Hurricane Forecast

Aug 9, 2007 11:30am

Don’t be lulled, says NOAA.  This morning it updated its hurricane outlook for this year, and basically stuck to its guns, giving much the same numbers it had in May. The summary is HERE.  It predicts:  –13-16 named storms (down from 13-17)
–7-9 of those are likely to be hurricanes, with winds over 75 miles an hour (the May number was 7-10)
–3-5 "major" hurricanes–Category 3 or higher on the Saffir-Simpson Scale, with winds over 110 miles an hour. Gerry Bell, the lead hurricane forecaster at NOAA’s Climate Prediction Center, cites three reasons to believe the season is still likely to be an active one: –Since 1995 we’ve been in the active part of the "Multi-Decadal Cycle" that typically lasts 25-40 years.  During these periods, winds and temperatures favor storm formation.  Since 1995, 9 of 12 hurricane seasons have been above average.
–The tropical Atlantic and Caribbean are both warmer than normal, providing fuel for storms.
–There appears to be a decent chance that a La Nina will form in the Pacific.  You’ll recall that a La Nina–the opposite of an El Nino–is a giant stripe of cooler-than-average water along the equator in the Pacific.  It tends to rearrange the jet streams blowing over it.  An El Nino tends to steer the jet streams southward as they reach the Atlantic–shearing the tops off of some hurricanes that would otherwise hit the U.S. coast.  In the case of a La Nina, no such luck. "This combination is known to produce very active seasons," said Bell in a teleconference a little while ago. How can this be, when the season’s been so quiet so far?  One graph that’s useful is HERE, showing that early storms–June to mid-August–are really very rare.  There have been three named storms in the Atlantic so far this year; NOAA says there are typically two.  The peak of the season is still a month away, in mid-September.  Bell cautions that all they’re offering is a forecast of prevailing conditions for this year, and giving the number of storms that tend to form in similar years.  They cannot say when or where specific storms might yet be, though Bell says that in years that looked like this one, there have, on average, been 2-4 storms that made landfall in the U.S.
======================== Added Note: To Wes, Chuck, Andy, and all others who may pass this way–it’s great to hear your voices…or see your posts…or whatever.

Wes and Chuck asked for more about the Atlantic Multidecadal Oscillation, which seems to be a major factor in the number of hurricanes each year, and I’m happy to oblige.  NOAA’s Atlantic Oceanographic and Meteorological Laboratory has done a helpful Q&A on it, which you can find HERE.

Nobody can say how long the "warm" phase of the cycle lasts; the best estimate is 25-40 years, which means that if the current phase began in 1995, it has another 15-30 years to go.  The last "cold period," when there were consistently fewer hurricanes, seems to have run through the 1970s and 80s, though it was only in the 1990s that meteorologists really caught on to it. 

Andy, I’m not in the least worried about hurricanes.  I’m totally freaked out about those colliding galaxies. 

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