#9 Postby wxman57 » Sun Apr 25, 2004 8:04 am
Since 1995, the North Atlantic has been dominated, overwhelmingly, but a negative NAO. When this happens, the "normal" Greenland low is displaced southward and the Bermuda high is much weaker and farther to the east. This has the general effect of reducing both pressures and tradewinds in the deep tropics, making the area quite conducive to tropical development. But this pattern also leaves the North Atlantic open to storms recurving northward before they reach the U.S.
But over the past few years, we've seen some changes. The PDO (Pacific Decadal Oscillation), which has been in the warm/positive phase since 1976 may be making a reversal to the cool/negative phase that existed from 1946-1976. When the PDO goes negative, the ridge/trof relationship downstream is affected. I've noticed a general trend for that protective east U.S. coast trof to retrograde (move westward) over the past two seasons. Remember all thos major U.S. landfalls between 1946-1976? For much of this time, the Atlantic SSTs were above normal, giving hurricanes more energy to develop into major storms. When the Atlantic SSTs are above normal (as they'll quite possibly be for several more decades) and the PDO goes negative/cool, that's a very bad setup for the U.S.
That's why I say to ignore those numbers. Whether there are 7-8-9 or 14-15-16 named storms is not important. Sure, it's fun to try to guess, but it's the patterns that govern whether there will be more major hurricanes and whether the chance of landfall is increasing, not the total number of named storms. And I see the pattern slowly shifting to a very threatening one for the U.S. Florida, in particular, is at a very high risk of a major landfall this season, and that'll be the case for the next 20 years or more. I think Florida can expect a major hurricane every 2-3 years, instead of one (peninsula) every 38 years which they've just experienced.
Scary, isn't it?
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