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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I am soooo behind on my watching....gotta figure this all out...... hello all :)



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Quoting BahaHurican:
Nawp... was a pretty lowkey day.... I'm more interested in tomorrow, to see what kind of interaction we'll see between 92 and 94.... could be interesting.


Agreed, it will be interesting indeed. I'm forecasting they will interfere with one another, weakening both, creating an enormous tropical wave that eventually works its way into the GOM.
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Quoting BahaHurican:
Nawp... was a pretty lowkey day.... I'm more interested in tomorrow, to see what kind of interaction we'll see between 92 and 94.... could be interesting.


Agreed, it will be interesting indeed. I'm forecasting they will interfere with one another, weakening both, creating an enormous tropical wave that eventually works its way into the GOM.
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St. Petersburg, Whitted Airport
Lat: 27.77 Lon: -82.63 Elev: 8
Last Update on Aug 12, 10:53 pm EDT

Fair

86 °F
(30 °C)
Humidity: 88 %
Wind Speed: N 6 MPH
Barometer: 29.93" (1013.4 mb)
Dewpoint: 82 °F (28 °C)
Heat Index: 104 °F (40 °C)

Visibility: 10.00 mi.
More Local Wx: 3 Day History:


just another steamy night in the Tampa Bay area :)


Ive been running in this weather a lot, it may not feel too great, but its great for health!
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love the activity but hard to believe that there hasnt been a hurricane yet
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Quoting GTcooliebai:
Maybe it won't make it to Franklin?


It's possible...
Member Since: July 15, 2006 Posts: 17 Comments: 10284
I checked this blog yesterday and all that was there was 92L now 3 new tropical systems!!! The Cape Verde season is starting!!! Getting active now!
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1203. nigel20
Quoting sunlinepr:


Looks like it is organizing all clouds around it.... Huge system.. for the moment...

The Atlantic is now in overdrive.
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Quoting MississippiWx:
300UTC image of 94L...still organizing steadily.



Btw, TD6 could exit stage right as quickly as it came upon us. It looks sickly at the moment.
Maybe it won't make it to Franklin?
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Complete Update

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

TS BUSTED FORECAST ALIBI





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Quoting nigel20:

93L showing nice spin


Looks like it is organizing all clouds around it.... Huge system.. for the moment...
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SHIPS still diagnoses some high shear over 93L but improves the environment soon...should see some decent organization in the next couple days.

Also, SHIPS makes 94L into a hurricane at 84 hrs, albeit barely.
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1198. JLPR2
Quoting Hurricanes12:
200mb Vorticity



500mb Vorticity



700mb Vorticity



93L is starting to show up on the 850mb vort with a nice bu displace to the SW mid-level circulation.
To me it seems 93L is getting ready to start developing, but very slowly.
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200mb Vorticity



500mb Vorticity



700mb Vorticity

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300UTC image of 94L...still organizing steadily.



Btw, TD6 could exit stage right as quickly as it came upon us. It looks sickly at the moment.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
1195. nigel20
Quoting KoritheMan:
Unfortunately I can't stick around, but I wrote a blog on the active Atlantic if anyone wants to read.

Nice informative blog, keep up the good work.
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Quoting MississippiWx:


The new convergence/divergence maps, as well as the shear maps should be coming out pretty soon.

You can also see banding on the NW and NE sides of it...another sign of organization.

They're out. Everything has remained about the same, with the exception of upper-divergence strengthening slightly.

Nice inflow moving in from all directions to the circulation which looks to be around 26.5˚N 57.5˚W.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting Grothar:


Should be very interesting. The early GFS is hinting at it already. The heavy storms in Central Africa are exceptionally large.

I have a feeling this week may be just the lead up to some major increase in ATL' activity as we approach the weeks ahead of peak season.
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1192. nigel20

93L showing nice spin
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Quoting MississippiWx:


The new convergence/divergence maps, as well as the shear maps should be coming out pretty soon.

You can also see banding on the NW and NE sides of it...another sign of organization.



Not much change on the convergence maps or vort maps...

However, 94L has a fairly small low level circulation, so I wouldn't expect the convergence map to show much.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
inevest 92L LOOKING LITTLE BETTER
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93L 11N, 33W
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Quoting MiamiHurricanes09:
We'll see how it fares throughout the night. Firing some moderate pockets of convection as we speak.

Yeah, kinda weird they have it at 30%. As far as percentage on the next TWO, I'm with you. Although the convective activity is somewhat lackluster, the circulation has become better defined over the past few hours as you noted.

Further organization shouldn't be a problem from my point of view, upper-level winds are a partially favorable 10-12kts or so.

Let's see if it can work on its divergence/convergence however, which at the moment is quite poor.


The new convergence/divergence maps, as well as the shear maps should be coming out pretty soon.

You can also see banding on the NW and NE sides of it...another sign of organization.

Member Since: July 15, 2006 Posts: 17 Comments: 10284
1186. Grothar
Quoting superpete:
Grothar..is that one blob on its own in east central Africa?? Interesting to see what that does when it hits the warm pond


Should be very interesting. The early GFS is hinting at it already. The heavy storms in Central Africa are exceptionally large.
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Quoting AllStar17:
93L is not as dead as one might think.


Correct. The structure of 93L is still pretty decent and can be seen more clearly on the TPW loop.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting CybrTeddy:
Very possible that TD6 will not become Franklin, and I see 94L has become better organized.
We'll see how it fares throughout the night. Firing some moderate pockets of convection as we speak.

Quoting MississippiWx:


94L should be adjusted closer to 50%, if not higher at the next TWO.
Yeah, kinda weird they have it at 30%. As far as percentage on the next TWO, I'm with you. Although the convective activity is somewhat lackluster, the circulation has become better defined over the past few hours as you noted.

Further organization shouldn't be a problem from my point of view, upper-level winds are a partially favorable 10-12kts or so.

Let's see if it can work on its divergence/convergence however, which at the moment is quite poor.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting JLPR2:


Something interesting there, you can see the next area emerging from Africa pulling the low level clouds towards it.

Also I see an increase on mid-level clouds with 93L, maybe a mid-level is ready to fire up too? Like 92L.


The thickening of the clouds associated with 93L makes me think it's going to pop tonight during d-max. It will be interesting to watch.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
1182. nigel20

The wave train continues.
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93L is not as dead as one might think.
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1180. JLPR2
Quoting MississippiWx:
This loop will be fun to watch tonight...You can see a fairly decent spin associated with 93L right now and notice the shape of the low level clouds that are forming around the relatively "naked" low. It appears to me that 93L is about to fire up some convection with the development of these low level cumulus clouds. We'll see...

Link


Something interesting there, you can see the next area emerging from Africa pulling the low level clouds towards it.

Also I see an increase on mid-level clouds with 93L, maybe a mid-level circulation is ready to fire up too? Like 92L.
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Grothar..is that one blob on its own in east central Africa?? Interesting to see what that does when it hits the warm pond
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Quoting Thunderpig75:


A total wak job with millions of listeners and dollars.
Kinda like Glen Beck and Rush Limbaugh, they got all the money,but make no sense, or is that nonsense?
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1177. nigel20

The models are pushing further west with 93L.
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Quoting MiamiHurricanes09:
I don't see any of your comments removed.
\

See posts 1131 and 1134.
Member Since: September 2, 2006 Posts: 110 Comments: 6878
1175. Grothar
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Quoting MiamiHurricanes09:
Wouldn't that be something? If the two invests designated today became tropical cyclones before the other two tropical waves we've been monitoring for days.


94L should be adjusted closer to 50%, if not higher at the next TWO.
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Very possible that TD6 will not become Franklin, and I see 94L has become better organized.
Member Since: July 8, 2005 Posts: 259 Comments: 24548
This loop will be fun to watch tonight...You can see a fairly decent spin associated with 93L right now and notice the shape of the low level clouds that are forming around the relatively "naked" low. It appears to me that 93L is about to fire up some convection with the development of these low level cumulus clouds. We'll see...

Link
Member Since: July 15, 2006 Posts: 17 Comments: 10284
Quoting tropicfreak:
Oh god not again, whoever is trying to remove my comments please stop, that is very childish, and represents an idiot.
I don't see any of your comments removed.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Late night check in, good evening everyone. I see some of the latest model runs showing Invest 93L taking more of a southerly- longer track thru the Caribbean, may be of interest for us here in Cayman next week. Watch and wait for the short term ahead.
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Quoting MississippiWx:
A vigorous low level circulation can be seen spinning just west of the convection in 94L...a little gain in convection and we could have TD7:

Wouldn't that be something? If the two invests designated today became tropical cyclones before the other two tropical waves we've been monitoring for days.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
1168. j2008
There goes the blog, I'll be back in a couple hours LOL.
Member Since: December 19, 2008 Posts: 1 Comments: 224
Oh god not again, whoever is trying to remove my comments please stop, that is very childish, and represents an idiot.
Member Since: September 2, 2006 Posts: 110 Comments: 6878
Caribbean Storm Update



















Spainsh

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Quoting MississippiWx:
I'd recommend you to view this loop of 94L and you can see what I'm talking about with regards to the low level spin...I'd expect 94L to continue its organization trend with such a vigorous spin at the surface...

Link

Agreed.
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Quoting MississippiWx:
A vigorous low level circulation can be seen spinning just west of the convection in 94L...a little gain in convection and we could have TD7:



Looks like TD 6 may have some competition getting to Franklin.
Member Since: September 2, 2006 Posts: 110 Comments: 6878
Africa, please be Quiet!!!!

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I'd recommend you to view this loop of 94L and you can see what I'm talking about with regards to the low level spin...I'd expect 94L to continue its organization trend with such a vigorous spin at the surface...

Link
Member Since: July 15, 2006 Posts: 17 Comments: 10284

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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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