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  • Weekly Weather Event -Week of Aug. 12

Weekly Weather Event -Week of Aug. 12

August 14, 2019

As of August 8th, NOAA’s Climate Prediction Center officially declared the end of the 2019 El Niño. Throughout July, below average sea surface temperatures were recorded in the eastern equatorial Pacific and above average sea surface temperatures were recorded in the central Pacific. These conditions in combination with suppressed tropical convection over Indonesia and easterly upper level winds are consistent with a transition from El Niño to ENSO-neutral. NOAA researchers favor ENSO-neutral conditions to continue into the fall and winter.

The El Niño/Southern Oscillation, or ENSO, is a reoccurring climate pattern that takes place in the equatorial Pacific. Coupling both atmospheric and oceanic processes, ENSO can influence weather patterns around the world. Though considered a single climate phenomenon, it has three distinct phases: El Niño (the warm phase), La Niña (the cool phase), and neutral (temperatures are near their long-term average). Certain changes must be present in both the atmosphere and the ocean for a phase to be officially recognized.

During El Niño, the surface winds along the equatorial Pacific are weaker than normal. Warmer waters build up along the eastern coasts of Central and South America while cooler waters develop off the western coast of Indonesia. This leads to low air pressure and heavy rainfall in the eastern Pacific, while the western Pacific tends to have higher air pressure and dry conditions. During La Niña, these conditions are reversed.

Changes in weather patterns along the tropics also impact weather patterns at higher latitudes. During El Niño, the U.S. Pacific Northwest tends to be warmer than normal while the southern states tend to be wetter. El Niño’s influence is strongest during the winter months in the United States, though effects can linger into spring.