[Hurricane John of 2006 about to strike Baja California.] NASA has a new analysis of why the 2006 hurricane season in the Atlantic was much tamer than expected by seasonal forecasters. Interestingly, some of what the agency says contradicts what I've been hearing from other sources. Notably:
1. NASA says that El Nino quashed Atlantic storms in two ways: "a sinking motion in the middle and upper atmosphere and increased wind shear in the Caribbean." By contrast, earlier this week in a talk at the AMS meeting in San Antonio, National Hurricane Center forecaster James L. Franklin said that El Nino had indeed been associated with sinking motions and drier, more stable air, but not with wind shear. "Basically, we think it was the thermodynamics, rather than the kinematics," he said according to my notes. 2. NASA says that the 2006 Atlantic sea surface temperatures were significantly cooler than they were in 2005, by as much as 2 degrees (I'm assuming Fahrenheit). But yet again, Franklin in his talk said he didn't think that cooler sea temperatures could explain why 2006 was so much less active than 2005.
I don't know what to make of these discrepancies. Maybe we just don't know what the real causes for the less active 2006 season were. There is at least one reason for distrusting NASA, though. The NASA analysis repeatedly claims that there were 25 storms (like John, pictured above) in the Northeast Pacific, which saw a much more active season than the Atlantic in 2006. But no matter how you count those Northeast Pacific storms, I only get 21 at max, and it seems like a more reasonable number is 18, which is the number of storms that actually received names. So NASA seems way off in this respect.
