On Sun, 19 Aug 2007 14:51:18 -0400, "Jonathan"
wrote:


"Adam Lea" wrote in message
...

"Jonathan" wrote in message
...





OK a few more moints:

Just out of interest, are you aware of the Atlantic Multidecadal Cycle?
This
is the 20-30 year oscillation in Atlantic ocean temperatures which is
closely linked with hurricane activity. That is, there are 20-30 year
periods of enhanced activity when the AMO is in its positive phase and
20-30
years of reduced activity when the AMO is in its negative phase. The AMO
changed sign in 1995 so we will expect enhanced hurricane activity to
continue through to at least 2015, with or without global warming.



That's correct, but enhanced in terms of numbers of storms. My point
is that during this period they are larger and stronger due to
global warming, not more numerous. Katrina and Wilma were
the most powerful hurricanes, in terms of combined size and
strength, ever witnessed on this half of the planet. And Dean is
currently a borderline 5 that as we speak is increasing in size
and could/should become another Katrina.

So it's ok to use local weather events as proof of AGW? What was the
intensity the of hurricanes during the period between 1000 and 1500
AD? How about 500 BC to the birth of Christ? How about 125,000 years
ago when temperatures and ocean levels were higher than today?





The destructive 2004 and 2005 hurricane seasons were together a freak
event.
Historical records back to 1900 show that there has been only one instance
of four intense hurricane landfalls in the Gulf in consecutive years
(1915/16). Fitting a Poisson distribution to the historical data suggests
that probability of this happening is about 1 in 200.

Yet Jamaica is about to get hit by a very intense hurricane in about
10 hours from now. Sooner of later enough flukes add up to a trend.

Like I said, we're in the middle of establishing a new trend.
Dean is currenty 10 knots short of a category 5, but with it's 18 knot
forward motion the northern half of the storm, which will be hitting
the southern coast of Jamaica, is essentially a category 5.


Similarily for intense
Gulf hurricanes in one year the chance of another season like 2005 (five
intense Gulf hurricanes) is about 1 in 1000. In fact, even if the mean
number of Gulf hurricanes were to double due to global warming, the chance
of another year like 2005 would still only be about 1 in 200. Thus a
knee-jerk reaction to the losses of 2004/5 should be avoided.


If 2007 is another 04/05? For Jamaica this is probably going to be
a once in a century storm.




The reason that the 2004/5 hurricane seasons were so destructive was that
the high at sea activity combined with favourable steering currents which
steered the storns towards the US mainland instead of recurving them back
out to sea.


That's the reason there were so many storms, not the reason
Katrina and Wilma were so large. Both of those storms went
over my house, and they were unique in size over typical hurricanes
by an order of magnitude or more. A category 5 with an eye
about 20 miles across, such as Andrew, is how much less
total energy than a category 5 with a ...hundred mile eye?
I think one is the square of the other. Two different classes
of storms imho.

The eye wall of Andrew went past my house 25 miles away
at category 5 strength. Wilma missed by 15 miles at
category 2 strength. There was no comparison between
the two storms at all, Wilma was a goliath that, had it
been 20 knots stronger, would have rivaled Katrina in
property destruction.



Prior to 2004 the US has been very lucky as the number of major
hurricane landfalls has been unusually low relative to the total activity.
This is due to the presence of a upper level trough off the east coast
which
steered the storms away from the mainland. You can go back to previous
active phases of the AMO and find destructive hurricane seasons as well
(1893, 7 hurricane landfalls, 1926, Great Miami hurricane, 1950, 3 major
hurricane landfalls, 1969, hurricane Camille, strongest landfalling
hurricane ever).


None of them were the combined strength and size of Katrina
and Wilma, not even Camille.




Finally, seaonal hurricane forecasters were predicting high activity to
high
probability for 2004 and 2005 many months in advance. Had insurers acted
on
these forecasts then they would have reduced their losses.


Well they're acting on them now. What has changed to make that happen?




Adam




--
The object of life is not to be on the side of the majority but to
escape finding oneself in the ranks of the insane. -- Marcus Aurelius

Wherever I go it will be well with me, for it was well with me here, not
on account of the place, but of my judgments which I shall carry away
with me, for no one can deprive me of these; on the contrary, they alone
are my property, and cannot be taken away, and to possess them suffices
me wherever I am or whatever I do. -- EPICTETUS

Joseph R. Darancette