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 not gonna be like Ivan... chill.
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Quoting TropicalAnalystwx13:

You expect it to show the same exact path every run? LOL. The Caribbean is not that big, so a difference in the southern Caribbean and the northern Caribbean is not that significant.
Actually one of the runs had it dying over Haiti and redeveloping off the coast of South FL. and moving up the East Coast. These past 2 runs have it dying over the Central Caribbean. I think the CMC has been the most consistent so far. I'm just stating what I see and not model bashing at all.
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Quoting TropicalAnalystwx13:

You expect it to show the same exact path every run? LOL. The Caribbean is not that big, so a difference in the southern Caribbean and the northern Caribbean is not that significant.


so it should show all scenarios still at this point?..no..the models should be able to grasp some type of track and keep with it especially with the lesser antilles islands ahead of it..if the NOGAPS and the CMC can do it, then surely the GFS and Euro should be able to do the same..but again, all that can change in the 12z suite for all models
Member Since: August 19, 2006 Posts: 13 Comments: 15678
Quoting StormTracker2K:


Yeah well see about that! Caribbean is not as hostile as one would think. I will laugh if you poof 99L and it turns out to be an Ivan.



I, for one, will NOT laugh if it turns out to be another Ivan! Ivan was not a system to laugh about.
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Quoting LargoFl:
..georgia storms...get ready for the second wave
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Quoting LargoFl:
..Uless it turns northward which i highly doubt..its a south american or maybe panama's problem IF it even stays together..its way too low in latitude and look at most of the other waves down there..all headed westward almost in a straight line..what would cause it to move north at all?

It's already moving more northerly. It was at 8.7N this time yesterday, and today it is at 9.3N.
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Quoting GTcooliebai:
If I had to choose the CMC is the 3rd most reliable model, so a NW track is possible, especially if the system strengthens to a strong tropical storm.


The GFS has shown about every scenario with these waves, then drops them, picks them back up on a later run and then does it all over again..Im surprise it hasnt shown it heading back to africa..
Member Since: August 19, 2006 Posts: 13 Comments: 15678
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Quoting LargoFl:
..Uless it turns northward which i highly doubt..its a south american or maybe panama's problem IF it even stays together..its way too low in latitude and look at most of the other waves down there..all headed westward almost in a straight line..what would cause it to move north at all?

I agree. It's embedded in the ITCZ, need to break free and more north to have any chance to become more than invest 99L.
Member Since: September 30, 2007 Posts: 9 Comments: 15940
Quoting ncstorm:


yeah um humm, north-middle-south of the caribbean..come on..those are not consistent runs

You expect it to show the same exact path every run? LOL. The Caribbean is not that big, so a difference in the southern Caribbean and the northern Caribbean is not that significant.
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Quoting TropicalAnalystwx13:

The images we posted were of the GFS ensembles, not the operational run. The actual GFS has shown a track into the Caribbean since the day it began to develop the system.


yeah um humm, operational runs were north-middle-south of the caribbean..come on..those are not consistent runs
Member Since: August 19, 2006 Posts: 13 Comments: 15678
Quoting Bluestorm5:
102 HR: 99L is very close to South America coastline.

..Uless it turns northward which i highly doubt..its a south american or maybe panama's problem IF it even stays together..its way too low in latitude and look at most of the other waves down there..all headed westward almost in a straight line..what would cause it to move north at all?
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Quoting ncstorm:
The GFS and the Euro has been very inconsistent with this potential storm..If the Nogaps and the CMC continue to show the same NW path in the 12z suite, Im siding with them..
If I had to choose the CMC is the 3rd most reliable model, so a NW track is possible, especially if the system strengthens to a strong tropical storm.
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Quoting stormchaser19:
The wave in the carribean is fighting with the Wind shear and trade, yes, you can!!!!!! says obama





Two things...

1. Wind shear is 5-10 knots, conditions are currently favorable under that wave..

2. Don't mention politics on here.
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108 HR:

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I hope this thing can 'thread the needle' through the Yucatan channel and then go into Texas. We need the water up here in Kansas - BAD!
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Quoting ncstorm:


um the GFS had it going into the SE coast and into the GOM on several different occasions..the Euro as well..and now the GFS is trying to take it into SA..that aint consistency..

The images we posted were of the GFS ensembles, not the operational run. The actual GFS has shown a track into the Caribbean since the day it began to develop the system.
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351. RayT
Hey guys. I dont often post, but I was just curious.

I've always noticed that there is a sizeable difference in strength between a 40 MPH tropical storm and a 70 MPH tropical storm.

Why do we not have two classifications of tropical storm?

Perhaps cateogory 1 tropical storms for up to 55 MPH and category 2 for anything between 55 and 75 MPH?

Maybe there is some reason for it.

Mostly just curious.
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The wave in the carribean is fighting with the Wind shear and trade winds, yes, you can!!!!!! says obama



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102 HR: 99L is very close to South America coastline.

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Quoting TropicalAnalystwx13:

How have they been inconsistent?


um the GFS had it going into the SE coast and into the GOM on several different occasions..the Euro as well..and now the GFS is trying to take it into SA..that aint consistency..
Member Since: August 19, 2006 Posts: 13 Comments: 15678
Will the System coming off Mississippi play any roll in the next few days or once it clears land it dissipates.


@NHC_Atlantic..."probable" recon. mission into the low to the east of the Antilles on Friday.
Member Since: September 30, 2007 Posts: 9 Comments: 15940
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Quoting TropicalAnalystwx13:
Carl Parker said this is getting close to tropical depression status. And it would be if it weren't connected to the Intertropical Convergence Zone still. Once we see it detach, we should see classification.


I agree with this! :)
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Quoting HurricaneHunterJoe:


The wave almost looks like Tropical Storm Olga in 2007...

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did it go up
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Quoting ncstorm:
The GFS and the Euro has been very inconsistent with this potential storm..If the Nogaps and the CMC continue to show the same NW path in the 12z suite, Im siding with them..

How have they been inconsistent?
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The GFS and the Euro has been very inconsistent with this potential storm..If the Nogaps and the CMC continue to show the same NW path in the 12z suite, Im siding with them..
Member Since: August 19, 2006 Posts: 13 Comments: 15678
96 HR:

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I expect the NHC to up the chance to 40% at 2PM



We might see A T.D in 24 hours!
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Quoting Pipejazz:
Please please everyone in the high heat, check your tires for proper pressure and tread depth. Tire blowouts can cause wrecks with fatalities at the highway speeds (Houston area news reported blowout wreck with fatalities).
Yeah, and get off those CELL PHONES while driving! That is just as dangerous as your bald tires on your vehicles in the heat!
Member Since: May 16, 2010 Posts: 0 Comments: 1472
84 HR: Still hanging in there

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Quoting Pocamocca:

Soundz about right to me...


Link
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I think it's safe to say 99L will make for an interesting week. Anything can happen.. I'm not writing this one off.
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Quoting Tropicsweatherpr:


Do you have graphics that support less Caribbean Trade winds?

Caribbean - False Color RGB Loop

:)
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78 HR: 99L WAYYY south. About to get killed by GFS.
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Quoting Pocamocca:

Soundz about right to me...


It will not be that strong by the time 99L enters the Caribbean.
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Quoting Articuno:

Hello Reed. How are ya?


I'm doing alright, I have the day off today.

Quoting Pocamocca:

Won't likely be seeing another Earl from 2010 with that setup Mr. Reed!


Well with a strong trough set up off the East Coast, we could see an East Coast cruiser, but anything more east is just nearly impossible with that large ridge.
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Please please everyone in the high heat, check your tires for proper pressure and tread depth. Tire blowouts can cause wrecks with fatalities at the highway speeds (Houston area news reported blowout wreck with fatalities).
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Quoting TropicalAnalystwx13:
Carl Parker said this is getting close to tropical depression status. And it would be if it weren't connected to the Intertropical Convergence Zone still. Once we see it detach, we should see classification.

When should it detach?
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Quoting TropicalAnalystwx13:

Huh?



Do you have graphics that support less Caribbean Trade winds?
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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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