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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Long-Lasting La Niña Poised to Control Weather

Earlier this month the Climate Prediction Center (CPC) announced that we officially moved into a La Niña pattern, and recent images from NASA's Jason-2 oceanography satellite verify. The opposite of El Niño, La Niña is the cooling of the equatorial Pacific Ocean.

Both El Niño and La Niña play a major role in global weather. During a La Niña, trade winds in the western equatorial Pacific Ocean are stronger than normal, and the cold water that normally exists along the coast of South America extends to the central regions. La Niñas are associated with less moisture in the air, resulting in less rain along the coasts of North and South America. They also tend to increase the formation of tropical storms in the Atlantic.

So what exactly does that mean for the United States? What impact can we expect?

• An increase in the number of tropical storms as a result of La Niña boosts the chances that a storm (or hurricane) will enter the Gulf of Mexico, home to about 30 percent of U.S. oil and 12 percent of U.S. natural gas production, as well as the anomaly of an oil slick this year.
  
  
• La Niña's cooling pattern often brings dryer, warmer weather to the southern half of the United States, thus increasing the wildfire threat in Florida and California.
  
  
• During La Niña, the northern third of the United States often has colder winters.
  
  
• Increased rainfall in the Pacific Northwest is also common during La Niña.
  

Experts expect the central equatorial Pacific Ocean to stay colder than normal throughout the summer and beyond, so the risk for long-lasting La Niña-type weather conditions to affect North America in coming months is quite likely.

Looks like next winter could be VERY different from last, which was largely controlled by El Niño!

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!

Weakening El Niño's Last Punch

Recent ocean satellite imagery continues to indicate a weakening El Niño, but one last punch by the warm Pacific-driven weather phenomenon is likely to impact our weather in coming weeks and months.

According to sea-level height and temperature data, another strong, eastward-moving wave of warm water, known as a Kelvin wave, is heading towards the United States west coast.

Now in the central and eastern equatorial Pacific, this Kelvin wave is not expected to impact global weather events as the full-fledged El Niño has for the better part of the past year, but this could be the last hurrah before El Niño's dry sibling, La Niña, takes over.

January 2010 Was Warmest Month In 32 Years

On its path to breaking records set 32 years ago, January 2010 was recorded as the warmest month across the globe since 1978... and it's being attributed to the strong El Niño climate pattern we are currently experiencing.

In a USA Today article published on Friday, it states that according to climatologists, the Earth was about 1.3 degrees above average last month. Sounds a bit skeptical to those of us in the United States and Europe that have been experiencing winter weather extremes in the form of record breaking low temperatures and snowfall. But our weather conditions are only a very small fraction of Earth's overall dynamic atmospheric environment.

The main heat in January is said to have come from the subtropical areas, especially from the Sahara through Arabia and South Asia.

Meanwhile in the United States, nearly three quarters of the nation is snow covered and for the first time in 14 years, Lake Erie, with an average depth of 62 feet, completely froze over!

And these crazy extremes are why we love weather!

Nor'easters: Winters Most Ferocious Storms!

Time for a Meteorology Lesson

Everyone has been asking why there has been so much snow! What is causing this crazy, abnormal winter pattern? No matter what the cause is, which is likely ‘attributable’ to El Niño, atmospheric conditions this winter have been absolutely perfect for Nor'easters to form.

But what is a Nor'easter? The term has been thrown around in the news more times this winter than in the past decade, but what is it? For those inquiring minds, here's some insight.

A Nor'easter is a large-scale cyclonic storm with extremely deep low pressure that forms along the east coast of the United States. Conditions need to come together perfectly for a Nor’easter to form, and that is usually when the very cold Labrador current meets the warm Gulf Stream current (see image 1). Typically this will take place between 50 and 250 miles off the southeast United States. At the same this is occurring there needs to be a steady flow of arctic air from the north. The friction that occurs from the cold air to the north moving across the North American continent, and the warm air being pulled up from the Atlantic, causes the developing low pressure to begin to spin and move northeastward along the jet stream (see image 2). As it does so a Nor’easter is born and its tight rotating center of circulation will cause fierce winds from the northeast to affect any land in its path. Coastal areas are often battered by high seas and coastal erosion, and just inland you’ll find crippling snowfall amounts, deadly wind chills, damaging winds and torrential rains.

In addition to the impending blizzard tonight into tomorrow, recent memorable Nor'easters are the DelMarVa Blizzard of February 2010, the December 19 Blizzard of 2009, the Blizzard of 2006 (absolutely epic for NYC, three feet of snow in three hours / total snowfall near 30 inches in less than 24 hours), the Blizzard of 2003 (also known as the President's Day Storm II), and let's not forget a very, special Nor'easter that occurred in the off-season this past Autumn: Nor'Ida! Nor'Ida developed from the remnants of Hurricane Ida which after crossing the Gulf Coast, rode up the Atlantic seaboard, causing extremely heavy rain, coastal destruction and damaging winds! In New Jersey alone Nor'Ida caused coastal flood damage that left $168 million in losses.