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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99L is in a similar position to Ivan. If it can pull off the ICTZ fully it will develop quickly, due to high SST's and low shear, no saharan dust to impede.

Just my layman's opinion.

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Please a page for HWRF
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http://www.necn.com/pages/weather/
the radar shows our mini mid-summer nor'easter.
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Even with DMIN and detaching from the ITCZ 99L is still looking decent.
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I'm actually more worried about the tropical wave over the Dominican Republic than 99L at this point,here in Miami we can get some very nasty weather from this system coming from the East, at least a lot of rain and wind for the weekend,it looks very impressive,I know the Hurricane Center is giving 0% of development but this time of year you never know??,again at the very minimum we should get some bad weather from Friday-Sunday (IMO).
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Quoting hurricane23:


This things future is not bright at all if you ask me. It has about 3 days to do somethig before reaching much more hostile conditions in the eastern carib. The tropical wave over Puerto Rico has flared up today partly in response to its closer proximity the upper TUTT low north of the southeastern Bahamas. Weekend looks rainy :0(


The TUTT axis is north of the Greater Antilles. If it stays south of there, it will escape the strongest shear. At that point it comes down to the strength of the trade winds and the influence of South America.

But I agree that a conservative approach is needed for now. I've seen too many of these systems just die in the Caribbean, or fail to develop and instead become something in the Pacific.
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Quoting TropicalAnalystwx13:
How strong will 99L peak as before reaching the Leeward Islands?

A. Invest
B. Tropical Depression (<35 knots)
C. Tropical Storm (35-45 knots)
D. Severe Tropical Storm (50-60 knots)
E. Hurricane (>65 knots)

Going with D.


Weak E)
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Quoting Patrap:


Why they could always Poll us here.

Save fo me as I never Poll on a Tuesday.


To poll or not to poll...

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1362. ncstorm
Quoting nrtiwlnvragn:


GFDL not much development, HWRF up to/close to hurricane.


HWRF..wow..I hope the Islands are preparing for the worst just in case..
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I posted this at 3:36pm regarding my opinion on the 8pm TWO.
My tropical tracking map, NOT OFFICAL
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Also saw the image that showed Hurricane Hunter's measurement through the eye of Hugo. There is a mark of 190 MPH WINDS in SW section of the storm!!! That must be from Dr. Masters' scary flight story of Hugo...
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Quoting Methurricanes:
So is 46-49 Knot storm just Impossible?

Yes, because it will be rounded to either 45 knots or 50 knots. XD
Member Since: July 6, 2010 Posts: 113 Comments: 32870
Quoting ncstorm:


Dont worry..it was Buffet night here at WU, you wont be eating alone..
Aww man I thought it would be at 90% oh well I like mine smoked with A1 Hickory Sauce.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting GeorgiaStormz:
ENVIRONMENTAL CONDITIONS
ARE AT LEAST MARGINALLY CONDUCIVE FOR SOME GRADUAL DEVELOPMENT OF
THIS DISTURBANCE

not too excited it seems


The key words are " Environmental conditions are at least marginally conducive" which I would interpret as overall reasonably conducive and not just as if had been written as "marginally" alone, of course some would interpret it differently!
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1355. JLPR2
Quoting ProgressivePulse:


Pretty decent turning, there is not much to stop it from becoming a depression at the moment.


99L deserves it, I'm just surprised the conservative NHC went with 50%. xD
Member Since: September 4, 2007 Posts: 7 Comments: 8747
Quoting TropicalAnalystwx13:
How strong will 99L peak as before reaching the Leeward Islands?

A. Invest
B. Tropical Depression (<35 knots)
C. Tropical Storm (35-45 knots)
D. Severe Tropical Storm (50-60 knots)
E. Hurricane (>65 knots)

Going with D.


I say D or E
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Quoting KoritheMan:
Ever notice how some of these systems in the rotation tend to follow cycles? 2006's Ernesto plowed through the Caribbean on a trajectory this one is likely to follow. In 1983, Alicia hit Houston. In 1989, Allison hit the same location.

Interesting, that.


This things future is not bright at all if you ask me. It has about 3 days to do somethig before reaching much more hostile conditions in the eastern carib. The tropical wave over Puerto Rico has flared up today partly in response to its closer proximity the upper TUTT low north of the southeastern Bahamas. Weekend looks rainy :0(
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A little off topic but this is a real nasty storm... Take cover if you're in the path:

...A TORNADO WARNING REMAINS IN EFFECT FOR NORTHERN WARRICK...
SOUTHEASTERN GIBSON...SOUTH CENTRAL PIKE AND NORTHEASTERN VANDERBURGH
COUNTIES IN SOUTHWEST INDIANA UNTIL 700 PM CDT...

AT 645 PM CDT...RADAR INDICATED A SEVERE THUNDERSTORM CAPABLE OF
PRODUCING A TORNADO. THIS DANGEROUS STORM WAS LOCATED NEAR
LYNNVILLE...OR 9 MILES NORTH OF CHANDLER...MOVING SOUTHEAST AT 30
MPH. GOLF BALL HAIL WAS JUST REPORTED IN LYNNVILLE. ESTIMATED 70 TO
80 MPH WINDS HAS BEEN PRODUCED OUT OF THIS STORM. A TORNADO...OR
TORNADO LIKE WINDS...IS POSSIBLE...SO TAKE COVER!
Member Since: February 11, 2012 Posts: 84 Comments: 8049
Quoting TropicalAnalystwx13:
How strong will 99L peak as before reaching the Leeward Islands?

A. Invest
B. Tropical Depression (<35 knots)
C. Tropical Storm (35-45 knots)
D. Severe Tropical Storm (50-60 knots)
E. Hurricane (>65 knots)

Going with D.
So is 46-49 Knot storm just Impossible?
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1350. Patrap
Quoting Stormchaser2007:
?

Whole lotta unecessary wording there.

ARE AT LEAST MARGINALLY CONDUCIVE FOR SOME GRADUAL DEVELOPMENT OF
THIS DISTURBANCE


Why they could always Poll us here.

Save fo me as I never Poll on a Tuesday.
Member Since: July 3, 2005 Posts: 428 Comments: 129904
Quoting Stormchaser2007:
?

Whole lotta unecessary wording there.

ARE AT LEAST MARGINALLY CONDUCIVE FOR SOME GRADUAL DEVELOPMENT OF
THIS DISTURBANCE

He wanted to make it longer I guess. LOL, I don't know.
Member Since: July 6, 2010 Posts: 113 Comments: 32870
Quoting Dragod66:
cant seem to find a sat image of Hurricane Hugo at cat 5 strength!


You can find the pictures of Hugo at peak intensity here:

Link

Can't post it on the blog or the site will block it.
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Quoting ncstorm:


okay good! Thanks


GFDL not much development, HWRF up to/close to hurricane.
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We have a stationary high over the western gulf, a stationary low north of FL and the A/B high (currently bridged). So, if the trade winds and or shear does not take a toll and it can gain some intensity, it should take the path of least resistance . . . and that is towards the conus, east coast, around the Bermuda high. I'm using the 18z surface analyses for this amateur's observation.
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Got the pictures of Hugo from this link:

http://huracanado1.tripod.com/hugo.html
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1343. ncstorm
Quoting nrtiwlnvragn:


They are running on this cycle, 18Z.


okay good! Thanks
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?

Whole lotta unecessary wording there.

ARE AT LEAST MARGINALLY CONDUCIVE FOR SOME GRADUAL DEVELOPMENT OF
THIS DISTURBANCE
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1341. Houdude
I think the NHC is treating the wave south of P.R.-Hisp way too lightly. It's been persistant over the last four days, is a Cape Verde system, and could be trouble down the line if it makes it to the GOM.
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Why haven't the GFDL and HWRF been running on 99L? They made one run yesterday but that's all...
Member Since: February 11, 2012 Posts: 84 Comments: 8049
Quoting ncstorm:


Dont worry..it was Buffet night here at WU, you wont be eating alone..
Thanks goodness, lol.
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orange 50% for 99L
yellow 0% for Carib wave
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Quoting ncstorm:
Dust off the HWRF and GFDL because they will start running them again on 99L..probably the 00z runs..


They are running on this cycle, 18Z.
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1335. ncstorm
nobody posted the circles?

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Quoting Dragod66:
cant seem to find a sat image of Hurricane Hugo at cat 5 strength!


Well, picture got blocked... whoops.
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Quoting TropicalAnalystwx13:
How strong will 99L peak as before reaching the Leeward Islands?

A. Invest
B. Tropical Depression (<35 knots)
C. Tropical Storm (35-45 knots)
D. Severe Tropical Storm (50-60 knots)
E. Hurricane (>65 knots)

Going with D.

D for me
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1332. ncstorm
Quoting washingtonian115:
Now Wu will be having a crow sale/special over the next few weeks.Get your crow now while it's still cheap.


I fear it will be sold out even before the weekend..high demand unfortunately..
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Quoting TropicalAnalystwx13:
How strong will 99L peak as before reaching the Leeward Islands?

A. Invest
B. Tropical Depression (<35 knots)
C. Tropical Storm (35-45 knots)
D. Severe Tropical Storm (50-60 knots)
E. Hurricane (>65 knots)

Going with D.

D, as well.
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Quoting TropicalAnalystwx13:
How strong will 99L peak as before reaching the Leeward Islands?

A. Invest
B. Tropical Depression (<35 knots)
C. Tropical Storm (35-45 knots)
D. Severe Tropical Storm (50-60 knots)
E. Hurricane (>65 knots)

Going with D.


mid D before islands, then peaking at mid to possibly high D shortly after
Member Since: February 11, 2012 Posts: 0 Comments: 9760
1329. WxLogic
I'm actually surprised that it was given 50% at this time. Was expecting such % by tomorrow AM if convection persisted.
Member Since: August 14, 2008 Posts: 4 Comments: 5038
Quoting TropicalAnalystwx13:
How strong will 99L peak as before reaching the Leeward Islands?

A. Invest
B. Tropical Depression (<35 knots)
C. Tropical Storm (35-45 knots)
D. Severe Tropical Storm (50-60 knots)
E. Hurricane (>65 knots)

Going with D.

C.
Member Since: February 11, 2012 Posts: 84 Comments: 8049
Quoting ncstorm:


Dont worry..it was Buffet night here at WU, you wont be eating alone..
Now Wu will be having a crow sale/special over the next few weeks.Get your crow now while it's still cheap.
Member Since: August 14, 2010 Posts: 10 Comments: 17850
Quoting TropicalAnalystwx13:
How strong will 99L peak as before reaching the Leeward Islands?

A. Invest
B. Tropical Depression (<35 knots)
C. Tropical Storm (35-45 knots)
D. Severe Tropical Storm (50-60 knots)
E. Hurricane (>65 knots)

Going with D.

C
Member Since: February 13, 2012 Posts: 11 Comments: 3885
Quoting TropicalAnalystwx13:
How strong will 99L peak as before reaching the Leeward Islands?

A. Invest
B. Tropical Depression (<35 knots)
C. Tropical Storm (35-45 knots)
D. Severe Tropical Storm (50-60 knots)
E. Hurricane (>65 knots)

Going with D.


D as well.
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Hugo at peak intensity (far right):

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How strong will 99L peak as before reaching the Leeward Islands?

A. Invest
B. Tropical Depression (<35 knots)
C. Tropical Storm (35-45 knots)
D. Severe Tropical Storm (50-60 knots)
E. Hurricane (>65 knots)

Going with D.
Member Since: July 6, 2010 Posts: 113 Comments: 32870

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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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