One third of Arctic ice cap now missing; Midwestern floods; tropical update

By: Dr. Jeff Masters , 12:46 PM GMT on August 24, 2007

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Sea ice in the Arctic continues its record decline, thanks to unusually cloud-free conditions and above-average temperatures. For August 21, the National Snow and Ice Data Center estimated that fully one third of the Arctic ice cap was missing, compared to the average levels observed on that date from 1979-2000. Sea ice extent was 4.92 million square kilometers on August 21, and the 1979-2000 average for the date was about 7.3 million square kilometers. Arctic sea ice has fallen below the record low absolute minimum of 4.92 million square kilometers set in 2005 by about 8%, with another 3-5 weeks of the melting season still remaining. Reliable records of sea ice coverage go back to 1979.


Figure 1. Extent of the polar sea ice on August 21, compared to the average for the date from the 1979-2000 period (pink line). Image credit: National Snow and Ice Data Center.

With one third of the Arctic ice cap already gone, and another month of melting to go, we need to consider what effect this will have on weather, climate, and sea level rise. Well, we don't need to worry about sea level rise, since the polar sea ice is already in the ocean, and won't appreciably change sea level when it melts. However, the remarkable melting of the ice cap will likely lead to unusual weather patterns this fall and winter. The lack of sea ice will put much more heat and moisture into the polar atmosphere, affecting the path of the jet stream and the resultant storm tracks. Expect a much-delayed arrival of winter to the Northern Hemisphere again this year, which may lead to further accelerated melting of the ice cap in future years.

Last week, I remarked that the most recent images from the North Pole webcam show plenty of melt water and rainy conditions near the Pole. It turns out that was misleading, since the webcam is on a ship that was headed towards the pole, but had not reached it. There have been rainy conditions at the Pole this summer, and there is some open water there, but this is not uncommon in summer. Shifting ice frequently opens up leads (cracks) with open sea water at the Pole. It was one of these open leads that British swimmer Lewis Gordon Pugh swam in for 18 minutes this July to draw attention to global climate change.


Figure 2. Total rainfall from August 10-22 as estimated by NASA's TRMM satellite.

Midwest flooding
To get an idea of the magnitude of the flooding that has hit the Midwestern U.S. during the past ten days, take a look at the total amount of rain from August 10-22 (Figure 2). We can blame Tropical Storm Erin for the rain in Texas and Oklahoma (up to 11 inches), and for the nine flooding deaths that occurred in those states. However, the unbelievable rain amounts in excess of 20 inches in Minnesota and Wisconsin were primarily due to a frontal system--with the help of some copious moisture pumped northwards by the counter-clockwise circulation around Erin while it spun over Oklahoma.

Tropical update
There are no threat areas in the Atlantic to discuss. Two of our four reliable forecast models, the NOGAPS and ECMWF, are predicting that a tropical depression could form off the coast of Nicaragua on Sunday. The models forecast that this system would move inland over Nicaragua and Honduras by Monday.

I'll have an update on Saturday morning.
Jeff Masters

After Hurricane Dean (sprinter)
Bulldozer trying to clear sand and debris from Norman Manley Highway(Airport Road)
After Hurricane Dean
Findlay Ohio flood (prairieview)
The flood is over, now the cleanup
Findlay Ohio flood

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445. OUFan919
9:43 PM GMT on August 24, 2007
Nearly 40,000 people in St. Louis don't have power after some bad storms ripped through the area.
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443. corimorgan
5:39 PM EDT on August 24, 2007
well once this subsidence ends, we could have a burst of convective activity, which could mean maybe a burst of activity perhaps

What is subsidence and when is it forcast to end?
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442. BahaHurican
5:15 PM EDT on August 24, 2007
Posted By: gthsii at 2:46 PM EDT on August 24, 2007.

weatherhunter - been in three Frances, Jeanne and Wilma.


You must live in Palm Beach county ...
Member Since: October 25, 2005 Posts: 19 Comments: 22736
441. Skyepony (Mod)
9:38 PM GMT on August 24, 2007

If the time to melt peak (which really shows the warm fall to come) moves in a straight line. This looks like it would bottom out in October.
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440. extreme236
9:34 PM GMT on August 24, 2007
well once this subsidence ends, we could have a burst of convective activity, which could mean maybe a burst of activity perhaps
Member Since: August 2, 2007 Posts: 19 Comments: 19234
437. extreme236
9:26 PM GMT on August 24, 2007
hey StormW, when did you say the MJO was supposed to become more favorable again?
Member Since: August 2, 2007 Posts: 19 Comments: 19234
436. CFL
9:23 PM GMT on August 24, 2007
if that's the case, then we might be in trouble once our phase of subsidence ends
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435. extreme236
9:18 PM GMT on August 24, 2007
Posted By: CFL at 9:17 PM GMT on August 24, 2007.

does anybody now why the tropics are so quiet? SAL is descreasing and shear isnt too bad. i'm not rooting for storms to form, but i'm wondering why storms aren't forming in what seem to be moderately favorable conditions.


there just seems to be a lack of disturbances. if we can get more disturbances, then more systems may form
Member Since: August 2, 2007 Posts: 19 Comments: 19234
432. CFL
9:05 PM GMT on August 24, 2007
does anybody now why the tropics are so quiet? SAL is descreasing and shear isnt too bad. i'm not rooting for storms to form, but i'm wondering why storms aren't forming in what seem to be moderately favorable conditions.
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431. BahaHurican
5:08 PM EDT on August 24, 2007
Posted By: sullivanweather at 12:20 PM EDT on August 24, 2007.

Nash28, what are you trying to say? That Greenland was named Greenland because it was green?


Ayup.
Member Since: October 25, 2005 Posts: 19 Comments: 22736
429. extreme236
9:08 PM GMT on August 24, 2007
I guess supposedly according to accuweather, they say the models are showing sfc pressures falling in the SW caribbean this weekend into early next week. right now, this appears to be the only real area of concern right now. but, once again, the tropics usually always give a surprise of somesort lol
Member Since: August 2, 2007 Posts: 19 Comments: 19234
428. Drakoen
9:06 PM GMT on August 24, 2007
Posted By: extreme236 at 9:05 PM GMT on August 24, 2007.

well what about that area of convection off the north panama coast? a few models appear to develop something weak hitting nicaragua. maybe a TD or weak TS


Maybe. Anything that develops would have little time to do so due to the proximity to land.
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427. extreme236
9:05 PM GMT on August 24, 2007
well what about that area of convection off the north panama coast? a few models appear to develop something weak hitting nicaragua. maybe a TD or weak TS
Member Since: August 2, 2007 Posts: 19 Comments: 19234
426. Drakoen
9:04 PM GMT on August 24, 2007
Posted By: extreme236 at 9:03 PM GMT on August 24, 2007.

hey drak did you see the image of that blob off the african coast? one of the first real convection to persist after coming off africa, since dean anyway


not interested. Looks low amplitude.
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425. extreme236
9:03 PM GMT on August 24, 2007
hey drak did you see the image of that blob off the african coast? one of the first real convection to persist after coming off africa, since dean anyway
Member Since: August 2, 2007 Posts: 19 Comments: 19234
424. Drakoen
9:01 PM GMT on August 24, 2007
Nothing interesting of the African coast. SAL continues to dissapate
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423. extreme236
8:59 PM GMT on August 24, 2007
hey StormW, have you seen the latest west african images? there is a nice blob of convection near the CV islands. what do you think?
Member Since: August 2, 2007 Posts: 19 Comments: 19234
421. DallasGumby
9:00 PM GMT on August 24, 2007
Posted By: StormW at 8:57 PM GMT on August 24, 2007.

CV= Cape Verde


Of course! Thank you!
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417. DallasGumby
8:56 PM GMT on August 24, 2007
Question: what does "CV" stand for?
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416. TheCaneWhisperer
8:53 PM GMT on August 24, 2007
Evening All!

Quiet, yayyyyy!

Pretty good gust front setting up in SFL.


Looks like burning fires, pretty neat.
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415. weathermanwannabe
4:54 PM EDT on August 24, 2007
Nice and quiet for now is a good thing...I'm off and everyone have a great weekend.....
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414. extreme236
8:52 PM GMT on August 24, 2007
take a look at the convection off the african coast (look at the nemoc images for latest images). convection is fairly strong so perhaps we are at that time of the year where higher latitude storms form off africa and become fish storms
Member Since: August 2, 2007 Posts: 19 Comments: 19234
413. sunnyandshear
8:51 PM GMT on August 24, 2007
Is it just me, or has anyone else noticed the Polar ice caps have jogged South? It's way to early to predict if this is a trend or a wobble. Nobody is is out of the woods yet, and nobody should let their guard down. When we get the 2079 AD models we'll have a better handle on where this thing is going . Stay tuned
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411. weathermanwannabe
4:45 PM EDT on August 24, 2007
Well, I do not "want" any major storms to threaten anyone, but, the SE US can still use lots of rain so I'm actually hoping for some tropical moisture to lower our rain deficits in the SE before Winter......A couple of weak tropical storms might actually be nice....
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410. KRL
8:41 PM GMT on August 24, 2007
Posted By: wrrice at 12:53 PM GMT on August 24, 2007.
With all the melting of arctic ice that has been documented, have we seen any corresponding rise in sea level? I've long heard that melting of this ice could be disastrous.


Take a glass of water with ice in it and leave it on your counter overnight. There wil be no change in the water level because the ice has a fixed displacement of the same volume of water, and it just changed its state back to a liquid from a solid.
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409. extreme236
8:42 PM GMT on August 24, 2007
well we have to remember that during la nina's, historically, la nina years dont have as active of CV seasons, as a lot of activity forms closer to the US
Member Since: August 2, 2007 Posts: 19 Comments: 19234
408. JLPR
8:35 PM GMT on Agosto 24, 2007
lol

all i see is a little rotation near 47w 10n and the one close to panama
Boring.....
ZzZzZzZzzz
but i guess is better boring than catastropic
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407. Weather456
8:42 PM GMT on August 24, 2007
sorry for the double post, suppose to be a discussion for the Caribbean.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
406. weathermanwannabe
4:39 PM EDT on August 24, 2007
Yeah; at some point the CV part of the season will "end" but it is still too early...There is still a good chance of a wave developing at some point in September......
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405. Weather456
8:41 PM GMT on August 24, 2007
Gulf of Mexico This afternoon

Developing deep convection is over the SE US. This activity is caused by instability associated with diffluent flow between an upper low over the Gulf and a ridge over the Eastern US, aided by surface inflow and daytime heating. Meanwhile, scattred clouds and rain are over the Gulf and the main culprit continues to be an upper low which stands out very clearly on water vapor imagery. The low is also interacting with a surface trough over the Bay of Campeche near 93-94W and, to a lesser extent, a tropical wave near 89W south of 22N. A weaker surface pressure pattern in place over the region this afternoon with light variable winds and pockets of fair weather most notable over Texas and Northern Mexico

by W456
Member Since: July 24, 2005 Posts: 407 Comments: 19076
404. icepilot
2:32 PM CST on August 24, 2007
Posted By: sammo at 2:13 PM CST on August 24, 2007.

Water doesn't expand because of air trapped in the crystal matrix. It reaches maximum density at around 4 degrees C, and as it gets colder, it expands again. When ice crystals form, the angle between the two Hydrogen bonds goes from about 105 degrees (when liquid and gas) out to 120 degrees due to the attractions between the Oxygen and Hydrogen atoms as they get close to one another to form the hexagonal crystal. Therefore, the molecules take up more space in crystalline form.

Damn. Learn something new every day - when was this process discovered? my point was that the expansion was not until just before/at freezing. Damn I could of sworn I was taught it was air in the crystal -grin
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403. Weather456
8:27 PM GMT on August 24, 2007
Gulf of Mexico This afternoon

Developing deep convections is over the SE US. This activity is caused by instability associated with diffluent flow between an upper low over the Gulf and a ridge over the Eastern US, aided by surface inflow and daytime heating. Meanwhile, scattred clouds and rain are over the Gulf and the main culprit continues to be an upper low which stands out very clearly on water vapor imagery. The low is also interacting with a surface trough over the Bay of Campeche near 93-94W and to a lesser extend a tropical wave near 89W south of 22N. A weaker surface pressure pattern in place over the region this afternoon with light variable winds and pockets of fair weather most notable over Texas and Northern Mexico

by W456
Member Since: July 24, 2005 Posts: 407 Comments: 19076
402. extreme236
8:39 PM GMT on August 24, 2007
Ok, here is my tropical outlook for today:

1) A couple sfc lows in the north atlantic and off the east coast, which may attempt to develop into a cyclone.

2) an area of disturbed weather off the northern coast of panama.

3) an area of cyclonic turning in the itcz
Member Since: August 2, 2007 Posts: 19 Comments: 19234
401. PensacolaDoug
8:38 PM GMT on August 24, 2007
Pressures are high in the eastern Atlantic. So odds are low for another long tracked storm currently.
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400. PensacolaDoug
8:36 PM GMT on August 24, 2007
Anyone got a close up visible of 9 north 50 west?
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399. extreme236
8:36 PM GMT on August 24, 2007
i agree weatherman. caribbean right now needs to be watched closely as it is mostly favorable in the caribbean. but its also the time of year when something can develop far out in the atlantic.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
398. extreme236
8:35 PM GMT on August 24, 2007
your welcome plylox :)
Member Since: August 2, 2007 Posts: 19 Comments: 19234
397. weathermanwannabe
4:27 PM EDT on August 24, 2007
As I mentioned yesterday, it will be an interesting second half of the season given the current lack of any viable tropical systems during the peak of the season. Notwithstanding what may develop in September (it was very active in 2005 as we know all too well), as the stonger cold fronts start to come down and cool off the waters in October, there will probably be a greater chance of "sub-tropical" and cold core systems if this becomes a "late season"....For right now, the Western Caribbean/GOM is one big pot of moisture and there is a lot of dry air just north of the ITCZ so I would not expect any CV waves to have the juice to develop over the next week..........The Carib/GOM will probably present the chances of development in the immediate short term......
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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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