Ag Weather Forum
NOAA Comment On Tepid El Nino
The following comment is taken from a blog entry on the NOAA Climate Prediction Center's Climate.gov web site. It is written by Michelle L'Heureux, a meteorologist at CPC, and has some interesting detail on how forecasters were challenged by the constant head-fakes that the Pacific Ocean threw out in the past 12 months regarding El Nino. The full article is at this link: http://tinyurl.com/…
Bryce
Twitter @BAndersonDTN
Throughout 2014, the range of possible (Pacific temperature) outcomes included both El Nino and no El Nino at all (or ENSO-neutral). Notably, very few models ever suggested a major El Nino event. We obtain the range, or spread, using many runs from one model (an ensemble) and/or many runs from many different models (multi-model ensemble). Informally, a "strong El Nino" occurs when the ONI (Oceanic Nino Index) is greater than or equal to 1.5 degrees Celsius (the ONI value for the 1997-98 El Nino was plus 2.4 deg C at its peak) and many of the model indications did not exceed this threshold. In contrast, most of the year, the average forecast of the models predicted a "weak El Nino" (ONI at least 0.5 deg C but less than 1 deg C).
The observations were generally within the "envelope" of what all of these models were predicting. In multi-model and ensemble prediction, one measure of success is whether observed reality occurs within this model envelope. While ideally you might prefer to be given just one answer or a very small range of possible outcomes for the future, this is of no use if what occurs is always outside of the prediction. The ensemble approach tries to incorporate the inherit uncertainty of the atmosphere-ocean system and also strives to provide reliable betting odds over time.
2014...Most folks on our team consider this among the trickiest forecasts we have ever been a part of. Such a borderline El Nino is a challenge and one we are still trying to communicate. But, on the up side, we hope you can see that this isn't an easy business to be in and there are still important questions we still need to work on. Leading us to…
El Nino prediction is not "solved." It wasn't at the beginning of 2014 and it isn't now. There are still big challenges we face and it will take a lot of time and effort to analyze the data to better understand ENSO and informed by that new knowledge, predict it with greater accuracy. And it is not just of consequence for seasonal prediction--many of the long-term projections of local and regional climate change critically depend on better understanding and modeling of ENSO and its.
At the beginning of 2014, the possibility of a major El Nino was just that: one among many possible outcomes. In other words, while forecasters couldn't rule out an event of that size early on, a strong El Nino was never the most likely outcome and, furthermore, there was always the chance of no El Nino at all. ENSO prediction comes with a large range of outcomes, and forecasters try to express this uncertainty with our probabilities (what is the percent chance of El Nino?) and more qualitatively in our regular monthly discussions.
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