Lala Impacting Hawaii; Flash Flooding Risks; Excessive Heat

Lala will continue to impact Hawaii through the weekend. Heavy rainfall, strong winds, dangerous surf and localized flooding are expected. Thunderstorms, heavy rainfall and flash flooding concerns from the mid-Mississippi Valley, Ohio Valley into the central Appalachians and the mid-Atlantic through today. Record heat continues for areas of the Mississippi Valley into the Southeast. 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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