[Source: NOAA Climate Prediction Center, http://www.cpc.ncep.noaa.gov/ ]
The EP pattern is evident in all months except August and September, and reflects a north-south dipole of height anomalies over the eastern North Pacific. The northern center is located in the vicinity of Alaska and the west coast of Canada, while the southern center is of opposite sign and is found near, or east of, Hawaii. During strong positive phases of the EP pattern, a deeper than normal trough is located in the vicinity of the Gulf of Alaska/ western North America, and positive height anomalies are observed farther south. This phase of the pattern is associated with a pronounced northeastward extension of the Pacific jet stream toward western North America, and with enhanced westerlies over the Pacific Northwest States, northern California, and sometimes southwestern British Columbia.
In contrast, strong negative phases of the EP pattern are associated with a pronounced split-flow configuration over the eastern North Pacific, and with reduced westerlies throughout the region. This circulation is accompanied by a confinement of the climatological mean Pacific trough to the western North Pacific, and possibly with a blocking flow configuration farther east.
The most persistent positive phase of the EP-Jet pattern occurred from 1973-1975, and the most persistent negative phase of the pattern occurred from early 1992 through mid-1993. This latter period was dominated by warm episode conditions in the equatorial Pacific, and by two distinct periods of mature ENSO conditions. During this period, the subtropical jet stream was generally stronger than normal and displaced well east of its climatological -mean position toward the southwestern United States. These conditions contributed to an end of prolonged drought conditions in California (Bell and Basist 1994), and brought abundant precipitation to the southwestern United States, particularly during the 1992/93 winter. These conditions were also associated with generally above-normal precipitation over the central United States during the year preceding the onset of the Midwest floods of June-July 1993 (Bell and Janowiak 1995, Chagnon 1996). This enhanced precipitation then contributed to above-normal soil moisture levels throughout the Midwest during the period, and to near-saturated soil conditions just prior to the onset of the floods.
Access to EP documentation, graphs and data
Data Set Citation
East Pacific Teleconnection Pattern
Dataset Series Name:
NOAA/NWS/CPC Indices and Forecasts
Dataset Release Date:
Dataset Release Place:
Camp Springs, MD
NOAA National Weather Service, Center for Climate Prediction
Ed.Olenic at noaa.gov
Bell, G. D., and A. N. Basist, 1994: Seasonal Climate Summary: The global climate of December 1992- January 1993: Mature ENSO conditions continue in the tropical Pacific, California drought abates. J. Climate, 7, 1581-1605.
Bell, G. D., and J. E. Janowiak, 1995: Atmospheric circulation associated with the Midwest floods of 1993. Bull. Amer. Met. Soc., 5, 681-695.
Chagnon, S. A., 1996: The Great Midwest Flood of 1993, Westview Press, 321 pp.