Winter 2010 Rewind: El Niño, NAO Convergence

This past winter was for many, absolutely epic! The rarest of events for big east coast cities unfolded between December and March, blanketing locations from Washington, DC to New York with record snowfall in the form of fierce blizzards and historic nor'easters.

As winter 2010 concluded I conducted two interviews with seasoned meteorologists having expertise in not only northeastern United States weather, but with nor'easters such as those that plowed through in months prior. In both my interviews with winter weather authority, Paul Kocin; and chief forecaster for AccuWeather, Elliot Abrams; the anomalies of two unique weather patterns converging was mentioned as the likely cause of that winter's wrath. Those anomalies were El Niño, the cyclic warming of the tropical Pacific, and the strong negative phase in a pressure cycle called the North Atlantic Oscillation (NAO).

Well alas... this week a new study appearing in the journal, Geophysical Research Letters, states that these two weather patterns did indeed converge along the east coast and are both responsible for the historic winter that unfolded. The study was conducted by a team of scientists at Columbia University's Lamont-Doherty Earth Observatory who analyzed 60 years of snowfall measurements to conclude that the negative NAO this particular winter made the air colder over the eastern United States, causing more precipitation to fall as snow. El Niño brought even more precipitation to the area, which when interacting with the NAO's presence, led to even more snow.

The last time the NAO experienced a strong negative phase was in the winter of 1995-1996. During that winter the east coast was also hammered with above average snowfall. This winter, the NAO was even more negative – a state that happens less than 1 percent of the time.

It is important to note, however, that while the heavy snow on the east coast dominated headlines this winter, the Great Lakes and western Canada (remember this?) actually saw less snow than usual – typical for an El Niño year. The arctic also experienced warmer weather than usual.

Finally, I'd like to once again showcase this radar rewind, courtesy of AccuWeather.com. You will see 22 major storms that doused the northeast in a four month radar animation from December 1 through March 30. AMAZING!

* Note: This video is best viewed in Firefox, Chrome, Safari or any web browser other than Explorer (go figure) and it's totally worth launching those browsers if you have one of them, because this is just awesomeness!



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A Future of Harsh Winters Could Rule Mid-Lats

Despite global warming and climate change, recent statements by NOAA's Pacific Marine Environmental Laboratory (PMEL) point towards a future of more cold and snowy winters (in other words, the potential for patterns to evolve similar to that of this past winter) for Europe, eastern Asia and eastern North America.

Why the claim? El Niño and the North Atlantic Oscillation (NAO) aside, the exceptional cold and snowy winter of this past year in the above-mentioned regions, is connected to unique physical processes in the Arctic. The Arctic is warming more than twice as fast as the rest of the planet. This is known as Arctic amplification, and these changes are happening a great deal faster than the scientific community expected.

It seems a warmer Arctic climate and a loss of sea ice is influencing the air pressure at the North Pole and shifting wind patterns, allowing for the disruption of the memory and stability of the Arctic climate system. This will be an important driver of major change in the world's climate system in the years to come and will likely be seen first across the mid-latitudes.

Experts say that given the recent reduction of the area of multi-year sea ice and reduced ice thickness, it is unlikely that the Arctic can return to its previous condition.

El Niño, NAO Fade Fast... So What's Next?

Two Major Weather Phenomenon Losing Presence as Climate Variability Now Rules

For the past year we've blamed any and every weather extreme on El Niño and its interaction with the North Atlantic Oscillation (NAO). Wait, the NAO? Look, I'm not just talking to myself again. The NAO was really present this past winter and it, along with the famous El Niño warm-water effect in the Pacific Ocean, sent moisture-soaked air up from the Gulf of Mexico as a linebacker high pressure block kept the jet stream on a steady ride up the East Coast, therefore forcing Arctic air deep into the South and throwing a plume of wintry precipitation along the I-95 corridor.

The result: record-breaking cold east of the Mississippi, powerful and damaging tornadoes in the southern plains, dozens of snowstorms and even several epic blizzards across the Mid-Atlantic and Northeast, and historic flooding in the Ohio Valley.

But what about this past weekend's torrent in Tennessee, which caused the city of Nashville to become water-logged, causing the famous Grand Ole Opry to flood? Well, climatologists say that El Niño has weakened so much already that it likely had very little impact on the event, and the NAO has pretty much spun itself out by now. That said, our weather pattern is now largely going to be affected by climate variability, or pretty much whatever happens, happens.

Ever-changing and unpredictable! This blog post has been brought to you by reason # 198,765,499,876,534 why I love weather! Enjoy it, it's the only weather you've got!