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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471. etxwx
Standing up to severe weather
July 28, 2012 CBS News: With tougher building standards, severe weather doesn't have to be so destructive anymore.
This is a brief video report from CBS news on building damage during severe storms. About 40 seconds in, it shows a strip mall style building model subjected to Cat 2 winds in a research lab . Video Link
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12z CMC..180 hours

1008mb open low
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Quoting robert88:
It's about time that worthless model came to it's senses. I have never cared much for the CMC. It's all coming down to if 99L can survive the Caribbean. I don't think it will...but you can never say never in the tropics.


It does have an anticyclone over it so it can help ventilate 99L and shear will have little effect on it.
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Quoting HurricaneDean07:

No. Just a rainmaker for Florida during the weekend and monday.


Great, just what FL needs, more rain! We've had anywhere between 10-25 inches of rain in NW Florida the month of July, time to send some of that rain to parts of the country suffering a drought!
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Quoting Grothar:


Not much.
Ok thanks.
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Canadian Model still has north of the islands at the end of its run:



Member Since: August 31, 2009 Posts: 0 Comments: 5628
Could 99L bomb in the Caribbean if shear doesn't kill him (Ernesto
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It's about time that worthless model came to it's senses. I have never cared much for the CMC. It's all coming down to if 99L can survive the Caribbean. I don't think it will...but you can never say never in the tropics.
Member Since: May 22, 2010 Posts: 0 Comments: 907
Quoting Grothar:


And a little attitude!
who knows.. get some hot towers brewing and we're talking altitude too! up, up, up, and away!!!
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The latest 1600 run of the M.O.D. (model of doom) indicates that there has been little change in the projected path of 99L from the last run. MOD continues to show a track into the SE Caribbean on a course very similar to Ivan across the Caribbean into the GOM.
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Going to FL!!
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Quoting GTcooliebai:
The caribbean wave between DR. and PR. looks good, do you see any chance for development with that one?


Not much.
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Quoting stormchaser19:
CMC is going to the south



And also weaker.
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Afternoon KMan. I was just thinking, I wonder what your thoughts on 99l were.Could develop into something for us to monitor closely as we head towards the weekend
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Invest 99L should make it to tropical storm status between 30-60 hrs.

Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting TropicalAnalystwx13:

My point is that it may not turn out well if we get a storm in that area over the next two months under low wind shear. Especially considering this is expected to be a close to home season.


Doesn't mean you can't get a storm or two to form east of the Leeward Islands. This may be one of those exceptions.

Hey all, long time no talk, seems like the tropics are finally beginning to ramp up after a nearly dead July.
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CMC is going to the south

Member Since: June 20, 2012 Posts: 0 Comments: 2159
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.


Depends on where ya live as to if it's important or not.....lol
Member Since: September 18, 2010 Posts: 0 Comments: 5222
Quoting kmanislander:


Try July 2005 for starters but even that hyper active year had less than this year in coverage of extremely high values




Oh man, Imagine tracks like this and a Florida-bound could really make things ugly this season (Or any other storm passing through the Yucatan strait).

It's like Herbert Box 2.0, only bigger and badder.




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IMO even with the wave looking better on Satellite until it gains a little more Lat. the NHC will keep it at 20% until tomorrow AM at best. I do not think the Diurnal cycle will help enhance this wave until it nears the islands. If it stays too far south the influence of SA land mass will impede if not destroy any chance it has of making a run at major status.
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Onshore flow in the bay area today mean scattered showers and thunderstorms throughout the day. Rain chances about 50% area wide.

Member Since: August 31, 2009 Posts: 0 Comments: 5628
I don't get the deal about a storm forming out of the "monsoon trough" or not forming out of it. What's the difference? I mean if it forms it's still a tropical storm/ hurricane..... I see people making comments "oh it will do this or not do this because it came from monsoonal origins" ????????? Is it not still a tropical system?
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445. 7544
is that blob heading for the gulf thats over fl now
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Quoting GTcooliebai:
The caribbean wave between DR. and PR. looks good, do you see any chance for development with that one?

No. Just a rainmaker for Florida during the weekend and monday.
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For 99L today I say it follows the GFS track.
Its not detaching from the ITCZ and its not organizing fast enough to detach for now at least.
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Quoting kmanislander:


I agree entirely and that is why I say that 99L needs to be watched very carefully. If it skirts the SA coast and gets to 75W a few things happen there. One, there is open water on the South side of the circulation all the way down to Panama, no more dry air issues. Second, the TCHP values go off the scale. Finally, the system will then be near the Western periphery of the high to the N in terms of steering. That would mean a more WNW track through the NW Caribbean.

We all know what that might mean.


Anything that gets into the GOMEX will have ample fuel!
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Don't be surprised if we get 3-4 storms at a time come mid to late August. Even 2009 was able to produce three storms at the same time out of no where.

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Make or break time for 99L, in terms of what shape it will arrive into the Caribbean, will happen between the 50-55W mark in about 48 hours. It's embedded in the ITCZ but in a Tutt free area at the moment so the organization looks better. Once it approaches that Tutt cell just on/off the Coast of SA around 55W (assuming it remains draped in that general location in 48 hours time), it could enhance the convection just enough to jump-start some greater development, or, hider development before it enters the Caribbean. It's going to be a tough call either way IMHO at this early juncture whether it will make TD status or just be a rainmaker/open wave after it gets into the Caribbean.

Current Tutt cell position at 200mb level

Link

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Finished run of the Nogaps
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Quoting Grothar:
The caribbean wave between DR. and PR. looks good, do you see any chance for development with that one?
Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting TropicalAnalystwx13:

My point is that it may not turn out well if we get a storm in that area over the next two months under low wind shear. Especially considering this is expected to be a close to home season.


I agree entirely and that is why I say that 99L needs to be watched very carefully. If it skirts the SA coast and gets to 75W a few things happen there. One, there is open water on the South side of the circulation all the way down to Panama, no more dry air issues. Second, the TCHP values go off the scale. Finally, the system will then be near the Western periphery of the high to the N in terms of steering. That would mean a more WNW track through the NW Caribbean.

We all know what that might mean.
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436. SLU
99L has become much better organised today. Anything under 50% at 2pm would be a gross injustice to the poor little guy..
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Outgoing Longwave Radiation for the past month tells the story of an active Pacific and a dead Atlantic.

Member Since: June 9, 2007 Posts: 4 Comments: 15889
Quoting Tropicsweatherpr:


And gaining a little bit of latitude.


And a little attitude!
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Quoting Grothar:
The best it has looked so far.



And gaining a little bit of latitude.
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Quoting Articuno:
I am starting to think that 99L will run into South america. :(


I think when 99L start to gain strength the models will trends to move the system west- northwest something near the south coast of Hispanola, with the GFS far to the south maybe is because he is developing a weak tropical storm, and the ridge is more strong in GFS model, i don't want doubt the GFS because of the debby but this is were i'm seeing right now .
Member Since: June 20, 2012 Posts: 0 Comments: 2159
430. ackee
I am begin to think that if 99L don't start to develop soon it will track into south america or stayed in the southern Caribbean before going heading for central America
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The best it has looked so far.

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Like I said earlier, if 99L can continue to organize the LLC and become more defined...then it should be helped to some extent by an easterly progressing Convectively Coupled Kelvin Wave that will enhance convection with the system. In the short term, this could possibly aid it enough for it to become a cyclone before crossing the islands. This all depends on how it handles detaching from the trof. 850mb vort continues to become better defined as well, so we may see continued gradual organization today.



Member Since: June 9, 2007 Posts: 4 Comments: 15889
Quoting kmanislander:


Try July 2005 for starters


My point is that it may not turn out well if we get a storm in that area over the next two months under low wind shear. Especially considering this is expected to be a close to home season.
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The big picture:



Invest 99L:

Member Since: August 31, 2009 Posts: 0 Comments: 5628
Quoting ilovehurricanes13:
this is crazy over 140 in white color!!


Water over there is boiling if a storm sit over that for awhile they will EXPLODE!!!
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Quoting TropicalAnalystwx13:

Hey Kman.

When's the last time you saw TCHP values in excess of 140 kJ/cm^2..in July?



Try July 2005 for starters but even that hyper active year had less than this year in coverage of extremely high values

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Quoting reedzone:
Wonder whats taking the SPC soo long for the next outlook. Was scheduled to be out at 12:30.







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Quoting TropicalAnalystwx13:
Typhoon Saola and Tropical Storm Damrey:

Saola gathering a lot of moisture. Bad news for China.
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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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