NAO Most Negative since last Summer-Maybe a Record for June
By Ralph Fato on June 5, 2012, 3:59pm
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If you're wondering why we have been cooler than normal in the northeast, thank the NAO being in the negative phase.
The NAO (North American Oscillation) is a higher pressure near Iceland or Greenland that causes a buckle in the jet stream, forcing it around the high pressure ridge. That in turn forces the cold air southward into U.S instead of Eastward in Canada. I usually say it's “cold air bleeding south”.
Many times it’s just a “tongue” of cold air, other times it’s a large area trough.
Another term for Negative NAO is “Greenland Block.” This blocking can shift East or West and weaken and strengthen.
Lets go through some data...