Two African waves worth mentioning

By: Dr. Jeff Masters , 3:51 PM GMT on July 18, 2009

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There are two African tropical waves worth mentioning today, though neither looks particularly threatening. A tropical wave near 12N 45W, about 1200 miles east of the Lesser Antilles Islands (97 L), is moving west at 15 - 20 mph. This wave is now surrounded by an area of very dry air from the Sahara Desert. The dry air has disrupted most of the wave's heavy thunderstorm activity, and will continue to make it difficult for this system to develop over the next 2 - 3 days. Wind shear is a modest 10 knots over the disturbance, and should remain in the moderate 10 - 15 knot range over the next 2 - 3 days. Thereafter, shear is expected to rise to 20 - 30 knots. This morning's QuikSCAT pass showed no evidence of a surface circulation, and only a modest wind shift associated with 97L. The National Hurricane Center is giving this system a low (less than 30% chance) of developing into a tropical depression in the next 48 hours.

A second tropical wave now approaching the northern Lesser Antilles Islands is under 30 knots of wind shear, and has little prospect of development due to the high shear. However, the wave will bring heavy rain to the islands over the next two days.

None of the computer models are forecasting tropical storm development over the next seven days, and I don't expect either of the two African waves mentioned today to develop over at least the next three days.


Figure 1. Current satellite image of African wave 97L, 1200 miles east of the Lesser Antilles Islands.

I'll have an update Sunday afternoon.
Jeff Masters

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1700. WxLogic
Quoting weathermanwannabe:
Unless I am missing something; are you guys giving 97L a chance "above" the current NHC 30%?............While 97L looks good, I see it heading towards the same wall of sheer that tore apart the Antilles system in the overnight hours....Am I way off?.............Thanks


Hehe.. at least I'm still with NHC on this one with a <30% chance.
Member Since: August 14, 2008 Posts: 4 Comments: 5038
1699. SLU
Quoting WPBHurricane05:
1000 PM HST SAT JUL 18 2009

FOR THE CENTRAL NORTH PACIFIC...BETWEEN 140W AND 180

1. A cluster of thunderstorms located 500 to 700 miles south of the Big Island of Hawaii has shown signs of increased organization over the past 12 hours. Some additional development of this system is possible over the next 48 hours as it moves west at 20 to 25 mph.



Central Pacific cyclones normally form in el nino seasons.
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Breakfast break..........Back in about an hour..
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1697. WxLogic
Quoting Seflhurricane:
i think its going to get an orange circle today :)


Hmm... I'm not sure about an orange circle quite just yet. I believe it will be kept the same with some wording of increased convection but nothing more than that.

In regards the INVEST around 60W... I'm expecting that one to be dropped, but I guess we'll see if NHC gives it another 12HRs.
Member Since: August 14, 2008 Posts: 4 Comments: 5038
1000 PM HST SAT JUL 18 2009

FOR THE CENTRAL NORTH PACIFIC...BETWEEN 140W AND 180

1. A cluster of thunderstorms located 500 to 700 miles south of the Big Island of Hawaii has shown signs of increased organization over the past 12 hours. Some additional development of this system is possible over the next 48 hours as it moves west at 20 to 25 mph.
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1695. DDR
Morning all,
My fellow Caribbean people,you all want rain,now here it comes,we've had our share over the past 2 weeks.
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1694. IKE
Quoting TampaSpin:
Look at this loop......it is very clear that out of the Shear has increased over 97L out of the NW.....LOOK!

Gang i don't just make things up....LOL!


Looks like you're wrong TS.
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Unless I am missing something; are you guys giving 97L a chance "above" the current NHC 30%?............While 97L looks good, I see it heading towards the same wall of sheer that tore apart the Antilles system in the overnight hours....Am I way off?.............Thanks
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Quoting Weather456:
My update is ready, Thanks


Typhoon Molave; Carlos's Hot Towers; Tropical Update

Great update and great graphics.
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Quoting WxLogic:
Well... seems X97L has kept and improve on that little vorticity it was developing last night at mid level and low lever vorticity has improved enough too to have some decent low level convergence. Took advantage of DMAX as well so now the question will be will it be able to sustain itself long enough to consolidate better.

The 8AM TWO should be out soon, NHC might have it out in 25 to 30 min.

Finally, if it's able to stay low in latitude and able to get underneath that developing upper high in the Carib... thing might get interesting. Of course shear won't bet that great but low enough to see something more organized.
i think its going to get an orange circle today :)
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The SSTs are getting warmer as ex 97L moves further to the west. Also, a high is supposed to form over the islands so shear shouldn't inhibit it too much....
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1689. WxLogic
Well... seems X97L has kept and improve on that little vorticity it was developing last night at mid level and low lever vorticity has improved enough too to have some decent low level convergence. Took advantage of DMAX as well so now the question will be will it be able to sustain itself long enough to consolidate better.

The 8AM TWO should be out soon, NHC might have it out in 25 to 30 min.

Finally, if it's able to stay low in latitude and able to get underneath that developing upper high in the Carib... thing might get interesting. Of course shear won't bet that great but low enough to see something more organized.
Member Since: August 14, 2008 Posts: 4 Comments: 5038
what would be the track of this system if it gets into the caribbean we are in truble in the gulf of mexico and south florida there is a cold front in central florida and that would act as a magnet lets wait and see how this play out
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1687. WxLogic
Good Morning...
Member Since: August 14, 2008 Posts: 4 Comments: 5038
24 hr Infrared loop of 97L
Member Since: July 24, 2005 Posts: 407 Comments: 19076
Good Morning All and nice to see 456 back...Looks like sheer continues to rule in the Antilles and Caribbean at the moment....Hardly any sheer in the Gulf and around Florida but nothing there except nice stable air after the "cold front" came through yesterday....A nice dry/cool 66 degress in Tallahassee this morning...
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conditions should start to deteriorate late tonight, with the brunt of the activity tomorrow....
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morning storm dude 77
system south of you have you notice. no mention in the barbados weather this morning
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morning all guess we were all right ex97L has really exploded overnight
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winds coming from the north indicative of a developing system south of st lucia
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morning all

very overcast here in Barbados....
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Vorticty up again at 5AM

Member Since: July 24, 2005 Posts: 407 Comments: 19076
1676. SLU
Quoting stoormfury:
SLU hope NEMO and carnival people are monitoring the situation



lol .. maybe NEMO .. not the carnival ppl
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1675. SLU
Quoting leftovers:
good morning slu hopefully things stay north of you this yr


i love to experience those "weak" systems but let's hope the big ones stay clear of here and near you too!
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SLU hope NEMO and carnival people are monitoring the situation
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Ok Thanks Weather456
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yes conditions are conducive and i expect continuing development of this system as it moves west or north of due west
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Quoting willdunc79:
What is normal invert V amplifying mean?


A normal tropical wave has an invert-V pattern in the cloud pattern (an upside down V) and that is becuz of the SW-NE wind shift along the axis. As the wave amplifies, the inverted V pattern becomes more convective as convergence occurs. It is a sign that a wave is developing.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
1669. SLU
Quoting stoormfury:
morning SLU

EXCITING TIMES .LOOKS LIKE ALLEN DEVAJU


How easily those systems blow up past 50W.
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yes 456finitely a dveloping system. upper levels is very moist in the wave of yesrerday"s wave
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My update is ready, Thanks


Typhoon Molave; Carlos's Hot Towers; Tropical Update
Member Since: July 24, 2005 Posts: 407 Comments: 19076
What is normal invert V amplifying mean?
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1665. Kibkaos
I am curious to see how 97L is going to behave today. It looks like it is getting better organized.
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Those bands are reminisce of developing tropical waves. Ther indicate that the normal inverted V is amplifying.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
97l/x is impressive, more than at 3 a.m. I was just blown out of bed for a structure fire two towns north. The summer house is toast, and I heard a child might have been entrapped. It's out of my emergency management area, so I CAN GO BACK TO SLEEP. I hope that when I awake, I hear that it was property damage only, and no one hurt.
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Looking east

Member Since: July 24, 2005 Posts: 407 Comments: 19076
morning SLU

EXCITING TIMES .LOOKS LIKE ALLEN DEVAJU
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1660. SLU
This will definitely be reactivated this morning once they can pinpoint the center with the first visible images. I'm desperate to see the new track.
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1659. SLU
Morning folks

Looking forward to the rush i'll get when 97L arrives by tomorrow.

But yeah it really has gained organisation overnight. It shows you that the conditions have significantly improved since yesterday. It looks like it's being hampered by some slight northerly wind shear which is actually not as bad as due westerly shear. It has also developed a lot more circulation lastnight. Interesting to see if it will continue to organise today.
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Quoting willdunc79:
so 97L is reactivated now?


It's still deactivated, but the Navy still has it up and are updating the satellite imagery. However, they have not re-locate the image meaning no positioning is being done, so the invest remains deactivated for now.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
so 97L is reactivated now?
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While the NAVY has not re-centered the images of 97L, they countine to update the images, which is pretty decent

Member Since: July 24, 2005 Posts: 407 Comments: 19076
close to barbados and south of martinique
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Quoting stoormfury:
morning,
hello 456
it looks like some excitind times for us here in st lucia. it is carnival weekend here, as well as tropical troubles.

the past few dats i have been dead on with my forecast track of this disturbance and the problem we in the windwards would face when it gets nearto 50w.


Hey, I'm going to have an update for you guys but regardless of development some showers in the forecast for you guys.
Member Since: July 24, 2005 Posts: 407 Comments: 19076
system getting better organise with banding in ne and sw quadrants
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stoormfury what is your forecast and forecast track with this wave?
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morning,
hello 456
it looks like some excitind times for us here in st lucia. it is carnival weekend here, as well as tropical troubles.

the past few dats i have been dead on with my forecast track of this disturbance and the problem we in the windwards would face when it gets nearto 50w.
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On the current path of motion, 97L is expected to enter the Carribbean in 36-48 hrs

48 hrs

Member Since: July 24, 2005 Posts: 407 Comments: 19076

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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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