Isolated severe storms and localized flash flooding are possible over parts of the central and northern Rockies into the northern High Plains. Heavy rainfall may lead to localized instances of flooding from Florida to the Carolinas. Read More >
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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