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.

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

Jeff Masters

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Quoting muddertracker:
Good evening...so which of these are we really watching? I've been on a cruise and way out of the loop!


All of them, but 93L especially (threat to land).
Member Since: July 6, 2010 Posts: 113 Comments: 32855
Good evening...so which of these are we really watching? I've been on a cruise and way out of the loop!
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93L looks good all it this needs is t-storms may and a closed low and we have a TD





92L and 94L are RIP
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
1057. klew136
Quoting BahaHurican:
4 of the 5 storms we've had so far have hit land. Even hitting the lowest forecast, that means 1/3 of storms were landfalling. Plus so many early landfalling storms suggests the pattern is leaning towards more activity in the western part of the basin, which means increased landfall. So I don't think we can call 2011 a fishstorm year.

I agree, and with the set up that is going on , someone is going to get hit, I like fish storms that do not hit anyone, to see a storm form and progress to a hurricane is exciting, especially if the storm stays out to sea and does not affect anyone.
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Quoting KoritheMan:


lol I'm not mad.
Kori, what are your thoughts on 93 L ?
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Quoting TORMENTOSO83:

Ok thnx, dont get mad, it was JUST a question!!!


lol I'm not mad.
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Quoting mrpuertorico:
Hello, you realize that each system when forecasting affecting Puerto Rico tends to weaken?
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Quoting KoritheMan:


People don't seem to understand how much we have time left for conditions to change. Even as it is, they are still much more favorable for US landfalls than they were last year (and still favorable for a Puerto Rico strike, in your case).

Ok thnx, dont get mad, it was JUST a question!!!
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Quoting OCF:
A question inspired by post 1001: has there ever, historically, been an extremely long track Pacific tropical cyclone? That is, declared in the EPAC region, staying far enough south, holding together through the Central Pacific, continuing into the WPAC, and making or nearing landfall in Asia (Philippines, Japan, etc.)? It seems very, very unlikely, and we'd probably only know of cases since satellite monitoring - but maybe it's not completely impossible?


To my knowledge no, though there certainly been several transpacific storms, such as John in 1994:

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Quoting jasoniswildman20x1:
lots of tropical storm going out to sea this years about 90%


Repeat:

...after they hit land.
Member Since: July 6, 2010 Posts: 113 Comments: 32855
Quoting stormpetrol:


I said it before and I'll say it again though I could be totally wrong , 93L will probably be the first real deal of the 2011 Season!!
IF YOURE WRONG WE WILL SERVE YOU CROW FOR DINNER
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Quoting stormwatcherCI:
In other words 93L has a much better chance to develop once it crosses 40 W ?


I said it before and I'll say it again though I could be totally wrong , 93L will probably be the first real deal of the 2011 Season!!
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1045. OCF
A question inspired by post 1001: has there ever, historically, been an extremely long track Pacific tropical cyclone? That is, declared in the EPAC region, staying far enough south, holding together through the Central Pacific, continuing into the WPAC, and making or nearing landfall in Asia (Philippines, Japan, etc.)? It seems very, very unlikely, and we'd probably only know of cases since satellite monitoring - but maybe it's not completely impossible?
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Quoting TropicalAnalystwx13:


It is a little too late for that - that ended when Arlene made landfall in Mexico.

Oh ok, thnx!!!
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Quoting Levi32:


Yes. 50W is where the SSTs get above 28-29C, so that is the big line the waves have to get across right now. They have a better chance west of that.






2005 & 2008.
Member Since: July 6, 2010 Posts: 113 Comments: 32855
Quoting TropicalAnalystwx13:


Where did you get 2/3rds from?

* Bret
* Cindy
* Six (Franklin)

That's 1/2
Why do I feel nobody's reading my posts? I made that point just a little while ago.... lol

Quoting AllStar17:
Blog seems rather quiet this evening despite a tropical depression and three invests with medium potential for development.
Friday night.

Quoting jasoniswildman20x1:
we had lots of name storms going out to sea so far this year!!
But only after they hit land...
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Quoting Levi32:


Yes. 50W is where the SSTs get above 28-29C, so that is the big line the waves have to get across right now. They have a better chance west of that.
93L is still East of 35W so I guess we have a while before development can really be expected. Seems to have a very good circulation but lacks convection.
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Quoting stormwatcherCI:
In other words 93L has a much better chance to develop once it crosses 40 W ?



yes
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
1039. Levi32
Quoting stormwatcherCI:
In other words 93L has a much better chance to develop once it crosses 40 W ?


Yes. 50W is where the SSTs get above 28-29C, so that is the big line the waves have to get across right now. They have a better chance west of that.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
ATCF's 0000Z update on 93L. Winds are unchanged; pressure is up a notch:

AL, 93, 2011081300, , BEST, 0, 116N, 326W, 25, 1011, DB, 34, NEQ, 0, 0, 0, 0, 1013, 200, 60, 0, 0, L, 0, , 0, 0, INVEST, S,
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Quoting presslord:


I meant to spell 'you're' ' your'
So why did I fix it??? Like I did't know that..... lol

Just couldn't think of any apostrophe-bearing words to put in my comment.... hey, it's Friday, after all.... lol
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Quoting Levi32:


A persistent monsoon trough isn't a bad thing. Rather, it promotes development. I have said from well before the season began that the abnormally high ocean heat content between 40W and 60W due to the wild North American winter would persist into the season and tend to focus tropical activity in that region, the central Atlantic towards the lesser Antilles, more so than usual. We have had a fair share of waves attempt to get going in that region, and precipitation has been well above normal in that area as well.

Ocean Heat Content Anomaly:



Precipitation anomaly last 30 days:


In other words 93L has a much better chance to develop once it crosses 40 W ?
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Quoting TORMENTOSO83:
Anyone thinks this could be a fishstorm season? Just a question!!!
4 of the 5 storms we've had so far have hit land. Even hitting only the lowest forecast, that means 1/3 of storms would be landfalling. Plus so many early landfalling storms suggests the pattern is leaning towards more activity in the western part of the basin, which means increased landfall. So I don't think we can call 2011 a fishstorm year.
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1029. Levi32
Quoting twincomanche:
Storms being a tropical storm or more?


Yes. The term generally refers to named storms.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting AllStar17:
Blog seems rather quiet this evening despite a tropical depression and three invests with medium potential for development.


it's Friday night...some people have lives...not me...but some people
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Quoting TropicalAnalystwx13:


Where did you get 2/3rds from?

* Bret
* Cindy
* Six (Franklin)

That's 1/2
opps Don was a Tropical wave, also an August 12th frontal storm, is sort of late.
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1026. Levi32
Quoting Tropicsweatherpr:
Levi,do you see the CV season that is upon us having systems classified in the MDR west of 40W instead of having formations In the Eastern Atlantic near the CV islands because of the persistant monsoon trough?


A persistent monsoon trough isn't a bad thing. Rather, it promotes development. I have said from well before the season began that the abnormally high ocean heat content between 40W and 60W due to the wild North American winter would persist into the season and tend to focus tropical activity in that region, the central Atlantic towards the lesser Antilles, more so than usual. We have had a fair share of waves attempt to get going in that region, and precipitation has been well above normal in that area as well.

Ocean Heat Content Anomaly:



Precipitation anomaly last 30 days:


Member Since: November 24, 2005 Posts: 635 Comments: 26700
1025. ncstorm
can someone explain why these are being force back?

Member Since: August 19, 2006 Posts: 13 Comments: 16225
Quoting TORMENTOSO83:
Anyone thinks this could be a fishstorm season? Just a question!!!


People don't seem to understand how much we have time left for conditions to change. Even as it is, they are still much more favorable for US landfalls than they were last year (and still favorable for a Puerto Rico strike, in your case).
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98E has a really broad circulation according to visible satellite imagery. The major thing it is lacking is convection over the center and eastern part of the invest. Still, 98E is on its way to becoming the next EPAC system.

Member Since: July 6, 2010 Posts: 113 Comments: 32855
Blog seems rather quiet this evening despite a tropical depression and three invests with medium potential for development.
Member Since: June 29, 2009 Posts: 13 Comments: 5315
1021. ncstorm
whats with all the "fish storms" wanting to come back?

Member Since: August 19, 2006 Posts: 13 Comments: 16225
Quoting P451:


+1

I hope that +1 is because you actually got the point, p541.... or both press and I will be disappointed in you... :o)

Quoting twincomanche:
Is that Shakespeare? Or perhaps original Keeper.
Biblical, if u mean the blink of an eye thing. Think it was "slang" back in Elizabethan times...

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1019. ncstorm
hold on..it might get bumpy

Member Since: August 19, 2006 Posts: 13 Comments: 16225
Quoting TomTaylor:


To add on to this, the NAM has been consistently developing 94L after it is split in two by the two ridges joining together. I know the NAM is not the most reliable model and it definitely has trouble over the tropics. However, since the NAM has a higher resolution than the global models and has had a pretty good handle on a few of our other small systems so far, we can't rule out the possibility it is showing.

To show what I mean by consistency, here's a loop of the last four runs for August 15th at 12 UTC.




So that makes the last 4 runs in a row from the NAM now showing potential development from part of 94L.


Anyway, just something to keep in mind, not saying it will actually come to fruition.


Just popping out of lurkdom while it is slow to say that I really enjoy your posts! Hope you stick around - ty!
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Quoting TropicalAnalystwx13:


It is a little too late for that - that ended when Arlene made landfall in Mexico.


LOL
Member Since: September 2, 2006 Posts: 110 Comments: 6878
Quoting Methurricanes:
so 2/3rds of the storms this year came from Fronts, thats unusual.


Where did you get 2/3rds from?

* Bret
* Cindy
* Six (Franklin)

That's 1/2
Member Since: July 6, 2010 Posts: 113 Comments: 32855
1014. Levi32
Quoting TropicalAnalystwx13:
Levi, how active do you foresee the rest of August being?



If that image proves to be accurate, we could see a few more storms yet.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting BahaHurican:
Just seizing the moment... nothing bad intended....


I meant to spell 'you're' ' your'
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so 2/3rds of the storms this year came from Fronts, thats unusual.
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Quoting TORMENTOSO83:
Anyone thinks this could be a fishstorm season? Just a question!!!


It is a little too late for that - that ended when Arlene made landfall in Mexico.
Member Since: July 6, 2010 Posts: 113 Comments: 32855

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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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