction models exhibit around a 90% skill (accuracy) rate to 10 days and 80-90 rate at 16 days. Beyond that, accuracy simply becomes nothing more than random noise. Running these types of models out past these thresholds quickly devolves into chaos theory which is not useful for long range or seasonal weather forecasting. This is a big part of why any forecaster predicting a specific event such as a snowstorm or ice storm at a specific date three weeks a month or even two months in the future does so at their own peril. It is also why predicting several damaging ice storms or a specific number of snowstorms simply cannot be done. Pure chance or a roll of the of the dice has an equal opportunity of giving you an accurate number of winter snow or ice storms per any given winter season.
Long range models such as the NWS Climate Forecast System’s Version 2 model, (CFSv2), the European Center for Medium Range Forecasting (ECMWF) model, the IRI and others shown here are not the same models used in forecasting near term weather. They operate on a different set of physics equations and programming.
An added challenge in forecasting snowfall totals lies in the location of our region. Average annual snow ranges from as little as 6″ south to as much as 20″ north. These totals are well within the range of one or two powerful winter storms. A case in point was the winter of 2012-13. That winter was warmer than average and on the whole (three month period) not very snowy. One late December snowstorm dumped an entire season’s worth of snow and then some over SE Missouri and S Illinois. That one storm, the only major storm, ensured those areas went down in the record books as a snowier than average winter. Kansas City and St. Louis fell victim to two to three major snows in February and March which dumped an entire season’s worth of snow and in the case of Kansas City, an entire season’s worth plus 10″.
The point being that even with a warm and dry winter prediction, it can only take the right combination of factors to come together once or twice in that multi-month period to bring an entire year’s worth of snow. That’s not the same as for areas further north where average snowfall is 2 to 4 feet plus, well out of the range of almost all individual winter storms. Below is a graphic showing the average annual snowfall total for the greater Midwest based upon the 1981-2010 climate period.
In this post, we will take a look at some of the factors we can look to for reliable clues for the winter ahead, and then take a look at several differing winter ideas.
For cold air to develop, you need darkness, ice and snow. Darkness at the north pole is always a given in winter and nothing will change that, so we’ll look first to the extent of the ice cap heading into Winter. The chart below shows the extent of Arctic sea ice. After a record low in 2012, 2013 is running well ahead of that year, but still on the low side of average.
Once cold leaves the Arctic, in order to stay cold, it needs snow and ice on the ground. Otherwise it begins to modify or warm up as it heads south. The graphic below shows the mid October extent of snow and ice for this year as well as 2012, 2011 and 2010 for comparison. This will become more important later in the season; late November, December and January, but at least we can compare where we are starting from.
Perhaps one of the most important factors outside of the cold and snow in the Arctic is the state of the ocean, and specifically how warm or cool it is and where those warm or cool areas are. The graphic below shows the sea surface temperature departure – or difference – from average in mid September of 2013, 2012 and 2011. A quick glance shows how different the ocean temperature is this year from that in 2012 and 2011. The location of the warm and cold pools is important as it plays into the strength and location of warm upper highs & ridges, as well as cold upper lows and troughs. Cold polar air contrasting with warm equatorial waters (El Nino) creates a strong temperature contrast which can create a stronger jet stream. That can result in a jet stream that remains strong and pulled back to the north, while cold polar air has less of a contrast with cooler equatorial waters (La Nina) for a weaker, and waiver jet stream.
At this point an El Nino or La Nina is not expected this winter so they will not be the overriding drivers of the winter weather. Whether a warm or cool neutral trend develops and where it develops may be a contributing factor.
As we have seen in winters past, the Atmospheric Oscillations (Arctic-AO, North Atlantic-NAO, Pacific North American-PNA) can play a really large role in the prevailing winter weather pattern. Note: These are notoriously hard to predict more than a few weeks ahead. In the past three winters, they’ve tended to remain stable for long periods each season.
Winter outlooks for 2013-2014 as of Mid October.
The first outlook is the U.S. National Weather Service’s Climate Prediction Center (CPC) outlook. This outlook focuses the greatest probability of warmth over an area from Louisiana to Arizona and from the Gulf and U.S./Mexico border north to the AZ/UT-NM/CO-KS/OK borders and then southeastwards through SW Arkansas and into Louisiana. A second warm area is forecast over northern New England. An increased probability of dryness is expected over an area centered over far west Texas and New Mexico and as far west as SE Arizona and as far east as the middle of Texas. A second area of dryness is placed over the southeastern states including Florida. The remainder of the country has equal chances for warmer/cooler or wetter/drier conditions. Signals are not strong enough in any way to tilt the odds one way or another. The warmth has been scaled back from the September outlook. In September, the local area was included in the area given a greater chance for above average temperatures. Several other models used in making these predictions have switched over to cold signals in the past month for our area. The intensity of the shading does not indicate how much warmer and drier these areas will be, but rather how confident that the forecast of warmth and dryness will verify.
THE NWS CPC verdict: Near average or no strong signals either way.
One of the models used in the above forecast is the Climate Forecast System’s Version 2 model, (CFSv2). This model’s most recent run expects temperatures to average nearly 2 degrees F above average over the region this winter. This model has been persistently warm over the past year.
The CFSv2 verdict: Warmer than average and wetter than average.
Here is that model’s forecast for winter precipitation. It forecasts above average precipitation.
This model is the Japanese Meteorological Agency’s (JMA) model of the prevailing upper air pattern for winter. It forecasts a high pressure ridge over Alaska and NW Canada to off the U.S. west coast and a low pressure area over Hudson’s Bay. The colors represent upper height departures from average and not specific surface temperatures. This type of pattern would favor cold for the central and eastern U.S. and warmth out west. It does indicate an occasionally active southern jet stream which could act to bring rain and or snow to some areas. This is overall a drier pattern for the region but one in which significant snows could occur given the right setups. It would also favor an increased chance for Arctic outbreaks due to cross polar flow. The prevailing pattern would be a positive Pacific North American (+PNA) pattern.
The JMA’s verdict: Colder and drier overall but increased potential for Arctic outbreaks and snow.
The following two graphics are generalized representations of a +PNA pattern:
A private forecasting company called AccuWeather issues a specific winter forecast each year. Here is the latest current forecast as well as the past two years. Also shown is how these verified for our local area. This blog does not endorse AccuWeather’s forecast nor dismiss it, these panels are shown for information only. AccuWeather owns the rights to their forecasts.
AccuWeather’s verdict: Snow and Ice for Kansas City with above average snowfall for the season and severe thunderstorms for St. Louis, SE Missouri and S Illinois and near average snow.
The next winter forecast is from the International Research Institute (IRI) which runs a number of differing climate forecasting models to come up with a winter outlook.
IRI verdict: Near average or no strong signals either way.
The next outlook comes from us from Japan, the JAMSTEC (Japan Agency for Marine-Earth Science and Technology) long range climate model. Their latest forecast is a bit dated, from September 1st.
JAMSTEC verdict: Warmer than average with near average precipitation.
Here are some additional models and what they expect:
NMME (National Multi-Model Ensemble) verdict: Warmer than average temperatures and no strong signal for precipitation.
NCAR (The National Center for Atmospheric Research) verdict: Cooler than average west and warmer than average east. No precipitation forecast is available.
The Canadian Meteorological Center’s verdict: Warmer and drier than average.
The US Navy model’s verdict: Slightly warmer and slightly drier than average.
A private forecasting company called WeatherBell issues a winter forecast each year. Forecasts are based upon a comprehensive detailed meteorological analysis of many different global models, sea surface temperature, temperature of the stratosphere and solar cycles. Here is the latest current forecast. Over the past few years, Weatherbell’s forecasts have verified quite well for our area. This blog does not endorse Weather Bell’s forecast nor dismiss it, these panels are shown for information only. Weatherbell owns the rights to their forecasts.
WeatherBell’s verdict: Colder and snowier than average.
Winter outlooks will be updated; and this post will be updated in mid to late November.