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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What is south of 95L? Pre-96L maybe?
Member Since: July 19, 2011 Posts: 12 Comments: 2402
am starting too wounder if we could see some in like we saw back in july look whats off the E coast could that be come 96L?

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Quoting GTcooliebai:
After that the GFS tries to bring it into Texas.


Bring it.
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Quoting HOTWHEELS99:
if i use the word (troll) will i fit in here?
kinda weird if you ask me lol


Why not? I mean, if the shoe fits, etc...
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I just love this blog, would make a good book LOL

Two things of current interest with 93L. The first is that it is now in an area of about 20 knots of shear and moving into a lower shear environment over the course of the next 24 horus. The second is that the 850 mb vorticity trails the surface feature by about 200 miles or so. Until that changes development will be real slow.

Conclusion ?. By tomorrow night it may start to look better
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12z ECMWF drags what is left of 93L over the Great Antilles and puts it in the Yucatan channel in 10 days.

No real development shown.
Member Since: June 9, 2007 Posts: 4 Comments: 15891
Quoting rmbjoe1954:


Wow- 93L is modeled out to hit Mexico. Future runs will change though.


been modeled to hit SC too...closes eyes and throws dart at map
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Quoting CosmicEvents:
It's a sore subject if you have a bothersome bunion. Anyway, he's around, and he generally agrees with the NHC. end of story
.
It's rainy and humid here.
Schwetty weather.


lol

Member Since: June 9, 2007 Posts: 4 Comments: 15891
Quoting FLdewey:

*chokes


Listen, he didn't mention cashews. Get a hold of yourself.
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Quoting GTcooliebai:
Things getting interesting...

216hrs.


240hrs.


Wow- 93L is modeled out to hit Mexico. Future runs will change though.
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Quoting Magical:
Ok. Not sure what any
of that means but it was
a sincre question.

If it is sore subject
sorry....I'll move on myself.
It's a sore subject if you have a bothersome bunion. Anyway, he's around, and he generally agrees with the NHC. end of story
.
It's rainy and humid here.
Schwetty weather.
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Quoting Magical:
You people are nuts!


Why do you say that?
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Things getting interesting...

216hrs.


240hrs.
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Quoting Tropicsweatherpr:
2007, why do you you think NHC kept 93L at 40%?


Because it has the potential to develop if it can begin to fire convection and re-organize. With the somewhat unfavorable stable air and moderate shear, I'm not so sure if it will be able to develop before entering the Caribbean. Of course this means that it will track farther south and west than originally thought.

Not really a huge concern if it never gets together.

Member Since: June 9, 2007 Posts: 4 Comments: 15891
Quoting CybrTeddy:
Detaching from the trough. 60% well warranted. Could be TD6 by end of day.
That area's been the only one for fairly rapid cyclogenesis in the basin so far this season.... not liking the odds for anything that gets in close as we progress... thinking anything N of 20, W of 65....
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Neapolitan, thanks for that explanation. It's great. Now I can know stuff. You rock for that.
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Quoting tropicfreak:


Oh god not another mexican system.
After that the GFS tries to bring it into Texas.
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Quoting Magical:
Ok. Not sure what any
of that means but it was
a sincre question.

If it is sore subject
sorry....I'll move on myself.


Best to keep it off the blog.

You have mail.
Member Since: June 9, 2007 Posts: 4 Comments: 15891
Quoting Magical:
Ok. Not sure what any
of that means but it was
a sincre question.

If it is sore subject
sorry....I'll move on myself.


first, you need to give at least 10-15 posts for someone to answer...the fact that you posted it almost back to back sounded lets say pushy...second, you were answered with a short, no longer here...

lastly, some things are not sore subjects, but due to circumstances beyond our control, that person is not here, and we choose to be able to stay here so it is not talked about...
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Nice explanation Nea, thanks

是天气是相当复杂的
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Quoting Neapolitan:


Mandarin, huh? I got your Mandarin right here: ;-)

AL, 93, 2011081218, , BEST, 0, 113N, 315W, 25, 1010, LO, 34, NEQ, 0, 0, 0, 0, 1013, 200, 60, 0, 0, L, 0, , 0, 0, INVEST, S,

AL: In the Atlantic basin,
93: in reference to area of interest #93,
2011081218: at 1800Z on August 12, 2011,
BEST: using the best track objective technique,
0: the AOI is currently located at
113N: 11.3 degrees north latitude
315W: and 31.5 degrees west longitude,
25: with an estimated maximum sustained wind speed of 25 knots
1010: and a minimum sea level pressure of 1010 millibars.
LO: The AOI's highest level of TC development is set as a "low".
34: The wind intensity for the following radii is 34 knots (or less),
NEQ: and that's found in the AOI's northeast quandrant.
0: The wind intensity hasn't been calculated for this quadrant,
0: nor for this one,
0: nor for this one,
0: nor even for this one.
1013: The millibar pressure of the AOI's last closed isobar is 1013,
200: and the radius of the last closed isobar is 200 nautical miles.
60: The maximum winds extend out to 60 nautical miles,
0: but maximum gusts haven't been calculated,
0: and because it's just an invest and doesn't have an eye, we don't know how big that eye is.
L: The AOI is in the Atlantic subregion,
0: The current sea height beneath the AOI is unknown,
[blank]: And the forecaster who wrote this is unknown.
0: The direction of the AOI hasn't been calculated,
0: and neither has the speed.
INVEST: The AOI doesn't have a name or a number,
S: and, finally, it's a shallow system.

天氣可以是一個非常複雜的問題。
Thanks for that definition Nea. I got most of it, but not all. Now the string of numbers will maybe make more sense to me, if I slow down and analyze them.
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382. Hugo7
95 will prolly get a special update saying it is a td, or will be pronounced as td next forcasting. 95 will be raised to around 80precent chances in next 24 hours, emily will be around 50precent. 93 will remain around 50 precent. disturbance off carolina coast could be given 10-20 precent chance. mentioning of a twave in carribeans could happen.
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Quoting JNCali:
So... when the polar ice all melts... granted we'll lose a bit of real estate, but won't it be nice being able to drink all that ocean water since it will be fresh??
is it melting? nothing to worry about in the tropics today models that jump all over development were wrong again seems as if the 1/2 emily is heading out of here
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Quoting Stormchaser2007:
18z models take 93L into the Caribbean as a weak to moderate system.

Needs to develop for this to even happen.
thanks for the info, we in florida need to watch this one i think
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Thanks for the warm welcome.
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2007, why do you you think NHC kept 93L at 40%?
Member Since: April 29, 2009 Posts: 75 Comments: 14260
Quoting presslord:


Look, pal....if you're gonna continue to post this Mandarin...you're gonna have to translate it for me....


Mandarin, huh? I got your Mandarin right here: ;-)

AL, 93, 2011081218, , BEST, 0, 113N, 315W, 25, 1010, LO, 34, NEQ, 0, 0, 0, 0, 1013, 200, 60, 0, 0, L, 0, , 0, 0, INVEST, S,

AL: In the Atlantic basin,
93: in reference to area of interest #93,
2011081218: at 1800Z on August 12, 2011,
BEST: using the best track objective technique,
0: the AOI is currently located at
113N: 11.3 degrees north latitude
315W: and 31.5 degrees west longitude,
25: with an estimated maximum sustained wind speed of 25 knots
1010: and a minimum sea level pressure of 1010 millibars.
LO: The AOI's highest level of TC development is set as a "low".
34: The wind intensity for the following radii is 34 knots (or less),
NEQ: and that's found in the AOI's northeast quandrant.
0: The wind intensity hasn't been calculated for this quadrant,
0: nor for this one,
0: nor for this one,
0: nor even for this one.
1013: The millibar pressure of the AOI's last closed isobar is 1013,
200: and the radius of the last closed isobar is 200 nautical miles.
60: The maximum winds extend out to 60 nautical miles,
0: but maximum gusts haven't been calculated,
0: and because it's just an invest and doesn't have an eye, we don't know how big that eye is.
L: The AOI is in the Atlantic subregion,
0: The current sea height beneath the AOI is unknown,
[blank]: And the forecaster who wrote this is unknown.
0: The direction of the AOI hasn't been calculated,
0: and neither has the speed.
INVEST: The AOI doesn't have a name or a number,
S: and, finally, it's a shallow system.

天氣可以是一個非常複雜的問題。
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So... when the polar ice all melts... granted we'll lose a bit of real estate,  but won't it be nice being able to drink all that ocean water since it will be fresh??
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Quoting tiggeriffic:


i know right...didn't give anyone time to answer before posting again...but alas...tis the season


Yup, and with all the Meds I am on.. my GAFF is pretty low :)
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Quoting Abacosurf:


Enviromentalistic cannibalism.....
Anybody see this story elsewhere besides Fox? I've gotten to the point where I have to have a supporting model w/ that particular news source; it's like one of the less reliable models.

Interesting points to be made though.... I can't see not making the positive choice towards the energy field, but I agree the wildlife should be as protected as possible. I also detect a possibility that the "neighbour" who's seen more than 30 tortoises has some distaste for having a huge electrical plant right next to her house... IMO
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Ok. Not sure what any
of that means but it was
a sincre question.

If it is sore subject
sorry....I'll move on myself.
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Quoting Orcasystems:


Hmm I wonder how many times I should let you say it before I put you on ignore... I think 2 is the limit


i know right...didn't give anyone time to answer before posting again...but alas...tis the season
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Quoting pottery:
While my brain turns to warm jello (gelatinous substance in several dread flavours).

I say when given Jello, make Jello shots ;)
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Oh, boy...
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Quoting Magical:
I has been a long time since I have been here, and admit I am only here when things get busy in the tropics, but am wondering what happened to the "Master Chief" who had a blog here last summer?


He has...moved on.

Not really much to say.
Member Since: June 9, 2007 Posts: 4 Comments: 15891
Wondering what happened to the
Master Chief who posted on here last
summer?
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Complete Update

Pick a line... any line... sooner or later... something will be there.. Choo Choo.

TS BUSTED FORECAST ALIBI





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I has been a long time since I have been here, and admit I am only here when things get busy in the tropics, but am wondering what happened to the "Master Chief" who had a blog here last summer?
Member Since: Posts: Comments:

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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.