Climatology of La Niña Events and California Precipitation
by Jan Null, CCM
Updated April 2016


 Summary:   With the periodic reoccurrence of La Niņa there are efforts to try and assess what the impact will be on California, especially the state's water supply.  This project quantifies California precipitation climatology for cool ENSO events.

Overview:  La Niņa events have are defined from the Oceanic Niņo Index (ONI) into Weak, Moderate Strong events.   Then the seasonal (July 1 through June 30) percent of normal precipitation for each category, plus a collective category of "all" warm events, was collated for a number of cities and geographic areas. These include three major watersheds, the Northern Sierra Nevada Eight Station Index (8SI, map), the Southern Sierra Nevada Five Station Index (5SI, map) and the Tulare Basin Six Station Index (6SI, map). Additionally the seven NCDC climate division (see map) and the entire state of California (CA) averages were compared to the ENSO events.  These comparisons was done in terms of both average seasonal precipitation and also the number of occurrences within percent of normal categories.

Observations:  The best wet "signal" associated with cool ENSO (La Niņa) events is, surprisingly, with the "Moderate" events, which statewide were wetter than those in the "Weak" or "Strong" categories.  Overall, there has been a strong bias toward below normal precipiation in the southern half of the state during past La NIņa events. For example, Climate Divison 6, the South Coast, below normal for 19 of 20 previous La Niņas, with 13 of those showing less than 80% of normal rainfall.

Also:  See El Niņo and La Niņa Winter Historic Precipitation & Temperatures for a graphical display of ENSO events for the entire United States from 1950-2015.

Important Caveat:  The data presented here is a climatology of past events and is made up of a broad range of events from a small sample that are averaged together.  Consequently, like all averages, this type of data should not be used as a forecast


La Niņa Precipiation

Table 1.  All La Niņa Events - Average Percent of Normal Seasonal Precipitation (20 events)
ENSO Type Div. 1 Div. 2 Div. 3 Div. 4 Div. 5 Div. 6 Div. 7 CA 8SI 5SI 6SI SF EKA SAC FAT LAX
All La Niņa 99% 92% 96% 84% 87% 77% 75% 90% 93% 89% 88% 85% 99% 85% 84% 83%
Weak La Niņa 92% 87% 90% 79% 84% 74% 76% 86% 86% 85% 84% 80% 95% 78% 77% 82%
Moderate La Niņa 109% 104% 110% 98% 99% 88% 76% 101% 107% 102% 99% 99% 108% 104% 98% 92%
Strong La Niņa 101% 88% 86% 71% 76% 68% 72% 86% 91% 77% 77% 75% 100% 75% 79% 67%

Table 2.  All La Niņa - Years by Percent of Normal Categories (20 events)
% of Normal Div. 1 Div. 2 Div. 3 Div. 4 Div. 5 Div. 6 Div. 7 CA 8SI 5SI 6SI SF EKA SAC FAT LAX
<80% 5 8 7 9 9 13 14 9 8 10 9 9 2 9 11 9
80-100% 5 4 4 7 5 6 4 6 2 2 7 5 8 6 6 7
100-120% 8 5 5 3 4 0 1 2 7 5 2 5 7 3 2 2
120-140% 1 3 3 1 2 1 1 3 2 2 1 1 3 2 0 2
>140% 1 0 1 0 0 0 0 0 1 1 1 0 0 0 1 0

Table 3.  Weak La Niņa - Years by Percent of Normal Categories (11 events)
% of Normal Div. 1 Div. 2 Div. 3 Div. 4 Div. 5 Div. 6 Div. 7 CA 8SI 5SI 6SI SF EKA SAC FAT LAX
<80% 4 6 5 6 6 8 7 6 6 6 5 5 2 5 6 5
80-100% 2 1 1 4 2 3 3 3 1 0 4 4 4 5 5 4
100-120% 5 4 4 1 3 0 0 2 4 4 2 2 4 1 0 1
120-140% 0 0 1 0 0 0 1 0 0 1 0 0 1 0 0 1
>140% 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Table 4.  Moderate La Niņa - Years by Percent of Normal Categories (6 events)
% of Normal Div. 1 Div. 2 Div. 3 Div. 4 Div. 5 Div. 6 Div. 7 CA 8SI 5SI 6SI SF EKA SAC FAT LAX
<80% 0 1 1 1 1 3 4 1 1 2 2 2 0 2 3 2
80-100% 2 2 2 3 3 2 1 3 0 2 2 1 2 1 0 2
100-120% 3 1 0 1 0 0 1 0 3 0 0 2 3 1 2 1
120-140% 1 2 2 1 2 1 0 2 2 1 1 1 1 2 0 1
>140% 0 0 1 0 0 0 0 0 0 1 1 0 0 0 1 0

Table 5.  Strong La Niņa - Years by Percent of Normal Categories (3 events)
% of Normal Div. 1 Div. 2 Div. 3 Div. 4 Div. 5 Div. 6 Div. 7 CA 8SI 5SI 6SI SF EKA SAC FAT LAX
<80% 1 1 1 2 2 2 3 2 1 2 2 2 0 2 2 2
80-100% 1 1 1 0 0 1 0 0 1 0 1 0 2 0 1 1
100-120% 0 0 1 1 1 0 0 0 0 1 0 1 0 1 0 0
120-140% 0 1 0 0 0 0 0 1 0 0 0 0 1 0 0 0
>140% 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0

Table 6.  Percent of Normal (1981-2010) Rainfall for All Seasons

Normal (in.) 49.96" 36.98" 20.75" 22.21" 20.99" 18.03" 6.37" 23.18" 54.52" 42.57" 30.50" 23.65" 40.33" 18.52" 11.50" 14.93"
1 2 3 4 5 6 7 CAL 8SI 5SI 6SI SF EKA SAC FAT LAX
Weak La Niņa 1950 - 1951 111% 108% 116% 86% 105% 56% 62% 100% 117% 116% 117% 101% 115% 95% 90% 55%
Weak El Niņo 1951 - 1952 122% 128% 132% 134% 133% 160% 147% 132% 130% 121% 145% 138% 118% 129% 121% 176%
Weak El Niņo 1952 - 1953 118% 101% 97% 80% 81% 74% 74% 97% 99% 73% 87% 89% 118% 88% 84% 63%
Weak El Niņo 1953 - 1954 106% 88% 77% 77% 81% 90% 77% 90% 91% 79% 85% 60% 105% 73% 77% 80%
Weak La Niņa 1954 - 1955 68% 68% 61% 79% 76% 78% 71% 71% 67% 66% 76% 67% 83% 81% 89% 80%
Moderate La Niņa 1955 - 1956 138% 133% 140% 119% 123% 83% 76% 124% 135% 133% 123% 115% 115% 138% 117% 107%
  1956 - 1957 89% 81% 91% 74% 78% 76% 65% 81% 82% 76% 74% 64% 91% 74% 71% 64%
Strong El Niņo 1957 - 1958 153% 141% 126% 160% 141% 158% 126% 145% 133% 122% 135% 154% 121% 155% 165% 142%
Weak El Niņo 1958 - 1959 77% 67% 72% 61% 58% 52% 59% 66% 71% 60% 47% 44% 81% 59% 60% 37%
  1959 - 1960 86% 78% 69% 65% 67% 68% 82% 77% 80% 69% 69% 65% 86% 71% 70% 55%
  1960 - 1961 97% 78% 72% 59% 60% 41% 52% 74% 71% 55% 50% 59% 110% 68% 60% 32%
  1961 - 1962 81% 85% 98% 96% 100% 119% 89% 91% 83% 95% 95% 75% 72% 94% 99% 126%
  1962 - 1963 116% 115% 129% 109% 103% 61% 58% 105% 117% 103% 97% 94% 109% 136% 101% 56%
Moderate El Niņo 1963 - 1964 78% 68% 84% 62% 70% 70% 79% 72% 66% 70% 69% 52% 93% 67% 59% 53%
Weak La Niņa 1964 - 1965 116% 112% 118% 96% 107% 81% 69% 106% 116% 121% 102% 94% 101% 99% 97% 92%
Strong El Niņo 1965 - 1966 88% 71% 78% 74% 72% 96% 109% 81% 71% 74% 62% 69% 80% 57% 53% 137%
  1966 - 1967 109% 122% 138% 134% 136% 128% 89% 120% 115% 132% 161% 124% 110% 142% 130% 147%
Weak La Niņa 1967 - 1968 79% 76% 77% 62% 66% 76% 95% 76% 70% 57% 59% 61% 70% 64% 63% 111%
Weak El Niņo 1968 - 1969 120% 127% 145% 160% 167% 172% 141% 140% 125% 160% 183% 106% 118% 130% 200% 184%
Weak El Niņo 1969 - 1970 110% 113% 113% 79% 85% 62% 69% 98% 110% 95% 78% 88% 95% 93% 79% 52%
Moderate La Niņa 1970 - 1971 119% 105% 123% 85% 84% 79% 63% 99% 103% 75% 75% 79% 119% 88% 74% 83%
Weak La Niņa 1971 - 1972 92% 67% 81% 48% 56% 50% 49% 69% 65% 66% 53% 47% 98% 50% 46% 48%
Strong El Niņo 1972 - 1973 94% 109% 103% 143% 120% 127% 113% 110% 95% 94% 126% 145% 86% 136% 121% 142%
Strong La Niņa 1973 - 1974 149% 131% 106% 115% 103% 86% 74% 121% 141% 108% 99% 117% 132% 112% 91% 100%
Weak La Niņa 1974 - 1975 103% 92% 100% 91% 93% 92% 74% 94% 92% 103% 94% 77% 99% 86% 67% 96%
Strong La Niņa 1975 - 1976 66% 48% 56% 39% 53% 62% 78% 57% 48% 54% 53% 34% 83% 36% 71% 48%
Weak El Niņo 1976 - 1977 41% 41% 67% 50% 49% 65% 83% 49% 37% 44% 53% 47% 44% 38% 66% 82%
Weak El Niņo 1977 - 1978 126% 130% 123% 156% 155% 204% 199% 146% 131% 145% 153% 114% 90% 142% 158% 224%
  1978 - 1979 73% 80% 79% 90% 98% 129% 128% 89% 76% 99% 88% 79% 62% 97% 93% 132%
Weak El Niņo 1979 - 1980 110% 117% 131% 120% 127% 163% 179% 126% 110% 132% 134% 104% 94% 128% 104% 181%
  1980 - 1981 73% 73% 78% 70% 72% 68% 70% 72% 68% 62% 66% 65% 73% 68% 72% 60%
  1981 - 1982 142% 144% 146% 131% 138% 99% 102% 135% 151% 149% 124% 157% 120% 164% 97% 72%
Very Strong El Niņo 1982 - 1983 161% 165% 162% 191% 183% 197% 190% 173% 164% 185% 191% 161% 147% 192% 205% 209%
Weak La Niņa 1983 - 1984 111% 107% 118% 77% 93% 63% 88% 99% 109% 107% 94% 95% 120% 78% 66% 70%
Weak La Niņa 1984 - 1985 78% 70% 77% 75% 76% 77% 124% 79% 65% 71% 85% 85% 87% 58% 69% 86%
  1985 - 1986 114% 125% 137% 121% 131% 115% 110% 121% 130% 136% 140% 121% 97% 128% 129% 120%
Moderate El Niņo 1986 - 1987 72% 62% 66% 60% 62% 60% 82% 66% 61% 55% 60% 59% 69% 56% 81% 51%
Moderate El Niņo 1987 - 1988 77% 72% 64% 72% 72% 98% 114% 78% 64% 62% 72% 75% 80% 75% 70% 84%
Strong La Niņa 1988 - 1989 88% 86% 96% 60% 70% 56% 63% 78% 85% 70% 78% 74% 86% 77% 76% 54%
  1989 - 1990 74% 74% 76% 57% 67% 52% 43% 67% 72% 71% 65% 61% 67% 96% 82% 49%
  1990 - 1991 63% 68% 79% 79% 78% 98% 106% 75% 60% 74% 77% 60% 62% 69% 85% 77%
Moderate El Niņo 1991 - 1992 68% 70% 62% 91% 77% 123% 155% 82% 66% 63% 63% 81% 54% 71% 96% 141%
  1992 - 1993 119% 127% 125% 138% 133% 185% 185% 135% 120% 131% 130% 113% 108% 138% 144% 183%
  1993 - 1994 62% 63% 66% 69% 66% 77% 57% 65% 58% 54% 67% 64% 73% 65% 74% 54%
Weak El Niņo 1994 - 1995 143% 162% 163% 160% 162% 179% 149% 157% 157% 167% 150% 144% 128% 127% 165% 163%
Weak La Niņa 1995 - 1996 118% 114% 127% 104% 104% 75% 51% 106% 111% 102% 100% 105% 111% 102% 95% 83%
  1996 - 1997 118% 115% 133% 111% 118% 86% 66% 111% 125% 127% 112% 96% 125% 107% 104% 83%
Very Strong El Niņo 1997 - 1998 153% 159% 130% 190% 166% 208% 176% 164% 152% 151% 176% 200% 145% 174% 175% 208%
Moderate La Niņa 1998 - 1999 109% 95% 100% 81% 84% 64% 64% 91% 102% 90% 78% 99% 124% 75% 61% 61%
Moderate La Niņa 1999 - 2000 94% 97% 84% 100% 95% 77% 64% 92% 102% 97% 90% 105% 90% 116% 112% 77%
Weak La Niņa 2000 - 2001 59% 66% 58% 89% 80% 99% 93% 72% 62% 69% 74% 82% 57% 81% 92% 120%
  2001 - 2002 93% 86% 75% 72% 76% 35% 32% 77% 86% 79% 82% 106% 101% 97% 61% 30%
Moderate El Niņo 2002 - 2003 117% 105% 90% 98% 92% 103% 90% 104% 107% 89% 102% 101% 132% 90% 85% 110%
  2003 - 2004 94% 90% 82% 75% 73% 59% 93% 85% 89% 69% 68% 87% 95% 71% 66% 62%
Weak El Niņo 2004 - 2005 100% 109% 113% 143% 138% 189% 205% 128% 105% 126% 125% 135% 110% 118% 138% 249%
  2005 - 2006 138% 140% 133% 120% 125% 92% 83% 127% 148% 132% 117% 146% 146% 127% 127% 88%
Weak El Niņo 2006 - 2007 75% 61% 55% 50% 53% 30% 32% 58% 66% 58% 55% 71% 88% 59% 52% 22%
Moderate La Niņa 2007 - 2008 81% 71% 74% 78% 71% 87% 82% 76% 66% 67% 83% 73% 85% 74% 73% 91%
  2008 - 2009 69% 77% 75% 70% 75% 67% 78% 74% 86% 92% 84% 77% 74% 88% 68% 61%
Moderate El Niņo 2009 - 2010 99% 96% 91% 115% 103% 112% 113% 102% 98% 105% 111% 102% 110% 112% 107% 110%
Moderate La Niņa 2010 - 2011 111% 122% 141% 124% 139% 138% 109% 123% 133% 151% 147% 122% 112% 129% 152% 135%
Weak La Niņa 2011 - 2012 82% 73% 59% 67% 63% 63% 59% 71% 77% 60% 72% 66% 101% 66% 71% 58%
  2012 - 2013 77% 77% 78% 59% 60% 46% 65% 70% 79% 62% 51% 70% 80% 82% 49% 39%
  2013 - 2014 55% 57% 65% 44% 47% 42% 63% 54% 56% 46% 48% 53% 52% 53% 42% 41%
  2014 - 2015 81% 77% 80% 72% 58% 60% 83% 74% 71% 44% 43% 77% 84% 86% 57% 57%
Very Strong El Niņo 2015 - 2016* 101% 92% 94% 90% 88% 60% 72% 90% 99% 91% 85% 96% 111% 82% 125% 64%
* 2015-2016 data is through April 13.

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