African tropical wave 99L slowly organizing

By: Dr. Jeff Masters , 1:26 PM GMT on July 31, 2012

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A tropical wave (Invest 99L) near 9°N 41°W, halfway between the Lesser Antilles Islands and the coast of Africa, has the potential to develop into a tropical depression later this week as it moves westward at 10 - 15 mph. Visible satellite loops show that the disturbance now has a moderate amount of poorly-organized heavy thunderstorms that continue to slowly increase in intensity and areal coverage. There is no surface circulation, but some counter-clockwise rotation of the large-scale cloud pattern is evident. Water vapor satellite loops show that 99L has a reasonably moist environment. The latest Saharan air layer analysis shows that the dry air from the Sahara lies to the north of 99L and is currently not affecting the storm. WInd shear over the disturbance is a light 5 - 10 knots, and ocean temperatures are 28°C, (82°F) which is well above the 26.5°C (80°F) threshold typically needed to allow formation of a tropical depression.


Figure 1. Morning satellite image of Invest 99L.

Forecast for 99L
Wind shear is expected to remain light through Friday, and ocean temperatures will remain near 28°C, according to the 8 am EDT run of the SHIPS model. However, a band of high wind shear of 20 - 40 knots associated with the subtropical jet stream lies just to the north of 99L, and it would not be a surprise to see 99L experience some higher shear conditions than are currently forecast. The farther north 99L gets, the higher the shear it will experience, and the SHIPS model is predicting shear in the moderate range, 10 - 20 knots, for Saturday - Sunday, as the storm works its way to 15°N. The disturbance is at 9°N, which is close enough to the Equator that the storm will have some difficultly getting spinning. Most of the models are showing some slow development of 99L. There are some major differences in the predicted forward speed of 99L, with the ECMWF and UKMET models predicting the storm will reach the Lesser Antilles on Friday, and the GFS predicting a later arrival, on Saturday. At 8 am Tuesday, NHC gave 99L a 20% chance of developing into a tropical depression by Thursday morning. I expect the storm will begin having trouble with tendrils of dry air reaching down from the north at times this week, but give 99L a 50% chance of eventually developing into Tropical Storm Ernesto sometime in the next ten days. Residents and visitors to the Lesser Antilles Islands should anticipate heavy rains and strong winds from 99L beginning to affect the islands as early as Friday morning. The long-range fate of 99L next week is uncertain. A track west to west-northwest through the Caribbean, or to the northwest towards the U.S. East Coast are both possible. The storm is less likely to survive if it heads northwest towards the U.S.

Extreme heat in the Central U.S.
The withering heat in America's heartland continued on Monday, with high temperatures of 112° recorded in Winfield, Kansas and Searcy, Arkansas. Little Rock, Arkansas hit 111°, their 3rd hottest temperature ever record, behind the all time record of 114° set just last year on August 3, and the 112° reading of 7/31/1986. Wichita and Coffeyville in Kansas both hit 111° Monday, and in Oklahoma, Enid, Tulsa Jones Airport, and Chandler all topped out at 111°. Carr Creek, Missouri hit 110°, the hottest temperature measured in the state so far this year. Highs temperatures Tuesday and Wednesday in this region could reach 110° again, as the most extreme heat this week will stay focused over Oklahoma and surrounding states.

Jeff Masters

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821. JLPR2
Quoting MississippiWx:


I think you're referring to the TUTT circulation.


Ah, I see, thought I had heard that term last year.
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99L
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Quoting nigel20:

Not much is going on at the moment in my area.


You have to watch there 99L as down the road it may track close to that island but intensity is uncertain.
Member Since: April 29, 2009 Posts: 75 Comments: 13926
Quoting JLPR2:


Wasn't that the same thing that made Tropical Storm Maria explode with convection when it was east of the islands last year?



I think you're referring to the TUTT circulation.
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Huh...

Looking at todays OSCAT from earlier, it seems that there was a second surface low that formed to the west of 99L that was also embedded in the monsoon trof. This may have disrupted 99L's circulation for a good portion of the day.

Regardless...short term looks favorable for development into a tropical cyclone.
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Quoting wxchaser97:
My tropical tracking map, NOT OFFICAL


Blue track looks pretty good
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.
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Quoting RitaEvac:
You'd be dead if this was legit, but it's not

W SIDE OF WOODWARD, WOODWARD, Oklahoma (PWS)
Clear
110 °F
Clear
Humidity: 50%
Dew Point: 87 °F
Wind: 0.0 mph from the ESE
Wind Gust: 3.0 mph
Pressure: 28.10 in (Rising)
Heat Index: 150 °F


I think that reading would be physically impossible on earth. Lol. A 110 degree temp with an 87 degree dew point. Not happening...
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My tropical tracking map, NOT OFFICAL
Member Since: March 16, 2012 Posts: 127 Comments: 7927
Quoting Tropicsweatherpr:
Hi nigel,plenty of rain today in PR.

(Over 3 inches in parts of island)

Hey Tropics! That's quite a bit of rain. We had some rain as a result of day time heating yesterday, but it was mostly light.

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Quoting MississippiWx:
99L looks to be in the process of departing the ITCZ as a surface low is consolidating around 10N 42.5W. Most likely will see another bump upwards in the TWO if this trend continues (50%).

Finally.
Member Since: October 15, 2011 Posts: 0 Comments: 3958
809. JLPR2
Quoting Stormchaser2007:
Should see convection blossom with 99L tonight due to the Kelvin Wave. Could push it to some higher probs by tomorrow morning.


Wasn't that the same thing that made Tropical Storm Maria explode with convection when it was east of the islands last year?

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You'd be dead if this was legit, but it's not

W SIDE OF WOODWARD, WOODWARD, Oklahoma (PWS)
Clear
110 °F
Clear
Humidity: 50%
Dew Point: 87 °F
Wind: 0.0 mph from the ESE
Wind Gust: 3.0 mph
Pressure: 28.10 in (Rising)
Heat Index: 150 °F
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Quoting LostTomorrows:
At this rate, 99L could become a TD later today, and the mess near PR is still persisting, and the low over northern Florida looks poised to start spinning up quickly over the Gulf Stream as soon as it exits land. I guess the wait is over soon.
and don`t forget the tw near Africa things are really becoming interesting.
Member Since: October 15, 2011 Posts: 0 Comments: 3958
99L looks to be in the process of departing the ITCZ as a surface low is consolidating around 10N 42.5W. Most likely will see another bump upwards in the TWO if this trend continues (50%).

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My post from an hour ago.

Expect convection to start building in the NW quadrant. If a strong low forms, it may be farther to the North than has been intialized.






Member Since: July 17, 2009 Posts: 68 Comments: 25064
Quoting nigel20:

100m, 200m and 4*100m...I'm hoping that he'll be fully fit, so that he can defend his titles.
I think he will make a good attempt but he says he thinks he is only about 95 % fit. Cayman has a newcomer this year but excellent. Kemar Hayman. High hopes for him.
Member Since: October 9, 2008 Posts: 0 Comments: 8263
Well I must book a flight to St Lucia or The Grenadines! 99L is very cute this afternoon and I'm jealous it will most likely affect the windwards instead of the leewards.. lol. Systems often go more north than predicted so WHY does 99L not want to do the same!! XD
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Quoting kwgirl:
You know that is just mean. We asked not to be told. I hope everyone reports you so you can be banned.


Someone needs to take a chill pill.
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Should see convection blossom with 99L tonight due to the Kelvin Wave. Could push it to some higher probs by tomorrow morning.
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Hi nigel,plenty of rain today in PR.

(Over 3 inches in parts of island)
Member Since: April 29, 2009 Posts: 75 Comments: 13926
Quoting TropicalAnalystwx13:

You can't be banned for that, Lol.


Still childish behavior when we all know that everything is tape delay..
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Quoting JLPR2:
99L seems to be getting inflow from the west now, that LLC seems to be closing off.



Earlier all we could see was the traditional ITCZ/Mon-trof flow from the south.



Yah buddy!
Member Since: August 16, 2007 Posts: 1 Comments: 2337
797. JLPR2
Quoting 900MB:


She is improving!


Yes, tonight's D-max could give 99L a push towards a red circle.
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Quoting HurricaneDean07:

Thats not good... Looks like a South texas set-up?

I doubt it... Chances are it wouldn't get out of the Caribbean.
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Quoting Pocamocca:
Afternoon, Nigel!

Hey!
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Quoting ncstorm:


Jamaica medal numbers will go up in track..do you know how many events Usain is competing in?

100m, 200m and 4*100m...I'm hoping that he'll be fully fit, so that he can defend his titles.
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793. 900MB
Quoting JLPR2:
99L seems to be getting inflow from the west now, that LLC seems to be closing off.



Earlier all we could see was the traditional ITCZ/Mon-trof flow from the south.



She is improving!
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Quoting islander101010:
storms.can.intensify.in.the.e.carib/...http://www .h istory.com/this-day-in-history/hurricane-gilbert-s lams-jamaica
Dean, Felix 2007
Member Since: October 9, 2008 Posts: 0 Comments: 8263
Quoting MAweatherboy1:
This may have been posted already, but here's the 12z UKMET:


Thats not good... Looks like a South texas set-up?
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99L
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Quoting nigel20:

US is now leading the medal table with 21 medals to China's 19. I'm also very proud of Jamaica's 4th place finish in the 100m breaststroke(female) just missing the podium by 0.47s yesterday.


Jamaica medal numbers will go up in track..do you know how many events Usain is competing in?
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This may have been posted already, but here's the 12z UKMET:

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787. JLPR2
99L seems to be getting inflow from the west now, that LLC seems to be closing off.



Earlier all we could see was the traditional ITCZ/Mon-trof flow from the south.

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At this rate, 99L could become a TD later today, and the mess near PR is still persisting, and the low over northern Florida looks poised to start spinning up quickly over the Gulf Stream as soon as it exits land. I guess the wait is over soon.
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Quoting kwgirl:
You know that is just mean. We asked not to be told. I hope everyone reports you so you can be banned.

You can't be banned for that, Lol.
Member Since: July 6, 2010 Posts: 112 Comments: 31327
Quoting HurricaneDean07:
When you really think about it..
If 99L was in the Epac. It wouldve already been declared a TD.
It looks like a TD to me. I have definately seen worse looking systems


They waitin' for it to become a naked swirl first.
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Quoting kwgirl:
You know that is just mean. We asked not to be told. I hope everyone reports you so you can be banned.


this^^is just mean
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..careful with the "Corporate Jargon".

Bain and the Blackstone Group are deeply embedded here, and watching from those Ivory Tower's as well.


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Thanks Dr Masters...good afternoon everyone!

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Quoting Tropicsweatherpr:
Pat,I apologize as I didn't know the games are on tape tonight not live in US.


its okay..there are still other events tonight and phelps is not the only American swimmer
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Quoting kwgirl:
You know that is just mean. We asked not to be told. I hope everyone reports you so you can be banned.


I am outside the US and didn't know NBC tapes the events to pass them at night. I already apologized.
Member Since: April 29, 2009 Posts: 75 Comments: 13926
When you really think about it..
If 99L was in the Epac. It wouldve already been declared a TD.
It looks like a TD to me. I have definately seen worse looking systems
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Quoting RussianWinter:


No you're not. NBC is a large corporation



According to a certain someone, corporations are people. So whichever poster claimed they are going to kill NBC... maybe they can/will
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Quoting weathermanwannabe:
Gonna be real interesting to see how GFS performs with this system as compared to the other models. The GFS folks scored a major victory with the track forecast on Debby (as against all of the other models) but the CMC has been the outlier so far with this wave. Big difference between forecasting development of a wave and forecasting track with a more developed system however.


NOGAPS ALSO
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Quoting Tropicsweatherpr:
Phelps came second.
You know that is just mean. We asked not to be told. I hope everyone reports you so you can be banned.
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Last year:


Current:
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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.