US researchers have discovered a link between Atlantic hurricane
activity and thick clouds of dust that periodically rise up from the
Sahara Desert.

At times of intense hurricane activity, dust clouds were scarce, but in
years with stronger dust storms, fewer hurricanes swept across the
Atlantic.

More at http://news.bbc.co.uk/1/hi/sci/tech/6038296.stm

natures cloud seeding???


wrote in message
ups.com...
US researchers have discovered a link between Atlantic hurricane
activity and thick clouds of dust that periodically rise up from the
Sahara Desert.

At times of intense hurricane activity, dust clouds were scarce, but in
years with stronger dust storms, fewer hurricanes swept across the
Atlantic.

More at http://news.bbc.co.uk/1/hi/sci/tech/6038296.stm

wrote in message
ups.com...
| US researchers have discovered a link between Atlantic hurricane
| activity and thick clouds of dust that periodically rise up from the
| Sahara Desert.
|
| At times of intense hurricane activity, dust clouds were scarce, but in
| years with stronger dust storms, fewer hurricanes swept across the
| Atlantic.
|
| More at http://news.bbc.co.uk/1/hi/sci/tech/6038296.stm
|

And this is exactly what happened this year. According to the "blogs" on
WeatherUnderground from earlier in the Summer, clouds of Sahara dust blown
out into the Atlantic interfered with the development of tropical waves
leaving Africa and were partly responsible for the hurricane season being
below the originally predicted intensity. The dust reduces the heating of
the sea surface and also interferes with the temperature structure of the
atmosphere.

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. Most of the significant storms formed in a
period of a few weeks when windshear was less than normal for this summer.
The circulation pattern which produced this shear also helped those storms
which did develop to recurve out into the Atlantic before the reached the
continental USA.
--
- Yokel -
oo oo
OOO OOO
OO 0 OO
) ( I ) (
) ( /\ ) (

"Yokel" now posts via a spam-trap account.
Replace my alias with stevejudd to reply.

"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.

Adam

"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.

Adam

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.

--
Graham Davis
Bracknell

"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.

Adam Lea wrote:


"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.

I've been having another think about this. What I've seen this season with
the development - or non-development - of tropical storms in the Atlantic
and East Pacific seems typical of an El Nino year. East Pacific storms have
been moving eastwards towards the USA and Atlantic storms have been
diverted away from the Caribbean and East Coast of the US. Any Atlantic
tropical depression, if it hasn't been pushed N then NE, has been destroyed
by SW shear.

A difference I've seen between this year and last is that last year the
development of storms and hurricanes occurred in the west of the area
you've looked at for shear and some formed in the Caribbean, which is not
in your area. This year, most if not all development has been in the east
of the area. Although shear in your area may be lower overall than usual,
in the important part of that area, and to the west of it, where sea
temperatures are highest, I suspect that shear has been higher than usual.

One small depression just east of the Caribbean at the moment is moving
north and being demolished by strong SW upper winds. Actually, if
90L.Invest is included, it makes two being destroyed, as the one I was
watching is to the SE of 90L.Invest.

--
Graham Davis
Bracknell