Friday, October 10, 2014
There’s a wonderful, wonderful website hosted by the National Weather Service’s Climate Prediction Center that you can access right here, and it is an animation of the current sea-surface-temperatures in the tropical Pacific. As I’m sure many of you know, the tropical Pacific is where the single most influential short-term atmospheric/oceanic oscillation occurs. El Nino, and its sister phase, La Nina, influence weather throughout the world. And it looks as though after teetering on the edge of an El Nino, we may finally enter one in the near future.
Before we take a look at how the SST have evolved over the past few months, lets review our El Nino “regions.”
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| Retrieved from the National Climatic Data Center |
Atmospheric scientists and oceanographers refer to certain regions when talking about SST in the tropical Pacific. For example, they might say “temperatures were 1 degree Celsius above average in Nino 1+2, and 0.7 degrees Celsius above average in Nino 3.4.” Nino 3.4 is the most commonly cited region, and El Nino conditions are often classified as anomalies of 0.5 degrees C or above in Nino 3.4.
Now, we can take a look at the SST traces.
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| ENSO Discussion |
You can see that we had neutral conditions until May in most locations, after which we turned slightly El Nino. By August though, things were on the decline, and we have been in borderline El Nino conditions ever since. However, if you will recall that SST animation link I gave you above, the most recent charts show an increase in warm water in the eastern Pacific, particularly in Nino 1+2. The water that upwells off Peru propagates westward, meaning it won’t be long before this newly-formed poll of warm water ends up in Nino 3.4. The big “blob” of warm water in the Northern Hemisphere north of Hawaii is related to the Northeast Pacific Mode (NEPM), and I shall talk about it in a different blog.
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| ENSO Discussion |
In addition, the CPC and IRI (International Research Institute for Climate and Society) have climate models that predict whether ENSO will occur or not. These models are far from perfect… they originally predicted that this year would feature a very strong El Nino rivaling the 1997-1998 El Nino event, which was the strongest on record, though an El Nino from 1982-1983 was very strong as well. Instead, now models are leaning towards a weak El Nino, with some not even developing an El Nino. The CPC lists a 2/3 chance of an El Nino developing within the next 4-8 weeks and continuing into next spring. As I said before, based on the latest SST profiles from the tropical Pacific, I believe that we will see a weak El Nino this winter.
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| ENSO Discussion |
Alright, enough of this tropical Pacific stuff. What’s in it for us, here in the Pacific Northwest?
Below are some diagrams of patterns associated with El Nino and La Nina (which, by the way, describes cooler than average SST in the tropical Pacific). With El Nino, the Pacific Northwest is often warm and dry, while California gets clobbered with big storms. Los Angeles had F2 tornados in 1983 and 1998, both strong El Ninos. Coincidence? I think NOT!
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| Climate Prediction Center |
Many people may welcome a warm and dry winter, but I certainly do not. I like my winters to be dark, rainy, stormy, and above all, snowy. However, even El Nino winters can feature snow, particularly weak ones. In fact, our snowiest winter ever occurred during an El Nino winter. December 1968 and January 1969 combined for an astonishing 67.5 inches of snow (thank you Scott Sistek for that statistic). Scott wrote an excellent blog on this; you can read it here.
We don’t have any snow data for the 1997-1998 winter, but the snowfall accumulation for 1982-1983? “Trace.” If we had a strong El Nino, I’d abandon all hope now, but history tells us that we aren’t completely out of the snow game yet. Not by a long shot.
Long range forecasts keep us warm and dry. The thing is, long range forecasts have always been keeping us warm and dry since El Nino started to appear, yet July, August, and September were all wetter than normal, primarily due to heavy precipitation events. As we all know, they were all much hotter than normal, making for a spectacular summer. I personally hope that we go the way of 1968-1969, and even if we can’t get 6 1/2 feet of snow in the lowlands, we can try and get a significant amount in the mountains for winter recreational activities and water storage purposes.
With a weak El Nino, you never know what can happen. 😉
Charlie