ENSO Blog

Some people have probably noticed that over the past year, this blog has mentioned several different ways to measure and monitor ENSO—whether we are in an El Niño, La Niña, or neither. At NOAA, the official ENSO indicator is the Oceanic Niño Index (ONI), which is based on sea surface temperature (SST) in the east-central tropical Pacific Ocean. But we have also mentioned other ways of measuring ENSO. Here, we will review some of them and then provide reasons why several different indicators are best for monitoring ENSO. Historically, an index has been a common way to summarize the ENSO status. An index is a number scale in which all the individual factors needed to describe a complicated …   Read article

*Okay, maybe not.  While not as popular as “polar vortex,” oceanic Kelvin waves did break into media reports in early 2014 (here, here, here) when a really strong wave traveled eastward across the tropical Pacific Ocean.  In this post, we’ll go into a little more detail on what these waves are and why they are important in ENSO prediction.   And if Kelvin waves ever get as popular as the polar vortex some day, we are confident our readers will be able to describe them in a way that doesn’t generate a heavy sigh from scientists.      Not all waves curl and crash The waves that most of us are familiar with are the waves at the beach—waves that e…   Read article

In my last post, I showed the last ten years’ worth of December through February (DJF) winter forecasts and observations (2004-2013) and allowed our eyes to tell us their thoughts on just how well those forecasts did. It appeared that some forecasts were better than others, but there was a wide mix of forecast performances not only from year to year, but from place to place.  It was hard to tell, on average, how well the forecasts did. “Eyeballing” the difference between a forecast and observations, while easy, is subjective and potentially inaccurate, in the end. We need verification metrics – statistical analyses that boil down everything our eyes see into numbers—to really put for…   Read article

A month ago, I wrote about the factors we look for when declaring the presence of “El Niño conditions.” Last month we were close: monthly average sea surface temperature anomalies in the Niño3.4 region were above +0.5° Celsius, and they looked to stay that way for at least another few seasons. However, signs that the atmosphere was responding to the warmer-than-average ocean waters were inconclusive, and we decided to hold off on declaring the presence of El Niño conditions for the moment. Was that the right decision? Why is this particular forecast so difficult? This month, I’m going to take you behind the scenes, into the forecast process. The CPC/IRI ENSO* team currently consists of…   Read article

The articles posted on this blog have described ENSO, its regional and global impacts, and the challenge of forecasting it, among several other topics. Here we introduce another important player on the tropical stage: the Madden-Julian Oscillation, or MJO. While the MJO is a lesser-known phenomenon, it can have dramatic impacts in the mid-latitudes. Several times a year the MJO is a strong contributor to various extreme events in the United States, including Arctic air outbreaks during the winter months across the central and eastern portions of the United States. So what is the MJO? Imagine ENSO as a person riding a stationary exercise bike in the middle of a stage all day long. His u…   Read article