Four invests in the Atlantic; fair weather in Arctic to drive rapid sea ice loss

By: Dr. Jeff Masters , 3:38 PM GMT on August 12, 2011

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It's a busy day in the tropical Atlantic, with the National Hurricane Center tracking four areas of interest (Invests.) None of these systems is a danger to any land areas over the next three days. The disturbance of most concern is the one farthest from land, a tropical wave that emerged from the coast of Africa two days ago. This wave, (Invest 93L), is located about 500 miles southwest of the Cape Verde Islands, and is moving westward at 15 - 20 mph. Recent visible satellite loops show that 93L has lost some of its heavy thunderstorms since yesterday, and the system is poorly organized, though there is a good deal of spin to the system. There is dry air to its north that is interfering with development. The SHIPS model and University of Wisconsin CIMSS wind shear analysis are showing high wind shear in excess 20 knots affecting 93L, which has undoubtedly contributed to the storm's loss of organization. Sea surface temperatures are 27.5°C, which is one degree above the 26.5°C threshold usually needed to support a tropical storm.


Figure 1. Morning satellite photo of the four Invests in the Atlantic today.

Forecast for 93L
High wind shear above 20 knots is predicted along 93L's path through Saturday afternoon, followed by a drop to the moderate range, 10 - 20 knots, for the succeeding four days. This should allow the storm to organize over the weekend. The latest 00Z and 06Z model runs of the four best models for predicting tropical storm formation (GFS, ECMWF, NOGAPS, and UKMET), have only one model, the GFS, that is indicating significant development of 93L. This model brings 93L near the northern Lesser Antilles Islands by Wednesday. NHC gave 93L a 40% chance of developing into a tropical depression by Sunday morning in their 8am outlook. Given 93L's recent struggles, I'd put these odds at 30%.

92L
An African wave midway between the northern Lesser Antilles Islands and the coast of Africa, near 18°N 45°W, is moving west-northwest at 20 mph. This system, (Invest 92L), is being given a 40% chance of development by NHC. Recent visible satellite loops show a modest amount of heavy thunderstorm activity, but no signs of a surface circulation. A Windsat pass from 8:04 am EDT this morning also showed no surface circulation, and noted top winds of around 35 mph. Water vapor satellite loops show that a large area of dry air surrounds 92L, and this dry air is causing problems for the storm. The SHIPS model and University of Wisconsin CIMSS wind shear analysis are showing moderate wind shear of 10 - 20 knots affecting 92L. Sea surface temperatures are 27 - 27.5°C, which is a degree above the 26.5°C threshold usually needed to support a tropical storm.

Forecast for 92L
Moderate wind shear of 10 - 20 knots is predicted along 92L's path over the coming five days, which should allow the storm to organize if it can handle the dry air surrounding it. The latest 00Z and 06Z model runs of the four best models for predicting tropical storm formation (GFS, ECMWF, NOGAPS, and UKMET) show weak development or no development of 92L, and NHC gave 92L a 40% chance of developing into a tropical depression by Sunday morning in their 8am outlook. A steady west-northwest motion for 92L is predicted by all of the models, which should make the storm miss the Lesser Antilles by a comfortable margin. However, Bermuda may be at risk from 92L next week.

94L
A broad low pressure system about 700 miles northeast of the northern Lesser Antilles Islands has developed a small amount of heavy thunderstorm activity, and may be a threat to become a tropical depression early next week. This system, (Invest 94L), is currently headed west-southwest at 10 mph, but is expected to turn northwest later today. Recent visible satellite loops show some spin to the cloud pattern at middle levels of the atmosphere, but no signs of a surface circulation. This system is also battling dry air, which is keeping the its heavy thunderstorms relatively meager. The SHIPS model is showing moderate wind shear of 10 - 20 knots affecting 94L. Sea surface temperatures are 28°C.

Forecast for 94L
Moderate wind shear of 10 - 20 knots is predicted along 94L's path over the coming five days, which should allow slow development, if it can handle the dry air surrounding it. None of our reliable models for predicting tropical storm formation (GFS, ECMWF, NOGAPS, and UKMET) show no development of 94L, and NHC gave 94L just a 20% chance of developing into a tropical depression by Sunday morning in their 8am outlook. Bermuda is the only land area that needs to be concerned with 94L.

95L
The final invest out there is an area of disturbed weather along on old frontal boundary several hundred miles off the coast of North Carolina. This sytem, Invest 95L, is headed northeastwards out to sea, and is not a threat to any land areas.



Figure 2. Arctic sea ice extent on August 11, 2011, was the 2nd lowest on record for the date. The Northeast Passage and Northwest Passage (southern route) were both ice-free. Image credit: UIUC Cryosphere Today.

Arctic sea ice poised to undergo record decline in mid-August
A strong high pressure system with a central pressure of 1035 mb has developed over the Arctic north of Alaska, and will bring clear skies and warm southerly winds to northeast Siberia and the Arctic during the coming week, accelerating Arctic sea ice loss. Widespread areas of northeastern Siberia are expected to see air temperatures 4 - 12°C (7 - 22°F) above average during the coming week, and the clockwise flow of air around the high pressure system centered north of Alaska will pump this warm air into the Arctic. Arctic sea ice extent, currently slightly higher than the record low values set in 2007, should fall to to its lowest extent for the date by the third week of August as the clear skies and warm southerly winds melt ice and push it away from the coast of Siberia. This weather pattern, known as the Arctic Dipole, was also responsible for the record sea ice loss in 2007, but was stronger that year. The weather conditions that led to the 2007 record were quite extreme--one 2008 study led by Jennifer Kay of the National Center for Atmospheric Research showed that 2007's combination of high pressure and sunny skies in the Arctic occur, on average, only once every 10 - 20 years. The 2011 summer weather pattern in the Arctic has not been nearly as extreme as in 2007, but the total sea ice volume has declined significantly since 2007, leading to much loss of old, thick, multi-year ice, making it easier to set a new low extent record with less extreme weather conditions. The GFS model is predicting that the Arctic Dipole will weaken by 8 - 15 days from now, with cloudier weather and weaker high pressure over the Arctic. This should slow down the rate of Arctic sea ice loss to very near the record low values observed in 2007. It remains to be seen if 2011 Arctic sea ice extent will surpass the all-time low set in September 2007; it will be close, and will depend on the weather conditions of late August and early September, which are not predictable at this time. It is already possible to sail completely around the North Pole in ice-free waters through the Northeast Passage and Northwest Passage, according to sea ice maps maintained by the UIUC Cryosphere Today website. This marks the fourth consecutive year--and the fourth time in recorded history--both of these Arctic shipping routes have melted free. Mariners have been attempting to sail these passages since 1497. This year, the Northeast Passage along the north coast of Russia melted free several weeks earlier than its previous record early opening.

Next post
I'll have a new post by 1pm Saturday.

Jeff Masters

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See you guys later.
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Tropical Evening Update Aug. 12th., 2011
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Quoting TomTaylor:
pretty large area of purples though. Indicates the large uncertainty that far out


Yup. There is a lot to work out yet. The pattern is again fragile, which is a theme along the east coast so far this season.
Member Since: November 24, 2005 Posts: 635 Comments: 26647
Quoting TropicalAnalystwx13:


lol, now you know how I feel :P
I started on Wednesday, and all these crazy things are happening now.

Well, it's Friday, looking forward to the weekend(not singing it).
Also, did 93L die or something? It looks horrible on IR.
Member Since: Posts: Comments:
Dont think that I want hurricanes but I'm not impressed with the looks of any storms this year. This could be the new year of the ugly storm. 2007 was the old. LOL.

Let D-MAX decide that for now...
Member Since: July 19, 2011 Posts: 12 Comments: 2401
Quoting MiamiHurricanes09:
Really? I still got 10 more days...


Yeah, we start earlier because we get out earlier.

What will you be? (freshmen, etc)
Member Since: July 6, 2010 Posts: 113 Comments: 32033
Quoting TropicalAnalystwx13:


lol, now you know how I feel :P
I started on Wednesday, and all these crazy things are happening now.
Really? I still got 10 more days...
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting IKE:

93L looks like the only game in town and that could take awhile.
not long just taking a little nap you know those sleepers some can be heavy
Member Since: July 15, 2006 Posts: 171 Comments: 53827
Quoting WeatherNerdPR:
This day is not normal...wish I hadn't gone to school today. LOL


lol, now you know how I feel :P
I started on Wednesday, and all these crazy things are happening now.
Member Since: July 6, 2010 Posts: 113 Comments: 32033
Quoting stormpetrol:
92L up to 70% at 7pm, 93L despite lack of convection will go up to 50-60% JMO.


Egg on my face, :), well that's life, btw still kinda weary of 93L, still think its the main player!
Member Since: April 29, 2007 Posts: 0 Comments: 7862

Atlantic wide view.
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This day is not normal...wish I hadn't gone to school today. LOL
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Quoting CaneHunter031472:


Or fortune cookie wisdom?
well at least its not six pack stupity
Member Since: July 15, 2006 Posts: 171 Comments: 53827
SAB a little higher:

12/2345 UTC 36.1N 62.3W T2.0/2.0 06L -- Atlantic
Member Since: September 2, 2009 Posts: 130 Comments: 21193
Quoting twincomanche:
Is that Shakespeare? Or perhaps original Keeper.


Or fortune cookie wisdom?
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2011 Storms
All Active Year


Atlantic
94L.INVEST
93L.INVEST
92L.INVEST
06L.SIX

East Pacific
98E.INVEST

Central Pacific

West Pacific
13W.THIRTEEN

Indian Ocean

Southern Hemisphere
Member Since: July 15, 2006 Posts: 171 Comments: 53827
93L is naked! Maybe Dmax will help it tonight.
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938. IKE

Quoting CaneHunter031472:
Wow pretty impressive the Atlantic right now and we have not reached the peak yet! Just wondering if they will be fish storms or threats. I see the onw north of PR moving to the SW. Any opinion on this anyone?
93L looks like the only game in town and that could take awhile.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
Wow pretty impressive the Atlantic right now and we have not reached the peak yet! Just wondering if they will be fish storms or threats. I see the onw north of PR moving to the SW. Any opinion on this anyone?
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This is going to be the year of 20 tropical storms. LOL
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Quoting P451:
AL06

Warming tops...


wait for Dmax to kick in
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Quoting TropicalAnalystwx13:


Do you monitor ATCF 24/7? Every time we get a new invest or tropical system, you are the first one to post it.

What is your secret? ;)

No secrets. Just a man with many interests and a fast internet connection... ;-)
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Quoting Chucktown:


Hey Press, just read your latest Facebook entry, CLASSIC !!


;-)
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Quoting presslord:


theirs no excuse for this....your just being mean


Hey Press, just read your latest Facebook entry, CLASSIC !!
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Quoting Levi32:
ECMWF ensembles show their suggestions of where 93L should be in 10 days with their member variance (purple/pink colors). The mean is farther north than the operational run, which I mentioned this morning may be a bit too aggressive on the southerly track. The weakest link in the ridge should remain near the eastern seaboard, Florida, and southeast U.S. area, which could still pull this northward a little bit as it comes through the Caribbean area. Fine details of track are unknown right now as we have a weak system that could dissipate or develop several days from now when it finally gets into more favorable conditions farther west. If it does develop, chances are it will threaten land, as the pattern is shaping itself into the kind of pattern that can draw storms toward the Caribbean islands and SE US if they are coming in from far enough south.
pretty large area of purples though. Indicates the large uncertainty that far out
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Quoting Neapolitan:
A brand new invest in the EPAC, as well:

BEGIN
NHC_ATCF
invest_ep982011.invest
FSTDA
R
U
040
010
0000
201108122346
NONE
NOTIFY=ATRP
END
INVEST, EP, E, , , , , 98, 2011, DB, O, 2011081218, 9999999999, , , , , , METWATCH, , EP982011
EP, 98, 2011081218, , BEST, 0, 128N, 1206W, 25, 0, DB, 0, , 0, 0, 0, 0,


Do you monitor ATCF 24/7? Every time we get a new invest or tropical system, you are the first one to post it.

What is your secret? ;)
Member Since: July 6, 2010 Posts: 113 Comments: 32033
Quoting P451:
AL06

Warming tops...

whatever it was is going to be soon gone
Member Since: July 15, 2006 Posts: 171 Comments: 53827
A brand new invest in the EPAC, as well:

BEGIN
NHC_ATCF
invest_ep982011.invest
FSTDA
R
U
040
010
0000
201108122346
NONE
NOTIFY=ATRP
END
INVEST, EP, E, , , , , 98, 2011, DB, O, 2011081218, 9999999999, , , , , , METWATCH, , EP982011
EP, 98, 2011081218, , BEST, 0, 128N, 1206W, 25, 0, DB, 0, , 0, 0, 0, 0,
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evenin everyone, just dropping by for a sec

Quoting kmanislander:


Hi there,

93L has three problems, one of which is resolving itself now. The one that is resolving is shear, which has fallen steadily from close to 30 knots all the way down to about 15 knots or less now on the South side of the circulation and still falling.

Problem 2 is that it is still stuck in the monsoon trough and looks to remain there for another day or two.

Problem 3 is a quirky upper level structure. The 850 mb vorticity lags the surface feature by about 200 miles but the 700 mb vort is close to overhead though elongated from East to West. Not quite sure what to make of this but that is what the maps show.Could be the result of mid level shear ( which is fairly high ) hitting the vertical strucutre in such a way to create a "bowing " effect to the East at the low to mid levels around 5000 feet.

Until these three things sort themselves out 93L will just continue chugging along to the West doing little to organise IMO


Yep, all good points. I would add a fourth in there as well, if I may. The fourth problem would be upper divergence which is fairly poor due to the large field of upper level easterlies over and around 93L preventing air from spreading out aloft. According to the SHIPS text forecast, this will remain an issue.
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93L will be another Emily.
Member Since: July 6, 2010 Posts: 113 Comments: 32033
So far all of the 2011 Atlantic system's are small in size and quite disorganize.
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Quoting BahaHurican:
Interestingly, only one storm so far DIDN'T hit land... 2 if u count upcoming Franklin-from-TD-6. And as somebody said already, conditions here [in the ATL] have been pretty crappy. These tracks so far have not inspired me to believe we won't get a couple of noxious hits as conditions improve into Sept....

Doubt it... some of the energy came from elsewhere, and the nominal coc of Emily went off to the NE...



ITS act; no apostrophe needed unless meaning it is.

94L is more like Katrina in this sense. Katrina's complex cyclogenesis involved a part of the entity formerly known as TD10...



theirs no excuse for this....your just being mean
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Quoting WeatherNerdPR:
What the heck? Three invests and a TD?
things sometimes change but in a blink of an eye
Member Since: July 15, 2006 Posts: 171 Comments: 53827
Predictions for 2am advisory and suggestions?
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Downward Motion...
Member Since: July 6, 2010 Posts: 113 Comments: 32033
Quoting TropicalAnalystwx13:
Why would the NHC lower 92L's chances? Its become BETTER organized since 2PM, not less organized.

Makes no sense.

Maybe they are seeing a different 92L
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What the heck? Three invests and a TD?
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Quoting TropicalAnalystwx13:
Why would the NHC lower 92L's chances? Its become BETTER organized since 2PM, not less organized.

Makes no sense.
Stewart has left the building...
Member Since: September 2, 2009 Posts: 130 Comments: 21193
913. IKE

Member Since: June 9, 2005 Posts: 23 Comments: 37858
Why would the NHC lower 92L's chances? Its become BETTER organized since 2PM, not less organized.

Makes no sense.
Member Since: July 6, 2010 Posts: 113 Comments: 32033

TD6
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About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.