Pakistan monsoon floods kill at least 800

By: Dr. Jeff Masters , 5:56 PM GMT on July 31, 2010

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The deadliest weather disaster of 2010 is unfolding in Pakistan, where heavy monsoon rains have triggered flooding that has left at least 817 people dead. A death toll may reach 3000, according to the local head of Pakistan's largest rescue service, and more monsoon rains are on the way. Monsoon floods have also hit southeastern Afghanistan hard, where at least 64 have been killed. The heavy rains were caused by a monsoon depression (also called a monsoon low) that formed over the Bay of Bengal on July 24, crossed over India, and reached Pakistan on July 27. The rains increased in intensity over the next two days, peaking on July 29 and 30, when a low pressure system that moved across Pakistan from the west enhanced rainfall from the monsoon depression. Over the 3-day period July 28 - 30, torrential rains in excess of 8 inches (203 mm) fell in many regions of northwest Pakistan, resulting in that nation's worst floods since at least 1929. Rainfall amounts at two stations in the catchment basins of the Jhelum River and Indus River reached 19.49" (495 mm) for the month of July, and 7.56" (192 mm) fell in a single day, July 30, at Tarbela.

A monsoon depression is similar to a tropical depression, but forms in the Indian Southwest Monsoon over the Bay of Bengal. Like tropical depressions, monsoon depressions are hundreds of miles in diameter, have nearly calm winds near the center, and can have sustained winds of 30 - 35 mph. Four monsoon depressions originated in the Bay of Bengal in 2009; the average is 6 - 7. A new monsoon depression developed over the Bay of Bengal yesterday, and is headed westward towards Pakistan. Heavy rains from this new monsoon depression will begin affecting Pakistan on Monday, according to the Pakistan Meteorological Department.


Figure 1. The heavy thunderstorms of a monsoon depression lie over northwestern Pakistan near Islamabad in this visible satellite image taken by NASA's MODIS instrument on July 29, 2010. Image credit: NASA.

Tropical Atlantic may get active by mid-week
The Invest 90L tropical wave off the coast of Africa has grown disorganized, and NHC is no longer generating forecast tracks for the system. A tropical wave that moved of the coast of Africa Thursday is in the eastern Atlantic near 10N 25W, a few hundred miles south of the Cape Verdes Islands. This morning's 12Z run of the NOGAPS model predicts that this wave will develop into a tropical storm by Wednesday, and reach the Lesser Antilles Islands Friday. This morning's 12Z run of the GFS and ECMWF models predict that an area of disturbed weather near 8N 37W, in the east-central Atlantic, will develop into a tropical storm that will move through the Lesser Antilles on Thursday. Wind shear is low to moderate, sea surface temperatures are at record highs, and the dust and dry air of the Saharan Air Layer (SAL) are far enough to the north of these disturbed areas to potentially allow formation of a tropical storm. However, the Madden-Julian Oscillation currently favors downward motion over the tropical Atlantic, which will act to decrease the chances of tropical storm formation. NHC is giving a 30% chance that a tropical depression will form by Monday afternoon from one of these areas of disturbed weather.

Next update
I'll have an update Monday morning at the latest.

Jeff Masters

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1370. Levi32
Thunderstorm tops are getting nice and high especially with that blob on the east side of the broad low.

Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting bohonkweatherman:
Good news on Texas heat, No humidity.

Not the case in SETX, unfortunately... XP
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Member Since: September 2, 2009 Posts: 130 Comments: 21194
1365. Levi32
Quoting TropicalAnalystwx13:


By developing tropcial cyclone, you mean we could see Colin Tuesday?


Perhaps. By that term I mean either a low that is starting to close off and nearing depression status, a TD, or a weak TS.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting StormW:
Impressive convective burst. Is it likely that the broad low pressure area could relocate under it?
Member Since: September 2, 2009 Posts: 130 Comments: 21194
1363. Hhunter
Quoting StormW:
Back.
gettin a little more interesting hey storm
Member Since: Posts: Comments:
Good Evening.....Just checking in from Tallahassee to report that the overland "low" over North Florida/South Georgia is really firing up come serious convection and t-storms this evening.........This thing would be a tropical storm by now if it were over water.
Member Since: Posts: Comments:
Yes it is but I get called a dork for it and the weatherman at work lol. How do I put a approved pic on my avatar?
Member Since: June 20, 2010 Posts: 0 Comments: 73
Quoting F4PHANTOM:
Could the reason NHC hasn't named an invest is due to the fact that the AOI is still in the ITCZ???



nop it dos not have any thing to do with that
Member Since: May 21, 2006 Posts: 5091 Comments: 115454
Quoting F4PHANTOM:
Could the reason NHC hasn't named an invest is due to the fact that the AOI is still in the ITCZ???


No.
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Pinhole eye
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Quoting Levi32:


Indeed. I had a post a while back pondering the potential evolution during the next 48 hours. If I'm right, and if the trend of slow organization continues, we could have a developing tropical cyclone by Tuesday.

Visible satellite imagery shows the broad low center of ex-90L near 8N, 36.5W with an elongated trough extending ENE from the center towards the north side of the new area of convection that has recently developed to the east. This trough appears to be trying to work its way north, and during the course of the next few days we may see this continue to work north and try to rotate around the broad low center's north side. Meanwhile, the tropical wave and associated mid-level circulation will be closing in from behind as it is moving faster, and its motion should take it just north of the broad low center as well. This should result in all of these features coming closer together and conglomerating.

Again, if the system continues to organize instead of falling apart, the net effect will be the system appearing to "wrap around" on the north side and bring everything into a slowly tightening low pressure center that may start to become more concentrated by 48 hours and onward. This is how the merging process may work, and the end-result could be a developing tropical cyclone if conditions allow. This is what the northern Antilles Islands, Virgin Islands, and Puerto Rico should be watching for, as this low will be there in 5-6 days.



By developing tropcial cyclone, you mean we could see Colin Tuesday?
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Quoting bohonkweatherman:
Good news on Texas heat, No humidity.


SmileyCentral.com
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1353. KEEPEROFTHEGATE (Mod)
AOI/XX/XL
MARK
8.6N/35.9W

Member Since: July 15, 2006 Posts: 178 Comments: 56059
Quoting JLPR2:


That one would have people running to the hills here XD LOL!

LOL
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Quoting CybrTeddy:
ASCAT shows a better organized system than the last pass it showed, at that time ex-90L just had a sharp wind shift now it shows a broad low trying to close off.

Could you show me the image?
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Quoting Bordonaro:

It has been a cooler than normal summer than normal, until now :o)~~


Yeah...

By the way, I made a new blog entry earlier :)
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Evening everyone!

Seems like X-90L (as they like to call it) is slowly organizing well, and the TWO proves that! Satellite imagery suggest a broad low is forming around 30-35W and 8-11N. It's still embedded in the ITCZ and models don't lift it north for another 2-3 days. Once it lifts north, gradual development should start to occur and I believe "Colin" will come into the big picture. I believe this could be our first real *potential* threat of the season, then the GFS is back to normal spitting out storms after this one.
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Quoting Tazmanian:
this is looking better and better by the hr sll so if this where too keep going like this we could vary well have a we could have a TD by no later then sunday PM all so i see red comeing at the next two


Wow, there's a WHITE dot in that image. I'd hate to be there!
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1346. Levi32
Quoting StormW:
Levi, I think once that circulation to the north gets by it, we should see the things you and I are speaking of, begin to happen.

IR2 LOOP


Indeed. I had a post a while back pondering the potential evolution during the next 48 hours. If I'm right, and if the trend of slow organization continues, we could have a developing tropical cyclone by Tuesday.

Visible satellite imagery shows the broad low center of ex-90L near 8N, 36.5W with an elongated trough extending ENE from the center towards the north side of the new area of convection that has recently developed to the east. This trough appears to be trying to work its way north, and during the course of the next few days we may see this continue to work north and try to rotate around the broad low center's north side. Meanwhile, the tropical wave and associated mid-level circulation will be closing in from behind as it is moving faster, and its motion should take it just north of the broad low center as well. This should result in all of these features coming closer together and conglomerating.

Again, if the system continues to organize instead of falling apart, the net effect will be the system appearing to "wrap around" on the north side and bring everything into a slowly tightening low pressure center that may start to become more concentrated by 48 hours and onward. This is how the merging process may work, and the end-result could be a developing tropical cyclone if conditions allow. This is what the northern Antilles Islands, Virgin Islands, and Puerto Rico should be watching for, as this low will be there in 5-6 days.

Member Since: November 24, 2005 Posts: 635 Comments: 26700
1345. STXpat
Quoting cirrocumulus:




You're welcome. How about Sasquatch, Lochness, and Great White for names. Just kidding.
How about 'Legion' ?
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1344. SeALWx
Hmmmm...

Ho7700 sure does have a knack for posting relevant questions.

Makes one wonder.
Are they 'knowledge sandbagging'?

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1343. SLU
I'd be really surprised if ex-90L isn't reactivated tonight. I can't remember ever seeing a system with such a high chance of development which didn't have models being ran on it.
Member Since: July 13, 2006 Posts: 13 Comments: 5367
Quoting Levi32:


What has to happen is it has to start gaining latitude so that the Coriolis effect can help it out and also so that it can become more independent from the ITCZ. This should start to happen during the next 48 hours. For the system to become more consolidated it also has to assimilate that tropical wave coming in from behind and form one, well-defined area of low pressure instead of a large, elongated trough.
Quoting StormW:
Levi, I think once that circulation to the north gets by it, we should see the things you and I are speaking of, begin to happen.

IR2 LOOP


Thanks Levi and Storm. I appreciate you both sharing your knowledge.
Member Since: August 18, 2008 Posts: 0 Comments: 884
1341. JLPR2
Quoting StSimonsIslandGAGuy:


How about Hurricane Chupacabra?


That one would have people running to the hills here XD LOL!
Member Since: September 4, 2007 Posts: 7 Comments: 8747
Quoting TropicalAnalystwx13:
**sniffle, sniffle** **cries**


It has been a cooler than normal summer than normal, until now :o)~~
Member Since: August 25, 2009 Posts: 20 Comments: 6785
1339. KEEPEROFTHEGATE (Mod)
<
Member Since: July 15, 2006 Posts: 178 Comments: 56059
Quoting bohonkweatherman:
Good news on Texas heat, No humidity.
Yeah, dry heat isn't that bad. Down here in Miami when you have the humidity near 90% with 100F temperatures it feels much worse.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Quoting bappit:

Going with the idea of a vortex that is likely to develop into a named system, the only thing to prevent calling 95L a tropical depression was its proximity to land. If it had had a little more runway, no doubt it would have taken off.


I believe that definition applies only to how the phrase "tropical depression" is used in that paper.

Excerpt:

3. the so-called “tropical depression” disturbances of the
western tropical Pacific (Liebmann and Hendon, 1990;
Lau and Lau, 1990; Takayabu and Nitta, 1993; Dunkerton,
1993; Dunkerton and Baldwin, 1995; Wheeler and
Kiladis, 1999; Sobel and Bretherton, 1999; Wheeler et
al., 2000).
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Quoting nrtiwlnvragn:


That was the previous version, but here is the link to NHC verifications Link
That's ok. Thanks by the way.
Member Since: September 2, 2009 Posts: 130 Comments: 21194
Good news on Texas heat, No humidity.
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**sniffle, sniffle** **cries**

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Quoting MiamiHurricanes09:
Not just the GFS verification. A couple days ago you gave me a link to all the models' verification.


That was the previous version, but here is the link to NHC verifications Link
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Quoting nrtiwlnvragn:


That is a difficult question to answer because we just had a major revision to the model so past assumed characteristics may no longer apply. Many think it was just a resolution increase but the physics were changed quite a bit. So it is going to take time to actually measure the performance.
Not just the GFS verification. A couple days ago you gave me a link to all the models' verification.
Member Since: September 2, 2009 Posts: 130 Comments: 21194


Quoting StSimonsIslandGAGuy:


Thanks! It's all good!


You're welcome. How about Sasquatch, Lochness, and Great White for names. Just kidding.
Member Since: September 30, 2005 Posts: 0 Comments: 1606
this is looking better and better by the hr sll so if this where too keep going like this we could vary well have a we could have a TD by no later then sunday PM all so i see red comeing at the next two

Member Since: May 21, 2006 Posts: 5091 Comments: 115454
1326. Levi32
Quoting weatherwart:


Hi Levi. What's it going to take for this broad low to become more consolidated? What has to happen? Thanks.


What has to happen is it has to start gaining latitude so that the Coriolis effect can help it out and also so that it can become more independent from the ITCZ. This should start to happen during the next 48 hours. For the system to become more consolidated it also has to assimilate that tropical wave coming in from behind and form one, well-defined area of low pressure instead of a large, elongated trough.
Member Since: November 24, 2005 Posts: 635 Comments: 26700
Quoting MiamiHurricanes09:
LOL! You need to download Firefox preferably to post images.


REALLY? cool thanks for the info!!
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Quoting MiamiHurricanes09:
I would say it is the second most accurate model we have behind the Euro. Nrt will give you the link for the model verifications.


That is a difficult question to answer because we just had a major revision to the model so past assumed characteristics may no longer apply. Many think it was just a resolution increase but the physics were changed quite a bit. So it is going to take time to actually measure the performance.
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Tomorrow is August 1st, the real tropical season starts.
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Quoting ho77yw00d:
Thank you guys so much you are teaching me a lot and I am catching on so... Thank you if I knew how to put a image up on post I would send you guys a kiss... so here ya go muah lol back to weather Its so exciting!!!
LOL! You need to download Firefox preferably to post images.
Member Since: September 2, 2009 Posts: 130 Comments: 21194

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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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