"Graham P Davis" wrote in message
...
Adam Lea wrote:


"Yokel" wrote in message
...
Another major reason for the low hurricane activity was higher wind
shear
this season, which disrupted many of the storms before they had a chance
to
become full-blown hurricanes.

This isn't true. I have looked at the average August-September 200-850mb
wind shear over the Atlantic main development region (10-20N, 20-60W) and
it is actually below average this year. If you look at the tropical
cyclone formation probability throughout this summer:

http://rammb.cira.colostate.edu/proj...ent/tatfpr.gif

you will notice that it has been well above climatology virtually all
summer and is similar to 2005 and 2004. August-September Atlantic sea
surface temperatures have been warmer than average and trade winds have
been weaker than normal and together have been consistent with seasons
with twice as much activity as this year. I have also looked at mid level
relative humidity and that has been slightly unfavourable this summer but
was similar to 2005 and 2004. Overall it seems the reason why the
activity
this year has been supressed is a mystery.


That's odd. Hurricane activity this year was expected to be reduced by El
Nino. Part of the reasoning behind this was an associated increase in
shear. However, another El Nino effect, the eastward displacement of
hurricane tracks, has occurred.


Yep - it's odd. In other El Nino years the low level trade winds are
stronger than normal which is correlated with reduced cyclonic vorticity
over the tropical atlantic and thus reduced hurricane activity. That is not
the case this year.