Sunday, September 30, 2007

[Jyo_hurricane] The Tropical Remains of the Day: October 1, Update A

TD Karen has been downgraded to a low with no more NHC advisories. TS
Melissa is a TD but is so weak that the NHC has also stopped advisories.
There is still some circulation with both systems, so I will check up on
them once in a while, but this is my last entry on both.

The wind shear was really strong - too much for them to cope with. I'm
sure you've been on the edge of your seats wondering what I wanted to say
about wind shear... so here you go...

Maybe you have heard that in an El Nino year we have fewer Atlantic storms
because the wind shear is strong, and conversely, in a La Nina year we
have more storms because the wind shear is weak? An El Nino year is when
the waters in the central/eastern Pacific are warmer than usual, with
associated changes in the overlying atmosphere. A La Nina is when the
waters are colder than usual. The temperature change usually peaks in the
winter months.

I do not agree that there is such a strong connection between El Nino/La
Nina and the hurricane season - there is *some* connection, but not as
much as some folks would like everyone to believe.

Last year the much-vaunted justification for an "unexpectedly" quiet
season was because of a surpise El Nino that resulted in a strong wind
shear, which supressed the storms. That (in my humble opinion) is
incorrect (and hence not unexpected). The 2006 season was weak for a
number of other reasons.

This year, we heard that the season would be strong partly because of a La
Nina that would result in weaker wind shear. I agree with one part of
this. We are, indeed, in a La Nina. You can check the temperatures in the
Pacific at any time by going to
you click on the figure with the colorful panels, the map will get big
enough to see the details. At the moment, temperatures are -2.5 deg C
below the average in the Pacific - most definitely a La Nina.

So the slight flaw in the wind shear argument is that we are in a La Nina
and the wind shear is pretty strong.

Clearly, there are still a "couple of things" we need to work out about
hurricanes and our present-day climate in general. But for now, it's time
for a glass of wine. Priorities you know. ;)

If you have any questions, about this or some other aspect of hurricanes,
please don't hesitate to ask.

So, until there's something else out there... or it's the last day of the
season - whatever comes first, ciao,

Blogs archived at:
These remarks are just what I think/see regarding tropical storms - not
the opinion of any organization I represent. If you are making an
evacuation decision, please heed your local emergency management and the
National Hurricane Center's official forecast and the National Weather
Service announcements. This is not an official forecast. If I "run away,
run away" (Monty Python), I'll let you know.

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