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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the new TWO is out and its up to 40%

A LARGE AND COMPLEX AREA OF DISTURBED WEATHER CONTINUES OVER THE
TROPICAL EASTERN ATLANTIC. THE ASSOCIATED SHOWER ACTIVITY HAS
BECOME SLIGHTLY BETTER ORGANIZED THIS EVENING ABOUT 850 MILES
WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS. CONDITIONS APPEAR
FAVORABLE FOR ADDITIONAL SLOW DEVELOPMENT AS THE DISTURBANCE MOVES
WESTWARD AT 5 TO 10 MPH...AND THERE IS A MEDIUM CHANCE...40
PERCENT...OF TROPICAL CYCLONE FORMATION DURING THE NEXT 48 HOURS.
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Color me 40% orange!
Member Since: September 10, 2007 Posts: 0 Comments: 11002
Quoting Levi32:


They usually do, which is one reason why this will continue to be very slow in getting going, and will have a better chance once it gains some more latitude, which will also start happening during the next 48 hours.
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Now it's time for, "invest watch...invest watch".
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1115. NASA101
8pm EST NHC now at 40%...
Expect this area to be 91L pretty shortly
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1113. Patrap
1100 Post on nothing.

Wu-tastic.

Member Since: July 3, 2005 Posts: 421 Comments: 127631
1112. KEEPEROFTHEGATE (Mod)
Quoting CybrTeddy:
ex-90L up to 40%.

91L TO BE ACTIVATED SHORTLY
Member Since: July 15, 2006 Posts: 169 Comments: 53296
1111. Levi32
Quoting KEEPEROFTHEGATE:
maybe thats the problem too much favorable conditions too much heat too less of shear


I don't think it's a problem for tropical development. You're thinking of large areas of disturbed weather that are so large and complex that sometimes they never develop or are very slow in doing so. That is something you often see in other basins in the northern hemisphere, but here in the Atlantic it's not as much of a "problem" because we have tropical waves, features that are unique to our basin and provide local focus-points for air to pile up and tropical cyclones to form. And besides, I can think of several ways conditions could have been more favorable so far this year. This isn't perfect.
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1108. divdog
Quoting clwstmchasr:


Jeff, there is no way to be that confident that the steering is so straight forward when you are talking 10-14 days out. A heck of a lot can change by then.
trust me you are wasting your breath jeff. btw i think he lives in c fla where he is forecasting the strike..imagine that
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Quoting KEEPEROFTHEGATE:
maybe thats the problem too much favorable conditions too much heat too less of shear


If that was the case then why did 2005 happen?
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I said this many many times before and I'll say it again , while modelsa are good for guidance and especially for storm tracks don't put your whole stock into them or you'll come out a loser most of the time! It takes models combined with human analysis, years of experience and a general knowledge of weather in general and climatology to come close to forecasting accurately the weather, even then its is a very difficult job, but one which you're paid quite highly to be totally wrong,jmo.
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.
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000
ABNT20 KNHC 312337
TWOAT
TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT SAT JUL 31 2010

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A LARGE AND COMPLEX AREA OF DISTURBED WEATHER CONTINUES OVER THE
TROPICAL EASTERN ATLANTIC. THE ASSOCIATED SHOWER ACTIVITY HAS
BECOME SLIGHTLY BETTER ORGANIZED THIS EVENING ABOUT 850 MILES
WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS. CONDITIONS APPEAR
FAVORABLE FOR ADDITIONAL SLOW DEVELOPMENT AS THE DISTURBANCE MOVES
WESTWARD AT 5 TO 10 MPH...AND THERE IS A MEDIUM CHANCE...40
PERCENT
...OF TROPICAL CYCLONE FORMATION DURING THE NEXT 48 HOURS.

A TROPICAL WAVE LOCATED OVER THE WEST CENTRAL CARIBBEAN SEA
CONTINUES TO PRODUCE LIMITED SHOWER AND THUNDERSTORM ACTIVITY.
UPPER-LEVEL WINDS ARE CURRENTLY NOT CONDUCIVE...AND DEVELOPMENT OF
THIS SYSTEM APPEARS UNLIKELY BEFORE IT MOVES INTO CENTRAL AMERICA
IN A COUPLE OF DAYS. THERE IS A LOW CHANCE...10 PERCENT...OF THIS
SYSTEM BECOMING A TROPICAL CYCLONE DURING THE NEXT 48 HOURS AS IT
MOVES WESTWARD AT ABOUT 15 MPH.

ELSEWHERE...TROPICAL CYCLONE FORMATION IS NOT EXPECTED DURING THE
NEXT 48 HOURS.

$$
FORECASTER BEVEN/LANDSEA
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ex-90L up to 40%.
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Hey Jeff. Do you think we might see a florida thretter around september 14? Im going on vacation then.
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1099. JLPR2
bamm, 40% I feel accomplished LOL!
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Oh the suspense...!

*Movie trailer voice*: "Will it stay at 30%...or will the NHC lift it to 40%? Find out momentarily...
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I see the COC near 8.5N 32.7W
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Quoting CybrTeddy:


Still far to early to determine that.


Exactly. Even at 120 hours it is sketchy.
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Quoting FLdewey:
It's never too far out for Jeff.

+1 XD
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1094. Levi32
Quoting StormSurgeon:
Nice analysis Levi. Isn't it true that systems south of 10 degrees have a hard time spinning up (Coriolis Effect)?


They usually do, which is one reason why this will continue to be very slow in getting going, and will have a better chance once it gains some more latitude, which will also start happening during the next 48 hours.
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1093. KEEPEROFTHEGATE (Mod)
Quoting Levi32:


Because conditions in the tropical Atlantic favor high levels of activity.
maybe thats the problem too much favorable conditions too much heat too less of shear
Member Since: July 15, 2006 Posts: 169 Comments: 53296
Quoting Tazmanian:
384hrs out and look FL




if you look 384 hours out not saying that it will verify. The GFS has a trough off of the east coast and the ridge retreating eastwards which would most likely cause that system to either recurve and effect no land or just skirt the eastern seaboard
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Nice analysis Levi. Isn't it true that systems south of 10 degrees have a hard time spinning up (Coriolis Effect)?
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Holy Smokes, TAZ! The
east coast better start preparing now!
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1086. Levi32
Quoting WeatherNerdPR:

Why are systems so far this year developing in these "dynamic" situations?


Because conditions in the tropical Atlantic favor high levels of activity.
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1085. xcool
KerryInNOLA .na
Member Since: September 26, 2009 Posts: 2 Comments: 15625
1084. Levi32
Quoting cirrocumulus:
Yes Levi. Only it has already moved a little farther north than 8N. That was this morning. Also, the visible showed a lot more development than was expected.


It's near 8N. It could be as far north as 8.5N but it is a rough estimate due to the high clouds which are making it hard to pin down the exact center.
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1083. xcool
Jeff9641 .too far out .
Member Since: September 26, 2009 Posts: 2 Comments: 15625
Quoting IKE:


LOL.



Yeah...I don't see the heaviest convection over the spin at 35W. They could up it to 40% or leave it at 30%. I doubt they go higher than 40% for now. Wait til Sunday morning.

Agree... this is a case of slow development ... just give it time ... if the outlook was longer than 48 hours .. say over the next 4 day ... Id give it a 60% chance ... over the next two days? 3/10 looks good.
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Quoting Levi32:
A little meso-analysis since I'm a bit bored lol:

Now if very slow organization continues with ex-90L and convection continues to fire healthily, this is how we may see things go down over the next 48 hours.

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 days.


Why are systems so far this year developing in these "dynamic" situations?
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Sorry for the off-topic post.

Phoenix, AZ has had 1.73" of rain in 72HRS. AMAZING!!!
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Yes Levi. Only it has already moved a little farther north than 8N. That was this morning. Also, the visible showed a lot more development than was expected.
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Quoting alfabob:
All of that wind sheer earlier was holding back the development. The center of the "blob" is around 8.6N, 32.6W which means that it has a relatively large area in front of it without much wind sheer. I would keep an eye on 41041 for the next few days. The entire area seems to have low pressure, although there's not enough bouys to give a full explanation.
That is pretty close to what I just wrote, basically 1 degree off which is acceptable under most circumstances.
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Quoting Jeff9641:
With all the crap I got yesterday while I was saying the steering is straight forward and that this would be a SE US threat well guess what I told you guys. The same ridge that has been baking FL is going to give us many fits this hurricane season in FL. C FL looks to get hammered by what will be Colin.


I am hoping this is not the way we make up our lost rainfall in Florida.
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384hrs out and look FL

Member Since: May 21, 2006 Posts: 5091 Comments: 114758
1070. IKE
Quoting StormSurgeon:


Is that the spin at the far right in Miami's post 996? that's what I see.


Yeah.
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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.