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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Quoting Pocamocca:

Yeah, the TUTT is quite the force. I agree it has to start moving further north. I think in the short term that's probably the way to go for it. I know Dr. Master's mentioned it encountering more adverse conditions the more northerly route it would take. But I think he was more or less referring to the longer term solution...

But yeah, it has it's obstacles to overcome. Not going to disagree with you there!


Yeah either way it has to go through the TUTT. At this point i'm not sure which would be the better route for it to be a more significant system in the long term??? The longer it hangs around the more time atmospheric conditions can change...so who knows. :)
Member Since: May 22, 2010 Posts: 0 Comments: 907
1168. KEEPEROFTHEGATE (Mod)
there are yet more to follow
Member Since: July 15, 2006 Posts: 170 Comments: 53773
Quoting washingtonian115:
If you notice it tries to develop that impressive wave as well.
Link please!,is the impressive wave you are talking about that the GFS is trying to develop is the one over Puerto Rico & Espanola,thank you!!!.
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1166. ncstorm
Quoting Pocamocca:

Is that the troublemaker you were highlighting with the CMC earlier today and yesterday? And is it still trending toward warm-core??

That's nothing to turn you head on for sure. Those systems always ramp up in a hurry!

The CMC, GFS, Nogaps and the weaker Euro..but yeah this is it..
Member Since: August 19, 2006 Posts: 13 Comments: 15276
1165. KEEPEROFTHEGATE (Mod)
99l will skirt trinny
enter stage right
deep se carb
into the dead zone
Member Since: July 15, 2006 Posts: 170 Comments: 53773
Quoting Pocamocca:

Yeah, the TUTT is quite the force. I agree it has to start moving further north. I think in the short term that's probably the way to go for it. I know Dr. Master's mentioned it encountering more adverse conditions the more northerly route it would take. But I think he was more or less referring to the longer term solution...

But yeah, it has it's obstacles to overcome. Not going to disagree with you there!
Quoting robert88:


It won't make it. That TUTT will strip it right apart and that is a fact. The best globals ECMWF and GFS are sniffing out those conditions and that's why they are starting to consistently show a weak system in the Caribbean. 99L has a small window to show off and then it's all downhill. The only way I think it could survive is if it really ramped up quick in the next couple of days and started heading more N.


The TUTT is way over by Cuba

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GFS very unimpressive this run; Loses it before it even gets into the Caribbean:

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Is that another low in front of 99L?

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99L appears to have survived DMIN very well:

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1159. Grothar
Quoting sunlinepr:


The Fujiwhara effect or Fujiwara interaction, named after Sakuhei Fujiwhara, is a type of interaction between two nearby cyclonic vortices, causing them to appear to "orbit" each other.



Link

Not expected


In China Fujiwhara would be called the Téngyuán effect.
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1158. scott39
The TCHP in the caribbean and parts of the GOM are rocket fuel and could rapidly intensify an approaching TC. Im not saying 99L will do this, but its only a matter of time before it happens. I think time has run out in the 2012 season.
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1157. ncstorm
Potential off the NC Coast

NWS in wilmington, NC
POTENT VORT ON THE HEELS OF THE MCS WILL ROTATE UNDERNEATH THE BASE
OF 500MB LONGWAVE TROUGH TOWARDS THE COAST TONIGHT. GUIDANCE IN VERY
GOOD AGREEMENT IN TIMING AND OVERALL DEVELOPMENT...BUT SIGNIFICANT
DIFFERENCES EXIST IN SPATIAL EXTENT OF RAINFALL OVERNIGHT. AS THIS
VORT APPROACHES...DECENT PVA EXISTS AHEAD OF IT...AND AS THIS
ENCOUNTERS THE SURFACE BOUNDARY DRAPED ACROSS THE SOUTHEAST
COAST...IT WILL COMBINE WITH LOW LEVEL WAA TO SPAWN CYCLOGENESIS
SOMEWHERE NEAR THE SC COAST.
THIS LOW PRESSURE WILL THEN MOVE SLOWLY
UP THE COAST INTO THE MORNING...SPREADING RAINFALL ACROSS MUCH OF
THE EASTERN CAROLINAS. WITH DEEP COLUMN SATURATION AND PWATS
APPROACHING 2.25 INCHES...SEEMS PLAUSIBLE THAT PERIODS OF HEAVY
RAINFALL IN SHOWERS/ISOLATED TSTMS WILL DEVELOP TONIGHT AND EXPAND
THROUGH MORNING. NOTE THAT THE HIGH RES GUIDANCE IS REALLY NOT
BULLISH AT ALL IN COVERAGE...AND WONDER IF IT IS REACTING TO THE MID
LEVEL DRY AIR AND SOME SUBSIDENCE NEAR THE REMNANT MCS. IT IS THIS
CONCERN THAT KEEPS POP FROM RISING TO CATEGORICAL...BUT STILL HAVE
LIKELY POP ALL ZONES EXCEPT FAR N/W. HIGHEST QPF WILL BE NEAR THE
COAST WHERE ONE HALF TO ONE INCH OF RAINFALL MAY FALL BEFORE 8AM
WEDNESDAY.
Member Since: August 19, 2006 Posts: 13 Comments: 15276
1156. JLPR2
Another image to show. :)



18z Surface analysis is interesting, shows a future WNW movement and deepening into a 1008mb low.
Member Since: September 4, 2007 Posts: 7 Comments: 8687
how is the 200MB vort doing???
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Quoting MAweatherboy1:
18z GFS is running:

If you notice it tries to develop that impressive wave as well.
Member Since: August 14, 2010 Posts: 10 Comments: 16964
1151. JLPR2
Quoting Pocamocca:

That's very strong.


With a vort like that it deserves at least 40-50%, 30% just doesn't seem right.
Member Since: September 4, 2007 Posts: 7 Comments: 8687
1150. Grothar
Quoting KEEPEROFTHEGATE:
yes the good old days i have an extensive list



How much do you want for them?????? I'll pay anything.:)
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Quoting trHUrrIXC5MMX:


could both storms eventually merge?
POOR CHINA!



Damrey ("David" according to Ningbo news agency) looks almost annular to me.
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Quoting Pocamocca:
He will be getting into much better conditions soon.

I see much lessening sheer near the islands in the days to come when he makes it that way. But after that, I don't see any reason why that sheer is suppose to lessen. I have not checked the SHIPS 12Z run for the sheer potential but if 99L comes anywhere near Jamaica, just not quite sure how it'll make it....CDO or not.





It won't make it. That TUTT will strip it right apart and that is a fact. The best globals ECMWF and GFS are sniffing out those conditions and that's why they are starting to consistently show a weak system in the Caribbean. 99L has a small window to show off and then it's all downhill. The only way I think it could survive is if it really ramped up quick in the next couple of days and started heading more N.
Member Since: May 22, 2010 Posts: 0 Comments: 907
1147. Grothar
Let's see how much yellow it can build in the next few hours. Uh oh. Somebody is making dinner. Got to go for awhile. If I'm not back, you know I ate it!

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1146. KEEPEROFTHEGATE (Mod)
Quoting Grothar:


Too bad I didn't save any of your posts and show them what you used to do me and Canes on chat. LOL (Remember the good old days??)
yes the good old days i have an extensive list
Member Since: July 15, 2006 Posts: 170 Comments: 53773
18z GFS is running:

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Quoting trHUrrIXC5MMX:


could both storms eventually merge?
POOR CHINA!



The Fujiwhara effect or Fujiwara interaction, named after Sakuhei Fujiwhara, is a type of interaction between two nearby cyclonic vortices, causing them to appear to "orbit" each other.



Link

Not expected
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Desert rains

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1142. KEEPEROFTHEGATE (Mod)
Fleet. Weather. Center. Norfolk. Virginia.



No Active Atlantic Tropical Warnings
July-31-12, 5:30:01 PM | Maritime.CDO@navy.mil (FWC-N CDO)
As of Tue, 31 Jul 2012 21:30:01 GMT
Member Since: July 15, 2006 Posts: 170 Comments: 53773
1140. JLPR2
Very circular and strong 850mb vort, all it has left of its past linear appearance is a little leg to the west.

Member Since: September 4, 2007 Posts: 7 Comments: 8687
Quoting wunderkidcayman:
looking at top 10 best anolog track for 99L
is emily 05



I think 99L may take this one



not as intense right?
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Quoting wunderkidcayman:
looking at top 10 best anolog track for 99L
is emily 05



I think 99L may take this one


LOL I just posted that yesterday...
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Quoting sunlinepr:


could both storms eventually merge?
POOR CHINA!

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Pay attention to the disturbance south of the cape verde islands as well...
Member Since: August 14, 2010 Posts: 10 Comments: 16964
Wunderground made a VERY cool adjustment to its SST maps, but when I checked it a few minutes later, it had reverted back to its original version.

I've just published an original blog entry, focusing mostly on the West Pacific and the two typhoons currently heading toward China. You are all welcome to check it out.

This is also the first time I've tried incorporating climate-skeptic information and a multitude of views into my blog. As it is currently though, the entry was prepared rather haphazardly so it may not be as well-organized as you may like.
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Quoting TropicalAnalystwx13:

Yeah...those days....

LOL.


Love how you have an auto-reply. Lol.
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Quoting pcola57:


That's a good read and pics like you mentioned.. :)


And mentions Dr. Neil Frank's research to boot in the cites....He was as much of a pioneer in the area as Dr. Gray.

Have a good one.............Heading home..... :)
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Quoting Grothar:


Too bad I didn't save any of your posts and show them what you used to do me and Canes on chat. LOL (Remember the good old days??)

Yeah...those days....

LOL.
Member Since: July 6, 2010 Posts: 113 Comments: 31989
Quoting RussianWinter:


Forward me the emails..

Though last time I remember it's Jason that does emails.. Including that email about Grothar last season.


forward it to me too
Member Since: February 11, 2012 Posts: 0 Comments: 9727
Quoting wunderkidcayman:
looking at top 10 best anolog track for 99L
is emily 05



I think 99L may take this one
Charley deserves to be up there, also an El Nino year:

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Quoting MississippiWx:


Lol. You don't have the emails that I have, bud.


Forward me the emails..

Though last time I remember it's Jason that does emails.. Including that email about Grothar last season.
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Cutting out but have a safe afternoon. Will check on the appearance of 99L in the am. Not betting against NHC with this one just yet as it is a bit tricky because of the continued attachment to the ITCZ. The area behind it to the east is clearing out and creating some nice separation but you can see the sheer impacting the area (within the ITCZ) in front of it right at around 55W to which it is still attached. The next 24 hours should determine whether it can detach and reach TD status before it hits the sheer pocket caused by the ULL on the coast of SA in about 36 hours so I am thinking NHC might go with 50% by tomorrow at some point unless there is some pretty impressive organization and a move to the North in the overnight hours.

We shall see what happens.
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1127. Grothar
Quoting TropicalAnalystwx13:
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Too bad I didn't save any of your posts and show them what you used to do me and Canes on chat. LOL (Remember the good old days??)
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Quoting TropicalAnalystwx13:

^ Yeah Mississippi, this is really JFV. LOL.

Sarcasm Flag: ON


But don't worry... He is going to behave this time....
Anyone wants to make a survey/poll about it?
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1125. JLPR2
Quoting Vlad959810:

Leeward Islands is from Dominica, north of the 15° to the Virgin Islands.


Ah I see, thank you. One learns something new every day. :)
Member Since: September 4, 2007 Posts: 7 Comments: 8687
Quoting GeorgiaStormz:


No.
You made your own hook, line, and sinker, an then bit it.


Lol. Whatever. You can believe what you want, but I have the proof. It's on ignore anyway.
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Quoting MississippiWx:


Lol. You don't have the emails that I have, bud.

Send them to me.
Member Since: July 6, 2010 Posts: 113 Comments: 31989
If you look at the motion on WV Loop and compare 99L with the t-wave in the NE Caribbean, you can see why one is an invest and one isn't.
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hmmm


could this be right lol


Bird Land, Altus, OK

temper

111.4 °F

heat index

288 °F

dew point

111 °F


99%
Member Since: May 21, 2006 Posts: 5091 Comments: 115072

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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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