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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Still No rain showers from the nearby tropical wave,
here in TCI.... I'm starting to think all the rain may stay South of us.
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If it comes near the Fl coast, when would that be? Can anyone anticipate at this point or is it too far out? My girls' birthdays are on the 17th and 18th, crazy odds right there lol. I also need to prepare as I have a special needs daughter on a feeding tube.

And since I'm a newbie coming out of lurkdom, can you also please post some links with easy to read info in addition to this great site, or any other blogs?

Thank you.
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Quoting WeatherfanPR:
I say 50% for 99L at 8pm TWO

Well we got 20-30 more min to find out
Member Since: June 13, 2009 Posts: 2 Comments: 9548
Good Evening Everyone!!!
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Quoting wunderkidcayman:

DUH
really un-called for..
Member Since: August 14, 2010 Posts: 10 Comments: 15704
1265. TXCWC
GFS and EURO 12z runs both in agreement right now that 99L eventually makes its way into the Bay of Campeche timing is very diffrent however w/Euro being much faster...interesting

Euro


GFS
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Quoting ncstorm:
I tell you what..the Nogaps is still calling for that NW track..18z still running...if its wrong, this blog will never give it any props but if its right, this blog will never give it any props..






Even a blind squirrel finds a nut once in a while.
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For now it is a 30% invest. I do think it will be bumped up to 50% at 8 however. I also wouldn't be surprised to see em pull out the red card.
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Quoting washingtonian115:
TCHP is off the charts in the caribbean.So if shear stays low then watch out.All though it is still a week out as some people have pointed out.But conditions could change in the caribbean.

DUH
Member Since: June 13, 2009 Posts: 2 Comments: 9548
I say 50% for 99L at 8pm TWO
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1260. ncstorm
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TCHP is off the charts in the caribbean.So if shear stays low then watch out.All though it is still a week out as some people have pointed out.But conditions could change in the caribbean.
Member Since: August 14, 2010 Posts: 10 Comments: 15704
ok I agree maybe not a cat 3 but still it could happen

I agree max Cat 2 for now
Member Since: June 13, 2009 Posts: 2 Comments: 9548
1257. ncstorm
Updated HPC map
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gilbert.intensified.in.the.eastern¢ral.carib.
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Quoting wunderkidcayman:

dude have you seen the TCHP the answer is NO because if you did you would not be saying that

I've seen it and I agree with him. This is at least one week out and we don't even have a tropical depression yet. Just sayin'.
Member Since: July 6, 2010 Posts: 108 Comments: 30241
Quoting wunderkidcayman:

dude have you seen the TCHP the answer is NO because if you did you would not be saying that


All due respect but we don't even have a depression yet.
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Quoting Pocamocca:

Local DC mets??...cuz your from DC, right? Or just like the weather channel guys?
No.Not here.We don't talk about T.C unless they have the potential to affect us.Their is this site called myoxhurricane.com.
Member Since: August 14, 2010 Posts: 10 Comments: 15704
Quoting wunderkidcayman:

dude have you seen the TCHP the answer is NO because if you did you would not be saying that


TCHP does not guarantee anything, its just another factor. Plus this is about a week away from getting to that point
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Quoting Hurricanes101:


I think you are getting waaaaay ahead of yourself even mentioning this to be a major hurricane

dude have you seen the TCHP the answer is NO because if you did you would not be saying that
Member Since: June 13, 2009 Posts: 2 Comments: 9548
Quoting wunderkidcayman:

I don't think that the trades will stop further strenghening but rather slow down the development speed I still think by the time it reaches the W caribbean it would be or on the verge of being a Cat3 hurricane or maybe cat 2 so if the trades were really calm it would do some rapid intensfication to a cat 4 I think the trades won't be a problem for development however I think it will just slow the speed of strengthening


In your dreams
Ernesto will not pass of Cat.1 hurricane
max.cat2

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@reedtimmerTVN

Tornado warnings in Calgary to Drumheller, AB areas. Chaos up there


Well, we got tornado threatening one of major cities in Canada. Not a good day up there!
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Quoting wunderkidcayman:

I don't think that the trades will stop further strenghening but rather slow down the development speed I still think by the time it reaches the W caribbean it would be or on the verge of being a Cat3 hurricane or maybe cat 2 so if the trades were really calm it would do some rapid intensfication to a cat 4 I think the trades won't be a problem for development however I think it will just slow the speed of strengthening


I think you are getting waaaaay ahead of yourself even mentioning this to be a major hurricane
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Quoting KEEPEROFTHEGATE:

yep saw that from earler
Member Since: June 13, 2009 Posts: 2 Comments: 9548
Quoting washingtonian115:
cWe should see the anti-cyclone intensify over time with 99L.IMO 99L will probably be a moderate to strong tropical storm when it reaches the islands.Pottery where are you?.

Pottery probaly pick up supplys lol
Member Since: June 13, 2009 Posts: 2 Comments: 9548
Quoting canehater1:
My thinking is that if it moves through the C. Carib.

The trades may hinder strengthening , but will not

shear it to pieces as some have stated. Am I wrong?


I don't think that the trades will stop further strenghening but rather slow down the development speed I still think by the time it reaches the W caribbean it would be or on the verge of being a Cat3 hurricane or maybe cat 2 so if the trades were really calm it would do some rapid intensfication to a cat 4 I think the trades won't be a problem for development however I think it will just slow the speed of strengthening
Member Since: June 13, 2009 Posts: 2 Comments: 9548
1241. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 163 Comments: 52173
Quoting tropicfreak:


Actually, there is an anticyclone associated with 99L.

cWe should see the anti-cyclone intensify over time with 99L.IMO 99L will probably be a moderate to strong tropical storm when it reaches the islands.Pottery where are you?.
Member Since: August 14, 2010 Posts: 10 Comments: 15704
Quoting tennisgirl08:
Wasn't 2004 an el niño year? You can't just assume storms will get sheared apart just because el niño. It is August, SSTs are scary high in the Caribbean, and any low pressure moving West should be taken seriously.

Also....I think the tropical wave in the Caribbean is only helping 99L because it is moistening the environment.

Modiki el nino, 99L is a threat to the Caribbean, the enviorment is getting moistened but dry air will still be a factor in hindering development.
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Quoting washingtonian115:
Some models show the TUTT retreating to the Bahamas which is my thinking as of now.And it'll be another week before 99L is fully in the caribbean so conditions could change between now and then.I wonder if 99L will develop a anti-cyclone in order to help it in the caribbean.More than likely it will.


Actually, there is an anticyclone associated with 99L.

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Some models show the TUTT retreating to the Bahamas which is my thinking as of now.And it'll be another week before 99L is fully in the caribbean so conditions could change between now and then.I wonder if 99L will develop a anti-cyclone in order to help it in the caribbean.More than likely it will.
Member Since: August 14, 2010 Posts: 10 Comments: 15704
Quoting canehater1:
My thinking is that if it moves through the C. Carib.

The trades may hinder strengthening , but will not

shear it to pieces as some have stated. Am I wrong?

Nope, you are correct.
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1235. JLPR2
Quoting stormchaser19:
In this part of the atlantic aren't present buoys?,because i think 99L is producing some gusty winds about 40kt in the convective parts


Sadly no, it's too far to the south for the buoys to register anything.
Member Since: September 4, 2007 Posts: 7 Comments: 8459
Wasn't 2004 an el niño year? You can't just assume storms will get sheared apart just because el niño. It is August, SSTs are scary high in the Caribbean, and any low pressure moving West should be taken seriously.

Also....I think the tropical wave in the Caribbean is only helping 99L because it is moistening the environment.
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Quoting Tazmanian:



we all ready had TD 4 wish was skip wish be came deddy so the next one would be TD 5

fixed

Quoting TropicalAnalystwx13:

Simple mistake. It would be Tropical Depression Five, not four.


You mean as it enters the Caribbean? It won't be that weak. Should be near hurricane intensity by the time it reaches the islands. According to the intensity models, anyways.


fixed

I think it will be either 70-75mph by the time it gets there
Member Since: June 13, 2009 Posts: 2 Comments: 9548
Quoting canehater1:
My thinking is that if it moves through the C. Carib.

The trades may hinder strengthening , but will not

shear it to pieces as some have stated. Am I wrong?


I agree.
Member Since: July 6, 2010 Posts: 108 Comments: 30241
In this part of the atlantic aren't present buoys?,because i think 99L is producing some gusty winds about 40kt in the convective parts
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My thinking is that if it moves through the C. Carib.

The trades may hinder strengthening , but will not

shear it to pieces as some have stated. Am I wrong?

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Out of the blog category but on the extreme heat front:-

Greenland again sees widespread melt.
Satellite imagery showed that the week peaked on Saturday with 74 percent of the giant ice sheet seeing melt.

Here's the link to copy and paste:-

http://worldnews.nbcnews.com/_news/2012/07/31/130 55658-greenland-again-sees-widespread-melt?lite

So I supose,(yawn,) that last weeks melt was a short hundred years or so event!
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I'm back, seems like 99L is still looking good.
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Quoting robert88:
So I guess 99L can go through 30-40kts of shear as a TD or TS with no problems?


Remember though, you have to factor the anticyclone that is ventilating 99L protecting it from high shear.
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Quoting wunderkidcayman:
I think 99L/PRE-TD4 does not have shear to worry about and the trade winds I think will not be a problem either I think people are overestimating the trades

Simple mistake. It would be Tropical Depression Five, not four.

Quoting robert88:
So I guess 99L can go through 30-40kts of shear as a TD or TS with no problems?

You mean as it enters the Caribbean? It won't be that weak. Should be near hurricane intensity by the time it reaches the islands. According to the intensity models, anyways.
Member Since: July 6, 2010 Posts: 108 Comments: 30241
Quoting wunderkidcayman:
I think 99L/PRE-TD4 does not have shear to worry about and the trade winds I think will not be a problem either I think people are overestimating the trades



we all ready had TD 4 wish was skip wish be came deddy so the next one would be TD 5
Member Since: May 21, 2006 Posts: 5089 Comments: 114041
Quoting stormpetrol:


That 83 knot wind on SW coast of DR has to be an error one would think so anyway!
I think there are to obs there lol.
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Quoting stormpetrol:


That 83 knot wind on SW coast of DR has to be an error one would think so anyway!


Those are just 2 wind barbs that are close to each other. One is measuring 8 mph while another is measuring 3 mph.
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So I guess 99L can go through 30-40kts of shear as a TD or TS with no problems?
Member Since: May 22, 2010 Posts: 0 Comments: 907

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About JeffMasters

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.