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Winter 2008-09 Outlook
Updated November 21, 2008 - Jeff Boyne

Temperature Outlook

Precipitation Outlook

Similar Winters

Potential Wild Cards This Winter

Winter Climatology La Crosse, WI Rochester, MN

On November 20, 2008, NOAA's Climate Prediction Center (CPC) released their last outlook for the 2008-09 meteorological winter (December 1, 2008 to February 28, 2009).  They are forecasting above normal temperatures across southeast Minnesota, northeast Iowa, and western Wisconsin.  Meanwhile their precipitation forecast is for equal chances of above normal, below normal, and near normal precipitation. See information below for additional historical climate information relevant to this upcoming winter.

Climate Prediction Center (CPC) Outlook

CPC Temperature Outlook:

For the upcoming 2008-09 winter, NOAA's Climate Prediction Center (CPC) is forecasting warmer-than-normal temperatures across much of the eastern half of the United States, western Hawaiian Islands, and Alaska.  Their highest probabilities for above normal temperatures is located across the Central Plains and Mid Mississippi River Valley (Missouri, eastern Kansas, Oklahoma, and northern and eastern Arkansas).

CPC's Winter 2008-09 U. S. Temperature Outlook

This forecast represents a southward shift of the highest probabilities of above normal temperatures from the Upper Mississippi River Valley and Great Lakes to the Central Plains and Mid Mississippi River Valley.  The reason for this shift was some conflicting information in their statistical tools and probabilistic models across the Upper Mississippi River Valley.  This lowered their confidence that this winter would be warmer-than-normal in this region of the country. 

While their probabilities still favor above-normal temperatures across southeast Minnesota, northeast Iowa, and western Wisconsin for this upcoming winter, the chances have decreased some and this in turn has raised the probabilities that this winter could end up being colder-than-normal.  For example, in La Crosse WI the October 16th temperature outlook the terciles were broken up as follows:  51% above normal, 34 percent near normal, and 15 percent below normal.  In the November 20th outlook, these terciles had changed to the following:  37% above normal, 34 percent near normal, and 29 percent below normal.   Below is a list of the downscaled temperature probabilities for various locations in the Upper Mississippi River Valley.

CPC Temperature Probabilities for the 2008-09 Winter
Region	Location	County	Dec-Feb Temperature Probabilities
Northeast Iowa	Charles City	Floyd	42% - Above (Higher than 18.9F) 33% - Near Normal (14.8-18.9F) 25% - Below (Lower than 14.8F)
	Decorah	Winneshiek	42% - Above (Higher than 20.3F) 34% - Near Normal (16.4-20.3F) 24% - Below (Lower than 16.4F)
	Fayette	Fayette	42% - Above (Higher than 19.8F) 33% - Near Normal (15.9-19.8F) 25% - Below (Lower than 15.9F)
Southeast Minnesota	Austin	Mower	36% - Above (Higher than 16.6F) 34% - Near Normal (12.3-16.6F) 30% - Below (Lower than 12.3F)
	Rochester	Olmsted	36% - Above (Higher than 18.1F) 34% - Near Normal (14.0-18.1F) 30% - Below (Lower than 14.0F)
Western Wisconsin	La Crosse	La Crosse	37% - Above (Higher than 21.2F) 34% - Near Normal (17.3-21.2F) 29% - Below (Lower than 17.3F)
	Lancaster	Grant	42% - Above (Higher than 21.1F) 33% - Near Normal (17.3-21.1F) 25% - Below (Lower than 17.3F)
	Mather 3NW	Jackson	37% - Above (Higher than 19.4F) 34% - Near Normal (15.7-19.4F) 29% - Below (Lower than 15.7F)
	Medford	Taylor	36% - Above (Higher than 15.8F) 34% - Near Normal (12.1-15.8F) 30% - Below (Lower than 12.1F)
	Viroqua	Vernon	42% - Above (Higher than 18.9F) 33% - Near Normal (14.8-18.9F) 25% - Below (Lower than 14.8F)
For other seasonal temperature outlooks, consult the following experimental web site: http://www.weather.gov/climate/l3mto.php

CPC Precipitation Outlook:

For the upcoming 2008-09 winter, NOAA's Climate Prediction Center (CPC) is forecasting below normal precipitation from Arizona to south Texas to the southeast United States.  Meanwhile they are forecasting above normal precipitation across eastern Colorado, southern Nebraska, Kansas, northern Texas, Oklahoma, Missouri, and Arkansas.  The remainder of the country will see equal chances for above normal, below normal, and near normal precipitation.

CPC's Winter 2008-09 U. S. Precipitation Outlook

Review of Past Winters with Similar Global Characteristics

Temperatures:

This upcoming winter will not be affected by either an El Niño or a  La Niña, so it will be classied as either a "Neutral" or "La Nada" winter. A review of twenty-three similar past winters suggest that there is a possibility that the winter of 2008-09 could end up being colder-than-normal.  A composite analysis of these winters showed that the average temperatures varied quite dramatically across Alaska, Canada, Northern Plains, Upper Mississippi River Valley, and Great Lakes.  While these regions have quite variable temperatures, Greenland is typically warmer-than-normal.  This is illustrated well in the two images below provided by NOAA's Earth System Research Laboratory.

Warmer-than-Normal "Neutral" or "La Nada" Winters	Colder-than-Normal "Neutral" or "La Nada" Winters

In the Upper Mississippi River Valley, there was nearly an even split between winters which were warmer-than-normal and those which were colder-than-normal.

In La Crosse WI, there was even split amongst the twenty-two winters (one winter had no temperature data available) between those that were warmer-than-normal and those which were colder-than-normal.  The coldest of these winters occurred back 1978-79 when the average temperature was 12.8 degrees (7.2 degrees below normal).  Meanwhile the warmest of these winters occurred back in 2001-02 when the average temperature was 29.2 degrees (9.2 degrees above normal).  This is a spread of 16.4 degrees.
	Variability of Temperatures during "La Nada" or "Neutral" Winters in La Crosse, WI
Meanwhile in Rochester MN, twelve winters were warmer-than normal, ten were colder-than-normal, and one winter ended up being normal.  The coldest of these winters occurred back 1978-79 when the average temperature was 5.6 degrees (10.1 degrees below normal).  Meanwhile the warmest of these winters occurred back in 2001-02 when the average temperature was 25.5 degrees (9.8 degrees above normal).  This is a spread of 19.9 degrees.
	Variability of Temperatures during "La Nada" or "Neutral" Winters in Rochester, MN

Many of the signals (such as a La Niña-like atmosphere and ocean) that showed up in the colder-than-normal winters are already showing up this autumn and they are expected to continue into the upcoming winter season.  As a result, there is a possibility that this winter could end up averaging colder-than-normal temperatures.  Only time will tell.

Precipitation:

Composites show that in La Crosse, WI there was nearly an even split amongst the twenty-two "La Nada" or "Neutral" winters (one winter had no precipitation data available) between those that were wetter-than-normal and those which were drier-than-normal.  The driest of these winters occurred in 1962-63 when the total precipitation was 1.46 inches (1.95 inches below normal).  Meanwhile the wettest of these winters occurred in 1966-67 when the total precipitation was 5.17 inches (1.76 degrees above normal). This is a spread of 3.71 inches.
	Variability of Precipitation during "La Nada" or "Neutral" Winters in La Crosse, WI
Meanwhile in Rochester MN, there was a tendency for the "La Nada" or "Neutral" winters to be drier-than-normal.  Out of the 23 winters in the study, fifteen were drier-than-normal or 65.2 percent.  The driest of these winters occurred in 2005-06 when the total precipitation was a mere 1.29 inches (1.42 inches below normal).  Meanwhile the wettest of these winters occurred in 1966-67 when the total precipitation was 4.25 inches (1.54 degrees above normal). This is a spread of 2.96 inches.
	Variability of Precipitation during "La Nada" or "Neutral" Winters in Rochester, MN

Snowfall:

Composites showed that "Neutral" or "La Nada" winters had highly variable seasonal snowfalls (July 1st through June 30th).

In La Crosse WI, nine seasonal snowfalls were above normal and thirteen seasonal snowfalls were below normal (one snow season had no snowfall measured).  The least amount of snow in a season occurred back 1953-54 when a mere 18.8 inches (25.5 inches below normal) fell.  Meanwhile the greatest amount of snow in a season occurred in 1961-62 when 78.7 inches of snow (34.4 inches above normal) fell. This is a spread of 59.9 inches.

Variability of Snowfall during "La Nada" or "Neutral" Snow Seasons in La Crosse, WI

In Rochester MN, ten seasonal snowfalls were above normal and thirteen seasonal snowfalls were below normal.  The least amount of snow in a season occurred in 1953-54 when a mere 24.8 inches (27.9 inches below normal) fell.  Meanwhile the greatest amount of snow in a season occurred in 1996-97 when 84.7 inches of snow (32 inches above normal) fell. This is a spread of 59.9 inches.
	Variability of Snowfall during "La Nada" or "Neutral" Snow Seasons in Rochester, MN

Potential Wild Cards for this upcoming Winter

The following wild cards may affect the Upper Mississippi River Valley temperatures and precipitation during this upcoming winter:

North Atlantic Oscillation (NAO): The North Atlantic Oscillation (NAO) was discovered in the 1920s by Sir Gilbert Walker. Similar to the El Niño phenomenon in the Pacific Ocean, the NAO is one of the most important drivers of climate fluctuations in the North Atlantic and surrounding humid climates. The NAO phase can greatly affect the temperatures across the eastern half of the United States.  This includes the Upper Mississippi River Valley.  When the NAO is in its positive phase, low pressure is located across Iceland and high pressure is located across the Azores.  In this phase, temperatures across the Upper Mississippi River Valley average above normal.  Meanwhile when the NAO is in its negative phase, the high and low pressure systems are reversed and the Upper Mississippi River Valley experiences below normal temperatures. The images below from NOAA's Earth System Research Laboratory show what the typical surface pressure and temperature anomaly pattern looks like in each phase.
Sea Level Pressure Anomalies during the NAO's Positive Phase			Sea Level Pressure Anomalies during the NAO's Negative Phase
Temperature Anomalies during the NAO's Positive Phase			Temperature Anomalies during the NAO's Negative Phase
While meteorologists know that the NAO can greatly affect the temperatures across the Upper Mississippi River Valley, its predictability beyond a week to two weeks is quite low. As a result, meteorologists can't base a seasonal forecast such as winter on it. In addition, the phases can oscillate back and forth during the winter which can make temperature predictability very low.
La Niña: While the Oceanic Nino Index (ONI) will not likely meet NOAA's definition of a La Niña (a minimum of 5 consecutive over-lapping seasons where the index equaled or was less than -0.5), both the ocean (since August 2008) and atmosphere (since January 2007) have been behaving La Niña-like. This has been affecting the global circulation, and this is expected to continue during the upcoming winter.  If this becomes the predominant winter pattern, temperatures will likely end up being below normal across the Upper Mississippi River Valley.  In addition, one of the predominant storm tracks would be located from Mid Mississippi and Tennessee River Valleys northeast into the eastern Great Lakes (very typical of a weak La Niña).  If this does indeed occurs, the heaviest precipitation and snow would be south and east of the Upper Mississippi River Valley.
Sea Surface Temperature Anomalies during a Warmer-than-Normal "Neutral" or "La Nada" Winter			Sea Surface Temperature Anomalies during a Colder-than-Normal "Neutral" or "La Nada" Winter
North American Snow Coverage: Through doing composites of the fifteen "La Nada" or "Neutral" winters since 1967, it was found that the North American snow coverage was important on determining the potential of the winter having below normal temperatures in the Upper Mississippi River Valley.  Seven of the nine colder-than-normal winters (77.8 percent) had above normal November snow coverage (11.8 million square kilometers) across North America.  Meanwhile only two out six warmer-than-normal winters (33.3 percent) had above normal snow coverage during this month.  As of November 21st, North America snow coverage was close to normal, so it is still unclear whether this will be a factor or not for this upcoming winter.  The maps below show the snow coverage across the Northern Hemisphere along with their departures from normal on this date.  These images are compliments of Rutgers University's Global Snow Lab.
Areas where snow covered the ground on November 20, 2008			Departure from normal of snow on the ground for November 20, 2008. Red areas denote below normal snow depth.  Blue areas indicate areas of above normal snow depth.
Madden Julian Oscillation (MJO): The Madden-Julian Oscillation (MJO) is a tropical disturbance that propagates eastward around the global tropics.  It typically originates over the Indian Ocean and then propagates around the world anywhere from 30 to 60 days.  As this occurs, it can affect temperatures and precipitation from the tropics into the mid latitudes.  For example when the MJO is over Indonesia, the temperatures in the Upper Mississippi River Valley typically range from near to below normal. Meanwhile when the oscillation is located over the equatorial western Pacific basin, the temperatures in the Upper Mississippi River Valley typically range from near to above normal. The temperature then returns to near to below normal as the oscillation moves into the central equatorial Pacific. With its time scale, it mainly affects the weather on a sub seasonal time scale and it is not useful in determining the average temperature for a 3-month season such as winter.
Unusually Warm Water in the Western Pacific & Indian Ocean:
The surface water temperatures in the northwest Pacific Ocean are currently running 2 standard deviations above normal.  This may be related to the cool phase of the Pacific Decadal Oscillation (PDO).  There is some concern that these warm waters may cause an increase in shower and thunderstorm activity across these areas and
			Sea Surface Temperature Anomalies as of October 22, 2008
this may result in the eventual development of an anomalously deep trough of low pressure.  When this occurs, a trough of low pressure typically develops across central United States.   This would allow polar and arctic air masses to move southward into the Upper Mississippi River Valley. In addition, the waters of the Indian Ocean and western equatorial Pacific Ocean have anomalously warm waters. This makes it favorable for the formation of several Madden Julian Oscillations (MJOs). In addition, this is typical of a La Niña. As stated earlier, this winter is likely not going to be a La Niña, but it may behave like one.
East Asian Jet: A composite study of the twenty-three "La Nada" or "Neutral" Winters since 1950 showed that the warmer-than-normal winters had an unusually strong East Asian jet stream and this jet extended eastward into the west coast of the United States.  When this occurs, Pacific air masses (which are typically warmer-than-normal) cover much of the western United States including the Upper Mississippi River Valley.  This jet shows up as yellows, oranges, and reds across the north Pacific Ocean basin in the left image below (compliments of  NOAA's Earth System Research Laboratory).  This type of jet stream is more common when there is either an El Niño or when you have warmer-than-normal water temperatures across the central equatorial Pacific Ocean.  We will likely not see either of these for this upcoming winter. Meanwhile the colder-than-normal winters showed that this jet stream remained generally west of the International Dateline (right image below).  This makes it less likely that these Pacific air masses will be able to move into the Upper Mississippi River Valley as frequent.  As a result, it is not too surprising why the Upper Mississippi River Valley experiences colder-than-normal temperatures during these winters. With the warmest waters remaining across the western Pacific, it is likely that we will likely see a jet stream more similar to these winters.
200 mb Wind Anomalies during a Warmer-than-Normal "Neutral" or "La Nada" Winters			200 mb Wind Anomalies during a Colder-than-Normal "Neutral" or "La Nada" Winters

Winter Climatology

La Crosse, WI

Temperatures:

La Crosse, WI averages 20.0 degrees during a typical meteorological winter (December 1 through February 28 or February 29).  This is based upon the 1971 through 2000 (30-year) climate normals.  Their coldest winter occurred during the winter of 1872-73 when the average temperature was 8.2 degrees.  Meanwhile their warmest winter occurred during the winter of 1877-78 when the average temperature was 34.2 degrees.  The image below provides average temperatures from the winter of 1872-73 through the winter of 2007-08.

Precipitation:

La Crosse, WI normally receives 3.41 inches of precipitation during a typical meteorological winter (December 1 through February 28 or February 29).  This is based upon the 1971 through 2000 (30-year) climate normals.  Their driest winter occurred during the winter of 1963-64 when just 0.92 inches of precipitation fell.  Meanwhile their wettest winter occurred during the winter of 1875-76 when 7.47 inches of precipitation fell.  The image below provides precipitation totals from the winter of 1872-73 through the winter of 2007-08.

Snowfall:

La Crosse, WI normally receives 44.3 inches of snow during a typical snow season (July 1 through June 30).  This is based upon the 1971 through 2000 (30-year) climate normals.  Their least amount of snow in a season occurred during the 1967-68 snow season when just 7.7inches of snow fell.  Meanwhile their snowiest season occurred during the 1961-62 snow season when 78.7 inches of snow fell.  The image below provides snow totals from the 1884-85 snow season through the 2007-08 snow season.

Rochester MN

Temperatures:

Rochester, MN averages 15.7 degrees during a typical meteorological winter (December 1 through February 28 or February 29).  This is based upon the 1971 through 2000 (30-year) climate normals.  Their coldest winter occurred during the winter of 1978-79 when the average temperature was 5.6 degrees.  Meanwhile their warmest winter occurred during the winter of 1930-31 when the average temperature was 26.1 degrees.  The image below provides average temperatures from the winter of 1929-30 through the winter of 2007-08.

Precipitation:

Rochester, MN normally receives 2.71 inches of precipitation during a typical meteorological winter (December 1 through February 28 or February 29).  This is based upon the 1971 through 2000 (30-year) climate normals.  Their driest winter occurred during the winter of 1957-58 when just 0.71 inches of precipitation fell.  Meanwhile their wettest winter occurred during the winter of 1887-88 when 5.47 inches of precipitation fell.  The image below provides precipitation totals from the winter of 1929-30 through the winter of 2007-08.

Snowfall:

Rochester, MN normally receives 52.7 inches of snow during a typical snow season (July 1 through June 30).  This is based upon the 1971 through 2000 (30-year) climate normals.  Their least amount of snow in a season occurred during the 1967-68 snow season when just 9.1inches of snow fell.  Meanwhile their snowiest season occurred during the 1996-97 snow season when 84.7 inches of snow fell.  The image below provides snow totals from the 1949-50 snow season through the 2007-08 snow season.