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 tropicfreak:


Wow LOL they may have to end up designating two tropical systems today. Would it be named Emily if it develops?


I don't think so. The TWO doesn't call it "the Remnants of Emily" or "an area of low pressure associated with the Remnants of Emily". I think the "real" remnants of Emily got sucked out to the NE. 94L is a part of Emily that split and went south, but I don't think the NHC recognizes it as the remnants of Emily, so it would likely get a new name.
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i think 93L will become hurricane irene. 92L will be hurricane harvey. and 94L will be t.s. gert
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Quoting PolishHurrMaster:
Which seasons excluding this and 2005 had 6 storms on 12nd August?(this seaśon don't have 6 storms now,but i think at 11PM will have)


1933, 1936 (which had 7) and 1995 (which had 7) also did.
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Quoting TropicalAnalystwx13:


2005: 9 named storms by now

1995: 7 named storms by now



Pssst. The post said excluding 2005... ;)
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Break one


Im outta Fresca's !!!!

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here my new poll at 8pm two


92L gos too a high 60%


94L gos too 50 or a high 60%


93l may go too 50%



and we may see some in off NV
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INIT 12/2100Z 36.0N 63.9W 30 KT 35 MPH
12H 13/0600Z 37.0N 61.4W 35 KT 40 MPH
24H 13/1800Z 38.5N 57.8W 40 KT 45 MPH
36H 14/0600Z 39.8N 53.9W 40 KT 45 MPH
48H 14/1800Z 40.6N 49.8W 40 KT 45 MPH...POST-TROP/EXTRATROP
72H 15/1800Z...DISSIPATED
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From a yellow circle to possibly a TD, unreal for both TD 6 and 94L
Member Since: September 2, 2006 Posts: 110 Comments: 6874
Quoting PolishHurrMaster:
Which seasons excluding this and 2005 had 6 storms on 12nd August?(this seaśon don't have 6 storms now,but i think at 11PM will have)


2005: 9 named storms by now

1995: 7 named storms by now
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Quoting P451:


94L


So is it or is it not associated with the remnants of Emily?
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650. j2008
Quoting Thunderpig75:


Don't they all develop as weak cat 1's?

No they all start as TS or TD, I was saying at maximum it will be a Cat 1 at peak. Hope that clarafys a little.
Member Since: December 19, 2008 Posts: 1 Comments: 224
CyberTeddy,

At the end of that loop, it definetly looks like 94L could be getting it's act together.
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Quoting P451:


94L


Wow LOL they may have to end up designating two tropical systems today. Would it be named Emily if it develops?
Member Since: September 2, 2006 Posts: 110 Comments: 6874
Quoting Tazmanian:
so 92L would be TD 7


93L would be TD 8


94L would be TD 9



what you guys think


I think 94L will develop before 93L
Member Since: September 2, 2006 Posts: 110 Comments: 6874
Quoting j2008:

Have to agree, I think 92L will become a weak cat 1 too, if and when it develops.


Don't they all develop as weak cat 1's?
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Quoting P451:


It's not just that but so far we've had nothing but crappy systems that struggled to organize. Half of which that track to no man's land.

Like Don, for example, tracked from Africa to the Rio Grande for a net of 9 raindrops that evaporated on contact.
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Quoting Tazmanian:



93L will be come the 1st hurricane this give 93L little time and befor you no it we have a strong hurricane too track


So you're thinking 93L becomes TD 8, so then most likely Harvey. Hurricane Harvey. Let's see if you're right!
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641. j2008
Quoting Tazmanian:



93L will be come the 1st hurricane this give 93L little time and befor you no it we have a strong hurricane too track

Have to agree, I think 92L will become a weak cat 1 too, if and when it develops.
Member Since: December 19, 2008 Posts: 1 Comments: 224
Mexico and the Caribbean islands sure aren't no man's land for those of us who live here.
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Which seasons excluding this and 2005 had 6 storms on 12nd August?(this seaśon don't have 6 storms now,but i think at 11PM will have)
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Quoting HurricaneGeek:


That sounds reasonable. Which one do you think will be the first hurricane?



93L will be come the 1st hurricane this give 93L little time and befor you no it we have a strong hurricane too track
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Quoting weatherh98:


They would still develop pretty far out the waves are African waves unlike 94 l and td 6


Don and Emily were African waves, but formed too far out to be classed as CV. Here is one definition (which is probably fairly common, and this apparently originated with someone in NOAA):

Link

Subject: A2) What are "Cape Verde"-type hurricanes?

Cape Verde-type hurricanes are those Atlantic basin tropical cyclones that
develop into tropical storms fairly close (<1000km or so) of the Cape
Verde Islands and then become hurricanes before reaching the Caribbean.

(That would be my definition, there may be others.) Typically, this may
occur in August and September, but in rare years (like 1995) there may be
some in late July and/or early October. The numbers range from none
up to around five per year - with an average of around 2.
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Quoting Tazmanian:
so 92L would be TD 7


93L would be TD 8


94L would be TD 9



what you guys think


That sounds reasonable. Which one do you think will be the first hurricane?
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Well in all likelihood, either Gert or Harvey will become a hurricane. So the streak will probably end at 6 or 7 TS to start the season.
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Quoting serialteg:


isnt 94 the emily remnants?


?
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so 92L would be TD 7


93L would be TD 8


94L would be TD 9



what you guys think
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Wrote a Blog


check it out if you want
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i know we have a new td but do anyone see that a weak cold front coming down south and mite stall in the GOM.
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Quoting P451:


It's not just that but so far we've had nothing but crappy systems that struggled to organize. Half of which that track to no man's land.


Well, I wouldn't put Arlene in that category. But the reason we're seeing weak storms is because the conditions are fairly similar to what they where last year, which also saw weak storms just not as many of them develop, which doesn't bode well tbh if they're cranking out this fast.
Member Since: July 8, 2005 Posts: 259 Comments: 23627
94 and 92 - very close to each other. I recall some sort of 'dance' they do where they rotate CCW around a common center. Might that drive 94 into warmer waters and help it develop> And maybe hurt 92 by driving it north?
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Quoting CybrTeddy:
Well.. we're certainty knocking off names this year. Nearly non-stop since Bret.



yup but the thing wish stans a good ch


92L 93L or 94L


i think 92L will be next up in line



all so guys dont give up on 94L this yet it may come right back at you this like 92L is doing


all so 94L has a ch has well
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626. j2008
Quoting CybrTeddy:
94L.. believe it or not.. is looking better organized over the past few hours. Deeper convection is forming directly ontop of the center and has a more consolidated look to it.
Link

TD 7 soon??? LOL
Member Since: December 19, 2008 Posts: 1 Comments: 224
Quoting CybrTeddy:
94L.. believe it or not.. is looking better organized over the past few hours. Deeper convection is forming directly ontop of the center and has a more consolidated look to it.
Link


isnt 94 the emily remnants?
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It appears Franklin won't become a hurricane. That means we most likely will start the season 0-6 for hurricanes. What's the record? It's very interesting especially since the E PAC is 5-0.
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94L.. believe it or not.. is looking better organized over the past few hours. Deeper convection is forming directly ontop of the center and has a more consolidated look to it.
Link
Member Since: July 8, 2005 Posts: 259 Comments: 23627
I am willing to bet that if we have a threat to the US coast and it is the K or L storm a whole bunch of people are gonna say huh what happened to the rest of the alphabet.
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meh.
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Quoting MississippiWx:


How did the meteorologists miss this one? The NHC had this area highlighted for the past 3 days when it had little model support.


Agreed......It formed from the remnants of the vertical front that came down through Florida on Tuesday night and NHC yellowed it on Wednesday.....Generally speaking, these close to home and frontal systems can sometimes spin up pretty quickly in the absence of model support......This one went from 20% to TD without much warning and thank God it was already headed out to sea when it did.
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the low pressure system that has been embedded within a baroclinic
zone off the southeast United States coast during the past day or
two has lost its frontal characteristics over the warm Atlantic
waters. In addition...deep convection has been increasing over the
well-defined low-level center during the past several hours. Based
on its presentation in satellite imagery and earlier buoy
reports...this system is being designated as a tropical depression
with an initial intensity of 30 kt. Significant strengthening is
not forecast since the depression should remain within an
environment of increasing southwesterly shear...fairly dry
mid-level air...and progressively cooler waters. The official
intensity forecast is close to the lgem. Extratropical transition
is expected to occur in about 36-48 hours once the cyclone moves
over waters cooler than 25c and interacts with an approaching
frontal boundary.

The depression is moving 065/14 and is embedded within deep-layer
southwesterly flow between a ridge over the central Atlantic Ocean
and a trough offshore of the U.S. East Coast. This flow pattern is
not expected to change much over the next couple of days and that
should keep the cyclone moving in the same general heading until it
merges with a front. The official track forecast is a little faster
than the model consensus...and close to a blend of the GFS and
ECMWF models.


Forecast positions and Max winds


init 12/2100z 36.0n 63.9w 30 kt 35 mph
12h 13/0600z 37.0n 61.4w 35 kt 40 mph
24h 13/1800z 38.5n 57.8w 40 kt 45 mph
36h 14/0600z 39.8n 53.9w 40 kt 45 mph
48h 14/1800z 40.6n 49.8w 40 kt 45 mph...Post-trop/extratrop
72h 15/1800z...dissipated


$$
forecaster cangialosi/Stewart
Member Since: July 15, 2006 Posts: 17 Comments: 10160
Well.. we're certainty knocking off names this year. Nearly non-stop since Bret.
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Night falling on 93L... 92L/94L next in line for DMIN, TD 6 going to become franklin tonight(Likely)
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am starting to get sick of track TS i want a hurricane
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613. 7544
and we have a dud td6
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Member Since: July 15, 2006 Posts: 17 Comments: 10160
I am however gonna call for a recurve of TD6 before I go.
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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.