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 SouthDadeFish:
We now have surface obs showing a WSW wind. Worthy of code red in my opinion.





wish is that for 92 93 or 94L?
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
Quoting Levi32:


See but all of them kind of deserved classification of some kind because they have all been hybrid systems - subtropical. That's why they should be subtropical cyclones, but the definition is so messed up now that the NHC just calls them fully tropical. If they were classified as subtropical, it would be easy statistically to "cut them out" of the season totals and consider only the storms which represented activity in the tropics.


Indeed, having a total of tropical storms that developed from tropical waves and other similar disturbances can give a good indication of how active the season was, wheras including storms from frontal troughs kind of just inflates the numbers rather than indicating how active the season was.
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93L looked so prime to develop into a tropical depression but it has lost all of it's convection and it just reminds me of Emily a disorganized storm. So my question is does 93L have any chance to develop before of if it reaches if any land mass?
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I have been thinking of the idea that the NHC could stop their jurisdiction at a certain area of the North Atlantic and hand it over to the OPC to issue advisories for shipping.

Certainly would cause less headaches.
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Quoting Stormchaser2007:
18z GFS develops 92L and possibly 94L.

A few days ago 93L seemed like a great candidate.


Lets see what happens on the next few runs, it's still a week out or so. I'd be more than happy for it to run into SA, but we should to see for sure.
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Quoting hamla:
if the cool front makes it into the gom tuesday
something cud devolop in gom net week just a think
Same thing i said not too long ago
Member Since: July 25, 2010 Posts: 0 Comments: 2751
We now have surface obs showing a WSW wind. Worthy of code red in my opinion.

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Quoting Tropicsweatherpr:
And Levi, I have to ask about 93L because of where I am of course. Are enviromental conditions turning more favorable after 50W for it to start to organize?


The water gets warmer there, so that's a plus. However, upper-level conditions may be only marginal, as the GFS shows the TUTT splitting off an upper low that impinges upon the lesser Antilles area, possibly increasing wind shear near 93L once it gets there. It is very possible that conditions supporting significant development and strengthening may not be available to 93L until it gets even farther west than that, in the western Caribbean or near the islands, Bahamas, or Florida, when the MJO pulse moves in and intensifies upward motion there, along with even hotter water.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Going to lurk for a while...
Tryung hard to lurk, but i latch on to comments like a leach...
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Quoting Levi32:


See but all of them kind of deserved classification of some kind because they have all been hybrid systems, subtropical. That's why they should be subtropical cyclones, but the definition is so messed up now that the NHC just calls them fully tropical. If they were classified as subtropical, it would be easy statistically to "cut them out" of the season totals and consider only the storms which represented activity in the tropics.


interesting i guess it makes sense
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Quoting TropicalAnalystwx13:
Good night 94L:



Still think this could become an invest over the weekend...We'll see:



TD #6 will probably become Franklin at the next advisory, tomorrow morning at the earliest:



92L looks a lot better on Visible..lol:



you for got little 93L we sould not wirt here off yet in tell the nhc drop it too 0% but in tell then it has a good ch
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
18z GFS develops 92L and possibly 94L.

A few days ago 93L seemed like a great candidate.
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Evening all. I can tell it's the season. Go to school with three yellow circles, teach all day, come home to four. At least I didn't come home to a named storm or something in the Gulf. That works.
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Quoting Levi32:


It can't really help but acquire some gale-force winds with all the baroclinic support it's getting. Notice how the NHC forecast is 45mph even at post-tropical. This is a hybrid, sub-tropical system, not driven by purely tropical processes. The GFS has the 15C isotherm running straight through the middle of it through the next 48-60 hours. I don't think it deserves "tropical" designation, but if it acquires gale-force winds, it will deserve the name.



We will have to see where the gale force winds come about for TD 6. It very well could end up a a named Subtropical Storm.
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I made a joke this morning about GFS showing 93L going into South America..I guess the GFS heard me..
Member Since: August 19, 2006 Posts: 13 Comments: 16225
Quoting NICycloneChaser:


It almost seems like they are trying to see if they can name as many disturbances as possible to try and challenge for some records, lol.


See but all of them kind of deserved classification of some kind because they have all been hybrid systems - subtropical. That's why they should be subtropical cyclones, but the definition is so messed up now that the NHC just calls them fully tropical. If they were classified as subtropical, it would be easy statistically to "cut them out" of the season totals and consider only the storms which represented activity in the tropics.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Good night 94L:



Still think this could become an invest over the weekend...We'll see:



TD #6 will probably become Franklin at the next advisory, tomorrow morning at the earliest:



92L looks a lot better on Visible..lol:

Member Since: July 6, 2010 Posts: 113 Comments: 32859
And Levi, I have to ask about 93L because of where I am of course. Are enviromental conditions turning more favorable after 50W for it to start to organize?
Member Since: April 29, 2009 Posts: 75 Comments: 14911
18z GFS has 93L getting caught up in SA.

Probably no development.
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Quoting TropicalAnalystwx13:


Well, it has a TCFA right now. What do you think about 92L in regards to becoming a named storm?


Oh it might, perhaps in a while when it starts recurving northward around the western periphery of the ridge, when upper-level winds will be the most favorable. It won't be awfully strong either way.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting Levi32:


If 94L remains a defined entity of some kind, then they might start interacting on some level. If 94L, or some piece of it dives southwest around the ridge, then they could even merge together, or nearly so. It would be a little bit of a mess lol. 92L isn't going to be a significant threat for strengthening either way.

Thanks for your input.
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Quoting TropicalAnalystwx13:
The only thing stopping this from being declared is the National Hurricane Center. Even if it isn't fully detached from the frontal boundary, neither was Cindy or Bret IIRC.



92L is looking really good right now. This will probably become a TD/TS over the weekend, but will likely curve out to sea, without affecting anybody directly.



94L deserves a yellow circle at this point...not really organized. However, there is still hope! It will be interesting to see what happens between 94L and 92L...I think there may be a little Fujiwara if 92L and 94L both develop.


It's pretty clear that 92L is outpacing 94L at this point, and will contribute a nice shot of moisture into the mix of these two. It could get interesting if both deepen with the combined moisture.

I'm expecting 94L to continue slowing down, due to the lower pressure exerted by 92L's wave, but by how much I'm not sure. I can say one thing, this type of interaction is virtually impossible for the models to accurately predict.

If they were to combine, even as wave of low pressure, they could in theory, begin to weaken one another at first, pushing them both further west than anticipated now, because they would essentially become one giant wave of low pressure. Might even become some kind of superwave moving West.

This will be the most interesting interaction so far this season between two adjacent systems, I believe. We all may get an education in the Fujiwara effect.
Quoting Levi32:


If 94L remains a defined entity of some kind, then they might start interacting on some level. If 94L, or some piece of it dives southwest around the ridge, then they could even merge together, or nearly so. It would be a little bit of a mess lol. 92L isn't going to be a significant threat for strengthening either way.

"Some level" is correct ....

How about one giant tropical wave moving west into the GOM?

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Quoting nigel20:

What impact will 94L and 92L have on each other due to their close proximity?


If 94L remains a defined entity of some kind, then they might start interacting on some level. If 94L, or some piece of it dives southwest around the ridge, then they could even merge together, or nearly so. It would be a little bit of a mess lol. 92L isn't going to be a significant threat for strengthening either way.
Member Since: November 24, 2005 Posts: 635 Comments: 26700

New convection around 92L
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Quoting AllStar17:


Arlene caused 25 fatalities. Emily caused 5.


Oops was looking at 7 indirect, my bad. But so far Arlene is the most deadly storm, but we know that will change.
Member Since: September 2, 2006 Posts: 110 Comments: 6878
Tropicfreak,
Close but not quite right... Great guess though
The only to storms with a death toll so far this season,
Arlene: 19 Direct;6 Indirect
Emily: 4 Direct;1 Indirect
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Quoting TropicalAnalystwx13:


Well, it has a TCFA right now. What do you think about 92L in regards to becoming a named storm?


IMO could become Gert or Harvey this weekend.
Member Since: September 2, 2006 Posts: 110 Comments: 6878
Quoting Levi32:


Who knows lol. The NHC has been quite friendly to the random little thunderstorms out there this season. The two ridges on either side are closing in like walls, and there can't help but be an elongated region of cyclonic vorticity between them. Getting a well-defined, symmetric circulation will be difficult. If the current central cluster (northern one) does indeed move north, it might have a chance at another random name (Gert). If it dives south, then probably less of a chance due to subsidence (sinking air) from the southeastern flank of the ridge.


It almost seems like they are trying to see if they can name as many disturbances as possible to try and challenge for some records, lol.
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Quoting tropicfreak:


Those 7 deaths probably came from Arlene.


Arlene caused 25 fatalities. Emily caused 5.
Member Since: June 29, 2009 Posts: 13 Comments: 5315
Quoting MiamiHurricanes09:
720. KEEPEROFTHEGATE,

94L has a TCFA?


Yes.
Member Since: July 6, 2010 Posts: 113 Comments: 32859
it looks like the 18Z GFS is seeing 94L..
Member Since: August 19, 2006 Posts: 13 Comments: 16225
Quoting Levi32:


Who knows lol. The NHC has been quite friendly to the random little thunderstorms out there this season. The two ridges on either side are closing in like walls, and there can't help but be an elongated region of cyclonic vorticity between them. Getting a well-defined, symmetric circulation will be difficult. If the current central cluster (northern one) does indeed move north, it might have a chance at another random name (Gert). If it dives south, then probably less of a chance due to subsidence (sinking air) from the southeastern flank of the ridge.


Well, it has a TCFA right now. What do you think about 92L in regards to becoming a named storm?
Member Since: July 6, 2010 Posts: 113 Comments: 32859
Quoting WeatherfanPR:
I think 94L is moving wnw already but NAM Model still doesn't know. please someone tell him LOL !!!
split i think
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Quoting HurricaneDean07:
Death Toll This season:
30; 23 Direct:7 Indirect

Damage Amount:
N/A; Not none yet

ACE:
9.9

#'s:
(soon to be) 6 Named Storms
0 hurricanes
0 Major hurricanes

TC Formation:
92L: 50%(Currently); 60%(Forecasted by me)
93L: 40%(Currently); 40%(Forecasted by me)
94L: 20%(Currently); 50% to 60%(Forecasted by me)


Those 7 deaths probably came from Arlene.
Member Since: September 2, 2006 Posts: 110 Comments: 6878
Quoting NICycloneChaser:


Levi, what are your thoughts on 94L? It looks like two areas of convection have split, like you mentioned they may do in your tidbit, and the northerly one, somewhat trapped between the two ridges, is building some better convection.


Who knows lol. The NHC has been quite friendly to the random little thunderstorms out there this season. The two ridges on either side are closing in like walls, and there can't help but be an elongated region of cyclonic vorticity between them. Getting a well-defined, symmetric circulation will be difficult. If the current central cluster (northern one) does indeed move north, it might have a chance at another random name (Gert). If it dives south, then probably less of a chance due to subsidence (sinking air) from the southeastern flank of the ridge.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting Levi32:


It can't really help but acquire some gale-force winds with all the baroclinic support it's getting. Notice how the NHC forecast is 45mph even at post-tropical. This is a hybrid, sub-tropical system, not driven by purely tropical processes. The GFS has the 15C isotherm running straight through the middle of it through the next 48-60 hours. I don't think it deserves "tropical" designation, but if it acquires gale-force winds, it will deserve the name.


What impact will 94L and 92L have on each other due to their close proximity?
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T.C.F.W
06L/TD/F/CX
MARK
34N/66W


T.C.F.A.
XX/INV/94L
MARK
25N/55W


POSS T.C.F.A.
XX/INV/93L
MARK
11.35N/30.30W


T.C.F.A.
XX/INV/92L
MARK
18.85N/45.89W


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720. KEEPEROFTHEGATE,

94L has a TCFA?
Member Since: Posts: Comments:
Death Toll This season:
30; 23 Direct:7 Indirect

Damage Amount:
N/A; Not none yet

ACE:
9.9

#'s:
(soon to be) 6 Named Storms
0 hurricanes
0 Major hurricanes

TC Formation:
92L: 50%(Currently); 60%(Forecasted by me)
93L: 40%(Currently); 40%(Forecasted by me)
94L: 20%(Currently); 50% to 60%(Forecasted by me)
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Quoting tropicfreak:


And the trolls coming out. LOL



lol
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
Quoting ElConando:
Wow TD 6 formed, it formed early enough that it has a decent shot of making it to TS status before it is absorbed.


It can't really help but acquire some gale-force winds with all the baroclinic support it's getting. Notice how the NHC forecast is 45mph even at post-tropical. This is a hybrid, sub-tropical system, not driven by purely tropical processes. The GFS has the 15C isotherm running straight through the middle of it through the next 48-60 hours. I don't think it deserves "tropical" designation, but if it acquires gale-force winds, it will deserve the name.

Member Since: November 24, 2005 Posts: 635 Comments: 26700
Another oil leak, this time in the North Sea: Link
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768. hamla
if the cool front makes it into the gom tuesday
something cud devolop in gom net week just a think
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Quoting tropicfreak:


We also need to watch that area off the east coast and a wave that is about to emerge so yeah could be past Jose. Ok maybe I'm getting too far ahead of myself.

The Atlantic is going into overdrive. The Atlantic is making up for lost time.
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Quoting Levi32:


That's a good thing, since it is the only one likely to significantly threaten anybody if it develops. It's also a bad thing, because the weaker it is, if it does develop, it will be farther west, and more likely to impact land areas.


Levi, what are your thoughts on 94L? It looks like two areas of convection have split, like you mentioned they may do in your tidbit, and the northerly one, somewhat trapped between the two ridges, is building some better convection.
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Quoting Tazmanian:



no your no your find it keeps the blog going


And the trolls coming out. LOL
Member Since: September 2, 2006 Posts: 110 Comments: 6878
Quoting Levi32:


That's a good thing, since it is the only one likely to significantly threaten anybody if it develops. It's also a bad thing, because the weaker it is, if it does develop, it will be farther west, and more likely to impact land areas.



Yes...and that's what I am worried about. I appreciate your very accurate and informative forecasts! Are you going to work for the NHC one day?
Member Since: June 29, 2009 Posts: 13 Comments: 5315
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Quoting tropicfreak:


We also need to watch that area off the east coast and a wave that is about to emerge so yeah could be past Jose. Ok maybe I'm getting too far ahead of myself.



no your no your find it keeps the blog going
Member Since: May 21, 2006 Posts: 5091 Comments: 115456
Quoting HurricaneDean07:
Tropicfreak, lol
Yep, though 2 more storms this month likely wont happen, Maybe one more but anyhow that would put us at Jose and thats if everything works out with all of our current invests...


We also need to watch that area off the east coast and a wave that is about to emerge so yeah could be past Jose. Ok maybe I'm getting too far ahead of myself.
Member Since: September 2, 2006 Posts: 110 Comments: 6878

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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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