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It's interesting that prior to 2002, there was actually a fairly strong inverse correlation between the October NAO modality and the ensuing winter DJF NAO modality. However, since 2002, that correlation has certainly weakened somewhat. Personally, I believe the decreased solar constant has had significant influence in dampening the inverse correlation such that negative NAO episodes have become more persistent / longer duration. Over recent years, the prevalence of October blocking has foretold a tendency for blocky winters, while on the other hand, examining the longer term data reveals an inverse pattern. 

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winter months with the lowest AO average...

Feb...1956...Big snows in March 56...

Mar...1957...snow March 1st...

Feb...1958...big snow mid month...

Mar...1958...big snow 21st.

Feb...1960...big snow March 3rd..

Mar...1962...Ash Wednesday storm on the 5th...

Feb...1965...late March snows...

Jan...1966...Snowstorm on the 30th...

Feb...1968...Snowstorm March 1st...

Jan...1969...benign...

Feb...1969...Big snow 9th...

Feb...1970...average...

Mar...1970...late snowstorm...

Dec...1976...very cold...

Jan...1977...very cold...

Feb...1977...cold start...

Feb...1978...Big snow 6th...

Jan...1979...Big snow February...

Jan...1980...benign...

Mar...1984...cold/snowy...

Jan...1985...very cold...

Feb...1986...normal...

Dec...1995...cold/snowy...

Jan...1998...warm wet...

Dec...2000...big snow 30th...

Dec...2005...cold snowy start...

Dec...2009...big snow 19th...

Jan...2010...benign...

Feb...2010...big snows...

Dec...2010...big snow 26th...

Mar...2013...cold/snowy...

Not every month was very cold and snowy...January 1998 was very mild with hardly any snow...in recent years December had the most years -2.000 for the AO index...This is one reason December has seen so many major snowstorms since 1995...

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The current -AO has to be record breaking I imagine. Wasn't 2002 the last time it hit -3.5 and we are currently below that and may hit -4 or slightly lower.

From Don S. in another thread...

10 Lowest AO readings for October:

 

1. -5.098, 10/18/2002

2. -4.911, 10/17/2002

3. -4.850, 10/19/2002

4. -4.434, 10/16/2002

5. -4.350, 10/20/2002

6. -3.718, 10/15/2002

7. -3.516, 10/21/2002

8. -3.471, 10/8/1979

9. -3.415, 10/22/2009

10. -3.297, 10/15/2003

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winter months with the lowest AO average...

Feb...1956...Big snows in March 56...

Mar...1957...snow March 1st...

Feb...1958...big snow mid month...

Mar...1958...big snow 21st.

Feb...1960...big snow March 3rd..

Mar...1962...Ash Wednesday storm on the 5th...

Feb...1965...late March snows...

Jan...1966...Snowstorm on the 30th...

Feb...1968...Snowstorm March 1st...

Jan...1969...benign...

Feb...1969...Big snow 9th...

Feb...1970...average...

Mar...1970...late snowstorm...

Dec...1976...very cold...

Jan...1977...very cold...

Feb...1977...cold start...

Feb...1978...Big snow 6th...

Jan...1979...Big snow February...

Jan...1980...benign...

Mar...1984...cold/snowy...

Jan...1985...very cold...

Feb...1986...normal...

Dec...1995...cold/snowy...

Jan...1998...warm wet...

Dec...2000...big snow 30th...

Dec...2005...cold snowy start...

Dec...2009...big snow 19th...

Jan...2010...benign...

Feb...2010...big snows...

Dec...2010...big snow 26th...

Mar...2013...cold/snowy...

Not every month was very cold and snowy...January 1998 was very mild with hardly any snow...in recent years December had the most years -2.000 for the AO index...This is one reason December has seen so many major snowstorms since 1995...

 

Which of these years were weak El Nino years?

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Below is a 500mb composite of the 11 cases in which a < -0.75 October AO occurred, and their ensuing winters. 9/11 or 82% of those cases featured a -AO average for DJF. The glaring failures were 74-75 and 06-07 here. What's interesting is that this correlation does not really exist for > +0.75 AO Octobers as their ensuing winters featured mixed results. At this point in time, it's still early in the season, and generally when we examine -AO or +AO Octobers, there isn't much of a correlation when including the weakly positive or negative cases.

 

16c76rp.png

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winter months with the lowest AO average...

Feb...1956...Big snows in March 56...

Mar...1957...snow March 1st...

Feb...1958...big snow mid month...

Mar...1958...big snow 21st.

Feb...1960...big snow March 3rd..

Mar...1962...Ash Wednesday storm on the 5th...

Jan...1963...very cold...

Feb...1965...late March snows...

Jan...1966...Snowstorm on the 30th...

Feb...1968...Snowstorm March 1st...

Jan...1969...benign...

Feb...1969...Big snow 9th...

Feb...1970...average...

Mar...1970...late snowstorm...

Dec...1976...very cold...

Jan...1977...very cold...

Feb...1977...cold start...

Feb...1978...Big snow 6th...

Jan...1979...Big snow February...

Jan...1980...benign...

Mar...1984...cold/snowy...

Jan...1985...very cold...

Feb...1986...normal...

Dec...1995...cold/snowy...

Jan...1998...warm wet...

Dec...2000...big snow 30th...

Dec...2005...cold snowy start...

Dec...2009...big snow 19th...

Jan...2010...benign...

Feb...2010...big snows...

Dec...2010...big snow 26th...

Mar...2013...cold/snowy...

Not every month was very cold and snowy...January 1998 was very mild with hardly any snow...in recent years December had the most years -2.000 for the AO index...This is one reason December has seen so many major snowstorms since 1995...

 

Which of these years were weak El Nino years?

1955-56...La Nina...

1956-57...weak la nina...

1957-58...El Nino...

1959-60...neutral...

1961-62...weak la nina...

1962-63...weak la nina...

1963-64...El Nino...

1965-66...El Nino...

1967-68...weak la nina...

1968-69...El Nino...

1969-70...weak el nino...

1976-77...weak el nino...

1977-78...weak el nino...

1978-79...neutral...

1979-80...weak positive/neutral...

1983-84...neutral...

1984-85...weak la nina...

1985-86...weak negative/neutral...

1995-96...weak la nina...

1997-98...strong el nino...

2000-01...weal la nina...

2005-06...weak negative/neutral...

2009-10...El Nino...

2010-11...La Nina...

2012-13...neutral...

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lowest October daily AO reading for each year...the frequency of an October daily AO reading below -3 has gone up since 2002...winter low...

1950.....-1.698.....10/31.....-4.353.....12/27/50

1951.....-1.815.....10/01.....-3.805.....3/4/1952

1952.....-2.064.....10/05.....-3.766.....12/27/52

1953.....-1.522.....10/03.....-3.495.....1/30/54

1954.....-2.027.....10/06.....-3.064.....1/4/55

1955.....-2.188.....10/31.....-4.564.....2/15/56

1956.....-0.514.....10/31.....-4.473.....2/21/57

1957.....-0.551.....10/04.....-4.030.....3/11/58.

1958.....-0.466.....10/25.....-4.026.....1/7/59.

1959.....-2.021.....10/10.....-4.108.....1/28/60

1960.....-2.499.....10/23.....-2.719.....1/10/61

1961.....-1.176.....10/01.....-4.417.....3/4/62

1962.....-1.895.....10/12.....-5.010.....1/21/63

1963.....-1.880.....10/31.....-4.470.....12/20/63

1964.....-1.401.....10/11.....-3.973.....1/26/65

1965.....-1.915.....10/10.....-5.130.....1/28/66

1966.....-2.989.....10/22.....-4.147.....12/13/66

1967.....-1.039.....10/31.....-3.490.....2/7/68

1968.....-2.313.....10/08.....-5.282.....2/13/69

1969.....-1.549.....10/05.....-6.365.....3/5/70.

1970.....-1.746.....10/06.....-2.821.....2/6/71.

1971.....-0.262.....10/03.....-3.100.....2/5/72

1972.....-0.917.....10/16.....-2.044.....12/17/72

1973.....-1.845.....10/09.....-2.792.....12/19/73

1974.....-2.270.....10/22.....-1.695.....12/18/74

1975.....-1.375.....10/22.....-3.262.....1/24/76

1976.....-2.497.....10/23.....-7.433.....1/15/77

1977.....-2.318.....10/15.....-5.291.....2/5/78

1978.....-1.835.....10/07.....-4.387.....1/25/79

1979.....-3.471.....10/08.....-3.705.....1/24/80

1980.....-2.862.....10/14.....-4.318.....3/4/81

1981.....-3.076.....10/13.....-3.804.....12/30/81

1982.....-1.838.....10/10.....-3.410.....2/6/83.

1983.....-0.304.....10/16.....-3.706.....3/13/84

1984.....-3.087.....10/05.....-6.226.....1/19/85

1985.....-1.081.....10/31.....-3.894......2/6/86

1986.....-0.055.....10/31.....-3.507.....3/9/87

1987.....-2.689.....10/22.....-2.314.....2/28/88

1988.....-2.010.....10/24.....-0.318.....3/4/89

1989.....-0.661.....10/08.....-3.482.....12/10/89.

1990.....-0.690.....10/20.....-3.381.....3/9/91

1991.....-3.044.....10/29.....-2.597.....12/4/91

1992.....-2.362.....10/17.....-2.228.....3/2/93

1993.....-1.872.....10/08.....-3.503.....2/24/94

1994.....-2.055.....10/02.....-3.116.....3/9/95

1995.....-1.344.....10/15.....-4.353.....12/19/95

1996.....-1.710.....10/21.....-3.377.....12/30/96.

1997.....-2.109.....10/26.....-4.269.....1/10/98

1998.....-1.540.....10/01.....-3.856.....3/10/99

1999.....-1.731.....10/15.....-2.118.....2/18/00

2000.....-1.586.....10/04.....-4.854.....2/25/01

2001.....-1.234.....10/15.....-3.293.....12/28/01

2002.....-5.098.....10/18.....-3.575.....1/22/03

2003.....-3.297.....10/15.....-4.387.....1/17/04

2004.....-2.377.....10/18.....-4.337.....2/26/05.

2005.....-1.918.....10/08.....-3.569.....12/5/05

2006.....-3.192.....10/17.....-2.184.....2/4/07

2007.....-1.925.....10/09.....-2.468.....1/2/08

2008.....-1.856.....10/02.....-3.178.....2/3/09

2009.....-3.415.....10/22.....-5.821.....12/21/09

2010.....-2.555.....10/23.....-5.172.....12/18/10.

2011.....-1.203.....10/26.....-3.451.....1/28/12

2012.....-3.195.....10/24.....-5.688.....3/20/13.

2013.....-1.570.....10/13.....-2.605.....1/27/14

2014.....-4.057.....10/08.....???

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  • 2 weeks later...
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what happens when the AO reaches its winter low...some years the coldest temperature of the winter or the month came during the AO's lowest point of the season...some years had a snowstorm around the date...a few years didn't have either and are the exceptions...some years with a very low AO number -4 or lower had a big snow sometime during the winter...

lowest daily winter ao value since 1950.....Weather around the time in NYC...last year the lowest ao reading was a modest -2.605 on 1/27/14...there was a snowstorm on the 21st and a cold spell thru the 28th...
season.......value.....date.....
1949-50......-2.854.....3/15/50......1.4" 3/14...record cold the beginning of the month...
1950-51......-4.353.....12/27/50....3" snow 12/27 and 9 degrees...the biggest snow and coldest temperature of the winter...
1951-52......-3.805.....3/4/1952....4" snow 3/2...
1952-53......-3.766.....12/27/52....12 degrees is the coldest temp. of the season...4" snow 12/31...
1953-54......-3.495.....1/30/54......cold continues...Cold snowy January...
1954-55......-3.064.....1/4/55........cold continues...
1955-56......-4.564.....2/15/56......1.4" 2/17 and 2/22...Big March snows.....
1956-57......-4.473.....2/21/57......2.6" snow 3/1...
1957-58......-4.030.....3/11/58......snow storms 3/14 and 3/21...
1958-59......-4.026.....1/7/59........cold continues...

1959-60......-4.108.....1/28/60......18 degrees 2/3 is the coldest temp for Feb...Big March cold and snow...
1960-61......-2.719.....1/10/61......greatest snowy and cold period followed 1/15-2/12...
1961-62......-4.417.....3/4/62........record cold 3/2 and the Ash Wednesday storm 3/6...
1962-63......-5.010.....1/21/63......Near record cold 1/23 and 4" snow 1/26...Biggest snow of the season...
1963-64......-4.470.....12/20/63....1.4" 12/18...6.6" 12/23-24...11 degrees 12/20 coldest for that month...January Blizzard...
1964-65......-3.973.....1/26/65......ice storm 1/24 and continued cold...
1965-66......-5.130.....1/28/66......8 degrees is the coldest temp. of the season 1/28...storm 7" on 1/30...
1966-67......-4.147.....12/13/66....wet snow and rain 12/13-14 is the start of two weeks of snow and cold...7" snow 12/24-25...
1967-68......-3.490.....2/7/68........8 degrees 2/11...Cold and dry continues...
1968-69......-5.282.....2/13/69......17 degrees 2/17 is the coldest temp for the month...15" of snow 2/9-10....

1969-70......-6.365.....3/5/70........20 degrees 3/10 coldest temp for the month...4" of snow 3/29...
1970-71......-2.821.....2/6/71........12 degrees max 2/2...
1972-73......-2.044.....12/17/72...24 degrees max 12/17...
1973-74......-2.792.....12/19/73...big ice storm 12/16-17...17 degrees 12/19 is the coldest temp of the month...
1974-75......-1.695.....12/18/74...some minor cold in a mild month...one of the few times the weather was benign at the ao minimum...
1975-76......-3.262.....1/24/76......-1 degrees 1/23 is the coldest temp of the winter...1" of snow 1/23...
1976-77......-7.433.....1/15/77......-2 degrees on the 17th is the coldest temp of the winter...5" snow 1/14-15...
1977-78......-5.291.....2/5/78........10 degrees 2/5 is the coldest temperature of the season...18" snow 2/6-7...

1978-79......-4.387.....1/25/79......Very cold and snowy February....

1979-80......-3.705.....1/24/80......continued cold and dry...longest stretch of cold that winter...
1980-81......-4.318.....3/4/81........largest snowfall for the winter...8.6" 3/5...
1981-82......-3.804.....12/30/81...January 1982 was very cold and snowy...
1982-83......-3.410.....2/6/83........4" of snow 2/6 and 18" 2/11-12...
1983-84......-3.706.....3/13/84......record cold 3/10...7" snow 3/8-9...
1984-85......-6.226.....1/19/85.....-2 degrees 1/21 is the coldest temperature that winter...
1985-86......-3.894......2/6/86.......4.5" of snow 2/7 and 2/11...Snowiest period of the winter...
1986-87......-3.507.....3/9/87........2" snow 3/12...Near record cold 3/10...
1987-88......-2.314.....2/28/88......0.6" 2/27 is the last measurable snow...Thawing after...
1988-89......-0.318.....3/4/89........2.5" 3/6 and near record cold 3/7...

1989-90......-3.482.....12/10/89...One of the coldest Decembers on record...
1990-91......-3.381.....3/9/91.......24 degrees 3/12...benign after that...
1991-92......-2.597.....12/4/91.....0.7" 12/5...benign after that...
1992-93......-2.228.....3/2/93.......Super storm 3/13...Near record cold followed...
1993-94......-3.503.....2/24/94.....2.6" 2/23...12 degrees 2/27....
1994-95......-3.116.....3/9/95.......20 degrees 3/10 is the coldest temp for the month....
1995-96......-4.353.....12/19/95...8" of snow during a very cold period...January blizzard.
1996-97......-3.377.....12/30/96...11 degrees New Years Day....
1997-98......-4.269.....1/10/98.....14 degrees New Years day...Coldest of the winter...
1998-99......-3.856.....3/10/99......5" snow 3/14-15...17 degrees 3/8 is the coldest temp for the month...

1999-00......-2.118.....2/18/00......3" snow and ice 2/22..
2000-01......-4.854.....2/25/01......6" snow 2/22 and 17 degrees...coldest for the month...
2001-02......-3.293.....12/28/01...Coldest period of the winter followed but benign...
2002-03......-3.575.....1/22/03......7 degrees 1/24 is the coldest for the winter...
2003-04......-4.387.....1/17/04......1 degree 1/16 is the coldest temp of the season...6" of snow 1/15...Dec.
2004-05......-4.337.....2/26/05......6" of snow 2/25 and 8" 2/29...
2005-06......-3.569.....12/5/05......2" snow 12/4...1" 2/6 and 6" 12/9...14 degrees 12/14 is the coldest temp of the season...
2006-07......-2.184.....2/4/07........8 degrees 2/5 is the coldest for the winter...
2007-08......-2.468.....1/2/08........12 degrees 1/3 second coldest of the winter...
2008-09......-3.178.....2/3/09........4.3" 2/5 12 degrees...

2009-10......-5.821.....12/21/09...11" snow 12/19-20....16 degrees 12/18 is the coldest for the month...
2010-11......-5.172.....12/18/10...20" of snow 12/26-27...23 max on 12/14..

2011-12......-3.451.....01/28/12...4.3" of snow 1/21...Biggest of the season...

2012-13......-5.688.....03/20/13...3.0" of snow 3/18 and continued cold...

2013-14......-2.605.....01/27/14...5 degrees 1/22...11" of snow 1/21...21 max 1/28...

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