Have you ever heard of ENSO? El Nino – Southern Oscillation is a naturally set of re-occurring climate patterns involving changes in water temperatures across the central and eastern tropical Pacific Ocean. This fluctuation between warmer and cooler than average water temperatures directly impacts weather across the country. Roughly every 2 – 7 years, sea surface temperatures in the Pacific fluctuate between warmer, cooler and neutral phases. These three distinct phases create varying weather patterns across the globe.
THE THREE PHASES OF ENSO
El Nino: This is the warmer phase of ENSO. Easterly trade winds decrease, allowing for upwelling off the coast of Peru to weaken, which in turn, creates warmer sea surface temps in this region of the Pacific.
La Nina: This is the opposite of El Nino. La Nina is the cooler phase of ENSO. As easterly trade winds strengthen, enhanced upwelling of colder water along the equator generates cooler than average sea surface temperatures in the central and eastern tropical Pacific Ocean.
Neutral: This is the in between phase, where easterly trade winds are considered normal. The tropical Pacific sea surface temperature is generally within 0.9°F of average.
The graphic below highlights where cooler than average sea surface temperatures develop during a La Nina event.
LA NINA TO POTENTIAL EL NINO
Since 2020, we have been in the La Nina phase of ENSO. But as of lately, La Nina has decreased and we are now entering the neutral phase. As we march into spring, we’re likely going to experience the transition into the neutral phase of ENSO, with El Nino possible to form by late this summer.
El Nino generally leads to fewer tropical systems across the Atlantic basin. This is caused by increased wind shear, which is increasing wind speeds with increasing heights. Wind shear ‘tears’ apart any developing storm from the top, making it difficult for tropical systems to organize and develop.
The graphic below highlights where warmer than average sea surface temperatures develop across the equatorial Pacific Ocean during an El Nino year.
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