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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1046. Drakoen
9:13 PM GMT on August 25, 2007
Amystery how many computer models developed Erin?
Not everything is gonna get noticed by the computer models although it is nice when something is.
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1044. Drakoen
9:12 PM GMT on August 25, 2007
Posted By: StormW at 9:11 PM GMT on August 25, 2007.

Drak,
Check out the latest...directly south of the Cape Verdes


PSU eWALL still vis


I see it. Looks a bit elongated to the west and east.
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1042. boiredfish
9:11 PM GMT on August 25, 2007
Are the polar bears losing territory for a few years? Cry me a river....
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1041. extreme236
9:12 PM GMT on August 25, 2007
computer models dont have to agree on systems developing like they did with Dean amy. that was a rarity to see so much agreement
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1039. extreme236
9:11 PM GMT on August 25, 2007
that wave south of the CV islands looks fairly good on that image
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1037. Weather456
9:00 PM GMT on August 25, 2007
Central America Convection

Instability associated with a tropical wave near 82W south of 20N moving west near 10-15 knots aided by onshore flow and daytime heating is resulting in deep convection over most of Central America. Over Northern South America, classic "popcorn" convection is developing over Colobia, Venezuela, Gyuana and Suriname. This actvity is cleary enhance by the ITCZ east of 65W. The extent of showers are not confine the Central American landmass but exnteds well out into the Eastern Pacific, where two areas of interest is forecast to develop - a 1009 low attached to the ssouthern portion of the wave over the BOC and an area of showers southwest of Coasta Rica.

by W456
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1035. extreme236
9:10 PM GMT on August 25, 2007
I think everyone has forgotten what a little above average season is like. i think too many people got spoiled by the activity in 2005
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1034. Drakoen
9:10 PM GMT on August 25, 2007
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1033. extreme236
9:09 PM GMT on August 25, 2007
how are we below normal? lol. 4 is the average. so how are we below average? subtropical storms count as they have counted for the past 3 years
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1031. extreme236
9:08 PM GMT on August 25, 2007
People keep forgetting we are ABOVE average in terms of storms.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1030. extreme236
9:07 PM GMT on August 25, 2007
wow with all the downcasters on this blog now you would think there was a free money give away on here
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1029. Drakoen
9:06 PM GMT on August 25, 2007
Posted By: StormW at 9:05 PM GMT on August 25, 2007.

Drak,
Did you see my post earlier on the vis loop? If anyone notices, there is a west wind at the south of the wave off Africa, indicating a closed circulation.


Yes i saw the loop. Will be interesting to see how it fairs once it comes of Africa. The UKMET looks like it might be hinting at something.

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1027. extreme236
9:02 PM GMT on August 25, 2007
Right now I am laughing at all the people who think this year will be a bust. They think that because there is nothing out there all the time that it will be a bust. Must we all be reminded that in 2005 there was a 18 day period in AUGUST that had no activity? and look at all that activity
Member Since: August 2, 2007 Posts: 19 Comments: 19234
1025. Drakoen
9:01 PM GMT on August 25, 2007
Heres an image. 90L started out with a mid level to low level circulation on Africa. Something to watch. Look at 10N 10W to see the low.
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1024. Skyepony (Mod)
8:58 PM GMT on August 25, 2007
I agree STL the West Atlantic is looking about ripe.

Greece is on fire. Fire bug outta hand during a 3 day 104 heat wave. 46 have died.
Member Since: August 10, 2005 Posts: 174 Comments: 38198
1023. KEEPEROFTHEGATE (Mod)
8:53 PM GMT on August 25, 2007
just wait till sept
just wait till oct
just wait till nov
o no the season is over
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1022. Weather456
8:43 PM GMT on August 25, 2007
Bay of Campeche Update

An upper low in the Northern Gulf of Mexico due south of New Orleans, Louisianna, continues to interact with a tropical wave near 96-98W and a broad area of low pressure to produce scattred showers over the Bay of Campeche with lightning data suggesting isolated thunderstorms. Enviromental conditions are favourable for development but recent analysis showed that limited time is there to do so before the system moves ashore spreading moisture across Northern Mexico/Southern Texas. Recent surface observation indicate no surface circulation associated with this feature but vorticity charts indicate a possible one near 700-800 mb.

Possible chance of development

Current - 15%
12 Hrs - 10%
24hrs - 5%
36 hrs - less than 5%

by W456



Image by Ohio State Tropical Weather Center
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1021. boobless
8:54 PM GMT on August 25, 2007
Silly me.
S. of Cape Verdes Islands would be way more correct
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1020. BahaHurican
4:36 PM EDT on August 25, 2007
Our little recent rain.


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1019. hosweather
8:50 PM GMT on August 25, 2007
I guess the August "silly season" also extends to this blog.
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1018. Drakoen
8:51 PM GMT on August 25, 2007
The wave nearing the coast of Africa has a 1009mb SFC low. We'll have to watch it for development.
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1014. HopquickSteve
8:10 PM GMT on August 25, 2007
What I said before didn't disagree or agree with either side...and yet so many were ready to flame me. Dude...all I made was an observation and then everyone came out with their anti-GW quotes and the anti GW crowd was filled with a lot of "amening".

All I was saying is: there ISN'T anyway for us to get enough climatological information for us to conjecture ice cap coverage for all 4.5 billion years of earth history.

So what I said was:

a) We will NEVER have a large enough sample to satisfy people saying we don't have a large enough sample.

b) Then I posed the question: since whether we have 1 million years of information versus 40 years we will NEVER have a large enough sample, what standards should we use to claim data is actionable?

Instead I saw a lot of pro and anti GW dogma and no real wrestling with this core issue.
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1013. hosweather
7:48 PM GMT on August 25, 2007
If you're a CMC fan like me, there's lots to watch out there. Besides the system developing in the E Pac, with which GFS agrees, the CMC has two other systems developing.

First there is the wave currently south of the Cape Verdes which the CMC develops gradually over the next 6 days into a depression or tropical storm in the mid-Atlantic. Interestingly, the GFS also develops this wave initially but then has it lose structure as it races west at breathtaking speed. The CMC moves the system west at a more normal speed. It may be on to something here--definitely worth watching.

CMC also develops the wave now just north of Venezuela near the Colombian border. A system develops very gradually off this wave and tracks NW through the W Caribbean, across the Yucatan and into the Bay of Campeche. Note that conditions are forecast to be favourable for tropical storm development in the W Carib the next few days.

Happy storm watching! hos
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1011. boobless
8:11 PM GMT on August 25, 2007
StormW,
Thanks for the link.
20N 26W best thing out there.
My knowledge is not solid on wave interaction w/the ITCZ but it "looks" clear.
What would stop it from spinning up?
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1010. stoormfury
8:00 PM GMT on August 25, 2007
yes Storm W
That wave south of the cape verdes looks very interesting and could be what the GFS has been hinting would develop in the CATL. interesting because it is the general area where Dean wae spawned. now what about the wave at 11N 52W? There seems to be a little organisation with each frame
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1009. MissBennet
8:02 PM GMT on August 25, 2007
Its a plaintifs firm and he just works there. He doesn't even think it's going to fly. =) blame the firm, not the man.
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1006. extreme236
7:58 PM GMT on August 25, 2007
the MJO was favorable for about a week. Although it is forecasted to become more favorable by the end of the month
Member Since: August 2, 2007 Posts: 19 Comments: 19234
999. extreme236
7:54 PM GMT on August 25, 2007
But the caribbean isnt bone dry anymore and neither is africa. when the MJO gets favorable again then conditions will be more moist
Member Since: August 2, 2007 Posts: 19 Comments: 19234

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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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