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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Hurricane Cesar track, July 24th--29th 1996
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2170. ncstorm
Well the crappy Nogaps is still insisting on a NW path..oh well
Member Since: August 19, 2006 Posts: 13 Comments: 15284
Good morning all! Watching and listening to your chatter with interest and concern for all. I don't need a storm or anymore rain in my area - we don't have a drought anymore!..lol
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Quoting JrWeathermanFL:
Good Morning.
So why wont 99L form today?
Sarcasm Flag: On


Lol, i think he's already there by its satellite appearance
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Quoting wunderkidcayman:
I say 99L LLCOC is now located at 10.3N 46.5W


Thats right in the center of all the convection.
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2166. Grothar
Quoting StormTracker2K:


Notice that band to the north of the circulation about to wrap in.


Yes.
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I think we will have a TD at 5pm today. 99L is really looking good right now.

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I love the fact that we may have a storm to track. What I hate is we might have a storm to track through the Islands. What I really hate is the possibility of a storm at my front door next weekend. Heres to hoping for a civil blog the next few days. Hoping for a harmless fish storm....
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99L is very impressive. Can understand why NHC set it at 60%. It's almost a tropical storm right now.

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Good Morning.
So why wont 99L form today?
Sarcasm Flag: On
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Quoting Hurricanes305:


Agreed! the more this develop before the islands the more northerly path it could take.


Looking at a more northerly route. The Euro shifted north and now brings 99L to PR and then into the Bahamas.
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2159. LargoFl
I guess the people on the Islands should be finishing up with the supplies and kits and everything needed to ride out a storm, it looks pretty good right now, that 99l will go thru them, just dont know ..if its thru the northern islands or the southern ones..both should be finishing up with preparations, this may be the first of several storms coming thru until the pattern changes
Member Since: August 6, 2011 Posts: 4 Comments: 38424
Quoting pottery:

\


If 99L came your way, would you welcome it or pray it changes direction?
Member Since: September 30, 2007 Posts: 9 Comments: 15935
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Quoting Grothar:


Very nice looking, its been a while
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Quoting weathermanwannabe:
Good Morning. Two comments on 99L. Totally surprised to see such an early CV storm develop this year. Secondly, as you can see on the 250mb chart posted below, the Tutt cells in the way of 99L have regressed out of the way and it has clear sailing into the Caribbean or on the Northern track towards PR. With this favorable enviornment, expect the storm to stenghen into a TS or hurricane in the next 72 hours and take the more Northernly route towards PR..........The model guidance should be shifting in this general direction over the next two days once a depression/storm is initialized in the models.


Agreed! the more this develop before the islands the more northerly path it could take.
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From the NHC it is 10N now
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Quoting StormTracker2K:


That cat 2 on the CMC model is right over Melbourne,FL in 9 days not in the gulf. That could be really bad!

Remember error is expected to occur this far out XD.If 99L comes in weaker to the islands expect it to take a more southern path.
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2152. LargoFl
Member Since: August 6, 2011 Posts: 4 Comments: 38424
Quoting pottery:

Trinidad, 11n 61w.
Alright, thanks! Good luck!
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Rain rain rain rain and ps rain lol
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Quoting Grothar:


Notice that band to the north of the circulation about to wrap in.
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I say 99L LLCOC is now located at 10.3N 46.5W
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2147. SLU
Almost there ...


01/1145 UTC 9.3N 45.1W T1.5/1.5 99L
01/0545 UTC 9.4N 43.9W T1.0/1.0 99L
31/2345 UTC 9.2N 43.0W T1.0/1.0 99L
31/1745 UTC 9.2N 42.1W T1.0/1.0 99L
31/1145 UTC 9.2N 40.6W T1.0/1.0 99L
31/0545 UTC 9.3N 38.5W TOO WEAK 99L
30/2345 UTC 9.0N 37.7W TOO WEAK 99L
30/1745 UTC 9.0N 37.1W TOO WEAK 99L
30/1145 UTC 8.9N 35.1W TOO WEAK 99L
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2146. Grothar
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2145. LargoFl
Member Since: August 6, 2011 Posts: 4 Comments: 38424
What is going on??
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Quoting LargoFl:
...........unless it changes course big time..I think this path is logical and maybe really close to the path it WILL take
,further north and over central or western cuba towards the eastern gom or fl,for sure
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Quoting TropicalAnalystwx13:
If you ever needed any more proof that the Caribbean is not unfavorable:



Good Mourning WU, can you tell me exactly where is the COC is now? It has jump couple degrees N overnight and its starting to move more WNW. Which means a BIG shift North in the models.
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2141. pottery
Quoting Bluestorm5:
Hey, which island are you on? I'm wondering...

Trinidad, 11n 61w.
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99L is moving W with a slight drift to the N or is moving just N of due W
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Quoting washingtonian115:
Oh well that's just great....Well eh you Gulf coast residents watching this to?.


That cat 2 on the CMC model is right over Melbourne,FL in 9 days not in the gulf. That could be really bad!

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2138. pottery
Quoting washingtonian115:
I'm predicting a moderate to strong tropical storm Pottery.i know that's not making you feel any better.Be fore conditions go down hill could you give us updates on whats happening.

No prob.

Have to get busy for a while so I'm out.

Laters>>>>>>>>>>
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Quoting pottery:

Yep.
It's good to know that things are so clear......

And have no fear, I am well prepared for everything except wind and rain.
We don't do wind too well here.
And rain is fine once it's not heavy.
In fact, come to think of it, it would be nice if this #99 just went away right now.
Hey, which island are you on? I'm wondering...
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2136. LargoFl
Member Since: August 6, 2011 Posts: 4 Comments: 38424
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Quoting TropicalAnalystwx13:
If you ever needed any more proof that the Caribbean is not unfavorable:



well half do die.....

I know, i am the main antagonist of this blog XD
Member Since: February 11, 2012 Posts: 0 Comments: 9727
Quoting pottery:

Yep.
It's good to know that things are so clear......

And have no fear, I am well prepared for everything except wind and rain.
We don't do wind too well here.
And rain is fine once it's not heavy.
In fact, come to think of it, it would be nice if this #99 just went away right now.
I'm predicting a moderate to strong tropical storm Pottery.i know that's not making you feel any better.Be fore conditions go down hill could you give us updates on whats happening.
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Quoting StormTracker2K:


CMC and the Euro are right on top of each other in send a storm to FL. It looks as if FL may a 3rd storm to region so far this hurricane season. Storm could be here in 7 to 8 days.

CMC and to a degree the Euro say a TS or hurricane hits the east coast of FL in 8 days.

over 1,000 mile range with forecasts that far out,could end up from NO to Bermuda
though the trend has been thru the fl straits.
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Quoting TropicalAnalystwx13:
If you ever needed any more proof that the Caribbean is not unfavorable:



Interesting as every model that has a stronger system is more north in line with the CMC. My bet is this system cuts across Cuba and gets into the SE Gulf near Key West come mid next week.
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Good Morning. Two comments on 99L. Totally surprised to see such an early CV storm develop this year. Secondly, as you can see on the 250mb chart posted below, the Tutt cells in the way of 99L have regressed out of the way and it has clear sailing into the Caribbean or on the Northern track towards PR. With this favorable enviornment, expect the storm to stengthen into a TS or hurricane in the next 72 hours and take the more Northernly route towards PR..........The model guidance should be shifting in this general direction over the next two days once a depression/storm is initialized in the models.
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Quoting washingtonian115:
Oh well that's just great....Well eh you Gulf coast residents watching this to?.

yes Cat 2 at 75W just imagin what it would be at 80W with that screeming high TCHP
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2127. LargoFl
...........unless it changes course big time..I think this path is logical and maybe really close to the path it WILL take
Member Since: August 6, 2011 Posts: 4 Comments: 38424
It going WNW???

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Quoting SFLWeatherman:
It going WNW???

CMC has 99L going WNW
Member Since: September 30, 2007 Posts: 9 Comments: 15935
2124. CJ5
99L looks pretty health and like I mentioned yesterday, if it stays on a southern track it will have a better chance to develop. It appears most models are keeping it in that direction. There is also another nice storm about to exit Africa. Could be a busy few months now.
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2123. pottery
Quoting Grothar:


I always enjoy your analyses of these systems.

Thanks.
I always strive to be concise and pertinent.
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Quoting LargoFl:
..yes watching it but thats about it..just watching, I doubt this is OUR storm in the gulf, the Islands really need to watch it though
Well even if it doesn't come you all's way just take this as a sign to make sure you have all your preparations.
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Good Morning From America's Left Coast at 5:25 PDT
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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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