Severe Thunderstorm and Heavy Rainfall Potential Continues

A low pressure center tracking across the Great Lakes and its associated cold front extending across the Southern Plains will focus occasional showers and thunderstorms through tonight. A few of these thunderstorms may become severe alongside heavy rainfall that may cause flash flooding; Portions of the Southern Plains would be the greatest threat for these hazards through tonight. 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

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