Blogs

La Niña strengthened over October, with both the tropical Pacific Ocean and the atmosphere clearly reflecting La Niña conditions. Forecasters estimate at least a 95% chance La Niña will last through the winter, with a 65% chance of it hanging on through the spring. The October sea surface temperature anomaly (departure from the long-term average) in the Niño 3.4 region of tropical Pacific was -1.3°C according to the ERSSTv5 dataset, substantially cooler than the La Niña threshold of -0.5°C. This is the eighth-strongest negative October value in the ERSSTv5 record, which dates back to 1950. I’ll talk more about feats of strength (vis-à-vis La Niña, that is) later. Let’s count our ch…   Read article

We often get asked how El Niño or La Niña events form and increase in strength. The key is in the ocean-atmosphere coupling across the tropical Pacific Ocean. Without it, ENSO would not exist, and it would be considerably more difficult to predict climate impacts seasons in advance. Various ingredients of the ocean have to be combined with the atmosphere in order for ENSO to blossom and grow. Flour and yeast also would be pretty boring and inert on their own, but when put together, they reinforce each other, the combined product increases in size, and eventually it releases the heavenly scents of fresh baked bread. That’s right, I’m basically saying ENSO is fresh baked bread (…   Read article

La Niña’s reign continues in the tropical Pacific, with an approximately 85% chance of lasting through the winter. Forecasters currently think this La Niña will be on the stronger side. Let’s check in with the tropical Pacific The temperature of the ocean surface in the Niño3.4 region was about 0.8°C cooler than the 1986–2015 average, according to the ERSSTv5 dataset. We monitor the Niño3.4 index with a few different temperature datasets—more on that here—but they are all comfortably below the La Niña threshold of -0.5°C. The three-month-average Niño3.4 index, called the Oceanic Niño Index (remember this for later!) was -0.6°C. The Oceanic Niño Index is our primary metric for the El Ni…   Read article

Marybeth Arcodia is an Atmospheric Science Ph.D. Candidate at the University of Miami Rosenstiel School of Marine and Atmospheric Science. She works with Dr. Ben Kirtman (previous ENSO Blog guest writer) studying climate variability and predictability. Along with a few members from her lab group, Marybeth helped create a subseasonal-to-seasonal forecasting blog called Seasoned Chaos, for scientists and non-scientists alike. Her research looks at how particular atmospheric and oceanic conditions in the tropical Indian and Pacific Oceans can affect weather and extreme events in the United States to lead to more confident climate forecasts on two week to two month time scales. She received her …   Read article

La Niña conditions were present in August, and there’s a 75% chance they’ll hang around through the winter. NOAA has issued a La Niña Advisory. Just how did we arrive at this conclusion, and what does a La Niña winter portend? Read on to find out! Checking the boxes Let’s revisit our La Niña decision tree. The answer to the first question, “Is the monthly Niño3.4 sea surface temperature anomaly equal to or less than -0.5°C?” is an easy “yes.” August’s value was -0.6°C according to our most consistent sea surface temperature dataset, the ERSSTv5 (though that is not the only SST dataset we monitor). For a quick refresher, the Niño3.4 sea surface temperature anomaly is the differen…   Read article