California Rainfall Events and ENSO


The Golden State is called this not only because of the Gold Rush, but also because of its mediterranean climate, characterized by winter rainfalls, and prolonged dry season that runs from the end of March until October, during which time the hills and valleys turn a characteristic Golden Brown.


My colleague, James Goodridge, retired California State Climatologist, has collected and collated many thousands of time series of California's rainfall, climate and hydrostands. He shares these freely, and in the recent few years has also compiled some interesting commentary about extreme events, some of which I share with you herein, in respect for Jim's interests in similar phenomena, and the oceanography that portends such major events. A relativly recent update of his perspectives, entitled Historic Rainstorms in California, dated August 1997, is available from the State of California Department of Water Resources, Bulletins and Reports, P.O. Box 94236, Sacramento, CA 94236-0001. Its Free, too!

Jim Goodridge - and many other climsate researchers - are well aware of the role of the oceans in the hydrologic cycle. There are many ongoing efforts to decipher the longer-term patterns that precede major weather events, although the problem remains the poverty of historical data.

Since climate (weather) is so variable, its study and eventual opportunity to forecast will require many iterations of each type of signal before the various time and space scales of forecasts will gain credibility.

In perusing the records of Historic 1000 Year Return-Time Storms of California that Goodridge uses and presented at the 1996 Pacific Climate Conference I was pleased to find adequate information to be able to point out that there is much more to California's rainfall than only El Niño.

For example, in spite of the propensity for agency climatologists to begin their summaries in the data rich 1947-1950 post war period, and bring them forward, the Comprehensive Ocean and Atmosphere Data Set, or COADS as it is better known, allows one to revisit data from ocean observations made by sailing ships since 1854 - and today's modern ocean-going vessels. This permits some reconstructions, particularly useful to studies of ENSO and other global climate phenomena.

The Southern Oscillation Index has been reconstructed back to 1882 from COADS, when the SOI reached a low of -1.6 in June (on the unexpanded scale), from which one would infer an El Niño was in progress.

The Australian Bureau of Meteorology uses a slightly different method for calculating monthly mean SOI values, and updates them regularly, around the end of the first week in each month after. I try to keep these updated records available on my web-site, too.

Similarly, low values occurred in the years 1889, 1891, 1896, 1900-01, 1905, 1911-13, 1918-1919, 1925-26, mid 1939-1941, 1946, 1948-49, 1951, 1953, 1957-58, 1963, 1965-66, 1969, 1972, 1977-78, 1979-80, 1982-83, 1986-87, late 1989-90, and after a brief respite, the period from July 1990 until fall of 1994 remained below zero, with seasonal rises. The event of 1997-98 - well below zero, and likely the strongest of the century's warm Events, was followed by a similarly remarkable period of Cooling of the North Pacific, as well as an apparent shift in the Pacific Decadal Oscillation, the Atlantic Oscillation, and several other climate indices, including the Vangeneim-Girs ACI, indicating a general Climate Regime Shift has likely taken place.

The Periods marked in yellow indicate El Niños initiating in or about March of each year, and the blue marked events were remarkable only in their being periods of below zero, but without large deviations. The month of June is the most common month when the SOI dips below the zero point - leading into many of the more protracted Events.


To attempt any sort of analysis it is wise to begin with some sort of hypothesis.

In this case I have selected the one being promoted by those pushing for the 1997-98 ENSO Warm Event to be a disastrous year for California due to extreme rainfall. One alternative being simply that greater or similar rainfalls can also occur in the Cool eastern tropical Pacific period preceding these ENSO Warm Events, often called La Niña.

From the 1878 to 1994 COADS SST anomaly records provided by Allan et al. (1997), and the SOI reconstruction reaching back only to 1882, I have reviewed Goodridge's summary of major events, and found the following results:

California 1000 Year Return Storms

Water year is October 1 of preceeding Year to September 30

Numbers in brackets (1-10) are ranking amongst Top Ten storms from 1999 Economic, Climatic, and Return Rate analysis by James Goodridge

 1997-98 like Warm western Pacific and Arctic Ocean

  Pre-El Niño Cool Ocean / La Niña

  Other Niños / Cold Offshore


 Oct. 1889 Encinitas 7.6"


 1890 water year was 1 of 4 Wettest Years in Record, late 1889 SOI was very high

 Feb. 1891 Big Bear and Cuyamaca 32.2 "/ 22.4"    

 August 1891 Campo 16.1"


 Dec. 1906 Pacific Grove 6.1" to Sierra Foothills/ 9 records fall


 Jan. 1911 Los Gatos (17.34") to Galt/ late 1910 SOI high


 May 1915 Kennett/Shasta lake 8.93"


 Jan 1916 Descanso 27.79"/ Sweetwater dam overflows/ 8 reports of 10"/day

 Sept. 1918 Tropical Hurricane ashore at Santa Cruz to Red Bluff


 Dec. 1921 Werner Springs Opids Camp 14.89"

 April 1925 Fancher ranch, Merced 4" in day


 April 1926 Opids Camp 12.52"/1.03"/min.


 Feb. 1927 Henshaw Dam 25.38" in 4 days


 Sept 1932 Tropical Storm came ashore at Mexicali, northern Gulf of California, up valley to Tehachapi 7.11" in 4 days

(10) NewYear 1934 So. San Gabriel Mtns 16.33"/ 16 stations 10"/day


 Mar 1938 Niño Storm LA / San Bernardino Cos. 16 stations report 10"/day Floods


 Sep. 1939 Tropical Storm/Brawley 6.33" /cold offshore


 Extended Niño of 1940-42. 1941 rain totals exceed 5000 year return period.


 Jan 1943 largest measured rainfall in California/ Hoegees 26.12' in day


 Dec. 1955 Central Coast/Sieras/ 19 stations rept 10"/day /42.27" from storm at Lake McKenzie


 April 1958 Woodward 5.72" in day


  Sept 1959 Tropical Storm Kathleen/Boulder Creek and Shasta dam >11"


(2)  Oct 1962 Warm No. Pacific/Typhoon Frieda/Wake Island, brings 170 kt winds to Cape Blanco/214 staions rept highest ever 3 day totals.


(8) Jan/Feb 1963 Warm North Pacific continue / Storm ends worst mid winter drougt on record/ Floods Reno, Marysville, Napa


(5)  Dec. 1964 wettest ever at 78 No. Calif. stations.

     (7) Dec. 1966 wettest 5 days ever at 58 Calif. stations from Kern River to White Mountains, and into the Tulare and San Bernardino Counties.

(1)  Winter 1969 severe flooding/ Juncal dam/Santa Barbara 25.67" before observer, Brooks, washed away in cabin/Lytle Creek 24.92" in day.


 Aug 1976 - 8" at 2.5"/hr reported NW of Redding/2 yr drought across central California


 Sept. 1976 Tropical Cyclone Kathleen drops 12.1" on Fallsdale, 4" at Mecca


 Aug 1977 Hurricane Doreen came ashore at San Diego, Yuma valley 6.45"/floods


(4) Feb 1978 Ventura Co. 13.31" in day, floods and landslides/ Kern Co. 3.9" in day


(6)  Jan 1982 Berkley 6.98"/Ben Lomond 15.2"/ many stations report 10"


 1983 Wettest Records Flooding/Landslides 45 Stations report >1:1000yr levels attained

(3)  Feb 1986 Tropical storms soak Central California Floods/Mudslides 17.6" in day at Four Trees /Russian River floods/ Napa 29.61 " from 10 day period


 Dec. 1987 La Porte 12.84" in day


 Jan. 1988 Gulf of Alaska storm delivers Newman 4.1" Modesto 1.69"and Turlock 1.1"


 Feb. 1992 Flooding/ landslides Big Tujunga Dam 8.75" in day


 Jan. 1993 series of storms bring from 30" to 37.89" to mountain areas/ Lowlands Mission Creek 19.17" Flooding.deaths132 stations report >15 day totals, 10 report >1:1000yr levels.

SOI Has been low for several years with minor upswings into positive index zone sustained from mid 1995 through 1996.

(9)  Water Year 1995 is the 3rd highest total on record. Black Butte ranch 46.06", Florence Lake 50.29"/Oct. 1994 Cresta Park 1.02" In 15 MINUTES /Nov. 1994 Corte madera >8" in day/ Jan. 1995 Santa Barbara, 8"/day Granite Bay CC 7.57"/ Rancho Cordova 5.63" /12 Sacramento stations report> 5' in day. / March1995 Guerneville 9.07", Napa and Russian River flood. Salinas River Floods, Paso Robles 7.4"/ Many Central Valley stations exceed highs.


 1997 New Years Flood derived from a very warm area of ocean just west of Hawaii. The convection and atmospheric steering resulted in a convergence of cold arctic air and vast tropical moisture - carried east - from the source energy of the upper ocean. The entire water year's allocation was received by the end of January 1997. Little precipitation has fallen since, breaking other precedences.

 Flooding caused many hundreds of millions of dollars in damage across the northern California terrain. The flood control personnel were on day and night watch, attempting to minimize damage, given that these systems were not designed for the amounts of rainfall that were measured.

The storms leading up to this one had saturated the ground, and filled reservoirs. In retrospect this was a very dangerous situation, and were it not for the fact that the storms ended, much more significant damage could have occurred.

 1998 Winter Starts off with a steady sequence of Cold Jets stream incursions into lower latitudes, and associated rainfall and freezes throughout eastern Canada and Northeastern USA

 February North Pacific Storms increase in frequency arriving along US west coast in 2-3 day intervals. Many February 100+ year records fall, and annual rainfall surpassed.

 Although there was Major flooding and landslides in North/ Central California as ground saturated, intense winds and treefalls close roads/power losses, leaving many homeless, this was far from the major storm or water (ranked in the 30s) year on record.

 1998 -2002

 Strong coastal ocean cooling, and general opposite trends from the previous two decades has not been particularly wet, but has extended the rainfall season for much of the State.

 Coastal cities, large and small have all experienced general cooling, in parallel with the coastl ocean SSTs, stopping the general warming trend observed since 1976.

While much of what we worry about is focused on the local geographic region, including the Offshore Ocean, as is one important aspect of the climate and weather picture, there are other, more important scales to keep informed about, as the local weather reflects both ocean and global responses to solar forcing.


One should never forget that the sun is the Earth's heat engine!


The rainfall information used in this document are freely available from James Goodridge, at <>.

A similar series of studies by Oregon State Climatologist, George Taylor with some cogent comments and time series are available at:

My final comments are about the fact that we have yet to observe or measure the full extent of natural climate variability, here or anywhere on earth. These mere century-long records provide some feel for the melange of different processes and Events that can affect our lives. The storm of December 23, 1861 to January 21, 1862 was said to have inundated the entire central valleys, the Sacramento and San Joaquin, an extent of 250-300 miles, averaging 20 miles in breadth. The floods destroyed the entire commerce of the state. One needs to become a bit wary of each Dooms-Day statement about El Niño, given that it appears that there is more to the problem than just equatorial warming.

In fact, the greatest storms appear to be associated with either Pre-Niño conditions (e.g., January 1911, 1943, December 1955, December 1996-January 1997), far west of Hawaii - or Autumn (August to October) tropical storms emanating from the eastern Pacific Ocean south of Mexico, that follow warm surface waters within the eastern tropical Pacific Ocean, along the coastline - until they make landfall. Some years they make it as far north as mid-California (1918). In others they cause havoc in Mexico (1997).

Water is Life! Water is also Disaster - unless you are prepared for it.