Little change to 90L; new African tropical wave is worth watching

By: Dr. Jeff Masters , 8:53 PM GMT on July 30, 2010

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Invest 90L is a tropical wave in the eastern Atlantic near 10N 33W with a very limited amount of heavy thunderstorm activity but a decent amount of spin. It does not have a well-defined surface circulation, and has shown little change in organization today. CIMMS wind-shear analyses show a low amount of wind shear (5 - 10 knots) over 90L, and sea surface temperatures are a record warm 29°C. The wave currently is in a moist environment and is not being affected by the dry Saharan Air Layer (SAL) to its northwest. The disturbance has moved far enough away from the Equator to leverage the Earth's spin to help it develop. The Saharan Air Layer with its dust and dry air lurks just to the north of 90L, but the SHIPS model predicts 90L will remain far enough from the dry air over the next five days so that it will not interfere with development.


Figure 1. Afternoon visible satellite image from 2pm EDT 7/30/10 of the relatively tiny 90L, and the large new tropical wave that moved off the coast of Africa yesterday.

Forecast for 90L
One factor inhibiting development of 90L this week will be the Madden-Julian Oscillation (MJO.) The MJO currently favors downward motion over the tropical Atlantic, which will act to decrease the chances of tropical storm formation. The Madden-Julian oscillation is a pattern of enhanced rainfall that travels along the Equator from west to east. The pattern has a wet phase with large-scale rising air and enhanced thunderstorm activity, followed by a dry phase with large-scale sinking air and suppressed thunderstorm activity. Each cycle lasts approximately 30 - 60 days. When the Madden-Julian oscillation is in its wet phase over a hurricane-prone region, the chances for tropical storm activity are greatly increased.

Perhaps the main factor interfering with 90L's development will be the presence of the large tropical wave to the east of 90L that moved off the coast of Africa yesterday. This new wave is large enough and close enough to 90L that it will probably begin to dominate regional weather patterns this weekend, stealing away 90L's inflow of low-level moist air. The new wave may also act to bring sinking air over 90L that will tend to suppress 90L's thunderstorm activity. It may turn out that the new wave will also steal some of 90L's spin, and end up being a threat to develop itself later on this weekend.

The latest 8am EDT (12Z) model runs for 90L show very little in the way of development of the storm. The predominant track forecast takes 90L into or just north of the northern Lesser Antilles Islands about 6 - 8 days from now. Looking at climatology based on research done by Dr. Bob Hart at Florida State University,, 90L has a 19% chance of developing into a tropical cyclone by 2pm Sunday. NHC is putting these odds at 20%. Dr. Hart also has an experimental product showing that historically, about 30% of all tropical cyclones that develop at 90L's current position eventually hit land as a hurricane. Of course, 90L is not yet a tropical cyclone, and I think that the large tropical wave off the coast of Africa will kill 90L this weekend.

Tropical wave in the eastern Caribbean
A tropical wave in the eastern Caribbean, south of the Dominican Republic, is moving west at 15 - 20 mph with no signs of development. The wave is under a high 20 knots of wind shear, due to strong upper-level westerly winds from an upper level low centered north of Puerto Rico. This shear is expected to remain remain high through Saturday. By Sunday, when the wave will be approaching Nicaragua, the wave will be far enough away from the upper level low that shear should fall to the moderate range, 10 - 20 knots. Some development is possible on Sunday, but the wave will have only about a 1-day window to develop before its westerly motion brings it inland over Nicaragua on Monday. NHC is giving this wave a 10% chance of developing into a tropical depression by 2pm Sunday.

Extreme cold records for 2010
In my post yesterday, I reported that fourteen countries had set their all-time hottest temperature record this year. I neglected to mention that one country has also set its coldest temperature in recorded history mark in 2010. Guinea had its coldest temperature in its history on January 9, 2010, when the mercury hit 1.4°C (34.5°F) at Mali-ville in the Labe region. Of the 229 countries with extreme coldest temperature records, 14 of these records have occurred in the past ten years (6% of all countries). There have been five times as many (74) extreme hottest temperature records in the past ten years (33% of all countries.) My source for extreme weather records is Chris Burt, author of Extreme Weather.

New study finds huge drop in the plants that form the base of the oceanic food chain
A study published this week in the journal Nature documents that microscopic marine phytoplankton, which form the basis of the marine food chain, have declined by 40% globally since 1950. Joe Romm at climateprogress.org discusses the implications, using this headline:

Scientists may have found the most devastating impact yet of human-caused global warming — a 40% decline in phytoplankton since 1950 linked to the rise in ocean sea surface temperatures. If confirmed, it may represent the single most important finding of the year in climate science.

I plan to discuss this paper next week.

Next update
I'll have an update this weekend, probably by 8pm EDT Saturday.

Jeff Masters

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Quoting Hurricanes101:


It develops 4 systems

SW Caribbean, 90L and 2 waves behind 90L


If that were to verify, we'd have an average August's activity in just around two weeks time...and who knows what other systems could pop up.
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Oh well it's freezes my little brain just contemplating such things.
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GFS basically showing 2 potent systems in its run and 2 weak ones

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Quoting AllStar17:


No, I do not believe so. I do think it should be though.



Nothing on the ATCF site yet. I imagine it will be reclassfied after the next TWO.
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Quoting extreme236:
Interesting. GFS sends another CV storm in the same general direction after 90L.


It develops 4 systems

SW Caribbean, 90L and 2 waves behind 90L
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Quoting Snowlover123:


I'm not sure if I buy the NAM or not. Do you?


Eh, I'm not sure yet. I'd like to see if convection has redeveloped by tomorrow morning. If it hasn't, then I'd say most likely not.
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1535. Drakoen
Quoting bappit:

Where does the MJO come from?


The MJO is simply areas where convection is enhanced or suppressed. The MJO is governed by atmospheric circulations coupled with convection and is influenced by ENSO conditions.
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1534. 10Speed
Quoting texwarhawk:


You know those storm lines we get here in tornado alley with 60+ mph winds. Unless your close to the eye of a major its a lot like that only the storm line lasts a couple hrs. Can be frightning at night but during the day its amazing/intense. But then again I love the intensity of severe weather.


A couple of hours is an understatement. You can be substantially away from the eye and still get pounded with much more than the 60+ mph wind you refer to for many hours. Been there and done that several times and have never been in the eye. It's not fun.
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Interesting. GFS sends another CV storm in the same general direction after 90L.
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Quoting texwarhawk:


You know those storm lines we get here in tornado alley with 60+ mph winds. Unless your close to the eye of a major its a lot like that only the storm line lasts a couple hrs. Can be frightning at night but during the day its amazing/intense. But then again I love the intensity of severe weather.




Ive lived in Florida for 14 years, yes they get worse tornados and hail back in the plains, but such things are so isolated in their range, that's irrelevant, everyone thinks their storms are bad till they come to central Florida. Our every day thunderstorm on the sea breeze is worse then all the hype over frontal thunderstorms that have all those dang watch boxes further north and an overload of warnings.

Half the time when we get severe weather, we don't even gt warnings here, much less giant watch box hype. When we do get severe weather warnings in central Florida, you better prepare for one bada** thunderstorm!
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Quoting Orcasystems:
Anyone here from Gainesville?


Yes, been in Gainesville, FL since 1984.
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Quoting Snowlover123:

So 90L has been re-classified?


No, I do not believe so. I do think it should be though.

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Quoting extreme236:
12z NAM @ 48 hours:



I'm not sure if I buy the NAM or not. Do you?
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1528. DDR
Someone keeps hiding your posts ho77ywood,lol.
In the meantime its been rainy now in North Trinidad for 3 days.
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Quoting CybrTeddy:
Interesting that the GFS develops 90L now.


here is what was funny, I think IKE said earlier when 90L was deactivated that all the models were wrong; well it isnt like the system is just gone now that its not an invest and the models could still very well be right
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Quoting gordydunnot:
Yeah not bad for a 3 flavored ice cream if I must say so myself #1467. Where did all the blobs go are we down to just one. I'm warning you people I smell some GW blogs coming up, get busy #1467.


"Neapolitan" ain't just the goofy tri-colored ice cream; it's also what you call a resident of Naples...including Naples, Florida, where I live. (But thanks for the compliment.) :-)
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1525. OneDrop
Hollywood, Redfish are one of my favorites. Just got done cleaning a huge amount of snapper from fishing last night. Where did you catch your redfish?
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Quoting Hurricanes101:
12Z GFS has 90L just off the Florida East coast on August 10th

wow going even further; 90L moves up the east coast and then another system develops behind it

at the end of the run so far, a 3rd system develops right by the CV Islands

so much for the GFS not showing anything lol

So 90L has been re-classified?
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1523. bappit
Quoting KEEPEROFTHEGATE:


and ice still melts

I could make a gif of a series of images to give some animation to that.
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Interesting that the GFS develops 90L now.
Member Since: July 8, 2005 Posts: 259 Comments: 24016
Quoting Hurricanes101:
12Z GFS has 90L just off the Florida East coast on August 10th


Likely a slow-mover then. 10 days just to get to there.
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Quoting KEEPEROFTHEGATE:


and ice still melts


Ice @ the North Pole has to freeze @ lower temperatures, b/c it takes more energy to freeze salt water, so the real melting/freezing point of salt-ice is around 26 Degrees. Physics experiment from last year. :)
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1519. Drakoen
GFS 12z takes 90L all the way to the Bahamas.
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12Z GFS has 90L just off the Florida East coast on August 10th

wow going even further; 90L moves up the east coast and then another system develops behind it

at the end of the run so far, a 3rd system develops right by the CV Islands

so much for the GFS not showing anything lol
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good afternoon keeperofthegate :)
Member Since: July 3, 2010 Posts: 0 Comments: 427
1516. bappit
Quoting Drakoen:


I don't understand the question...

Where does the MJO come from?
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Yeah not bad for a 3 flavored ice cream if I must say so myself #1467. Where did all the blobs go are we down to just one. I'm warning you people I smell some GW blogs coming up, get busy #1467.
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Quoting Drakoen:


Read post 1430


I think I understand... :)
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Quoting bappit:

For life and death decisions do not rely on this blog. Go to www.nhc.noaa.gov.
Well, I do agree with you to a certain degree but I find that on here you get more up to date information whereas NHC does not update as often.
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Quoting Drakoen:


Thanks Nrt


NAM is also three hour on that site.
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1511. KEEPEROFTHEGATE (Mod)


and ice still melts
Member Since: July 15, 2006 Posts: 171 Comments: 53779
12z NAM @ 48 hours:

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Quoting MrMarcus:
Hey FloridaHeat. Couple of words of advice.

First, as StormwatcherCI noted, this site/blog can be a good source of information, and can be educational, but you will also find a good number of wishcasters, hoping for something tropical to give them something to worry about. I'm sure I'll get flamed for that comment, but it's true.

Second, living in Florida, we get our share of bad weather, tropical or otherwise. I've seen summer squalls that have been just as damaging as a tropical storm, and are far more dangerous, as they happen with very little warning.

Third, the key is simply being prepared and paying attention. You don't need to panic about a storm that's 1,500 miles away, and may never form. You panic when it's 15 miles away and you haven't prepared. Keep an eye on the weather and check this (and other) hurricane sites for information. Trust me, there will be plenty of other people panicking on this board if there's a problem. ;-)

In short, relax and enjoy the Florida lifestyle. I think your new neighbor is just having some fun with you.


well put
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1508. Drakoen
Quoting bappit:

So the MJO does not rule. Or is the Atlantic basin now an MJO originator?


I don't understand the question...
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Quoting Drakoen:


It seems the NCEP models see an increase in moisture in the Western Caribbean. FWIW, the NAM has a cyclone down there


Yup. I still think there is a chance for some development there.
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Quoting Drakoen:
What is this? A little MJO upward motion with our AOI SW of the CV islands.


Upward MJO is real evident over the Indian Ocean and the Arabian Sea regions. This will slowly progress eastward over the African continent and into the MDR next 7-10 days.

In other words, the lull will be coming to an abrupt end soon. Hopefully the MDR does not have a TC convention, because things may become rather ugly, real fast!!

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1505. bappit
Quoting Drakoen:
What is this? A little MJO upward motion with our AOI SW of the CV islands.


So the MJO does not rule. Or is the Atlantic basin now an MJO originator?
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1504. Drakoen
Quoting extreme236:


I don't know about this one. There definitely seems to be a chance for development in the SW Caribbean. We'll see if the convection redevelops as it gets closer to that area.


It seems the NCEP models see an increase in moisture in the Western Caribbean. FWIW, the NAM has a cyclone down there
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I'm thinking that ex90L and the twave to it's east won't really interact that much. They've kept fairly even spacing between each other for the past 24 hours.
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Hey FloridaHeat. Couple of words of advice.

First, as StormwatcherCI noted, this site/blog can be a good source of information, and can be educational, but you will also find a good number of wishcasters, hoping for something tropical to give them something to worry about. I'm sure I'll get flamed for that comment, but it's true.

Second, living in Florida, we get our share of bad weather, tropical or otherwise. I've seen summer squalls that have been just as damaging as a tropical storm, and are far more dangerous, as they happen with very little warning.

Third, the key is simply being prepared and paying attention. You don't need to panic about a storm that's 1,500 miles away, and may never form. You panic when it's 15 miles away and you haven't prepared. Keep an eye on the weather and check this (and other) hurricane sites for information. Trust me, there will be plenty of other people panicking on this board if there's a problem. ;-)

In short, relax and enjoy the Florida lifestyle. I think your new neighbor is just having some fun with you.
Member Since: January 2, 2008 Posts: 0 Comments: 97
Quoting AllStar17:
Can anyone believe that there is an area that has a 20% chance of development over the next 48 hours in the Caribbean? There's barely a cloud. That will probably be dropped off the TWO later.

yes, High divergence aloft in that area and good energy...wont take much. Clouds dont tell the whole story. this is the wave that the models are trying to develop and move into central america IMO. So I doubt they drop it and continue to track it. 20% means there are signs but highly unlikely it will form in 48 hours. Also means in 96 hours it might have a good shot.
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1499. Drakoen
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Quoting AllStar17:
Can anyone believe that there is an area that has a 20% chance of development over the next 48 hours in the Caribbean? There's barely a cloud. That will probably be dropped off the TWO later.


I don't know about this one. There definitely seems to be a chance for development in the SW Caribbean. We'll see if the convection redevelops as it gets closer to that area.
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1497. Drakoen
Quoting nrtiwlnvragn:
If you use NCEP's New Model Page you can see twice the GFS (image every three hours).


Thanks Nrt
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1496. bappit
Quoting stormwatcherCI:
Don't get freaked. This is the place for GOOD information. Pay attention and be as prepared as possible. Also make sure you have a back-up plan in case of evacuations. Where in Florida ?

For life and death decisions do not rely on this blog. Go to www.nhc.noaa.gov.
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1495. Drakoen
What is this? A little MJO upward motion with our AOI SW of the CV islands.

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I wonder why there hasn't been a re-activation of 90L or a designation of 91L. IMO, it should be coming this afternoon as the system does appear to be gaining organization.
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If you use NCEP's New Model Page you can see twice the GFS (image every three hours).
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1492. Boca
Forecast for 90L
One factor inhibiting development of 90L this week will be the Madden-Julian Oscillation (MJO.) The MJO currently favors downward motion over the tropical Atlantic, which will act to decrease the chances of tropical storm formation. The Madden-Julian oscillation is a pattern of enhanced rainfall that travels along the Equator from west to east. The pattern has a wet phase with large-scale rising air and enhanced thunderstorm activity, followed by a dry phase with large-scale sinking air and suppressed thunderstorm activity. Each cycle lasts approximately 30 - 60 days. When the Madden-Julian oscillation is in its wet phase over a hurricane-prone region, the chances for tropical storm activity are greatly increased.

I am confused. Is it in the WET phase or the dry phase?
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1491. bappit
Quoting Orcasystems:


Ahhhhh now there is the first problem in your theory. Your making the assumption that all of the people on here think. We know from many previous experiences, that is not necessarily true :)

Excellent point.
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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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