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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1041. docrod
Daybreak on 90L - looks like part of the ITCZ

Link
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1040. IKE
Quoting severstorm:

You finally got rid of the car with no air?


Yes...I would have died this week.
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Quoting IKE:


I know it reached 100 here....I've got a 2010 Ford Focus with all of the extras and it showed 100 as I was heading to my house. Kind of surprised me.


Thats the spiffy stuff. I got a '97 Silverado with a walmart indoor/outdoor thermometer- but it does give me indoor temp and humidity so it could be worse.
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1038. RTLSNK
Quoting IKE:


Reached 100 here yesterday, before the heat index.


Morning IKE, same thing here in Macon, Georgia.
Will have to leave early today for our breakfast ride on the Harley so we are back home before the tires start to melt! :)

Excessive Heat Warning
Statement as of 4:10 AM EDT on July 31, 2010


... Excessive heat warning remains in effect until 8 PM EDT
Sunday...

An excessive heat warning remains in effect until 8 PM EDT
Sunday. The warning is for areas along and south of a line from
Hamilton... to Thomaston... to Macon... to Swainsboro.

Temperatures across the area will range from 98 to 102 degrees
this afternoon... with temperatures only slightly cooler on Sunday.
With substantial moisture in place... heat index values will
increase to between 110 and 115. Nighttime temperatures will only
drop into the mid and upper 70s... which is not cool enough for
critical nighttime relief from the daytime high temperatures.

Remember... the elderly... the very Young... and people with heart
conditions are most at risk in extreme heat. People should check
on their friends... relatives... and neighbors who may be at risk.

Precautionary/preparedness actions...

An excessive heat warning means that a prolonged period of
dangerously hot temperatures will occur. The combination of hot
temperatures and high humidity will combine to create a dangerous
situation in which heat illnesses are likely. Drink plenty of
fluids... stay in an air conditioned room... stay out of the sun...
and check up on relatives and neighbors.


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1037. docrod
Quoting IKE:


I know it reached 100 here....I've got a 2010 Ford Focus with all of the extras and it showed 100 as I was heading to my house. Kind of surprised me.



Current heat index in the FL Keys is now a mere 85F - that will change significantly by 9-10 AM
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Quoting IKE:


I know it reached 100 here....I've got a 2010 Ford Focus with all of the extras and it showed 100 as I was heading to my house. Kind of surprised me.


You finally got rid of the car with no air?
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1035. IKE
Quoting severstorm:

I had 97 and the heat index got over 105 before that.Less humidity in your neck of the woods.


I know it reached 100 here....I've got a 2010 Ford Focus with all of the extras and it showed 100 as I was heading to my house. Kind of surprised me.

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I see the heat in the NE has gone away. I saw 39 in upstate NY this morning.
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Quoting IKE:


Reached 100 here yesterday, before the heat index.

I had 97 and the heat index got over 105 before that.Less humidity in your neck of the woods.
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Bouy just infront of wave in Caribbean (15.054 N 67.472 W)

Wind Direction (WDIR): ENE ( 70 deg true )
Wind Speed (WSPD): 13.6 kts
Wind Gust (GST): 17.5 kts
Wave Height (WVHT): 5.2 ft
Dominant Wave Period (DPD): 7 sec
Average Period (APD): 4.7 sec
Atmospheric Pressure (PRES): 29.81 in
Pressure Tendency (PTDY): -0.02 in ( Falling )

Bouy

wind speed has been increasing
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1031. IKE
Quoting severstorm:

Good Morning Ike, How about this heat!!!! From one extreme to the other this year.


Reached 100 here yesterday, before the heat index.
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Quoting IKE:


I Just Died In Your Arms Tonight

Good Morning Ike, How about this heat!!!! From one extreme to the other this year.
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1029. docrod
Good morning blog ... I see the models still take 90L in my general direction but it's way to early to call ... the future path will likely depend on its strength as anything else ... we shall see.
Link

I see that both yellow blobs are now at 20% according to the NHC. I have two more large trees to trim this weekend and after that I will feel semi-ready.

- fight nice today, yesterday was pretty silly - later
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Quoting IKE:


I Just Died In Your Arms Tonight


LOL great song- me and my friend donated it to a couple girls we took to homecoming a few years ago. Their father was a cop and was threating us the whole night.
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1027. IKE
Quoting texwarhawk:

Dang you beat me to the first comment in an hr and a half

geez this blog died...


I Just Died In Your Arms Tonight
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Quoting SwtHmeAla:
Ya that thing is spread out like these blog posts

Ya, I'd like to see how 90L does when the wave is right over it. My question is do they merge or does the wave take 90L's circulation or does 90L take the wave's convection. Seems today and tomorrow are going to be very interesting.
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Ya that thing is spread out like these blog posts
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Quoting SwtHmeAla:
From dry air, this is the best insulated wave
I have seen emerge from Africa. Low shear
ahead. Bad chances for those interests in the
caribbean .

I cannot imagine that anymore dust can be
left on the African continent. Jk

Dang you beat me to the first comment in an hr and a half

geez this blog died...
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Quoting alfabob:
Link


Those bouys are 10*-20* away from 90L and too far east for the caribbean wave. Pressure falling doesn't seem to be affiliated with anything threatening that I can see on IR. Also no major vorticity over the bouys.
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From dry air, this is the best insulated wave
I have seen emerge from Africa. Low shear
ahead. Bad chances for those interests in the
caribbean .

I cannot imagine that anymore dust can be
left on the African continent. Jk
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Quoting StSimonsIslandGAGuy:
It looks like that east Atlantic wave and low combo has some easterly shear. Could be wrong, those NHC sat pics are not detailed enough.


Looking like it does now, hard to see how it can organize in next 36 hours. However it has a long time after that...so I still think this will be Colin.


It's not in the best of environments right now...it'll be at least 3 days before it can sufficiently organize. And as Koritheman points out...that's not a good thing for the CONUS and the Caribbean.
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Quoting StSimonsIslandGAGuy:
It looks like that east Atlantic wave and low combo has some easterly shear. Could be wrong, those NHC sat pics are not detailed enough.


Looking like it does now, hard to see how it can organize in next 36 hours. However it has a long time after that...so I still think this will be Colin.


It might actually be worse for us in the long run if it doesn't begin to organize soon. Why? A more shallow system would tend to follow the low-level easterly flow, eventually entering the Caribbean, where vertical shear profiles will be low.
Member Since: March 7, 2007 Posts: 553 Comments: 19915
No night crew tonight? ;)

It's wayyyyyyy too hot to sleep right now.
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Quoting alfabob:
Link


Wow! Wonder what's up? Not a lot around there.
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Quoting CoopNTexas:


SmileyCentral.com
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Quoting SouthALWX:

Well, I think we can ... like the Nino last year .... hindsight shows it could've been better predicted.


We can predict some factors, but not nearly enough to make an accurate seasonal assessment before the season even begins.

We usually do fairly well with ENSO, but that's about it. And ENSO is not the be all end all of hurricane activity.
Member Since: March 7, 2007 Posts: 553 Comments: 19915
Quoting KoritheMan:


Therein lies the problem. We still don't fully understand the weather yet. And until we do, preseason forecasts are useless.

As far as the season being a bust goes, I'm not in that crowd at all. I didn't mean to make it seem like I was. I still fully anticipate an active season, probably something along the lines of 1998 or 1999, number wise.

Well, I think we can ... like the Nino last year .... hindsight shows it could've been better predicted.
Member Since: August 27, 2008 Posts: 0 Comments: 1497
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Quoting SouthALWX:

well, they were wrong for reasons we can comprehend ... which means if we can just predict those reasons we could have made the forecast. This season is far from over and all the bust season statements have no ground to stand on yet. We may see storms through december with these sea anomalies no one knows until it's over.


Therein lies the problem. We still don't fully understand the weather yet. And until we do, preseason forecasts are useless.

As far as the season being a bust goes, I'm not in that crowd at all. I didn't mean to make it seem like I was. I still fully anticipate an active season, probably something along the lines of 1998 or 1999, number wise.
Member Since: March 7, 2007 Posts: 553 Comments: 19915
Quoting KoritheMan:


True, but I'm finding it increasingly evident that even the former cannot produce reasonable accuracy.

How many times have the preseason prognostications been wrong over the last several years?

well, they were wrong for reasons we can comprehend ... which means if we can just predict those reasons we could have made the forecast. This season is far from over and all the bust season statements have no ground to stand on yet. We may see storms through december with these sea anomalies no one knows until it's over.
Member Since: August 27, 2008 Posts: 0 Comments: 1497
Quoting SouthALWX:

preseason forecasts for activity are a long way from " expect a threat from a hurricane around labor day " ....


True, but I'm finding it increasingly evident that even the former cannot produce reasonable accuracy.

How many times have the preseason prognostications been wrong over the last several years?
Member Since: March 7, 2007 Posts: 553 Comments: 19915
1006. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting KoritheMan:


That it is. In fact, after this year, I'm ready to throw preseason forecasts out the window, as well. Hell, even in season forecasts.

preseason forecasts for activity are a long way from " expect a threat from a hurricane around labor day " ....
Member Since: August 27, 2008 Posts: 0 Comments: 1497
1004. xcool
ha
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting SouthALWX:

skeptical would be an understatement ... it's simply impossible to make that forecast.


That it is. In fact, after this year, I'm ready to throw preseason forecasts out the window, as well. Hell, even in season forecasts.
Member Since: March 7, 2007 Posts: 553 Comments: 19915
Quoting KoritheMan:


I am just generally not a fan of long-range prognostications, particularly months out. Even if StormW tried to make such a prediction, I'd be skeptical.

skeptical would be an understatement ... it's simply impossible to make that forecast.
Member Since: August 27, 2008 Posts: 0 Comments: 1497
Quoting benirica:
Hola!
So if 90l is taken over by the wave by Africa, how do you all think a resulting TC would track? Probably a while north of where the models had 90 going?


Depends on how long it takes to develop.
Member Since: March 7, 2007 Posts: 553 Comments: 19915
post 1000! :D
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999. xcool
;;
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting JLPR2:
As of now its obvious not much is going on since we are talking about tacos. LOL!
Now I'm hungry :(


I'm eating cinnamon sugar poptarts at 230am. Mmm just what I wanted. Well that's my post for the day, goodnight.

Just so it's on topic, I have a bad feeling about the blob northeast of the bahamas.
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Hola!
So if 90l is taken over by the wave by Africa, how do you all think a resulting TC would track? Probably a while north of where the models had 90 going?
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996. xcool
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Quoting KerryInNOLA:
The last thing I will say on this Almanac topic I brought up. For instance, last PM I was watching Barometer Bob talk about 90L with his charts and models, because I don't want to miss anything important. They made it sound like such a big threat that some poor Cuban in Miami called Bob in a panic. He had me panicked too. Then I checked with the Almanac and they give the all clear. You have to almost be a phD to get a forecast from people like StormW. Maybe there is a quicker and as accurate way. I know this is an advanced weather blog for enthusiasts, but all kinds of folks check it out.


I am just generally not a fan of long-range prognostications, particularly months out. Even if StormW tried to make such a prediction, I'd be skeptical.
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994. xcool
bye EricSFL
Member Since: September 26, 2009 Posts: 2 Comments: 15620
Good night fellow bloggers.
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Quoting jasoniscoolman2010x:
its up to 20% now..why is that??

1. A TROPICAL WAVE LOCATED OVER THE SOUTHEASTERN AND SOUTH-CENTRAL
CARIBBEAN SEA CONTINUES TO PRODUCE DISORGANIZED SHOWERS AND A FEW
THUNDERSTORMS. LITTLE DEVELOPMENT OF THIS SYSTEM IS EXPECTED
UNTIL IT REACHES THE SOUTHWESTERN CARIBBEAN SEA IN A COUPLE OF DAYS.
THERE IS A LOW CHANCE...20 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT MOVES WESTWARD AT
ABOUT 15 MPH.



Have you been looking at the shear forecasts? Upper-level winds will begin to improve as the system nears Central America.
Member Since: March 7, 2007 Posts: 553 Comments: 19915

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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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