Negative North Atlantic Oscillation causing wet June

[steven johnson]

So now we can blame the negative NAO rather than la nina or el nino for this month's weird weather.

Alaska's Mount Redoubt has been erupting since late March sending plumes of ash clouds soaring tens of thousands of feet into the air. The March 22 explosion was the largest eruption, launching ash some 65,000 feet high. The impact on the North Atlantic Oscillation from these massive eruptions can be extreme. 
The North Atlantic what?! The North Atlantic Oscillation, or NAO, refers to the system of high and low pressure systems between Iceland and the Azores. The former has a permanent low pressure  while the latter a permanent high pressure and they effect the strength of the winds which blow across Europe. The strength of the west winds determines the amount of moisture Europe receives, and to a lesser extent, North America. When there is a "positive" NAO, we can get warmer winters and when their is a "negative" NAO we get colder, earlier ones. 



Blame Sarah Palin for Northeast's Rain



The key to understanding the cause of the wet pattern over the Mid Atlantic is to look at the interaction between the developing El Ninoand the position of stratospheric temperature anomalies.  The stratospheric temperature anomalies have produced an environment the past twenty days that has produced a negative NAO and negative AO pattern.  The negative NAO pattern is key here as the higher pressures at 500 MB over northeast Canada and Greenland produces a blocking environment over North America.  As a result, instead of troughs simply lifting through the Northeast, the upper troughs and upper lows tend to stall over the Eastern Great Lakes.  As the upper lows and troughs begin to stall over the Great Lakes, the cold fronts drive towards the East coast, but lose support by the time they reach the forecast area.  




http://www.examiner.com/x-5587-NJ-Weather-Examiner~y2009m6d21-The-cause-behind-the-heavy-rainfall-over-the-Mid-Atlantic">The cause behind the heavy rainfall over the Mid Atlantic

NAO
The North Atlantic Oscillation Impact on Temperatures, Precipitation, Snowfall, and Snow Depth



http://www.cep.rutgers.edu/~oman/NAO.htm




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[Bankhead_ATL]

1. This will cause a cooold winter if this happens in Dec or Jan