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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Jeff Masters

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Quoting MississippiWx:
156:



Models will keep updating and taking in consideration if the system stays as a wave or if it turns into a TS...
The weaker, the farthest it will go West...
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1260. Seawall
The Global IR, what goes around, comes around.
Link
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165..A TS headed toward Jamaica:

Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting JLPR2:


I actually think this one should get a little steam faster than what the GFS is showing making it gain a little latitude faster so I'm not sure, but there is always the possibility that the models are right.
so maybe a mexico landfall hopefully
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1257. j2008
Quoting bigwes6844:
by 4am i believe j2008 they would name it

They dont do an update at 4am but I think they might do a special advisory if thats what your refering to.
On a GOM situation on 93L I think it cant be ruled out. I think we all need to keep our eyes on it, could be pretty bad.
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Quoting MississippiWx:
144



I noticed the 60-84hr frames from this GFS run don't bode too well for Bermuda with regards to 92L.
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1255. JLPR2
Quoting bigwes6844:
do you see this in the GOM?


I actually think this one should get a little steam faster than what the GFS is showing making it gain a little latitude faster so I'm not sure, but there is always the possibility that the models are right.
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Quoting EYEStoSEA:
Thanks Sunliner....I will have to study up on this link..........your thoughts on a GOM situation ?


Looks like 93L is the only with posibilities... Will have to wait till Next monday... Hope you can use that link like a good tool for saving your videos.... It will save your posts up to 6 months...

Link
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156:

Member Since: July 15, 2006 Posts: 17 Comments: 10284
Thanks Sunliner....I will have to study up on this link..........your thoughts on a GOM situation ?
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Quoting JLPR2:
Eventually 93L gets going.

do you see this in the GOM?
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144

Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting j2008:

I have to agree, by 2Am I think we should see TS Franklin, doesnt mean we will though. I do agree, at some time between tonight and tommorow afternoon it will be TS Franklin.
by 4am i believe j2008 they would name it
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1248. JLPR2
Eventually 93L gets going.

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Quoting Thundercloud01221991:


you already posted this... if you post it again I will have to report you


Man, Please, I beg you... put me on ignore...

It was a typo.... But remember... put me on ignore...
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1246. j2008
Quoting extreme236:
TD 6 looks a little better than it did a couple hours ago to me...I think its got a decent chance to become TS Franklin before becoming extratropical.

I have to agree, by 2Am I think we should see TS Franklin, doesnt mean we will though. I do agree, at some time between tonight and tommorow afternoon it will be TS Franklin.
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132:

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Quoting nofailsafe:


On water vapor it sure looks like it.

http://www.ssd.noaa.gov/goes/east/eaus/flash-wv.h tml
oh okay i was thinking it was. Texas needs all of that rain they can get. Im happy for them
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post removed by poster
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Quoting redwagon:


It tries to rain right up until 4p or so, then poof! it's back to blazing hot sky until morning here, too.

Which is strange: we're used to convective rain everyday around 4p, well, in 'normal' years past.


The convective rain stopped short this year it seemed. Up until the last week of July, granted, it was kind of sparse, but we had it nonetheless. I really do wonder when this ridge is going to move though.
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Quoting EYEStoSEA:


That would be it....are you feeling chilly yet ?....lol..
nah nice and humid by me. Im still waiten on it. I heard that it may get into the GOM though. BAD NEWS!
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TD 6 looks a little better than it did a couple hours ago to me...I think its got a decent chance to become TS Franklin before becoming extratropical.
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Quoting nofailsafe:


Looks like that ridge is actually pretty far west, I'm surprised we haven't gotten anything here in Houston from how that looks.

One thing I've noticed the past few days are more clouds in the morning and the linger late into the afternoon/early evening, so perhaps the ridge is softening. We also have a chance of rain tomorrow and sunday, a 20% chance, but that's a lot better than 0%.


It tries to rain right up until 4p or so, then poof! it's back to blazing hot sky until morning here, too.

Which is strange: we're used to convective rain everyday around 4p, well, in 'normal' years past.
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Quoting bigwes6844:
is that the weak cold front coming through on here


That would be it....are you feeling chilly yet ?....lol..
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I just found out this EXCELLENT free service. Check out this link. It is called Short Text...

1. You can enter text
2. You can add a Video URL link to it
3. Then you hit CREATE URL

It will give you a URL with the comment you added and the video in the form:

http://shorttext.com/XXXXX

I created a test video

Click here to see the video

Link


The ShortText main window is

Link
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1233. JLPR2
Quoting AllStar17:
The classic dead invest turned cyclone was Felix. I'll never forget the constant RIP calls on this blog and then it instantly organized and went from a TD to a Cat. 5 in like 24 hours or something.


That was one crazy night. XD
I remember the afternoon before the explosion featured a Pre-Felix shooting tons of arc clouds due to dry air and then at night little cells of convection started firing up and the rest is history.
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Quoting bigwes6844:
is that the weak cold front coming through on here


On water vapor it sure looks like it.

http://www.ssd.noaa.gov/goes/east/eaus/flash-wv.h tml
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Thanks Bigwes and j2008.....I'm trying to digest all this.....geeez~~~~~~~~
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Quoting EYEStoSEA:


Yea....thanks, Redwagon :)



is that the weak cold front coming through on here
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The classic dead invest turned cyclone was Felix. I'll never forget the constant RIP calls on this blog and then it instantly organized and went from a TD to a Cat. 5 in like 24 hours or something.
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Quoting JLPR2:
93L, still as a low.


wait is that Cat 5 hurricane Felix you are showing? lol
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1227. JLPR2
93L, still as a low.
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Quoting MississippiWx:
00z NAM still really likes 94L:

Interesting. Since the NAM typically does better with the smaller systems, I might give it a little extra credence this time around.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting redwagon:

The convection spinning around the TX high also grows with DMAX and dies without. Interesting...one thing you rarely see is nighttime rain or storms here.


Yea....thanks, Redwagon :)



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1224. nigel20
Quoting clwstmchasr:


Models are getting more consistent with 93L to take a track similar to Dean in 2007. A straight west tracker into Central America.

That's what I was thinking too.
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1223. KEEPEROFTHEGATE (Mod)
Quoting Orcasystems:
Complete Update

You have to love it when the train cranks up :)

TS BUSTED FORECAST ALIBI





all aboard the 2011 express next stop the great unknown
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1222. j2008
Quoting EYEStoSEA:
Well darn....where did everyone go? I may get a complex :|

I'm here LOL. Looks as if by the weekend we may have TD 7 & 8. Busy busy out there.
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Quoting redwagon:

The convection spinning around the TX high also grows with DMAX and dies without. Interesting...one thing you rarely see is nighttime rain or storms here.


Looks like that ridge is actually pretty far west, I'm surprised we haven't gotten anything here in Houston from how that looks.

One thing I've noticed the past few days are more clouds in the morning and the linger late into the afternoon/early evening, so perhaps the ridge is softening. We also have a chance of rain tomorrow and sunday, a 20% chance, but that's a lot better than 0%.
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93L at 75 hours out...still a fairly strong wave.

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Quoting EYEStoSEA:
Well darn....where did everyone go? I may get a complex :|
may see an invest in the GOM by monday or tuesday
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Quoting EYEStoSEA:

The convection spinning around the TX high also grows with DMAX and dies without. Interesting...one thing you rarely see is nighttime rain or storms here.
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94L:

Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting nigel20:

93L showing nice spin


Clouds are starting to build on the northeast quad of the circulation, it's starting to look healthier at least.
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Well darn....where did everyone go? I may get a complex :|
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00z NAM still really likes 94L:

Member Since: July 15, 2006 Posts: 17 Comments: 10284
I am soooo behind on my watching....gotta figure this all out...... hello all :)



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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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