National Weather Service United States Department of Commerce

Snow Across the Great Lakes, Central Appalachians, and Northeast; Unsettled Weather in the West

Light to moderate snow will continue into Saturday over the Great Lakes, Central Appalachians, and Northeast. This weekend into next week, a series of atmospheric rivers will bring gusty winds, periods of heavy rain, and mountain snow to northern California and the Pacific Northwest. Colder temperatures are in store for the weekend from the Great Lakes to East Coast. Read More >

ENSO Indices

 

ENSO Regions

 

Southern Oscillation Index (SOI)
standardized anomaly of the mean sea level pressure difference between Tahiti and Darwin

  • traditional ENSO index

  • correlates strongly with SST anomaly indices


NOAA Oceanic Niño Index (ONI)
sea surface temperature anomaly index for Niño 3.4 (5°N to 5°S, 170°W to 120°W)

  • onset of El Niño declared when Niño 3.4 anomaly exceeds +0.5°C for 3-month period

  • to be "full-fledged" El Niño (or La Niña), onset conditions must be met for 5 consecutive 3-month periods


Japanese Meteorological Agency ENSO Index (JMA)
sea surface temperature anomaly index for Niño 3 (4°N to 4°S, 150°W to 90°W)

  • less noisy than traditional SOI and more vigorous than NOAA ONI

  • anomalies must exceed 0.5°C for 6 consecutive 5-month periods


Multivariate ENSO Index (MEI)
weighted anomaly average of 6 meteorological variables in the tropical Pacific

  • sea surface temperature

  • sea level pressure

  • surface air temperature

  • components of surface wind

    • zonal component

    • meridional component

  • total cloudiness fraction of the sky