WINTER OUTLOOK (December 1, 2011 - March 31, 2012)

[LARRYC...@aol.com]

 

Abstract

 

A comprehensive outlook for weather during the upcoming winter season, defined here as December 2011 through March 2012. The emphasis is on temperature patterns through the United States and Canada. Predictions for Europe and Asia are included also, along with outlines concerning snow and ice potential and general character of synoptic conditions in North America.

 

Methodology

 

A number of possible "contributors" to long-term weather forecasting were reviewed. Analog matches to currently evolving patterns and oscillations are averaged to produce a picture of apparent weather between December 1, 2011, and March 31, 2012.

 

In order to provide balance to the forecast against a possible warm or cold bias, past winters of a character that matched the ENSO signal (weak to moderate La Nina episode) were added together to derive a mean temperature.

 

Here are the parameters used in creating the averaged analog forecast, with modification based on currently-seen atmospheric trends:

 

1) El Nino Southern Oscillation (ENSO) Signature (Using Oceanic Nino Index)

A "neutral" ENSO register took shape in the summer following the moderate 2010-2011 La Nina episode. By the approach of autumn, all of the computer models dealing with SST anomalies over the equatorial Pacific Ocean were predicting a return to the colder version of the "Southern Oscillation", with most outlooks showing either a weak or moderate response. Therefore, this winter prediction will follow analogues of -0.7 to -1.2 C deviations from normal in the 3.4 sector. Since this is a "second year" La Nina, previous winter seasons of similar ONI character will be weighted doubly.

 

 

2) Alignment Of Pacific Decadal Oscillation (PDO)

So far in 2011, the Pacific Decadal Oscillation (PDO) has consistently been negative. Unique in over 110 years of charting, the current anomaly structure is matched against warmer than normal waters southwest of the Aleutian Islands and along the West Coast of the U.S. While many would argue that a -PDO favors semizonal flow and warm weather for the lower 48 states, the presence of so much cold water against equally warm pools may allow for an impressive display of -EPO or +PNA-styled ridging through Alaska, western Canada and the Intermountain Region. 1933 is the year which most closely resembles 2011 in a strictly quantitative PDO measure.

 

3) Character Of The Tropics And Madden Julian Oscillation (MJO)

The 2011 tropical cyclone season has been relatively active, with the total number of storms in the Atlantic Basin exceeding the aggregate of warm-core disturbances in the central/eastern equatorial Pacific Ocean by roughly two to one. With a projected 18 named Atlantic systems vs. a probable 9 Pacific declared events, comparison tests measure well against these years: 1995, 2007 and 2010. 2007 represented a building and initial La Nina sequence, and the current summer and fall are a second year -ENSO episode. As was the case with last year, which saw no landfalls on the U.S. coastline. 1995 was part of a one-year weak cold Pacific SST anomaly, with Allison, Erin, and Opal having impacts in the Gulf and Atlantic shorelines, and seems the best comparison test to this year.

 

The Madden-Julian Oscillation has repeatedly featured connections of energy and moisture with the polar westerlies this summer. Much of the linkage has occurred from Indochina and the Maritime Continent into the Aleutian Islands, with three cases of typhoons being absorbed into the jet stream and enhancing downstream ridging over North America. This phasing resulted in one of the hottest summers in the lower 48 states on record. If you factor in increased amplification common with the winter months, an enhanced +PNA bias should be applied to projections in the 500MB longwave pattern from Alaska and western Canada into the U.S. Thus, a warm West vs. cold Central/East alignment is favored when you combine perspectives of the MJO with tropical activity this season.

 

4) Position And Intensity Of 250MB Subtropical And Polar Jet Streams

Review of the character, intensity, and position of the polar westerlies is important in determining the outcome of autumn and winter. By averaging vector wind at 250MB for the period August 15 - September 30, we can then compare previous years with the same 45 day period in 2011. 1981 shows the greatest similarity, with velocity maxima in a cyclonic curve below Alaska, a weakness in the stream axis near the Great Lakes and a small equatorial wind core over and west of the Galapagos islands. Note the relative lack of Arctic or subtropical jet streams in both years.

 

5) Comparison Of 500MB Longwave Pattern And Similarity Of Apparent Weather To Previous Summers

Despite the fact that 2009 was an entrenched El Nino (strong, -1.8 C deviation in Sector 3.4) episode, the recent summer of this year (a neutral period following a moderate La Nina signal) bore remarkable similarities with Rex-styled ridging through Canada and a tendency for the formation of closed lows in a weakness over the Midwest and Old South. 2009 was thus used as an analog year for 500MB characteristic. 1974 could be used as well because of its match in terms of severe thunderstorm output. 1918, which featured a critical drought in the Great Plains and strong heat wave during its summer between the Rocky Mountains and the East Coast, is included in pure temperature and precipitation comparisons.

 

8) State Of The Cryosphere

There have been many media stories concerning the shrinkage of the global ice caps. Comparison of the status of the cryosphere in 2011 shows two close analogues: 1995 and 2010. Of these two years, 2010 seems a better match with its lack of ice adjacent to Alaska and Siberia.

 

9) Solar Activity

The number of sunspots can be used as a measure of how active or quiet the surface of the sun is. A highly active solar landscape implies more output of energy which will reach earth, whereas a heliosphere with few flares or spots is deemed to be "quiet". A general rule in longer term weather forecasting is that a sun sphere which is percolating can be correlated with warmer temperatures, whereas an unblemished rim favors colder readings on Earth. If you compare the current slowly ascendant Solar Cycle 24 with previous years, a good match is found in the 1978-1979 winter.

 

Favored Ridge Signals And Storm Tracks

Dominated by strong 500MB ridges in the -EPO, -AO, and -NAO positions, intrusions of bitterly cold (cAk) values look to be common during the upcoming winter. In terms of temperature, the Great Plains and Midwest will suffer the most, while Texas and the Dixie states may get some breaks from the harsh domain in December and February. The strongest storms will be those which occur just ahead of the frigid regimes, in the "Colorado/Trinidad" and "Panhandle Hooker" trajectories. Alberta Clipper systems may appear with some frequency as well (accounting for a major lake effect snowfall pattern in November, December and early January. In the first month of 2012, the rather expanse of the Alaskan and Siberian outbreaks may suppress the mean storm track into the "Gulf Coaster" and "Hatteras Low" positions.

 

Temperature Forecasts

The coming winter season should compare favorably with the past two cold seasons, and in fact could exceed those bitter months. Note on the analog temperature charts the Midwest catches NO breaks form the unrelenting procession of brutal cold air. The West may see some of the Arctic air in January and March, but look to have the lowest demand potential with two solidly temperate months. There will be warmings of note in the lower Great Plains and Dixie states in December and February. Even in those regions, however, an isolated cAk "Blue Norther" or a frozen precipitation event could occur.

 

December

With blocking returning to the -NAO, -AO and -EPO positions, Arctic air will start to build across Alaska and Canada. However, the 500MB analog strongly suggests that the cAk dome and vortex will reside much of the time in the northwestern portion of the continent. The storm track likely would roll along the southern rim of the Arctic air, in a Colorado/Trinidad or Great Plains Duster type of path. That trajectory will afford some periods of warming for the southern half of the nation, with Texas and the Deep South "dodging the bullet", so to speak, with a majority of December days being quite warm. Possible issue which may arise: mixed precipitation or ice storm events in the northern tier of the Midwest (Minneapolis MN, Milwaukee WI, Chicago IL and Detroit MI) and New England.

 

January

This map looks ugly, and infers that extreme cold will visit much of the U.S. with little evidence of a January thaw. That said, the 1995-96 analog would support a week of milder values for the East Coast. The core of the circumpolar vortex will likely be very close to James Bay, with the cAk motherlode building over the Prairie Provinces and shifting southeastward below the Alaskan and Greenland blocking ridges. The gap between those two ridge complexes may allow for one or two Siberian regimes to move into Canada and the U.S. The West Coast will likely escape the bitter values, but face the danger of Santa Ana/Canyon wind episodes. Favored storm tracks: Gulf Coaster, Colorado/Trinidad "B", and Hatteras Low. If a thaw does occur at mid-month, and argument can be made for a Georgia to Maine trajectory with heavy rain and thunder for the Interstate 95 corridor.

 

February

Some retrogression of the cAk vortex and the -EPO ridge complex is expected. But a neutral AO and strongly negative -NAO signal couplet implies a very cold February for all but the Southwest and the Gulf Coast. Ice storm possibilities loom large in the first week or two of the month from N TX....OK....N AR into the Mid-Atlantic region, while heavy snows visit the Midwest and Northeast. There may be some similarity to the 1993-94 season in this regard, even though that winter is not used in the computation of this forecast. Warming is likely across California and the Southwest.

 

March

Once again, analog data strongly supports a -EPO/-AO/-NAO alignment. Seasonal retrogression of the circumpolar vortex accounts for some warming along the immediate East Coast and cooler weather about the Pacific shoreline. Much of the U.S. and southern Canada, however, are still quite cold. Like 2009, late-season snow events may occur in a stretch from OK and N TX into the lower Great Lakes, with the Gulf and Atlantic Coasts seeing both stratiform and convective rainfall.

 

Precipitation (Emphasis On Ice And Snow) Forecasts

Keep in mind that the analog method in computing the weather works better with temperature than is the case with precipitation. If you review the aggregate data for the years selected, Appalachia, the Upper Midwest and the Pacific Northwest look to have the most snow and ice. Teleconnections on a dominant Hudson Bay cAk vortex with formative roots in northwestern Canada, however, favor the Great Lakes (lake effect related snow squalls) for important snow with the northern tier states from BC/WA/OR into Great Plains being very dry. The reason why is basic climatology for a La Nina episode, since past years may have followed the -ENSO trend. I strongly agree with the heavy precipitation threat for all of Appalachia (northern New England to AL/GA, as well as very dry conditions in KS, OK, TX. The heaviest of snows will be associated with Colorado/Trinidad "B" and Hatteras Low related systems.

 

European Winter Forecast

While the European Union will have its share of mild spells, the eastern third of the subcontinent look to be in a classic Caspian Sea ridging scenario. Against a vortex setting up across the North Sea, the ridge complex will align with the -NAO signature to dump numerous blasts of cAk readings into Russia and Eastern Europe. January through most of March could prove to be a very difficult period for the Russian Commonwealth.

 

Asian Winter Forecast

While not as bitterly cold as Europe and North America, much of Asia above the Himalayan Range will have problems from cold and dry weather. Retrogression of the -EPO blocking ridge into a -WPO (Kamchatka, Sakhalin, and Hokkaido placement) should ease the Siberian regime. Much of the PRC looks to be hard hit this winter season.

 

Summary

 

Following closely on HDD measures of the two previous winters, the 2011-2012 season will have similar stretches of bitterly cold weather. Both the West and Dixie regions look to get occasional breaks from the cAk regime. It is the Midwest that will have the most issues with unrelenting presence of frigid air. January looks to be the key month for HDDs.