An El Niño advisory has been issued by the Climate Prediction Center (CPC) and, now with our rainy season beginning, a wet winter season in California is being watched for. With the majority of the last ten years showing below normal precipitation in much of the state, researchers are examining long-range seasonal forecasts looking for a potential abundance of rainfall while hoping against flooding or coastal damaging storms.
Current Observations Warm equatorial waters can be seen in an animation from the Climate Prediction Center of the weekly sea surface temperature (SST) anomalies from August 12 to October 28 of this year:
Use "Reload/Refresh" button to restart animation
Global sea surface temperature anomalies for the week of October 25 to 31, 2009, are shown below. This image is from the Climate Diagnostics Center.
Current Forecasts The current forecast from the Experimental Climate Prediction Center at the Scripps Institution of Oceanography is forecasting El Niño conditions for the later part of 2009 and the early part of 2010. Below is the forecast sea surface temperature anomaly for the tropical Pacific covering the months of December 2009 through February 2010.
Find more forecast images and information about this forecast on the Experimental El Niño Forecast web page:
http://meteora.ucsd.edu/~pierce/elnino/elnino.htmlOther forecasts can be found at:
El Niño and California California does not always see an increase in precipitation during El Niño years.
Klaus Wolter (NOAA CIRES Climate Diagnostics Center, Boulder CO) has developed a Multivariate ENSO Index (MEI) based on six observed variables over the tropical Pacific: sea-level pressure, zonal wind, meridional wind, sea surface temperature, surface air temperature and total cloudiness. The time series of this index from 1950 to now is shown below. Red indicates times of El Niño events. Click here to see the MEI web page that Klaus has put together (note this web page has many El Niño related links).
In order to compare the current El Niño watch with previous events, Klaus had made a figure showing the MEI for 7 of the strongest transition events since 1950, with the current event in black (see black dashed '09+' line).
While an El Niño doesn't gaurantee a wet winter in California, the graphs below for San Diego (left) and an 8-station California index (8 stations in Northern Sierra used by the California Department of Water Resources, right), show that more often than not, precipitation is above normal during an El Niño:
Click for larger image Click for larger image From the Climate Prediction Center, we have an analysis of the El Niño impact by state. These impacts are derived from looking at what happened during moderate to strong El Niños of the last 100 years (1895-1997). In the image below, California rankings are shown for precipitation (top; wet [green] to dry [red]) and temperature (bottom; cold [blue] to warm [red]) by climate division. These rankings are for 3 three-month intervals over the winter-spring season: November to January, January to March and March to May
November-January January-March March-May Precipitation November-January January-March March-May Temperature Other atmospheric patterns associated with El Niño are shown in composites made using tools available from the Climate Diagnostics Center. The ten El Niño years chosen for the composites below are: 1966, 1973, 1978, 1983, 1988, 1992, 1993, 1994, 1995, and 1998. These composites are of data from the NCEP Reanalysis project (which covers the period 1948-present).
700mb height anomalies (in meters)
Surface temperature anomalies (in degrees C)
Surface wind anomalies (in meters/second)
Correlation of November to March surface precipitation with SST in the Niño3 region
