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:
The center had moved pretty much N since the last frame. That disturbance to the N is really causing trouble.



Maybe the center will merge with the NE component convection.
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Quoting JupiterFL:

Exposed like UM's football team?
I ain't goin' there...it's not like UF is gonna do better. :)
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Can you imagine what would occur to the blog if this stays as TD and not develop further?

As Ike reminds us 2010 is still at 3/1/0.
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Wow we have a bunch of testy people in here today

its official, the 2010 season has worn them down
Member Since: March 10, 2010 Posts: 1 Comments: 7354
what makes me wonder if we have a second coc that has developed under the convection. Remember storms of past that have raced away from shear and either relocated their coc's further south or jumped in a sense to escape shear. is that what we are looking at here?
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Quoting Hurricanes101:
TD 6 will be fine, it just needs time to get away from the other disturbance

to me in the long run, this is a bad thing as the models continue to trend westward, a weaker system may not recurve at all
Bingo!
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting MiamiHurricanes09:
That means it is exposed not decoupled. If it were decoupled the mid-level and lower-level circulation would be split up into two and heading into different directions. What it is is exposed. When it is exposed it is distanced from the convection. Try not to confuse the two.

Exposed like UM's football team?
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3279. Vero1


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3277. IKE
Quoting kmanislander:


The models have a longer time horizon and draw conclusions based upon the data input prior to the run. The current motion is expected to be a short term one BUT if it takes the center appreciably further North than forecasted then the new center position will go into the next set of model runs and may result in a shift to the right.

What you are seeing in the satellite imagery is within half an hour generally of being real time. Data in the last set of model runs is several hours old.


Good point. I'll give you a "+" for that post!
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TD 6 will be fine, it just needs time to get away from the other disturbance

to me in the long run, this is a bad thing as the models continue to trend westward, a weaker system may not recurve at all
Member Since: March 10, 2010 Posts: 1 Comments: 7354
THE UPWARD TREND IN ORGANIZATION OF THE DEPRESSION APPEARS TO HAVE
STOPPED FOR THE TIME BEING. THE SYSTEM HAS A WELL-DEFINED
CENTER...BUT THE CIRCULATION IS A LITTLE STRETCHED FROM NORTHEAST
TO SOUTHWEST DUE TO ANOTHER DISTURBANCE LOCATED ABOUT 350 N MI TO
THE NORTHEAST. THIS HAS ALSO CAUSED THE CENTER TO MOVE ALMOST DUE
NORTH OVER THE PAST FEW HOURS...PULLING IT FARTHER AWAY FROM THE
DEEP CONVECTION. SATELLITE INTENSITY ESTIMATES ARE 30 KT AND 45 KT
FROM SAB AND TAFB...RESPECTIVELY...AND AN 1134 UTC ASCAT PASS
SHOWED A MAXIMUM OF 30 KT. THE INITIAL INTENSITY WILL BE KEPT AT 30
KT SINCE THERE HAS BEEN LITTLE CHANGE IN ORGANIZATION
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Quoting AstroHurricane001:


OK, the circulation itself is not decoupling, but the CONVECTION is "decoupling" from the circulation. The convection is drifting W, while the circulation is heading NNW.
That means it is exposed not decoupled. If it were decoupled the mid-level and lower-level circulation would be split up into two and heading into different directions. What it is is exposed. When it is exposed it is distanced from the convection. Try not to confuse the two.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
What is causing the circulation to become exposed?
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Quoting StormChaser81:


Probably not going to end well for TD-6 after this is done.

Exactly
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Out to 39 hours on the GFS and it seems stronger and further south.
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3270. IKE
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Quoting jurakantaino:
Yes, that's exactly what Dr. Masters says in his update, plus i've notice this year most the systems that form are always influence by a second one, affecting development on the main feature. Another observation is ironic that the models are shifting west when TD#6 is heading NNW. Why is that?

Because the ridge is supposed to build in stronger than previously thought, possibly preventing the system from recurving
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Quoting jurakantaino:
Yes, that's exactly what Dr. Masters says in his update, plus i've notice this year most the systems that form are always influence by a second one, affecting development on the main feature. Another observation is ironic that the models are shifting west when TD#6 is heading NNW. Why is that?


The models have a longer time horizon and draw conclusions based upon the data input prior to the run. The current motion is expected to be a short term one BUT if it takes the center appreciably further North than forecasted then the new center position will go into the next set of model runs and may result in a shift to the right.

What you are seeing in the satellite imagery is within half an hour generally of being real time. Data in the last set of model runs is several hours old.
Member Since: August 19, 2006 Posts: 0 Comments: 15708
GHCC longer duration visable loop
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Quoting AstroHurricane001:


OK, the circulation itself is not decoupling, but the CONVECTION is "decoupling" from the circulation. The convection is drifting W, while the circulation is heading NNW.


Probably not going to end well for TD-6 after this is done.
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The center had moved pretty much N since the last frame. That disturbance to the N is really causing trouble.

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Quoting KEEPEROFTHEGATE:


Too grainy and spends my traffic.
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Quoting MiamiHurricanes09:
How is it decoupling? Where do you see the lower and mid-level circulation separated and heading in different directions? 06L remains vertically stacked, the circulation is just exposed.


OK, the circulation itself is not decoupling, but the CONVECTION is "decoupling" from the circulation. The convection is drifting W, while the circulation is heading NNW.
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Quoting Stormchaser2007:


Exactly.

Decouplement is when the circulation fractures and splits at the different levels (high, mid, and low)

Not when it becomes exposed from the convection.


I am no expert but from being on here the last five years, usually the two go hand in hand.
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12z GFS Hour: 024



12z GFS Hour: 030



12z GFS Hour: 036



12z GFS Hour: 042



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3260. KEEPEROFTHEGATE (Mod)
Member Since: July 15, 2006 Posts: 169 Comments: 53296
Following up on my TPW comment that the CoC that is moving north is dying out, and the circulation is ultimately slowly tilting north south and will reform.

Edit: I should rephrase this. Ultimately the CoC will be in a mean position north south in the vorticity before heading west. It may very well be the CoC we see now or a new one. Regardless, there will be consolidation and a westward motion later today into tonight.

I encourage you to page back about 24 hours using the -3 hours button here. You'll see the vorticity rotate to a more north-south orientation

850 Vorticity
Member Since: June 15, 2010 Posts: 0 Comments: 291
Quoting AstroHurricane001:


Decoupling is when the upper-level convection and lower-level circulation separate, causing the LLC to be dry and exposed.
No, it's not. I suggest you go and re-check the definition for what decoupling means.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting TexasHurricane:
ok, thank you everyone. I know there was a model or something suggesting a possible TD or something in the western GOM.....so I was just wondering if some models were still showing that or not.


GFS showed a low drifting in the GOM, then at the end of the run a Pacific system entering the GOM via Tehuantepec.
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Quoting AstroHurricane001:


Decoupling is when the upper-level convection and lower-level circulation separate, causing the LLC to be dry and exposed.


thats incorrect actually, decoupling is when the circulations and different levels become fractured and are no longer stacked with each other, as in the LLC going in one direction and the MLC going another.
Member Since: March 10, 2010 Posts: 1 Comments: 7354
3255. IKE
Quoting KEEPEROFTHEGATE:
its in trouble at the moment if it continues well that will put the blog in overload


Updated 1515UTC floater on it. COC is moving almost due north...near 13N now...convection continues to get further away.
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3254. Patrap
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Quoting Hurricanes101:


Its not decoupling, I really think some use this term way too much and don't really know what it means


Decoupling is when the upper-level convection and lower-level circulation separate, causing the LLC to be dry and exposed.
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Quoting kmanislander:


I just took a look at the close up vis loop and what I see is a short term motion that is almost NNW. There is the illusion of the exposed center heading off to the NNE due to the due West motion of the high cloud tops. Run the loop and cover the left half of the circulation with a piece of paper to obscure the cloud motion and you will see what I mean.

This is a classic case of a system being sheared out but it may only be temporary depending on the interaction with the system to its NE and the progression of the high.

Just my opinion FWIW.
Yes, that's exactly what Dr. Masters says in his update, plus i've notice this year most the systems that form are always influence by a second one, affecting development on the main feature. Another observation is ironic that the models are shifting west when TD#6 is heading NNW. Why is that?
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How is it decoupling? Where do you see the lower and mid-level circulation separated and heading in different directions? 06L remains vertically stacked, the circulation is just exposed.
Member Since: September 2, 2009 Posts: 130 Comments: 21091
Quoting Hurricanes101:


Its not decoupling, I really think some use this term way too much and don't really know what it means


Exactly.

Decouplement is when the circulation fractures and splits at the different levels (high, mid, and low)

Not when it becomes exposed from the convection.
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Quoting TexasHurricane:
Is this what may become an issue down the road in the western GOM?



THE ONE EXCEPTION TO
THE FORECAST REMAINS THE POSSIBILITY FOR SCT CONVECTION...AS A
WEAK COLD FRONT OUT OF THE NE SETTLES INTO THE NERN GULF AREA AND
UPPER DISTURBANCES BEGIN TO TRAVERSE E TO W ACROSS THE AREA. EVEN
WITH CONVECTION DEVELOPING.

This is what is causing convection in GOM..earlier forecasts mentioned possibility of a low developing on front along N gulf coast
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Quoting MiamiHurricanes09:
The circulation is not moving further from the convection, it is moving closer as it heads towards the NNW. Check it out here.


Non-functional link.
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ok, thank you everyone. I know there was a model or something suggesting a possible TD or something in the western GOM.....so I was just wondering if some models were still showing that or not.
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3246. Patrap
GOM IR Loop

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3245. SLU
Quoting mcluvincane:


Impressive


It has a large area of 20 - 25kt winds .. albeit not directly associated with the system.
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Quoting AstroHurricane001:


Looking at that image, the swirl at 18N, 30W looks even more pronounced than the decoupling center low. Also a strong ULL, likely to create shear, a slowdown in the system and a weakness in the ridge.


Its not decoupling, I really think some use this term way too much and don't really know what it means
Member Since: March 10, 2010 Posts: 1 Comments: 7354
12z GFS Hour: 012

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Quoting PanhandleChuck:


Looking at that image, the swirl at 18N, 30W looks even more pronounced than the decoupling center low. Also a strong ULL, likely to create shear, a slowdown in the system and a weakness in the ridge.
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Thanks for your comments OSUWXGUY,when you speak I listen
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3239. KEEPEROFTHEGATE (Mod)
3222 thanks kman will take another look
Member Since: July 15, 2006 Posts: 169 Comments: 53296
12z GFS Gour: 006

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3237. calder
Quoting AstroHurricane001:


Notice that the anticyclone is located directly over the northeastern convection. If it carries that convection with it and the COC continues drifting north, we could see a merger or the two convective areas with the COC, and a subsequent repulsion of dry air. This could cause rapid strengthening, causing the new wave to swing to the northeast of this storm.


1% at the most
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The circulation is not moving further from the convection, it is moving closer as it heads towards the NNW. Check it out here.
Member Since: September 2, 2009 Posts: 130 Comments: 21091

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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.