African tropical wave 99L has potential to develop

By: Dr. Jeff Masters , 3:10 PM GMT on July 30, 2012

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The first African tropical wave of 2012 with a potential to develop is Invest 99L, located in the Eastern Atlantic near 9°N 36°W, midway between the Lesser Antilles Islands and the coast of Africa. Visible satellite loops show a large area of the surrounding atmosphere has a pronounced counter-clockwise spin, though there is no surface circulation. The disturbance's heavy thunderstorm activity is pretty sparse, but appears to be slowly increasing. Water vapor satellite loops show that 99L has a reasonably moist environment, and the latest Saharan air layer analysis shows that the dry air from the Sahara lies well to the north of 99L. 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 for the next five days, and ocean temperatures will remain near 28°C, according to the 8 am EDT run of the SHIPS model. 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, with the storm reaching the Lesser Antilles Islands on Saturday, August 3. NHC gave 99L a 20% chance of developing into a tropical depression by Wednesday morning. I expect the storm will have trouble with dry air at times this week as it crosses the Atlantic, but I 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 night. The long-range fate of 99L is uncertain, but a trough of low pressure is expected to be present over the Eastern U.S. early next week, which would be capable of turning 99L more to the northwest.

Hot in the Central U.S.
The heat in America's heartland continued on Sunday, with Wichita, KS hitting 111°F, just 3° short of their all-time hottest temperature of 114° set on 8/12/1936. Other notable highs on Sunday:

111° Coffeyville, KS
111° Winfield, KS
110° Chanute, KS
110° Parsons, KS
109° Joplin, MO (all-time record is 115° on July 14, 1954)

The low temperature in Tulsa, Oklahoma this Monday morning dropped to only 88°F. This is the all-time warmest low temperature in the city since record keeping began in 1905. The previous record warmest minimum temperature was 87°F set on August 2, 2011 and July 16, 1980. The high in Tulsa Monday - Wednesday is expected to reach 110° - 111°, close to the city's all-time hottest temperature of 115° set on August 10, 1936.

Jeff Masters

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Quoting Bluestorm5:
So what's the health of 99L right now? Is it getting stronger or weaker?

Slowly organizing.
Member Since: July 6, 2010 Posts: 113 Comments: 32001
Somewhat relevant
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99L is slowly organizing
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but with 99L being very large it can with stan shear a little better then smallet storms can
Member Since: May 21, 2006 Posts: 5091 Comments: 115074
So what's the health of 99L right now? Is it getting stronger or weaker?
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BLOB IN TROPICAL ATLANTIC DETECTED

HYPER BLOG MODE ACTIVATED
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713. ackee
99L is very large I think it will. Take long to organize thus I am going with the Euro track weak TS the most we will see be it gets shear. Apart

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Quoting wxchaser97:
One can only guess where 99L goes until a TD/TS develops.

Major Hurricane Ivan



Different ridging scenario but yes that is a great example of a long track westward moving system. Was much further east when it developed.
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The predicted E Conus trough and the fluctuations
in strength and location of Ridging axis associated
with the A-B High will make good forecasting
reads for the next week...
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Quoting TropicalAnalystwx13:

That hasn't updated for the 12Z CMC yet.



12 z showing ts Link
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Quoting TropicalAnalystwx13:

It's a cold-core low.
oh ok thanks.:)
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Quoting ilovehurricanes13:
i do not like how the high to the north of this invest 99L its look like a bad set up!! if we get a hurricane nexct week its going to be bad!


You can wait until next week, can ya?
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The M.O.D. (model of doom) strengthens 99L into a moderate tropical storm as it approaches the central Lesser Antilles. The system weakens to a weak disorganized TS (trade winds) in the eastern Caribbean, causing it to take a more westerly track towards the NW Caribbean by day ten. M.O.D. indicates that upon reaching the NW Caribbean it will find a very favorable environment and explode into a strong CAT 2 now tracking NW through the Yucatan Channel. M.O.D. currently calls for a Cat 4 making landfall along the SE Texas coast.

End of speculation.
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Quoting allancalderini:
Is that a ts near new England or just a low?

It's a cold-core low.
Member Since: July 6, 2010 Posts: 113 Comments: 32001
Quoting TropicalAnalystwx13:

CMC @ 24 hours out:



36 hours:



48:



144:



CMC at 180 hours-993mb

Member Since: August 19, 2006 Posts: 13 Comments: 15282
Quoting TropicalAnalystwx13:

The GFS dissipates the system because of very fast trade winds present in the Caribbean. It has nothing to do with increased wind shear.


I watched the 850mb wind loop, and I see what you are saying, but I wouldn't say southerly wind shear has nothing to do with it.
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Quoting washingtonian115:
Then it'll be no point in discussing 99L.."let's just wait to see what it does tomorrow".Weather forecasting would be boring.Not trying to sound mean.


Oh, I'm not saying don't discuss track. But obviously right now it is all just speculation.
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Quoting TropicalAnalystwx13:

CMC @ 24 hours out:



36 hours:



48:



144:

Is that a ts near new England or just a low?
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Quoting AllStar17:
It would be wise to wait and see if 99L develops, which is certainly possible, before speculating on track.
One can only guess where 99L goes until a TD/TS develops.
Quoting Tazmanian:
dont forget iavn fourmed in the ITCZ and way way S if i re called

Major Hurricane Ivan
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Quoting Tazmanian:
dont forget iavn fourmed in the ITCZ and way way S if i re called


Ivan was in 04 wasn't it? That was the one that nearly hit NO but it ended up further east.

Was sort of pre katrina if I recall.


Here it is:


Number 9.
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Quoting DataNerd:



Edited my post with that very same cmc run, that is a ts btw. Use this: Link

More accurate intensity depictions.

That hasn't updated for the 12Z CMC yet.
Member Since: July 6, 2010 Posts: 113 Comments: 32001
Quoting AllStar17:
It would be wise to wait and see if 99L develops, which is certainly possible, before speculating on track.
Then it'll be no point in discussing 99L.."let's just wait to see what it does tomorrow".Weather forecasting would be boring.Not trying to sound mean.
Member Since: August 14, 2010 Posts: 10 Comments: 16968
695. yoboi
Quoting stormpetrol:
I think 99L will take more of an Emily 05 or Dean 07 path, just my opinion.


ivan comes to mind....
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Quoting SouthDadeFish:


You mean this trough?



Too early to say anything with this system, but yes there is a trough over the East Coast 192 hours out.


That's the one.
Member Since: July 17, 2009 Posts: 71 Comments: 26117
693. CJ5
Quoting washingtonian115:
Why can't we discuss where the storm might be going..I just can't with some of you people...


That is being done. Based on the current models, it will be tracking in a direction W to WNW for a few days and then then slowly begin a more WNW track. Right now, the predictions are a potential landfall from Mexico to the East Coast. That is if it develops at all.
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dont forget iavn fourmed in the ITCZ and way way S if i re called
Member Since: May 21, 2006 Posts: 5091 Comments: 115074
It would be wise to wait and see if 99L develops, which is certainly possible, before speculating on track.
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Quoting TropicalAnalystwx13:

CMC @ 24 hours out:



36 hours:



48:



144:




Edited my post with that very same cmc run, that is a ts btw. Use this: Link

More accurate intensity depictions.
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How about Allen in 1980? It's even the exact same time of the year too!
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Quoting washingtonian115:
I think it will be pulled north and recuvre around Puerto Rico or Hispanola and end up some where in the Bahamas.By then it could affect anyone from Florida to New England or just miss the east coast completely.

Since there is no storm we can only guess where it will go, that is a good guess.
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Quoting DataNerd:



Not seeing that.


CMC @ 24 hours out:



36 hours:



48:



144:

Member Since: July 6, 2010 Posts: 113 Comments: 32001
Quoting wxchaser97:
Where do you think 99L will go Wash?
I think it will be pulled north and recuvre around Puerto Rico or Hispanola and end up some where in the Bahamas.By then it could affect anyone from Florida to New England or just miss the east coast completely.
Member Since: August 14, 2010 Posts: 10 Comments: 16968
IMO invest 99L should be 30% even 40% if it continue to organize and people where do you think we will see invest 90l?
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Quoting Tropicsweatherpr:


Yes, I agree with 30% at 8 PM.
The NHC will only go to 30% until it detaches from the ITCZ and then they really up the chances and then give it a name.
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A majority of the models that take it through the NE Caribbean don't show intensification into a tropical storm for another 2 to 3 days actually.


Not seeing that.


1. Link

2. cmc shows ts Link


3. GFDL shows ts to cat 1 Link
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Quoting SouthDadeFish:
I'm aware of this, but this loop shows the strong 200mb winds reaching far enough south to disrupt the circulation.

Link


and again that is what the GFS is showing, other models are showing more favorable conditions
Member Since: March 10, 2010 Posts: 1 Comments: 7683
Quoting Hurricanes101:


I went back and corrected it, but again, the models taking it north of the islands strengthen the storm



Some do some don't.


It is far too early to take any of them without a grain of salt because none of them have a good handle on the system yet, as its a brand new system.

Wait and watch, biggest thing to look for is what the structure is looking like tomorrow morning.
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Quoting DataNerd:





The big question here, which tends to be the governing issue for these long track waves, is:

When does it develop and how fast?

That really is what's governing our track at this point. You get a TS by tomorrow morning be looking for a more northerly track along what GFDL and some others are showing. You get a TS two days from now be looking for it to end up in the western-central carrib and go from there.

A majority of the models that take it through the NE Caribbean don't show intensification into a tropical storm for another 2 to 3 days actually.
Member Since: July 6, 2010 Posts: 113 Comments: 32001
I think 99L will take more of an Emily 05 or Dean 07 path, just my opinion.
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Quoting SouthDadeFish:
I'm aware of this, but this loop shows the strong 200mb winds reaching far enough south to disrupt the circulation.

Link

The GFS dissipates the system because of very fast trade winds present in the Caribbean. It has nothing to do with increased wind shear.
Member Since: July 6, 2010 Posts: 113 Comments: 32001
Quoting DataNerd:





The big question here, which tends to be the governing issue for these long track waves, is:

When does it develop and how fast?

That really is what's governing our track at this point. You get a TS by tomorrow morning be looking for a more northerly track along what GFDL and some others are showing. You get a TS two days from now be looking for it to end up in the western-central carrib and go from there.


Most of the models taking it north of the Caribbean do not develop it for another 36-48 hours
Member Since: March 10, 2010 Posts: 1 Comments: 7683
Quoting washingtonian115:
Why can't we discuss where the storm might be going..I just can't with some of you people...
Where do you think 99L will go Wash?
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Quoting SouthDadeFish:
It does not move with the system... The 12Z GFS clearly shows possible Ernesto moving into this region of higher shear, and this is why the GFS weakens the cyclone....

Link


I went back and corrected it, but again, the models taking it north of the islands strengthen the storm
Member Since: March 10, 2010 Posts: 1 Comments: 7683
Quoting washingtonian115:
Why can't we discuss where the storm might be going..I just can't with some of you people...


I posted about that this morning..blog never changes
Member Since: August 19, 2006 Posts: 13 Comments: 15282
Quoting TropicalAnalystwx13:

The GFS doesn't take the storm north of the islands...

All of the models that take 99L north of the islands show the storm intensifying. The GFS wind shear is probably off...but that's largely due to the fact that it also shows a completely different track.





The big question here, which tends to be the governing issue for these long track waves, is:

When does it develop and how fast?

That really is what's governing our track at this point. You get a TS by tomorrow morning be looking for a more northerly track along what GFDL and some others are showing. You get a TS two days from now be looking for it to end up in the western-central carrib and go from there.
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The forecast for Irene was...messy. Yes the US did see some major damage but it wasn't where we expected it. There was no need for a Hurricane Warning from OBX to Cape Cod or any need to evacuate the entire East Coast. There was storm surge but not the worst case scenario hurricane nightmare like expected on the OBX, Delmarva, Jersey Shore, and NYC.
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Quoting TropicalAnalystwx13:

The GFS doesn't take the storm north of the islands...

All of the models that take 99L north of the islands show the storm intensifying. The GFS wind shear is probably off...but that's largely due to the fact that it also shows a completely different track.
I'm aware of this, but this loop shows the strong 200mb winds reaching far enough south to disrupt the circulation.

Link
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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.