Not what I ordered: How El Niรฑo is like a bad bartender
***Letโs face it: El Niรฑo is the life of the party. Heโs the Most Interesting Child in the World. The good folks over at The ENSO Blog have filled up a whole blog, and still there are enough leftovers for Beyond the Data, where we donโt always blog about teleconnections, but when we do, we prefer El Niรฑo.
Weโve already written about how El Niรฑo will push the needle toward 2015 being the warmest year on record. But thinking a little more directly about the state of the climate in the U.S., how might a strong El Niรฑo impact things here? Will it put a dent in the Western U.S. drought, one of the defining climate events of the decade? What about the rest of the country?
If youโve been following along over at The ENSO Blog, you know this El Niรฑo event is already one of the big ones. And, it will very likely take its place among the pantheon of El Niรฑos of the last 60-70 years. But the expectations in some places arenโt as cut and dried as you might think.
Letโs say you have a favorite establishment, where everybody knows your name, and they bring you โyourโ beverage on sight. And then one night you go in, and based upon your past experience, you sorta expect the bartender to bring you your favorite beer. Instead, maybe he unexpectedly brings you a warmer-than-normal beer, or even <shudder> a wine cooler. El Niรฑo is like that bartender. Seeing him when you walk in may tilt your odds toward getting your favorite beer, but itโs not a guarantee. In other words, sometimes El Niรฑo is the bartender who doesnโt bring you what you ordered.
El Niรฑo is important, so we appropriately pay attention to it when considering seasonal outcomes. However, El Niรฑo is not the only game in town, and just like external factors may distract your bartender, each El Niรฑo is born into a unique global situation, so its push on seasonal outcomes is unique as well. Indeed, this year, we have “the โBlob,โ reduced Arctic sea ice, and a persistent North Atlantic feature that werenโt in play in the 20th-century El Niรฑos of yore.
At NCEI, we turn to the official outlooks from NOAAโs Climate Prediction Center for predictions about the upcoming season. But we also sit on top of the worldโs best weather and climate data, and can illustrate some of the variability in outcomes from past El Niรฑo events.
Weโll look at some historical outcomes for arguably the six strongest El Niรฑo events since the mid 20th century: 1957-58, 1965-66, 1973-74, 1982-83, 1992-93, and 1997-98. Keep in mind that the significance of an El Nino is in the eye of the beholder; these six were identified based upon their duration, and by the level of interaction (โcouplingโ) between ocean and atmosphere. For convenience, weโll call them โstrongโ from here forward, recognizing that โstrongโ can be a loaded term in the ENSO world.
Letโs look at some historical precipitation outcomes for the cold season (October through March) for each year since 1950. Why cold season? Because itโs starting now, and it is also when much of the West gets the lionโs share of its precipitation. Itโs also more responsive to El Niรฑoโs influence, compared to other months on the calendar. Why 1950? That coincides with the beginning of the Oceanic Nino Index era, which was a factor in selecting historic El Niรฑos.
Northeast
Weโll start in the Northeast, if only to get used to these goofy images.
The image above is for New Yorkโs Climate Division Number Two (NY-CD2), covering the Eastern Plateau region. From left to right, youโre looking at the cold-season precipitation averaged across NY-CD2 for the 65 cold seasons between the fall/winter of 1950-51 ย to 2014-15 The higher the dot, the wetter the season.
The grey line represents the overall average for those 65 cold seasons. The red line represents the average during strong El Niรฑo events, which show up as red dots.
The gray line and the red line are very close, and the red dots indicating strong El Niรฑo years straddle the average line very evenly. This means that on average, a strong El Niรฑo cold season isnโt much different than a regular (average) cold season for NY-CD2.
California
Moving to the West, where drought is a raging issue, letโs jump straight into California. California isnโt the only drought-stricken state, but it draws upon water resources from throughout the West. In terms of waterโin some ways, at leastโCalifornia goes, so goes the West; as the West goes, so goes California.
The statewide graphic is revealing. First of all, the average outcome is fairly optimistic: the red line indicating average cold season precipitation during strong El Niรฑo years, sits six inches above the long-term average. However, two of those six strong El Niรฑos (red dots) actually delivered below-average precipitation. So, a strong El Niรฑo doesnโt guarantee a wet outcome for California statewide, even though it significantly pushes the odds towards wet conditions.
This situation is magnified in Northern California. Drilling down into CA-CD3 in Northeastern California, the modestly wet average outcome of all six strong El Niรฑos comes as a result of one whopper episode (1982-83), three near-average episodes, and two below-average (i.e., dry) episodes.
On the flip side, southern California has had a much more consistently wet relationship with strong El Niรฑos. This is best shown in Southern Coastal California (CA-CD5), where each of the six strong El Niรฑos have delivered at least nominally above-average precipitation, and five of them have come in notably above the norm. ย As such, the current winter outlook from CPC indicates the highest probabilities for increased precipitation are across southern California.
Northern Rockies
Persistent drought and wildfire have been year-long issues in the Northern Rockies. How might El Niรฑo play out here? Unfortunately, the influence of a strong El Niรฑo to the region is a drying one. Western Montana outcomes are almost the mirror image of Southern California: all of them at least nominally drier-than-average, and most of them seriously so.
Coda
El Niรฑo can play a huge role in seasonal outcomes. Itโs no coincidence that, for much of the country, the current seasonal outlook looks a lot like the pattern of average El Niรฑo outcomes. However, as forecasters can tell you, those average outcomes can be pulled apart into specific examples which may sometimes stray from the averages. Some places have a pretty consistent response, and for these areas, confidence in outcomes is higher. In other places, the signal is anything but consistent. For our friends in northwest Wyoming, both the wettest and the driest cold seasons on record came during strong El Niรฑo episodes.
One more point: the Western drought is entrenched. It took years to get into the current situation; it will take more than one wet season to get out of it. Letโs hope that we put a big dent in the drought this year, but one season, and probably even one El Niรฑo, is not a single magic bullet.
Thanks for reading. And stay thirsty for data, my friends.