95L growing more organized; Pakistan's Indus River flood peaking downstream

By: Dr. Jeff Masters , 2:23 PM GMT on August 21, 2010

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A tropical wave (Invest 95L) in the far eastern Atlantic about 350 miles southwest of the Cape Verdes Islands has become more organized this morning. Satellite loops show that the wave has some rotation, and heavy thunderstorm activity has increased in recent hours, after a period overnight with little change. Water vapor satellite loops show that there is some dry air to the north of 95L, but this dry air currently appears to be too far away to significantly interfere with development. The main impediment to development is the moderate 10 - 20 knots of wind shear over the system. The shear is forecast to remain in the moderate range through Monday, then decrease. This should allow 95L to develop into a tropical depression Monday or Tuesday. NHC is giving 95L a 30% chance of developing into a tropical depression by Monday morning. With 95L's recent increase in organization, these odds should probably be 50%.


Figure 1. Morning satellite image of 95L.

Forecast for 95L
A ridge of high pressure will force 95L to the west or west-northwest for the next five days, and the system should increase its forward speed from its current 5 - 10 mph to 15 - 20 mph by Monday. A series of two powerful troughs of low pressure are predicted to move off the U.S. East Coast next week and cross the Atlantic; these troughs should be able to pull 95L far enough to the northwest so that it will miss the Lesser Antilles Islands. If 95L stays weak or does not develop in the next five days, as predicted by the NOGAPS model, it has a chance of eventually threatening Bermuda. If 95L develops into a hurricane, as predicted by most of the computer models, it will probably recurve to the east of Bermuda and not threaten any land areas.

Elsewhere in the tropics
The ECMWF model is predicting formation of a tropical depression in the western Gulf of Mexico off the coast of Texas 6 - 7 days from now.

Pakistan's monsoon rains diminish; Indus River flood crest nears the coast
The flooding on Pakistan's largest river, the Indus, has slowly eased along the upper and middle stretches where most of the heavy monsoon rains fell in late July and early August. However, a pulse of flood waters from these heavy rains is headed southwards towards the coast, and flood heights have risen to near all-time record levels today at the Indus River gauge station nearest to the coast, Kotri (Figure 2.) The new flooding has forced the evacuation of an additional 150,000 people in Pakistan today. Flood heights at every monitoring station along the Indus have been the highest or almost the highest since records began in 1947. Fortunately, the monsoon has entered a weak to moderate phase, and heavy rain is not expected over the flood region over the next few days, according to the Pakistan Meteorological Department.


Figure 2. August flow rates along the Indus River, courtesy of the Pakistan Meteorology Department.

Some aid agencies helping with humanitarian crisis in Pakistan:

Doctors Without Borders

The International Red Cross

MERLIN medical relief charity

The mobile giving service mGive allows one to text the word "SWAT" to 50555. The text will result in a $10 donation to the UN Refugee Agency (UNHCR) Pakistan Flood Relief Effort.

Jeff Masters

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Quoting Stormchaser2007:
At 168 hours it really slows it down SSE of Bermuda.


and that weakness is closing
Member Since: March 10, 2010 Posts: 1 Comments: 7376
Quoting MississippiWx:


LOL...thank you for your concern! You are probably correct!
Quoting TexasHurricane:
Hi all, been off most of the day. How are things looking in the GOM in the next couple of days? I know there was something to be keeping an eye on I think....

Go to Central Atlantic and turn right.
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2333. angiest
Hour 162. Fiona in the wings.

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At 168 hours it really slows it down SSE of Bermuda.
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2331. scott39
Quoting bappit:
I suspect that all of these models are initialized with some well-defined vortex for the tropical depression. The beta-effect (see Atmo's post, 1518 and http://www.nrlmry.navy.mil/~chu/chap4/se100.htm) causes a well-defined vortex to move northward of the prevailing easterly flow. If TD 6 is moving due west then it means either that a ridge is building north of it to force it west or that there is no well-defined vortex. In the latter case we have the well-known case of GIGO. If a ridge were preventing it from moving on a more northwesterly course, then we have a puzzle as to why all the models are not recognizing the ridge.

I suspect that the vortex is not all that strong/well defined. The satellite images do not show convection wrapped around a center as far as I can tell. If the convection wraps around, I'll theorize that a more northwesterly motion will become evident. When it gains some latitude, I think we can start to consider whether a ridge will stop it from going further north or a trough will sweep it north and then northeastwards. Right now it is just a big baby system.
good post
Member Since: June 13, 2009 Posts: 0 Comments: 6740
162 hours, still heading NNW, likely out to sea. Major hurricane now.

Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting MiamiHurricanes09:
150 hours:



Similar to the 18Z run, strong ridging right after it misses the first trough. Interesting..
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Quoting MiamiHurricanes09:
150 hours:



Wow, the suspense! Could those two highs hookup??
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2327. bappit
I suspect that all of these models are initialized with some well-defined vortex for the tropical depression. The beta-effect (see Atmo's post, 1518 and http://www.nrlmry.navy.mil/~chu/chap4/se100.htm) causes a well-defined vortex to move northward of the prevailing easterly flow. If TD 6 is moving due west then it means either that a ridge is building north of it to force it west or that there is no well-defined vortex. In the latter case we have the well-known case of GIGO. If a ridge were preventing it from moving on a more northwesterly course, then we have a puzzle as to why all the models are not recognizing the ridge.

I suspect that the vortex is not all that strong/well defined. The satellite images do not show convection wrapped around a center as far as I can tell. If the convection wraps around, I'll theorize that a more northwesterly motion will become evident. When it gains some latitude, I think we can start to consider whether a ridge will stop it from going further north or a trough will sweep it north and then northeastwards. Right now it is just a big baby system.
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certainly seems like that weakenss is closing around the 144 hour mark
Member Since: March 10, 2010 Posts: 1 Comments: 7376
Hi all, been off most of the day. How are things looking in the GOM in the next couple of days? I know there was something to be keeping an eye on I think....
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Quoting DestinJeff:


on queue, or cue? not to be cute, just wondering.

Depends upon which side of the Atlantic you're on. We're separated by a common language, you see.
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2322. angiest
Out around 130-140 hours GFS goes to positive NAO. Look at the position of orientation of the A/B high.
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2321. scott39
How many times in the past has a TCs cone been put towards land, when it is still behind 40W?
Member Since: June 13, 2009 Posts: 0 Comments: 6740
2319. JLPR2
Quoting Stormchaser2007:


Thats becuase the wave isn't set to emerge from Africa for another 36-48 hours.

What you see is just a Mesoscale Convective Complex


That MCC is going to have the area ready and sweet for the TW to develop.
unless an explosion of Dry air occurs LOL I wont discount anything in 2010. XD
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150 hours:

Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting Chicklit:
MSWX, while your courage is admirable, you may want to change that image to perhaps shear over the mid-atlantic?
I will post the vortcity for you below:



LOL...thank you for your concern! You are probably correct!
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Quoting Chicklit:

ROFLMAO...Sorry, that's funny.
(He means they're totally off the mark.)
TD6 has not gone beyond 11N since about 8 o'clock this morning. And it's steadily strengthening. A trough is supposed to lift it up up and away...and no, I will not post the 'beautiful balloon' song.
ROFLMAO wow Chicklit that is very Funny....

Taco :o)
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MSWX, while your courage is admirable, you may want to change that image to perhaps shear over the mid-atlantic?
Vorticity posted below:

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Quoting Twinkster:



i'm telling you a lot of you are about to be shocked. ridge will start building in and push this west again


Out to 147 hours.

Smells like fish to me.
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2312. angiest
Quoting DestinJeff:


on queue, or cue? not to be cute, just wondering.


Its late. :)
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Quoting wxhatt:
They still don't have the wave emerging from Africa marked yet...

It is not a tropical wave.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting wxhatt:
They still don't have the wave emerging from Africa marked yet...



Thats becuase the wave isn't set to emerge from Africa for another 36-48 hours.

What you see is just a Mesoscale Convective Complex
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Quoting MiamiHurricanes09:
06L moving towards the NNW, PGI31L moving towards the WNW.




i'm telling you a lot of you are about to be shocked. ridge will start building in and push this west again
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Quoting DestinJeff:


Don't get me started on "poleward"


Lol, please don't. Taz would put you in a straight jacket faster than you could say "doom."
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06L moving towards the NNW, PGI31L moving towards the WNW.

Member Since: September 2, 2009 Posts: 130 Comments: 21091
2304. angiest
On queue, a 1016mb low forms in the middle of an area of ridging.

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is that two tropical systems at 90 hours. a hurricane and a tropical storm.
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2302. wxhatt
They still don't have the wave emerging from Africa marked yet...

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Quoting angiest:

Yep, showing a direct hit on the Cape Verde Islands.
What tropical irony. We rarely get that cosmic payback. Shouldn't be very strong and hopefully all will be safe.
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looking at gfs ridge might be building back in arounbd 120 hours and this might start heading west again
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2297. angiest
Quoting MiamiHurricanes09:
114 hours, 06L moving due north, PGI34L moving towards the WNW.



Do you see any reason for Danielle to move that far north? I mean, looking at what GFS is giving us.
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Quoting bigwes6844:
I think the storm from the african tip can sustain its production of being a possible strong wave because the enviornment is getting better to organize. I wouldn't have said dat last week or earlier this month! We about to see some active storms now!!


Ya, not a good time for this strong of a wave to come off the coast. It will have perfect conditions!
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I highly doubt that TD6 will even get close to taking on a Frances type track.

That was in 2004. This is 2010.

All of our guidance points to a system that doesn't affect the CONUS.

I would like to believe that the models have improved quite a bit since then.
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126 hours, 06L moving due north, PGI34L moving towards the WNW.

Member Since: September 2, 2009 Posts: 130 Comments: 21091
2291. angiest
There is also a developing EPac system hugging the coast of Mexico in this run.
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Sorry, Jeff. We're not all up on Airplane quips. Anyway, I'm still reeling from StormChaser being able to pull Frances out of his head like that.
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Quoting CaneFears:


Reported, just kidding, man.


Taz will report it soon enough!
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I think the storm from the african tip can sustain its production of being a possible strong wave because the enviornment is getting better to organize. I wouldn't have said dat last week or earlier this month! We about to see some active storms now!!
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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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