North atlantic ossilation
From Wikireedia
Positive NAO Index
- The Positive NAO index phase shows a stronger than usual subtropical high pressure center and a deeper than normal Icelandic low.
- The increased pressure difference results in more and stronger winter storms crossing the Atlantic Ocean on a more northerly track.
- This results in warm and wet winters in Europe and in cold and dry winters in northern Canada and Greenland
- The eastern US experiences mild and wet winter conditions
Negative NAO Index
- The negative NAO index phase shows a weak subtropical high and a weak Icelandic low.
- The reduced pressure gradient results in fewer and weaker winter storms crossing on a more west-east pathway.
- They bring moist air into the Mediterranean and cold air to northern Europe
- The US east coast experiences more cold air outbreaks and hence snowy weather conditions.
- Greenland, however, will have milder winter temperatures