New tropical depression could form off the coast of Africa

By: Dr. Jeff Masters , 1:12 PM GMT on September 25, 2009

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A tropical wave (99L) is located near 15N, 30W, about 300 miles west of the Cape Verdes Islands. This wave has seen an increase in heavy thunderstorm activity this morning, and low-level spiral bands have formed. The system can already be classified as a tropical depression using the satellite-based Dvorak technique. This morning's QuickSCAT pass showed a loose but closed circulation, with top winds of 30 mph in the heaviest thunderstorms. Wind shear is moderate, about 10 - 20 knots. There is a modest amount of dry air to 99L's west that does not appear to be interfering with the storm's organization.


Figure 1. Morning visible satellite image of Invest 99L (left side of image) and a new tropical wave moving off the coast of Africa.

As 99L moves west-northwest over the next two days, sea surface temperatures will cool by 1°C and winds shear will remain in the moderate range. Some dry air may also affect the storm. These conditions give 99L a good chance of forming into a tropical depression, and NHC has given the system a moderate (30 - 50%) chance of developing into a tropical depression by Sunday. By Monday, wind shear will increase to the high range, 20 - 30 knots, and 99L will probably weaken or be torn apart. None of the computer models forecast development of 99L or any other system in the Atlantic over the next seven days.

A new tropical wave with plenty of heavy thunderstorm activity and some spin is moving off the coast of Africa today. This wave is under a moderate amount of wind shear, 10 - 20 knots, and has some potential for development this week as it moves west or west-northwest past the Cape Verdes Islands.

The latest wind shear forecasts from our major computer models show high values of wind shear affecting most of the tropical Atlantic for the next ten days. This is typical for an El Niño year, and it will be difficult for any storms to get to hurricane strength over the next ten days because of the high shear. The latest 16-day GFS forecast predicts wind shear will decline some by the 2nd week of October, though.


Figure 2. Wind shear forecast for Thursday, October 2 at 00 UTC made by last night's 00Z run of the GFS model. Wind shear is expected to be high over most of the tropical Atlantic for the next ten days, including the Caribbean. Wind shear values below 8 m/s (about 15 knots, red colors), are typically needed to support tropical storm formation.

Jeff Masters

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Quoting yonzabam:


Firstly, I'm not sure if soot is classed as aerosol, I believe it's classed as 'particulate', and although carbon on snow will absorb heat and promote melting, carbon in the air will probably have a cooling effect by blocking sunlight. This is called 'global dimming' and is believed by some scientists to have been offsetting the warming trend and may explain why global increases in temperature did not begin until the late 70s despite increased atmospheric CO2, when clean air laws were introduced in North America and Europe.

An important aerosol produced by coal burning is sulfur dioxide. This causes cooling by reflecting sunlight back into space and also by acting as a condesation nucleus for water vapour, thus speeding up cloud formation and contributing to global dimming. Soot particles also do this.

It's all very complicated stuff and scientists have a very poor understanding of many of the physical processes. aircraft get a bad rep for their contribution to atmospheric CO2, but when aircraft were grounded in the US after 9/11, there was an increase in temperature in the US due to the lack of contrails reflecting back sunlight. So you could argue that aircraft are actually beneficial.

Anything particulate that is carried long distances by the air is an aerosol.

And you are thinking of Sulfate aerosols, which are the ones related to the global dimming, solar reflection phenomenon.
Black carbon aerosols are known to negatively effect cloud coverage when in the atmosphere and then (obviously) aid in the absorption of sunlight once on the formerly white surface.

Not sure about the data behind this plot, so take a large grain of salt with it. But, think industrial output combined with environmental regulation around the world over these years. Makes sense to me.

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Quoting OSUWXGUY:


Just a small point. Carbon based particulates are usually dark (black) in color and do more absorption than reflection warming the layer of the atmosphere they're in.

Sulfates from fossil fuel burning are generally light (white) colored and reflect and have a net cooling effect.

A lot of research continues to be done with satellites and ground based observation to understand the net overall effect.



True what you say about carbon particulates. They absorb sunlight and then act as microscopic airborne storage heaters, reradiating infrared. However, the fact that they prevent sunlight reaching the ground is (I think) believed to be their major influence and this is a cooling one.
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looks like we may have a tropical depression later today if trends continue
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Atlantic Tropical Weather Outlook
--------------------------------------------------------------------------------


000
ABNT20 KNHC 251730
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT FRI SEP 25 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWER ACTIVITY ASSOCIATED WITH A TROPICAL WAVE LOCATED ABOUT
400 MILES WEST OF THE CAPE VERDE ISLANDS HAS CONTINUED TO BECOME
BETTER ORGANIZED. A TROPICAL DEPRESSION COULD FORM IN THIS AREA
DURING THE NEXT 24 HOURS BEFORE UPPER-LEVEL WINDS BECOME LESS
CONDUCIVE. THERE IS A HIGH CHANCE...GREATER THAN 50 PERCENT...OF
THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN




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Quoting yonzabam:


Firstly, I'm not sure if soot is classed as aerosol, I believe it's classed as 'particulate', and although carbon on snow will absorb heat and promote melting, carbon in the air will probably have a cooling effect by blocking sunlight. This is called 'global dimming' and is believed by some scientists to have been offsetting the warming trend and may explain why global increases in temperature did not begin until the late 70s despite increased atmospheric CO2, when clean air laws were introduced in North America and Europe.

An important aerosol produced by coal burning is sulfur dioxide. This causes cooling by reflecting sunlight back into space and also by acting as a condesation nucleus for water vapour, thus speeding up cloud formation and contributing to global dimming. Soot particles also do this.

It's all very complicated stuff and scientists have a very poor understanding of many of the physical processes. aircraft get a bad rep for their contribution to atmospheric CO2, but when aircraft were grounded in the US after 9/11, there was an increase in temperature in the US due to the lack of contrails reflecting back sunlight. So you could argue that aircraft are actually beneficial.


Just a small point. Carbon based particulates are usually dark (black) in color and do more absorption than reflection warming the layer of the atmosphere they're in.

Sulfates from fossil fuel burning are generally light (white) colored and reflect and have a net cooling effect.

A lot of research continues to be done with satellites and ground based observation to understand the net overall effect.

Member Since: Posts: Comments:
114. IKE
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
200 PM EDT FRI SEP 25 2009

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

SHOWER ACTIVITY ASSOCIATED WITH A TROPICAL WAVE LOCATED ABOUT
400 MILES WEST OF THE CAPE VERDE ISLANDS HAS CONTINUED TO BECOME
BETTER ORGANIZED. A TROPICAL DEPRESSION COULD FORM IN THIS AREA
DURING THE NEXT 24 HOURS BEFORE UPPER-LEVEL WINDS BECOME LESS
CONDUCIVE. THERE IS A HIGH CHANCE...GREATER THAN 50 PERCENT...OF
THIS SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS.


ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN


Now back to the dreaded Global Warming discussion.
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WOW 56 degrees for Tallahassee on Tuesday!!!
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What is important to see in these graphs is that there was a natural cooling cycle as we go into another glacial period over the last 2000 years (we've been in an interglacial period), but that this has been superceded by warming in the last 200 years or so,

That warming is man-made and is very rapid in millenium terms.

These graphs confirm the original "hockey stick" scenario,
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Quoting atmoaggie:

I appreciate you bringing that up. I posted before about that one:

"This paper uses observations from ice cores and tree rings"
Besides the huge caveats in tree rings for temperatures...

The plot in the paper looks like our friend, the hockey stick, but maybe there is some truth to it.


It sure is pretty, and annotated with blue for the proxy study and (shocker) red for recent measurements (from the satellites starting before 1979?!?! No. It is from all of the many long term surface stations in the Arctic). (Note, if you find a version without the red, the blue only shows warming from ~1945 to ~1970)

Odd jump starting before 1950?

Rather disappointed that aerosol deposition isn't addressed as a potential primary contributor to the signal by the scientists I see writing about this article. Politicians and those with a lot to gain by blindly attributing the entire thing, if accurate, to CO2 makes sense, but not one scientist that I have seen in the blogosphere seems willing to ask how much of this signal is related to aerosol deposition, lowering albedo, earlier melt, lowering albedo again for large areas.

Back to the jump before/around 1950...anyone want to bet that if we had aerosol-measuring satellites back before, during, and after WWII that soot suddenly appeared in the Arctic in substantial quantities about the same time as that temp increase? And stayed high?

Only in the last few years did we have new research, admittedly based mostly on model simulations, that concluded that fully half of the warming measured by our satellites in the last 30 years was due to soot deposition and possibly more.
Now forgotten, apparently...

Plus, the largest changes in any given year in melt/freeze rate relative to the available satellite mean extent are in the spring and fall. Why?
Correct, the sun is present in the Arctic.

Lots of good pics/links/discussion here: http://www.scientificblogging.com/the_soot_files/soot_black_icebergs_and_arctic_ice
I'll wager that if we went after the low hanging fruit, soot emissions, we would be a large step closer to being able to correctly attribute changes in the Arctic.

Now if we could stop melting Kilimanjaro's glacier. ;-)


Firstly, I'm not sure if soot is classed as aerosol, I believe it's classed as 'particulate', and although carbon on snow will absorb heat and promote melting, carbon in the air will probably have a cooling effect by blocking sunlight. This is called 'global dimming' and is believed by some scientists to have been offsetting the warming trend and may explain why global increases in temperature did not begin until the late 70s despite increased atmospheric CO2, when clean air laws were introduced in North America and Europe.

An important aerosol produced by coal burning is sulfur dioxide. This causes cooling by reflecting sunlight back into space and also by acting as a condesation nucleus for water vapour, thus speeding up cloud formation and contributing to global dimming. Soot particles also do this.

It's all very complicated stuff and scientists have a very poor understanding of many of the physical processes. aircraft get a bad rep for their contribution to atmospheric CO2, but when aircraft were grounded in the US after 9/11, there was an increase in temperature in the US due to the lack of contrails reflecting back sunlight. So you could argue that aircraft are actually beneficial.
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Quoting 850Realtor:
I am a little concerned about the blob just east of the Lesser Antilles. I read somewhere ealier that the 00Z ECMWF has a weak tropical cyclone forming between Nicaragua and Jamaica by next Thu-Fri.
Would it be this area to the east of the L.A. to watch or would that be something else?


Without looking at anything else, nothing's going to make it through the caribbean with the shear atm.

Link
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Quoting Santamaria:
@ atmoaggie. The graph you show is NOT from the graphs presented in the study, Shouldn't you be talking about them instead of soot?

And what a pity about the snows of Kilimanjiro. :-(

No, it isn't. That is the press release version.

In this one is just about impossible to see the overall temperature concluded and one could debate the merits of the many other analyses shown for days.
(Although it is almost humorous how the tree rings in the top-most plot deviate so far from the others just after 1900...almost humorous.)


And I thought the cause of the temperature change was much of the point in the debate. If true, then yes I should be talking about soot...and I think more of the researchers should be, too.

And I have to apologize about yanking your chain about Kilimanjaro...totally unrelated to AGW.

2007: "Mote and Georg Kaser, a glaciologist at the University of Innsbruck in Austria, write in American Scientist that the decline in Kilimanjaro's ice has been going on for more than a century and that most of it occurred before 1953, while evidence of atmospheric warming there before 1970 is inconclusive.

They attribute the ice decline primarily to complex interacting factors, including the vertical shape of the ice's edge, which allows it to shrink but not expand. They also cite decreased snowfall, which reduces ice buildup and determines how much energy the ice absorbs -- because the whiteness of new snow reflects more sunlight, the lack of new snow allows the ice to absorb more of the sun's energy. "
http://uwnews.org/article.asp?articleID=34106
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@ atmoaggie. The graph you show is NOT from the graphs presented in the study, Shouldn't you be talking about them instead of soot?

And what a pity about the snows of Kilimanjiro. :-(
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Sorry if the posts referring to older blogs is off topic, but the one when StormTop had StormTop's "mom" come on was hilarious, imo post 483
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I am a little concerned about the blob just east of the Lesser Antilles. I read somewhere ealier that the 00Z ECMWF has a weak tropical cyclone forming between Nicaragua and Jamaica by next Thu-Fri.
Would it be this area to the east of the L.A. to watch or would that be something else?
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Quoting Santamaria:
@atmoaggie This should help you.

http://desdemonadespair.blogspot.com/2009/09/graph-of-day-2000-year-reconstruction.html

Recent Warming Reverses Long-Term Arctic Cooling by Darrell S. Kaufman et al.

I appreciate you bringing that up. I posted before about that one:

"This paper uses observations from ice cores and tree rings"
Besides the huge caveats in tree rings for temperatures...

The plot in the paper looks like our friend, the hockey stick, but maybe there is some truth to it.


It sure is pretty, and annotated with blue for the proxy study and (shocker) red for recent measurements (from the satellites starting before 1979?!?! No. It is from all of the many long term surface stations in the Arctic). (Note, if you find a version without the red, the blue only shows warming from ~1945 to ~1970)

Odd jump starting before 1950?

Rather disappointed that aerosol deposition isn't addressed as a potential primary contributor to the signal by the scientists I see writing about this article. Politicians and those with a lot to gain by blindly attributing the entire thing, if accurate, to CO2 makes sense, but not one scientist that I have seen in the blogosphere seems willing to ask how much of this signal is related to aerosol deposition, lowering albedo, earlier melt, lowering albedo again for large areas.

Back to the jump before/around 1950...anyone want to bet that if we had aerosol-measuring satellites back before, during, and after WWII that soot suddenly appeared in the Arctic in substantial quantities about the same time as that temp increase? And stayed high?

Only in the last few years did we have new research, admittedly based mostly on model simulations, that concluded that fully half of the warming measured by our satellites in the last 30 years was due to soot deposition and possibly more.
Now forgotten, apparently...

Plus, the largest changes in any given year in melt/freeze rate relative to the available satellite mean extent are in the spring and fall. Why?
Correct, the sun is present in the Arctic.

Lots of good pics/links/discussion here: http://www.scientificblogging.com/the_soot_files/soot_black_icebergs_and_arctic_ice
I'll wager that if we went after the low hanging fruit, soot emissions, we would be a large step closer to being able to correctly attribute changes in the Arctic.

Now if we could stop melting Kilimanjaro's glacier. ;-)
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LMAO!!!!! post 483
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Quoting tornadofan:


Tdude - lots of familiar folks back then. Thanks for the blast from the past.


No problem. I found it funny the way we introduced ourselves LOL
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Quoting tornadodude:
Tornadofan, if you are on here, you will get a big kick out of this, read the comments on this blog page LOL

I think the others will find it funny too


Tdude - lots of familiar folks back then. Thanks for the blast from the past.
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@atmoaggie This should help you.

http://desdemonadespair.blogspot.com/2009/09/graph-of-day-2000-year-reconstruction.html

Recent Warming Reverses Long-Term Arctic Cooling by Darrell S. Kaufman et al.
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no matter where it goes looks pretty nasty
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so that in the west gom is that the blow up your talking about. will that blob move into texas or will it go somewhere else
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Cyclone Larry Pictorial
Link
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Quoting tropicexpert:


Season will be done soon. Too much shear everywhere. I'm a happy homeowner in SEFLA not worried about my INS rates rising. Looks like I dodged another year till the next one.

The window for a western Caribbean to S. Florida-type system is not closed yet...think Wilma. Is still possible.
Her track was rather normal for the latter half of October.
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found my first ever post LOL post number 74 link
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INV/99/L
MARK
16N/31W
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Quoting btwntx08:
post 79 shear is gonna tear it apart no need to worry about


Season will be done soon. Too much shear everywhere. I'm a happy homeowner in SEFLA not worried about my INS rates rising. Looks like I dodged another year till the next one.
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Quoting KEEPEROFTHEGATE:
hold on for a few more weeks yet before raiding anything the window is still there no matter how wide its open


Awe shucks. :(

Puts mustard back in fridge.
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Quoting Elena85Vet:


KOG

Is it time to raid the hurricane survival kits?

SPAM sandwiches for everyone? :)
hold on for a few more weeks yet before raiding anything the window is still there no matter how wide its open
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The wind has started to blow pretty hard here, maybe Dust Storm part II is here already.
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nice to see all the fish storms. no one gets hurt and no one loses their home. always a good thing
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does anyone have any thoughts on that blow up by the mexico texas border
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Quoting Elena85Vet:


Wow.


Who needs the quikscat anyways. Worry about the storm after it becomes a depression. I don't believe in wasting time looking at invests to see if it has a coc.
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Quoting Orcasystems:


Link

Fitting and hilarious
i remember my grandfather many years ago tell me if anyone says don't worry this is easy, they are more than likly lying too you

you figure lol
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Quoting AussieStorm:

Woops... my bad... I ment D-min.
It is 2am here.


its fine, and I called it 96L haha
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Quoting tornadodude:


right, and it is the afternoon where 96L is, right?

Woops... my bad... I ment D-min.
It is 2am here.
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should we be worried about 99l or will this be a fish storm
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is their still something in the Caribbean that might develop, and do all here think that 99l will push more west than north
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Quoting nrtiwlnvragn:
QuikSCAT weather satellite on last legs

The QuikSCAT weather satellite, which helps forecasters track remote tropical systems, may be on its last legs, U.S. Rep. Ron Klein, D-Boca Raton, said today.

Klein said he received an internal memo from the National Oceanic and Atmospheric Administration, alerting that bearings on the satellite are experiencing increasing friction, making it more difficult for its antenna to turn.

Further, the motor that turns the antenna is starting to grind down, according to a separate memo from NASA. The memo says QuikSCAT is "likely to fail in the next several weeks to months."

Yep, all is fine. We don't need to get any more scatterometer coverage up there. Oh, and somebody fire Proenza.
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Quoting nrtiwlnvragn:
QuikSCAT weather satellite on last legs

The QuikSCAT weather satellite, which helps forecasters track remote tropical systems, may be on its last legs, U.S. Rep. Ron Klein, D-Boca Raton, said today.

Klein said he received an internal memo from the National Oceanic and Atmospheric Administration, alerting that bearings on the satellite are experiencing increasing friction, making it more difficult for its antenna to turn.

Further, the motor that turns the antenna is starting to grind down, according to a separate memo from NASA. The memo says QuikSCAT is "likely to fail in the next several weeks to months."

Lets hope it doesn't fail when we need it most.
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Quoting nrtiwlnvragn:
QuikSCAT weather satellite on last legs

The QuikSCAT weather satellite, which helps forecasters track remote tropical systems, may be on its last legs, U.S. Rep. Ron Klein, D-Boca Raton, said today.

Klein said he received an internal memo from the National Oceanic and Atmospheric Administration, alerting that bearings on the satellite are experiencing increasing friction, making it more difficult for its antenna to turn.

Further, the motor that turns the antenna is starting to grind down, according to a separate memo from NASA. The memo says QuikSCAT is "likely to fail in the next several weeks to months."


Ohh snap... well no wonder QS hasn't been performing so well this season. At least we have ASCAT... but sure hope we get a new one up there soon.
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Quoting AussieStorm:

In the morning (between 3-6 A.M.) a weak low is generally at its strongest point of the 24 hour day. That is called the diurnal maximum.


right, and it is the afternoon where 99L is, right?
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Quoting KEEPEROFTHEGATE:
yep all is good don't worry about a thing this is easy


Link

Fitting and hilarious
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Tornadofan, if you are on here, you will get a big kick out of this, read the comments on this blog page LOL

I think the others will find it funny too
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Quoting tornadodude:


It's not Dmax right now though, is it? I thought that was right around sunrise, maybe I'm wrong :P

In the morning (between 3-6 A.M.) a weak low is generally at its strongest point of the 24 hour day. That is called the diurnal maximum.
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Quoting nrtiwlnvragn:
QuikSCAT weather satellite on last legs

The QuikSCAT weather satellite, which helps forecasters track remote tropical systems, may be on its last legs, U.S. Rep. Ron Klein, D-Boca Raton, said today.

Klein said he received an internal memo from the National Oceanic and Atmospheric Administration, alerting that bearings on the satellite are experiencing increasing friction, making it more difficult for its antenna to turn.

Further, the motor that turns the antenna is starting to grind down, according to a separate memo from NASA. The memo says QuikSCAT is "likely to fail in the next several weeks to months."


Wow.
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Quoting Patrap:
Dont worry,those Co2 And Co3 and other Man Made gasses were dumping 24/7/365 into Gaia's atmosphere are all scrubbed nightly by the Fairies in yer heads.


No worries...just keep on keeping on...
All's well..no need to worry.

yep all is good don't worry about a thing this is easy
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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