Two African waves, 92L and 93L, worth watching

By: Dr. Jeff Masters , 2:59 PM GMT on August 11, 2011

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An African wave is near 13°N 35°W, about 700 miles west-southwest of the Cape Verde Islands. This system, (Invest 92L), is moving west to west-northwest at 10 - 15 mph, and has the potential to develop into a tropical depression or tropical storm before arriving near the northern Lesser Antilles Islands early next week. Recent visible satellite loops show that 92L has less heavy thunderstorm activity near where it is trying to develop its circulation center than yesterday. Water vapor satellite loops that a large area of dry air lies just to the west of 92L, but the atmosphere in the immediate vicinity of 92L is moist. Even so, the decline of heavy thunderstorm activity since yesterday implies that dry air is probably working its way into 92L. The SHIPS model and University of Wisconsin CIMSS wind shear analysis are showing moderate wind shear of 10 - 15 knots affecting 92L. Sea surface temperatures are 26.5° - 27°C, which is very close to the 26.5°C threshold usually needed to support a tropical storm.


Figure 1. Morning satellite photo of Invest 92L and Invest 93L.

Forecast for 92L
Low to moderate wind shear of 5 - 15 knots is predicted along 92L's path over the coming three days, which should allow the storm to organize, assuming it can shut out any incursions of dry air that might intrude. 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 30% chance of developing into a tropical depression by Saturday morning in their 8am outlook. A steady west to west-northwest motion for 92L is predicted by all of the models, which would put the storm in the vicinity of the northern Lesser Antilles Islands by Sunday. On Saturday and Sunday, 92L is expected to enter a region where an upper-level low pressure system will bring high wind shear of 20 knots to the storm, which should slow development. This upper-level low is also expected to turn 92L more to the northwest, so the storm is likely to pass north of the Lesser Antilles, though may pass close enough to give heavy rains to the northernmost islands. It is too early to know if 92L will recurve out to sea and potentially threaten Bermuda, or continue to the northwest towards the U.S. East Coast.

93L
An African wave that emerged off the coast of Africa is near 10°N 22°W, a few hundred miles south of the Cape Verde Islands. This system, (Invest 93L), is also moving west at 10 - 15 mph, and has the potential to develop into a tropical depression or tropical storm before arriving near the northern Lesser Antilles Islands near the middle of next week. Recent visible satellite loops show that 93L has a decent amount of heavy thunderstorms, but this activity is not well organized. There is not much spin associated with 93L yet. 93L is fairly well-protected from dry air to its north and west. The SHIPS model and University of Wisconsin CIMSS wind shear analysis are showing moderate wind shear of 10 - 20 knots affecting 93L. Sea surface temperatures are 27.5°C, which is one degree above the 26.5°C threshold usually needed to support a tropical storm.

Forecast for 93L
Moderate wind shear below 20 knots is predicted along 93L's path over the coming five days, which should allow the storm to steadily organize. 93L is about 600 miles east of 92L, which is close enough that the two systems may interfere with each others' organization. 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 20% chance of developing into a tropical depression by Saturday morning in their 8am outlook. Due to moister air, the potential for less wind shear, and a more southerly track, 93L is probably a greater threat to the Lesser Antilles than 92L.

Jeff Masters

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Does anyone have a good link to a forecast map of the ULL that is supposed to come down in a few days? One that shows where the ULL 'might' be in the future?

Thanks.
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Quoting Levi32:
92L seems a likely recurve at this time. The jury is still out on 93L. It could easily affect either the northeast Caribbean islands or the southeast U.S., or both, in the long term. It's too early to say for certain. That trough over the eastern seaboard is replaced by a zonal flow over southeastern Canada with a weakness underneath by all of the ensemble suites Days 8-12. That setup could easily bring something close to the coast if we have a storm approaching during that time frame. 93L could be that storm if it develops. Guarantees on its track would be unwise at this time.


So you're saying that by early next week, the long range models may start to show tracks based on the weakness?

Also about this time, they may also show any track modifcation based on closeness. Is it possible to predict the "warp" in path because of this (one will "rise" in latitude, while the other "drops" in latitude, right?)

Hope this makes sense...
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Quoting SouthDadeFish:
Reed to be honest, as long as is the Death Ridge is over Texas, we will see a pattern that favors troughing over the east coast.


The pattern does favor re-curving until further notice. The High over Texas won't really allow for any GOM storms for now. Which would be nice most of the time but last I checked they are still in a major drought along with other GOM states. Could see something like 2010 many strong storms re-curving out to sea with main threats to Bermuda and possibly the NE US and Canada. The pattern could change in the next couple of weeks but in my opinion, those windows of pattern change will be small, but if storms get there at the right time...
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Let's get back to the tropics please and stop talking about individual posters. They have their own blogs/pm's if you wish.

Latest visible for 92L:


Looks elongated to me.
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Quoting weatherman12345:
he wasnt right about emily... it dint hit florida which he predicted


Oh no, a 40 mile error, BIG WHOOP!!
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Quoting 800733:
hi all new here from daytona beach fl, think I might just read a while and maybe at some point ask a few questions.


I live in Palm Coast, FL
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I was doing a mail out for UNICEF at work tonight. It's about the crisis in the Horn of Africa that Dr Masters did a blog about a few weeks ago. Here is a link if anyone would like a copy. Its in PDF format.
Cheers and Goodnight
AussieStorm
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BUT, was he right about Earl, Emily and such? YES, so stop criticizing reed.

He wasnt he did change his forescast every minute after reading Levy
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Quoting weatherman12345:
he wasnt right about emily... it dint hit florida which he predicted


Never said it was gonna hit FL, just said it would come very close, if not a brief landfall, then head north, then recurve out to sea.
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Quoting nrtiwlnvragn:
OSCAT caught most of 92L


I wish it caught the other side of the circulation to see how elongated it really is...
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Quoting ProgressivePulse:



Looks well defined and closed to me.


Looks that way but don't know how much to trust OSCAT, what are it's biases etc.
Member Since: September 23, 2005 Posts: 14 Comments: 11212
Quoting Jedkins01:


I'm not jumping on him, I just don't think its a good idea to get people worrying that the U.S. is going to have an active season. People should always be prepared for hurricane season, but if we tell them a bunch of hurricanes could hit in a given year, and doesn't happen, it makes us weather people look bad. I know we aren't pros, but as someone who is seeking to be professional meteorologist, I don't want to get people panicking about a particular season. Even more so when the pattern has yet to show any signs of favoring hurricane landfalls.

As i clearly stated, yes the pattern could change, and hurricanes could start making landfall in the U.S. but it hasn't happened yet, so need to get stressed about anything. Even if the pattern does begin to favor southeast U.S. strikes. We still don't want to get people worried, neither should we be worried. When a hurricane comes within a few days of striking the U.S. and computer models have a consensus that it will do so. Then is when we need to start worrying, until then we should always be prepared, regardless if an active period is expected or not.
Well I guess that's because I took away something different from his posts than you do. Yes the pattern currently doesn't favor U.S. landfalls, but as long as people are aware there is chance that could change than so be it. It is not a good idea to get people worried for a storm ten days out even if it does favor a U.S. strike as you said. I guess it's awareness vs. worrying and apparently there is a fine line. No reason to get too worked up over two tropical waves still S and SW of the Cape Verde islands ;~) Not even a red circle yet either.
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hi all new here from daytona beach fl, think I might just read a while and maybe at some point ask a few questions.
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Honestly, I tend to agree with everyone who has chimed in regarding 93L and future tropical systems. Timing is a big factor regardless of if a strong/weak high or strong/weak trough is in place to steer or recurve storms.

The fact of the matter is that everyone keeps on talking about the EURO, GFS, NOGAPS, etc…. within 10 days or so.

If we all remember what Levi, the guy at Crown Weather and others have been saying (unless things have changed) is that the pattern change is coming up as early as 8-15 days, meaning it could be later but the consensus is that all the troughs should be moving westward making way for a westward stronger Bermuda High increasing the likelihood of storms to impact the SE CONUS

Is this a guarantee?? Well of course not but the logic and patterns favor this.

Models should be taken into account but not before a storm has even formed. If the High is strong and acts as a steering mechanism then a whole lot of people could be in a heap of trouble and if troughs are there at the right time, they will recurve

All I can say is that the patterns the past couple of years are certainly different from 2004 and 2005 when storms were slamming into Florida left and right.
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125. SouthDadeFish 4:50 PM GMT on August 11, 2011 +1
I don't get why everyone is jumping on Reed though. Although he may tend to forecast a little more west than others, he brings up a good point on not letting up your guard. He isn't saying this will be a Cat 5 hitting the east coast.... He has a good point of Earl and other storms not recurving as far east as expected early in the runs.

bla.bla.bla.Reedzone have a super perfect storm in his mind everytime that a wave come off Africa,,,,
the "recurvature" word he learned just last year when he missed every single of his "forescast" when the storms went out to sea .
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Quoting nrtiwlnvragn:
OSCAT caught most of 92L





Looks well defined and closed to me.
Member Since: August 19, 2005 Posts: 5 Comments: 5449
Quoting weatherman12345:
honestly, ur soooooo west bias its not even funny



BUT, was he right about Earl, Emily and such? YES, so stop criticizing reed.
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OSCAT caught most of 92L


Member Since: September 23, 2005 Posts: 14 Comments: 11212
Quoting SouthDadeFish:
I don't get why everyone is jumping on Reed though. Although he may tend to forecast a little more west than others, he brings up a good point on not letting up your guard. He isn't saying this will be a Cat 5 hitting the east coast.... He has a good point of Earl and other storms not recurving as far east as expected early in the runs.


I'm not jumping on him, I just don't think its a good idea to get people worrying that the U.S. is going to have an active season. People should always be prepared for hurricane season, but if we tell them a bunch of hurricanes could hit in a given year, and doesn't happen, it makes us weather people look bad. I know we aren't pros, but as someone who is seeking to be professional meteorologist, I don't want to get people panicking about a particular season. Even more so when the pattern has yet to show any signs of favoring hurricane landfalls.

As i clearly stated, yes the pattern could change, and hurricanes could start making landfall in the U.S. but it hasn't happened yet, so need to get stressed about anything. Even if the pattern does begin to favor southeast U.S. strikes. We still don't want to get people worried, neither should we be worried. When a hurricane comes within a few days of striking the U.S. and computer models have a consensus that it will do so. Then is when we need to start worrying, until then we should always be prepared, regardless if an active period is expected or not.
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Quoting reedzone:


Really, perhaps you weren't thee when I predicted Bill to glaze New England.. Or maybe you weren't there last year when I predicted Earl to scrape the East Coast while all models had it hitting Bermuda. Most models have an east bias, watch the models shift a bit more westward in time with both invests.
Reed don't let people tell you what you know or don't know. Keep making your forecasts and people will find out for themselves how much you know. I enjoy reading your posts, and I can tell you have improved over the years. I think you did a good job with Emily. Keep up the good work. Just keep an open mind to suggestions.

In other news, I don't think 93L is as impressive as I first thought. It doesn't have that much vorticity associated with it, and as a result I still think it has a few more days before we see any consolidation and intensification. 92L on the other hand has a decent amount of vortcity, and if it can consolidate some, isn't that far off from becoming a tropical cyclone in my opinion. Center is still much too elongated for now.
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Quoting reedzone:


There's just no use in arguing with a troll (STORMTOP).. I apologize.


Aquak told me that he was stormtop so I put him on ignore.
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Quoting tropicfreak:


Put cloudburst on ignore, he clearly has no idea what he is talking about.


There's just no use in arguing with a troll (STORMTOP).. I apologize.
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Quoting reedzone:


Really, perhaps you weren't thee when I predicted Bill to glaze New England.. Or maybe you weren't there last year when I predicted Earl to scrape the East Coast while all models had it hitting Bermuda. Most models have an east bias, watch the models shift a bit more westward in time with both invests.


Put cloudburst on ignore, he clearly has no idea what he is talking about.
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Quoting cloudburst2011:



reed you are not to smart when it comes to the tropics so give it a rest..


Really, perhaps you weren't thee when I predicted Bill to glaze New England.. Or maybe you weren't there last year when I predicted Earl to scrape the East Coast while all models had it hitting Bermuda. Most models have an east bias, watch the models shift a bit more westward in time with both invests.
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weakkkkk!!!
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92L is a mess right now. Way too much dry air and its' less organized than yesterday IMO. It's circulation is all stretched and more broad today, also less convection unless you count the monsoon trough to its south.

93L has a much better chance as many believe on here, but until we get a TD or Tropical storm, those models are what they are as REEDZONE pointed out. Emily is a perfect example of a type storm track that could very well be the norm this season. Anything can happen, but 7-10 days down the road is like tossing a quarter into a coffee cup from 20 feet away, ESPECIALLY when all we have are blobs...

One thing to point out is the SAL right now coming off the west coast of Africa is migrating west south west. 93L could VERY easily wrap that in. The biggest player this season to me anyway has been the dry air at mid levels which has significantly limited every system we have had this season up to now.
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I don't get why everyone is jumping on Reed though. Although he may tend to forecast a little more west than others, he brings up a good point on not letting up your guard. He isn't saying this will be a Cat 5 hitting the east coast.... He has a good point of Earl and other storms not recurving as far east as expected early in the runs.
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Member Since: July 15, 2006 Posts: 174 Comments: 54353
Interesting to note.

2005, the only true Cape Verde storm to effect land was Emily.

All others re-curved that developed in the MDR or formed beyond 60 west and went on to effect land.
Member Since: August 19, 2005 Posts: 5 Comments: 5449
Quoting weatherman12345:
interesting... looks fairly zonal in at the end of this run with a dominating high


Makes sense as the trough that recurves 92L lifts out.. Your troughing pattern is over with as a ridge builds in. Thus starting the blocking pattern as the ensembles are showing. It's really all about timing with both invests. If they are slow to move over the next few days, it allows the trough to quickly come and go.
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Quoting weatherman12345:
last time i checked 92l was 5 days from the northern islands... shows how much you know


Please don't be sarcastic with reed, he made a simple error, even the greatest of experts make mistakes.
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Quoting reedzone:


Adrian, I understand your rooting for recurvature.. but it's about a week away for us to watch, still too early and even Dr. Masters himself said it's too early to pinpoint a future for both 92L and 93L. Emily was supposed to recurve (according to the GFS) north of PR, instead, it was extremely close to Florida, to the point where wind and rain glazed the coastline. Earl last year was expected to recurve around Bermuda, instead it recurved dangerously close to the US. Even Igor was supposed to recurve east of Bermuda, rather then a bit west of the island. Things change and models recrve storms wayy too early then what mother nature does. It just needs to be watched and not taken for granted that a trough is gonna save us every time. This isn't 2010, the blocking pattern is coming quickly according to the ensembles of the GFS and EURO. If you listened to Levis video yesterday, he explains a good point. I'm not rooting for a landfalling storm, but I know in reality, models and models and they can be wrong, and have been wrong in the past. So it's just a wait and see if the EURO could be right and a huge unseasonable trough develops. I seriously doubt it. However, everybody on US Coastline should be preparing for a very active season.


I agree that its way too early to tell, but, we are allowed to have early speculations. I myself believe we will have more systems either heading too far south till they hit Central America, or Mexico, maybe Texas. Or the will curve out to sea.

The fact is, the pattern that is dominant now still favors storms curving out to sea. Until that changes, that is is going to often be the case. I'm not saying that can't or won't change, but looking ahead at the weather patterns in Florida, the trough pattern has not weakened, in fact, it has gotten stronger. The last trough sequence brought very heavy rains to much of Florida. Computer models are already showing another trough digging down for early next week.

Until this pattern changes, the highest chance is that tropical cyclones will curve out to sea. Or if they are far enough south in the Caribbean, they will go due west into Central America/Mexico.


Like I said, the pattern could change. But I don't want to be crying wolf by telling everyone that the Southeast could get battered by hurricanes later this season if the patterns don't favor so yet.

If the pattern changes, there will still be plenty of time to warn people if an approaching hurricane is a threat. But people have no need to be worried this season about storms that don't even exist yet, many of which may miss anyway.

If a hurricane develops and has a high threat to the Southeast U.S. there will be plenty of time to warn people. But there's no reason to warn them about threats that don't exist yet.



The fact is, people should always have a hurricane plan every year, and should have some sort of survival kit, and head warning of forecasters and evacuations. But people don't need to be, and shouldn't be told this year is going to be an active year for the U.S. they need to just prepared regardless. Telling people its going to be an active year will get people panicking.
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Quoting weatherman12345:
interesting... looks fairly zonal in at the end of this run with a dominating high


And exactly what Levi hinted to in his Tropical Tidbit today! Should be interesting to see how it actually plays out!
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Quoting reedzone:
92L and 93L is about two weeks away from nearing anybody at this point.. It's just something to watch for now.


If there is any immediate threat, it would be the lesser antillies, which they need to keep a close eye on that duo.
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Quoting ncstorm:


the euro didnt develop Emily..all these models have been inconsistent this season..you just have to hope one of them gets it right when it counts..
To be honest Emily was really never much of anything. The low and mid level centers never got stacked. Euro did show a weak reflection, which was pretty accurate. She was mostly just a bunch of convection.
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Quoting SouthDadeFish:
Reed to be honest, as long as is the Death Ridge is over Texas, we will see a pattern that favors troughing over the east coast.
Thank you. +1.
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92L and 93L is about two weeks away from nearing anybody at this point.. It's just something to watch for now.
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Quoting SouthDadeFish:
Yeah the Euro isn't too enthusiastic about cyclogenesis with these two waves either. It has done a pretty darn good job so far this season, so I'm siding with the Euro on this one. There will be plenty more waves though...


the euro didnt develop Emily..all these models have been inconsistent this season..you just have to hope one of them gets it right when it counts..
Member Since: August 19, 2006 Posts: 13 Comments: 15666

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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.