Climatology of La Niña Events
and California Precipitation

by Jan Null, CCM
Updated October 2017


 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 18 of 21 previous La Niņas, with 12 of those showing less than 80% of normal rainfall. However, two year were between 120% and 140% of normal; one of those being 2016-17.

Also:  United States La Niņa Winter Precipitation & Temperature Climatology or a graphical display of ENSO events for the entire United States from 1950-51 through 2016-17.

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


California La Niņa Precipiation Climatology
Table 1.  All La Niņa Events - Average Percent of Normal Seasonal Precipitation (21 events)
ENSO Type Div. 1 Div. 2 Div. 3 Div. 4 Div. 5 Div. 6 Div. 7 CA 8SI 5SI 6SI SF SJC EKA RDD SAC FAT LAX SAN
All La NIņa 102% 97% 102% 89% 93% 82% 78% 94% 100% 97% 93% 90% 86% 104% 100% 92% 89% 84% 81%
Weak La NIņa 98% 96% 101% 90% 95% 84% 85% 93% 99% 101% 95% 91% 90% 102% 98% 93% 87% 87% 87%
Moderate La NIņa 115% 107% 114% 95% 95% 76% 62% 101% 108% 94% 94% 91% 92% 112% 112% 99% 89% 83% 67%
Strong La NIņa 100% 94% 95% 86% 89% 82% 76% 92% 98% 93% 91% 89% 76% 102% 95% 89% 91% 81% 80%
All La NIņa Table 2.  All La Niņa - Years by Percent of Normal Categories (21 events)
% of Normal Div. 1 Div. 2 Div. 3 Div. 4 Div. 5 Div. 6 Div. 7 CA 8SI 5SI 6SI SF SJC EKA RDD SAC FAT LAX SAN
<80% 5 8 7 9 8 11 14 9 7 9 8 9 7 2 7 8 11 9 11
80-100% 5 4 3 5 6 7 4 4 3 3 6 5 8 8 4 6 5 8 6
100-120% 7 4 4 4 3 1 1 4 6 4 4 4 5 6 4 3 2 1 2
120-140% 2 3 4 2 2 2 2 3 2 3 1 2 0 3 4 3 1 3 2
>140% 2 2 3 1 2 0 0 1 3 2 2 1 1 2 2 1 2 0 0
Weak La NIņa Table 3.  Weak La Niņa - Years by Percent of Normal Categories (10 events)
% of Normal Div. 1 Div. 2 Div. 3 Div. 4 Div. 5 Div. 6 Div. 7 CA 8SI 5SI 6SI SF SJC EKA RDD SAC FAT LAX SAN
<80% 4 5 4 5 4 5 5 5 4 4 3 4 3 2 4 3 5 4 4
80-100% 1 1 1 3 3 3 3 2 2 1 4 4 5 4 1 5 3 4 3
100-120% 3 2 2 0 1 1 0 1 2 2 2 0 1 1 2 0 0 0 2
120-140% 1 0 2 1 1 1 2 1 0 2 0 1 0 1 3 1 1 2 1
>140% 1 2 1 1 1 0 0 1 2 1 1 1 1 2 0 1 1 0 0
Moderate La NIņa Table 4.  Moderate La Niņa - Years by Percent of Normal Categories (4 events)
% of Normal Div. 1 Div. 2 Div. 3 Div. 4 Div. 5 Div. 6 Div. 7 CA 8SI 5SI 6SI SF SJC EKA RDD SAC FAT LAX SAN
<80% 0 1 1 1 1 2 4 1 1 2 2 2 1 0 1 1 2 1 2
80-100% 1 0 0 1 1 2 0 0 0 0 0 0 1 0 0 1 1 2 2
100-120% 2 2 0 2 1 0 0 2 2 1 1 2 2 4 1 1 1 1 0
120-140% 1 1 2 0 1 0 0 1 1 1 1 0 0 0 1 1 0 0 0
>140% 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0
Strong La NIņa Table 5.  Strong La Niņa - Years by Percent of Normal Categories (7 events)
% of Normal Div. 1 Div. 2 Div. 3 Div. 4 Div. 5 Div. 6 Div. 7 CA 8SI 5SI 6SI SF SJC EKA RDD SAC FAT LAX SAN
<80% 1 2 2 3 3 4 5 3 2 3 3 3 3 0 2 4 4 4 5
80-100% 3 3 2 1 2 2 1 2 1 2 2 1 2 4 3 0 1 2 1
100-120% 2 0 2 2 1 0 1 1 2 1 1 2 2 1 1 2 1 0 0
120-140% 0 2 0 1 0 1 0 1 1 0 0 1 0 2 0 1 0 1 1
>140% 1 0 1 0 1 0 0 0 1 1 1 0 0 0 1 0 1 0 0
Table 6. Percent of Normal (1981-2010) Rainfall for All Years
  Normal 49.77" 36.69" 20.46" 22.03" 20.70" 17.80" 6.35" 24.10" 54.52 42.57 30.50 23.65" 18.42 40.33" 34.62 18.52" 11.50" 14.93" 10.34
ENSO Type Rainfall Season Div. 1 Div. 2 Div. 3 Div. 4 Div. 5 Div. 6 Div. 7 Calif 8SI 5SI 6SI SF SJC EKA RDD SAC FAT LAX SAN
* 1950-1951 111% 109% 117% 86% 106% 57% 62% 99% 119% 119% 118% 101% 88% 115% 116% 95% 90% 55% 62%
Mod. El Niņo* 1951-1952 123% 129% 133% 135% 135% 162% 147% 134% 132% 123% 148% 138% 127% 118% 140% 129% 121% 176% 189%
Weak El Niņo 1952-1953 118% 102% 98% 80% 82% 75% 75% 96% 100% 75% 88% 89% 62% 118% 127% 88% 84% 63% 68%
Weak El Niņo 1953-1954 107% 89% 78% 78% 82% 91% 77% 89% 92% 81% 86% 60% 65% 105% 106% 73% 77% 80% 95%
Weak La Niņa 1954-1955 68% 69% 62% 80% 77% 79% 71% 71% 68% 67% 77% 67% 76% 83% 75% 81% 89% 80% 75%
Mod. La Niņa 1955-1956 139% 134% 142% 120% 125% 84% 76% 125% 136% 136% 125% 115% 116% 115% 143% 138% 117% 107% 47%
  1956-1957 90% 81% 93% 74% 79% 77% 65% 83% 83% 78% 75% 64% 65% 91% 81% 74% 71% 64% 93%
Stg. El Niņo 1957-1958 153% 142% 128% 161% 143% 160% 126% 147% 134% 124% 137% 154% 141% 121% 179% 155% 165% 142% 145%
Weak El Niņo 1958-1959 77% 68% 73% 61% 59% 53% 59% 67% 71% 61% 48% 44% 63% 81% 66% 59% 60% 37% 55%
  1959-1960 86% 78% 70% 66% 68% 69% 82% 75% 81% 70% 70% 65% 67% 86% 104% 71% 70% 55% 78%
  1960-1961 97% 78% 73% 59% 61% 42% 52% 72% 72% 56% 50% 59% 64% 110% 93% 68% 60% 32% 36%
  1961-1962 82% 86% 100% 97% 101% 121% 89% 95% 84% 97% 97% 75% 80% 72% 99% 94% 99% 126% 100%
  1962-1963 116% 116% 131% 110% 105% 61% 58% 108% 118% 105% 98% 94% 130% 109% 114% 136% 101% 56% 41%
Mod. El Niņo 1963-1964 78% 68% 85% 62% 71% 71% 79% 73% 67% 71% 70% 52% 18% 93% 57% 67% 59% 53% 73%
Weak La Niņa 1964-1965 117% 112% 120% 96% 108% 82% 70% 107% 117% 123% 104% 94% 97% 101% 115% 99% 97% 92% 89%
Stg. El Niņo 1965-1966 88% 71% 79% 75% 73% 97% 109% 81% 71% 75% 63% 69% 68% 80% 90% 57% 53% 137% 157%
  1966-1967 109% 123% 140% 135% 138% 129% 90% 125% 117% 134% 163% 124% 129% 110% 131% 142% 130% 147% 111%
  1967-1968 79% 76% 78% 63% 67% 77% 96% 75% 71% 59% 60% 61% 84% 70% 69% 64% 63% 111% 83%
Mod. El Niņo* 1968-1969 120% 128% 147% 161% 169% 175% 142% 145% 127% 163% 186% 106% 136% 118% 151% 130% 200% 184% 121%
Weak El Niņo 1969-1970 111% 113% 115% 80% 86% 63% 69% 97% 111% 97% 79% 88% 73% 95% 154% 93% 79% 52% 66%
Mod. La Niņa 1970-1971 119% 106% 125% 85% 85% 80% 64% 102% 104% 76% 76% 79% 95% 119% 133% 88% 74% 83% 83%
Weak La Niņa 1971-1972 93% 68% 82% 48% 57% 51% 49% 69% 66% 67% 54% 47% 41% 98% 75% 50% 46% 48% 59%
Stg. El Niņo 1972-1973 95% 110% 104% 144% 122% 129% 113% 114% 96% 95% 128% 145% 150% 86% 123% 136% 121% 142% 119%
Stg. La Niņa 1973-1974 149% 132% 108% 116% 105% 87% 74% 120% 143% 110% 101% 117% 104% 132% 161% 112% 91% 100% 69%
Weak La Niņa 1974-1975 104% 92% 102% 92% 94% 93% 74% 96% 93% 105% 95% 77% 87% 99% 129% 86% 67% 96% 111%
Stg. La Niņa 1975-1976 67% 49% 56% 39% 54% 63% 78% 56% 48% 55% 54% 34% 37% 83% 63% 36% 71% 48% 95%
Weak El Niņo 1976-1977 41% 41% 68% 50% 50% 66% 84% 52% 37% 45% 54% 47% 58% 44% 58% 38% 66% 82% 84%
Weak El Niņo 1977-1978 127% 131% 124% 157% 157% 207% 200% 147% 132% 148% 155% 114% 141% 90% 179% 142% 158% 224% 195%
  1978-1979 74% 80% 80% 91% 99% 131% 129% 90% 77% 101% 90% 79% 78% 62% 95% 97% 93% 132% 162%
Weak El Niņo 1979-1980 110% 118% 133% 121% 128% 165% 180% 128% 111% 134% 136% 104% 121% 94% 109% 128% 104% 181% 164%
  1980-1981 73% 74% 79% 70% 73% 69% 71% 73% 69% 64% 67% 65% 71% 73% 95% 68% 72% 60% 84%
  1981-1982 142% 145% 148% 132% 140% 100% 103% 135% 153% 152% 126% 157% 98% 120% 156% 164% 97% 72% 120%
V. Stg. El Niņo 1982-1983 162% 166% 164% 193% 186% 199% 191% 176% 166% 187% 194% 161% 194% 147% 184% 192% 205% 209% 190%
Weak La Niņa 1983-1984 111% 108% 120% 78% 94% 64% 88% 99% 110% 109% 95% 95% 86% 120% 105% 78% 66% 70% 60%
Weak La Niņa 1984-1985 78% 71% 78% 75% 77% 78% 125% 78% 66% 72% 86% 85% 81% 87% 75% 58% 69% 86% 100%
  1985-1986 114% 126% 139% 122% 133% 116% 111% 124% 131% 139% 142% 121% 120% 97% 133% 128% 129% 120% 147%
Mod. El Niņo 1986-1987 72% 62% 67% 60% 63% 61% 82% 65% 61% 56% 61% 59% 50% 69% 63% 56% 81% 51% 100%
Stg. El Niņo* 1987-1988 77% 73% 64% 73% 73% 99% 115% 77% 65% 63% 73% 75% 72% 80% 84% 75% 70% 84% 137%
Stg. La Niņa 1988-1989 88% 86% 97% 60% 71% 57% 64% 79% 86% 71% 79% 74% 53% 86% 93% 77% 76% 54% 59%
  1989-1990 74% 74% 78% 58% 68% 52% 43% 68% 72% 72% 66% 61% 64% 67% 83% 96% 82% 49% 82%
  1990-1991 64% 69% 80% 80% 79% 99% 107% 77% 61% 76% 78% 60% 76% 62% 61% 69% 85% 77% 123%
Stg. El Niņo* 1991-1992 68% 71% 63% 92% 78% 124% 155% 82% 67% 64% 65% 81% 104% 54% 79% 71% 96% 141% 135%
  1992-1993 120% 128% 127% 139% 134% 188% 185% 137% 121% 134% 132% 113% 137% 108% 146% 138% 144% 183% 191%
  1993-1994 63% 64% 67% 70% 67% 78% 57% 67% 59% 55% 68% 64% 79% 73% 65% 65% 74% 54% 103%
Mod. El Niņo* 1994-1995 143% 163% 166% 161% 164% 182% 149% 161% 159% 169% 153% 144% 152% 128% 158% 127% 165% 163% 178%
Mod. La Niņa* 1995-1996 118% 115% 129% 105% 106% 76% 51% 109% 112% 104% 102% 105% 112% 111% 107% 102% 95% 83% 53%
  1996-1997 118% 115% 135% 112% 119% 87% 66% 114% 126% 129% 114% 96% 99% 125% 76% 107% 104% 83% 73%
V. Stg. El Niņo 1997-1998 154% 160% 132% 191% 168% 211% 177% 167% 154% 154% 179% 200% 186% 145% 181% 174% 175% 208% 185%
Stg. La Niņa* 1998-1999 109% 96% 101% 81% 85% 65% 64% 92% 103% 92% 79% 99% 88% 124% 85% 75% 61% 61% 70%
Stg. La Niņa* 1999-2000 95% 98% 86% 101% 97% 78% 64% 92% 103% 99% 92% 105% 80% 90% 95% 116% 112% 77% 60%
Weak La Niņa 2000-2001 59% 66% 58% 90% 81% 100% 93% 74% 63% 71% 75% 82% 88% 57% 83% 81% 92% 120% 89%
  2001-2002 93% 87% 76% 73% 77% 36% 32% 76% 87% 81% 84% 106% 72% 101% 80% 97% 61% 30% 31%
Mod. El Niņo 2002-2003 117% 105% 91% 99% 94% 105% 90% 103% 108% 91% 104% 101% 99% 132% 97% 90% 85% 110% 111%
  2003-2004 94% 91% 83% 76% 74% 60% 93% 83% 90% 71% 69% 87% 88% 95% 100% 71% 66% 62% 54%
Weak El Niņo 2004-2005 101% 110% 115% 144% 139% 192% 206% 130% 107% 129% 127% 135% 161% 110% 107% 118% 138% 249% 234%
Weak La Niņa* 2005-2006 139% 141% 135% 121% 127% 93% 84% 127% 150% 132% 119% 146% 147% 146% 125% 127% 127% 88% 56%
Weak El Niņo 2006-2007 75% 62% 56% 50% 53% 31% 32% 57% 67% 59% 56% 71% 58% 88% 63% 59% 52% 22% 40%
Stg. La Niņa* 2007-2008 81% 72% 75% 79% 72% 88% 82% 78% 67% 69% 85% 73% 71% 85% 66% 74% 73% 91% 76%
Weak La Niņa 2008-2009 70% 78% 76% 70% 76% 68% 78% 73% 86% 94% 85% 77% 74% 74% 66% 88% 68% 61% 95%
Mod. El Niņo 2009-2010 99% 97% 93% 115% 105% 114% 113% 103% 99% 107% 113% 102% 110% 110% 84% 112% 107% 110% 110%
Stg. La Niņa* 2010-2011 112% 123% 143% 125% 141% 139% 109% 127% 135% 154% 149% 122% 100% 112% 101% 129% 152% 135% 131%
Mod. La Niņa* 2011-2012 82% 73% 60% 68% 63% 64% 59% 70% 78% 61% 73% 66% 46% 101% 65% 66% 71% 58% 84%
Mod. La Niņa 2012-2013 77% 78% 79% 60% 61% 47% 65% 69% 80% 63% 51% 70% 61% 80% 79% 82% 49% 39% 68%
  2013-2014 55% 58% 66% 44% 48% 43% 63% 54% 56% 47% 49% 0.5302 41% 52% 49% 53% 42% 41% 53%
Weak El Niņo* 2014-2015 82% 78% 83% 35% 59% 60% 83% 75% 71% 45% 43% 0.7691 88% 84% 73% 86% 57% 57% 94%
V. Stg. El Niņo 2015-2016 111% 106% 116% 97% 102% 67% 89% 98% 99% 99% 89% 0.9797 96% 120% 114% 88% 129% 65% 113%
Weak La Niņa 2016-2017 141% 157% 178% 150% 155% 131% 122% 141% 175% 171% 154% 1.3687 118% 157% 130% 179% 150% 127% 135%

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