wacky weather pattern? please tell me the "normal" weather pattern?
A normal pattern is that hurricanes recurve eastward after they move north, instead of moving hard west like Sandy. This was due to the high pressure dome over Greenland, which extended far enough south to force Sandy westward.
This is called the "Greenland High" or "Greenland Block", and is associated with a negative phase of the Arctic Oscillation. For the previous 40 years or so, we've been mostly in a positive phase. No Greenland Block, so hurricanes curved back out to sea. The last couple years have switched mainly to a negative Arctic Oscillation.
Why? Good question. Some theories state that the loss of sea ice creates conditions favoring a negative phase. Or perhaps it's entirely natural. Too soon to tell there, but it definitely needs more investigation. An interesting thing is that while the Greenland Block is roasting the arctic, it will often be funneling arctic air down the sides into the USA and Europe.
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