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Livestock Wx for 11-29-18: Quasi-Biennial Oscillation – What the Heck Is That?
This article was adapted from an article written by John Feldt at Blue Water Outlook. For any questions about the article you can contact John at: [email protected].
The Quasi-Biennial Oscillation, or QBO for people who don’t like 10 syllable terms, is a variation of winds that flow high above the equator. Strong winds in the stratosphere travel in a belt around the planet, reversing direction from time to time. At a given altitude, the winds might start as westerlies, but over time they weaken and eventually reverse, becoming strong easterlies.
Looking at different heights, the band of westerly winds migrates slowly downward. When these winds approach the base of the stratosphere, they dissipate and are replaced with new bands of easterly winds.
The whole cycle progresses at a fairly (but not entirely) uniform rate, taking on average 26 months to return to the starting state.
A Predictor of Winter Temperature?
The jet stream is an important atmospheric feature that brings us our weather including the prospects of winter storms and changes in temperature. The QBO can influence the position of the Atlantic jet stream along with the speed and strength of the jet stream winds.
Easterly/Negative QBO – There is a strong connection between a weak El Niño (or neutral pattern with no El Niño or La Niña) and an east-based QBO with unusually cold U.S. winters. When the QBO is easterly/negative, the polar jet stream is weak which allows unusually cold weather to drop across the central and eastern U.S.
Westerly/Positive QBO – When the QBO is westerly/positive, the polar jet stream is strong and can bring more frequent winter storms and heavy precipitation.
Also, a moderate or strong El Niño tends to dominate the atmosphere more and can negate the influence from the QBO.
Heading into the fall, the QBO was significantly negative, near record levels, leading some to predict a colder-than-normal winter over the central and eastern U.S. The QBO levers, however, have changed over the past few months. The QBO level now is only slightly negative (-2.79).
Considering we are only at the 17-month time point for this easterly/negative cycle, it’s likely that a negative QBO, to some degree, will persist through the winter. The images below show the relationship between a negative QBO and winter temperatures different from the average. As you can see, when the QBO is moderately negative the Southern Plains can get colder than average temperatures. When it is highly negative (which is what it was looking like) it doesn’t seem to have the same influence and could even bring warmer than average winter temperatures.
What will likely happen this winter is that we will have a weak-to-moderate negative QBO along with a borderline-moderate El Niño. This combination could lead towards continued occasional intrusions of unusually cold air across the upper Midwest, Great Lakes, and Northeast U.S. However, odds for this occurrence are not as high as indicated just a few months ago (due to the weakening QBO intensity).
Furthermore, if the El Niño strengthens more than anticipated, it could negate any significant QBO influences.
Now that you know all about QBO next time you’re sitting around talking about the weather just throw out there…”so, how about that Quasi-Biennial Oscillation”.