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 ho77yw00d:


Thanks, I am almost 29 and all I was doing was answering a question... geez some people are so uptight in this blog!

29? good genes I guess..Lol
My daughters 22 so I guess you can take that as a compliment
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Quoting Levi32:


Indeed....another model war. The ECMWF looks to me to make more sense but we'll see how it plays out. I have a feeling that the pattern may be somewhat fragile in the SW Atlantic in 10 days.


Levi, just curious, what program do you use to put your graphs on Youtube?
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1689. bappit
More cool stuff.

The notion of bottom-up development (Halverson et al., 2007) is advanced as a counterpart to the more familiar “topdown” scenario advocated by Bister and Emanuel (1997) and Ritchie and Holland (1997), respectively; see also Ritchie et al. (2003). (This perspective was in vogue when M06 was written. The two scenarios are not mutually exclusive, as emphasized by Halverson et al.; see Glossary.) The top-down pathway begins with a recognition of the “top-heavy” nature of moist convective heating profiles in the presence of combined convective and stratiform precipitation processes. A top-heavy heating profile in a rotating environment necessarily leads to the conclusion that cyclonic vorticity is first concentrated in the middle troposphere by the induced vertical profile of convergence and must therefore find a way subsequently to burrow downward into the lower troposphere in order to provide the surface development needed for warmcore TC genesis. This pathway is inefficient (Tory and Montgomery, 2006) and invites a more direct route to genesis if one could be found, particularly in sectors where development is marginal to begin with. Observational findings of the top-down school were biased to the western Pacific warm pool, but in light of forecaster’s experience we are inclined to regard this pathway as largely irrelevant to the Atlantic and eastern Pacific sectors outside the ITCZ12. The genesis of depressions in this region of the world is almost always associated with a surface low along the wave (see Reasor et al., 2005, for a case study); examples of mid-level cyclonic vortices in developing tropical systems, without a corresponding cyclonic signature near the surface, are evidently rare.
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Sup hollywood? Oh man now I'm flirting oh geez! Haha! Looks like aug will explode. Just in time when I get back from working the nascar race up in ny next week then I come back on that mon geez.
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1687. Patrap
There is No 90L..its been de-activated.


Whatever and wherever something forms next in the Basin,,it will be 91L
Member Since: July 3, 2005 Posts: 426 Comments: 128667
1686. NASA101
Quoting Levi32:
Good morning all.

Blog update.

Tropical Tidbit for Saturday, July 31st, with Video


Great video! What's your background Levi..just curious?
I have Doctorate in Astrophysics but have a real interest in tropical weather! :)
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Quoting cirrocumulus:
Holy smokes! It looks like 90L is about to form into a tropical depression already.


Not really. Vorticity is extremely elongated, and convection is disorganized, although it does have a vigorous circulation, and a plethora of convection, it's associated with the ICTZ, and systems that come from the ICTZ usually develop slowly.
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1683. Ossqss
Hey Keeper, how is that weather station you put up doing? I am back in the market. Mine is on its last leg after 12 years (pressure has been at 1001 mb for a couple years now). Any recommendations would be appreciated :)
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Quoting cirrocumulus:
Holy smokes! It looks like 90L is about to form into a tropical depression already.


Probably not as 90L is still attached to the ITCZ.
Member Since: July 8, 2005 Posts: 259 Comments: 24181
Quoting hydrus:
If you prediction comes to fruition, it is my prediction that the U.S. will take a hit.


Or many...
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The pouch-analysis is on break or the info will be delayed today and tomorrow, however they did post this:

Special note: 17Z 31 July: Possible new pouch invest PGI23L ~51W
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Holy smokes! It looks like 90L is about to form into a tropical depression already.
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1678. NASA101
Quoting WeatherNerdPR:

Hello :)


Great video! What's your background Levi? I have Doctorate in Astrophysics but have real interests in tropical weather!
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1677. Patrap
Lordy Miss Gordy.

Get out and away from here.

Some have Tropical-itis Dysfunctional Syndrome.

Sheesh,..trouble will come soon nuff.

Enjoy a Fresca maybe.
Member Since: July 3, 2005 Posts: 426 Comments: 128667
Quoting IKE:


It's almost always been that way on here. I've seen a couple report someone for downplaying the season.


Yup.
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1675. hydrus
Quoting TropicalAnalystwx13:
I predict 5-8 named storms in August, consisting of 3-5 hurricanes, and 1-3 Majors.
If you prediction comes to fruition, it is my prediction that the U.S. will take a hit.
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bwt, could you explain your reasoning on why extreme's prediction is 'wishcasting'?
Member Since: July 8, 2005 Posts: 259 Comments: 24181
0z ECMWF 192Hr


12z GFS 102Hrs


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Is there any vorticity left in ex-90l?
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Quoting sporteguy03:


I don't it report either, it does not bother me that bloggers have different views, I would think they would have an interest in the tropics or weather still otherwise why blog here.


I don't report either for downcasting.. shocking I know. I only report JFV and stormtop, they have thousands of alts.
Member Since: July 8, 2005 Posts: 259 Comments: 24181
Holy hell! It's 99 degrees with a heat index of 120. I'm going to get slapped hard by the power company this month. Yeesh.
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Quoting bwt1982:


Fair enough and I will not report you for wishcasting or over hyping the season either!


I wouldn't call his prediction a wishcast or over hype...
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Good Afternoon.....I don't about the possibility of a very active early half to August, given the 100 year climatology pattern for late-Aug through September, but we may have the possibility of a few "rougue" storms in the the early half which could become very strong hurricanes because of all the heat out there. But the "clusters" of storms, which usually form from CV waves, will probably not start in earnest until September....Just my opinion.
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Quoting KEEPEROFTHEGATE:
i think maybe hes upset cause he really wants to flirt with you


lol oh well... maybe he was hoping I was a dude who knows
Member Since: July 3, 2010 Posts: 0 Comments: 427
1666. xcool
by Crown Weather, the writer mentioned 12/13 storms between Aug. and Oct.
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Quoting bwt1982:


Fair enough and I will not report you for wishcasting or over hyping the season either!


Well, I'm seriously not wishcasting. It is incredibly plausible, it's pretty obvious there is a distinct chance...and I've yet to see a reason why there isn't.
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting Levi32:
Good morning all.

Blog update.

Tropical Tidbit for Saturday, July 31st, with Video


Thanks, good stuff!
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1663. KEEPEROFTHEGATE (Mod)
03 i would never suggest anyone let there guard down i know all to well things can turn around in a blink of an eye
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1662. bwt1982
Quoting extreme236:
Well bwt1982 I'm not going to report you for "downcasting"...I was just curious as to the reasoning behind not seeing the levels of activity I describe, besides "its been "dead" so far"


Fair enough and I will not report you for wishcasting or over hyping the season either!
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Quoting bwt1982:


Bonnie could have been a whole lot worse had that ULL not been with it the whole time.
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1660. IKE
Quoting sporteguy03:


I don't it report either, it does not bother me that bloggers have different views, I would think they would have an interest in the tropics or weather still otherwise why blog here.


Whatever happens, happens. I'm just glad my AC is working... 97.3 °F
Partly Cloudy
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Quoting IKE:


It's almost always been that way on here. I've seen a couple report someone for downplaying the season.


I don't it report either, it does not bother me that bloggers have different views, I would think they would have an interest in the tropics or weather still otherwise why blog here.
Member Since: Posts: Comments:
Quoting gordydunnot:
Oh well I am off for awhile this blog is one or two post away from the dreaded you know what, sorry I can't mention it, you all would be wise not to even bring it up. Anybody seen Al Gore lately. Have a nice weekend get some sun. Adios Amigos.
Adios Amigo, No we haven't heard much about that distinguish gentlemen, other than all the charges against him about sexual misconduct failed. Otherwise I understand that he will continue helping with many of us on our struggles for keeping a greener and healthier emvironment on our planet.
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Quoting KEEPEROFTHEGATE:


to be honest 03 i had high expectations for this season
along with a lot of others
but something is not right
can not put my finger on it
but something is just not allowing systems to organize normally
every system struggle so far
except alex when making landfall
i am waitin to see if a more normal pattern
sets up for august
to confirm if season is to be
what has been expected
iam focusing on
the 15th to 20th
time frame in august
to see if i can see
what iam looking for


Its all good Keep, I don't mind it if people post different viewpoints, just wondering what some think will keep the season from being active. I just know better living in Florida to not let my guard down in August, September, and October. It would be nice to get a front though.
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I predict 5-8 named storms in August, consisting of 3-5 hurricanes, and 1-3 Majors.
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people are touchy and jealous in here today I'm out! 90l won't do anything today.
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1654. KEEPEROFTHEGATE (Mod)
Quoting ho77yw00d:


who was flirting? we were talking about fish... I am the one who started the fish conversation so... you tell me what guy was flirting and if you are so concerned with talking tropics then talk tropics I havent seen a post you wrote to do with anything weather related thus far!
i think maybe hes upset cause he really wants to flirt with you
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Nevermind, I understand now.
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1652. Levi32
Quoting Drakoen:
It's very interesting how the GFS and ECMWF continue to disagree of the 500mb longwave pattern in the long range. The GFS shows a deeper and less progressive trough while the ECMWF shows a fast flat trough that is quickly taken over by a trough.


Indeed....another model war. The ECMWF looks to me to make more sense but we'll see how it plays out. I have a feeling that the pattern may be somewhat fragile in the SW Atlantic in 10 days.
Member Since: November 24, 2005 Posts: 635 Comments: 26654
Well bwt1982 I'm not going to report you for "downcasting"...I was just curious as to the reasoning behind not seeing the levels of activity I describe, besides "its been "dead" so far"
Member Since: August 2, 2007 Posts: 19 Comments: 19234
Quoting Levi32:
Good morning all.

Blog update.

Tropical Tidbit for Saturday, July 31st, with Video

Hello :)
Member Since: July 7, 2010 Posts: 0 Comments: 5690
1649. IKE
Quoting bwt1982:


So you are allowed to over hype a season but I cant have my opionon? LOL


It's almost always been that way on here. I've seen a couple report someone for downplaying the season.
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Quoting extreme236:
I might be channeling my inner reedzone by going out on such a limb, but if the GFS verifies and we see 4 named storms in the first half of August, the second half in theory would be just as active or more active as it approaches the peak.


Just as long as you don't get pissy and defensive every time someone questions you, I'm fine with it.
Member Since: September 6, 2009 Posts: 2 Comments: 3759
I'd say look out for the lightening latter Ike.
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1645. Drakoen
It's very interesting how the GFS and ECMWF continue to disagree of the 500mb longwave pattern in the long range. The GFS shows a deeper and less progressive trough while the ECMWF shows a fast flat trough that is quickly taken over by a trough.
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1644. KEEPEROFTHEGATE (Mod)
i only hope your still as confused as me
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Nogaps strong Hurricane Mid Islands

Link
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1642. KEEPEROFTHEGATE (Mod)
Quoting sporteguy03:


Can you tell me why you think the season will continue to be inactive?


to be honest 03 i had high expectations for this season
along with a lot of others
but something is not right
can not put my finger on it
but something is just not allowing systems to organize normally
every system struggle so far
except alex when making landfall
i am waitin to see if a more normal pattern
sets up for august
to confirm if season is to be
what has been expected
iam focusing on
the 15th to 20th
time frame in august
to see if i can see
what iam looking for
Member Since: Posts: Comments:
Quoting Levi32:
Good morning all.

Blog update.

Tropical Tidbit for Saturday, July 31st, with Video
Hey bud!
Member Since: Posts: Comments:

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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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