Pakistan monsoon floods kill at least 800

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

Share this Blog
3
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 1270 - 1220

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61Blog Index

1270. Zegama
Member Since: Posts: Comments:
QUESTION how accurate is GFS?
Member Since: Posts: Comments:
Quoting StormW:


Good evening, Levi!


Good Evening Storm!
Member Since: Posts: Comments:
1266. KEEPEROFTHEGATE (Mod)
Quoting msgambler:
Behave Keeper
Member Since: July 15, 2006 Posts: 171 Comments: 53787
1264. Zegama
Funktop

Link
Member Since: Posts: Comments:
Good evening Storm!
Member Since: Posts: Comments:
So does Storm.
Member Since: Posts: Comments:
1258. Levi32
Good evening Storm.
Member Since: Posts: Comments:
1257. Levi32
Quoting bappit:


Ahhhhh, but what causes the "by a stronger than normal African Easterly Jet and an ITCZ located farther north than normal"? I don't know. The idea can't be rejected out of hand though.


The African Easterly Jet is just like any other jetstream. Think of our polar jetstream in the wintertime....a stronger jet results in larger waves within the jet.

The ITCZ farther north than normal is often correlated with a stronger AEJ and can be caused by a colder than normal Gulf of Guinea or a stronger than normal Indian Monsoon. The farther north position of the ITCZ contributes to larger waves because #1 it is again correlated with a stronger AEJ and #2 it sends more waves out over the Atlantic at a farther north latitude, where they get amplified down to where the Atlantic ITCZ is and yet extend farther north into the dry airmass of the subtropical high.
Member Since: Posts: Comments:
Quoting KEEPEROFTHEGATE:

thats normally where the centre is
right between the balls (of convection)


lol
Behave Keeper
Member Since: February 27, 2010 Posts: 0 Comments: 1125
Quoting nrtiwlnvragn:
Does the NHC throw a curve ball and initiate closer to the location in the TWD...stay tuned.


I know the NHC can call an Invest on anything. But do you find it unusual that they keep upping the percentage of the disturbance without wanting to run models on it?
Member Since: September 10, 2007 Posts: 0 Comments: 11150
Blog Update!

July 31, 2010 - 8:35 PM EDT - Ex-90L Organizing
Member Since: Posts: Comments:
1253. JLPR2
Quoting Levi32:
ASCAT pass just 90 minutes old shows a well-defined trough and associated wind shift with the tropical wave near 27W.



nice

i wonder if we'll get two systems then
Member Since: September 4, 2007 Posts: 7 Comments: 8690
Quoting KEEPEROFTHEGATE:

thats normally where the centre is
right between the balls (of convection)


lol


lol
Member Since: Posts: Comments:
1251. aquak9
hi granny - we are thick with humidity and haze, hope you had a good day at work.

GUT model need enhancement...laterzzz
Member Since: Posts: Comments:
1250. Levi32
Quoting Filibuster:
Levi, am i seeing things.....or is the ''center'' in between the two balls of convection tonight? if i'm wring, let me know, lol


Roughly yes, but it is soon to be just one ball, or oval, rather.
Member Since: Posts: Comments:
1248. KEEPEROFTHEGATE (Mod)
excuse the punt to any wunder women on the board
Member Since: July 15, 2006 Posts: 171 Comments: 53787
Quoting aquak9:
caicos- re, northeast florida- we are not really stormy all over, but thick and hazy in some areas, humidity at like 98%.

Even the trees are sweating.


Yes I certainly understand, as I was under the same "white" cold cloud tops when "Pre" Bonnie was here and had to explain to folks that I WASN'T getting "pounded".

Just a dark and stormy night.
Member Since: Posts: Comments:
1245. KEEPEROFTHEGATE (Mod)
Quoting Filibuster:
Levi, am i seeing things.....or is the ''center'' in between the two balls of convection tonight? if i'm wring, let me know, lol

thats normally where the centre is
right between the balls (of convection)


lol
Member Since: July 15, 2006 Posts: 171 Comments: 53787
1244. bappit
Quoting Levi32:


Warmer SSTs in the Atlantic have little to do with generating large, amplified tropical waves. Those are created over Africa by a stronger than normal African Easterly Jet and an ITCZ located farther north than normal.

They are correct that large waves extending far to the north end up embedded in dry air and entrain a stable airmass, which can prevent development in the eastern Atlantic, however, that makes them a big threat farther west because such waves can remain well-defined for a long time and then blow up convection when they encounter the TUTT near the Caribbean. Bonnie this year was the classic example of this. She was a massive, naked wave in the eastern Atlantic embedded in dry air to the north but then she blew up north of the Caribbean once she got west of 50-60W.


Ahhhhh, but what causes the "by a stronger than normal African Easterly Jet and an ITCZ located farther north than normal"? I don't know. The idea can't be rejected out of hand though.
Member Since: Posts: Comments:
1242. Levi32
ASCAT pass just 90 minutes old shows a well-defined trough and associated wind shift with the tropical wave near 27W.

Member Since: Posts: Comments:
1240. Becca36
Quoting ho77yw00d:
refresh* refresh* refresh* break... refresh* refresh* lol

LOL!
Member Since: Posts: Comments:
1238. bappit
tropical depression: Although no formal definition can be found, a tropical depression-strength vortex is thought to exist when circular horizontal winds approach 30 knots and deep, persistent convection is well-organized by a putative closed circulation. It can be said that forecasters regard a proto-structure with features loosely resembling a mature hurricane as a good candidate for a “depression” – the more such features, the better. Their classification evidently guarantees (in all but a few instances) subsequent growth to a named tropical storm. It is not only the statistical narrowness of the tropical depression classification, but a physical threshold for instability leading to intensification, that is responsible for their success. In other words, “tropical depression” is a physically meaningful, albeit imprecisely defined, concept.

Interesting.
Member Since: Posts: Comments:
Hello Aqua.How are you this evening?
Member Since: Posts: Comments:
refresh* refresh* refresh* break... refresh* refresh* lol
Member Since: Posts: Comments:
1234. aquak9
caicos- re, northeast florida- we are not really stormy all over, but thick and hazy in some areas, humidity at like 98%.

Even the trees are sweating.
Member Since: Posts: Comments:
Have we ever gone from a non-invest to a td?
Member Since: Posts: Comments:
LOL Mudder.
Member Since: Posts: Comments:
When this blob experiences a change in lattitude, this blog will experience a change in attitude.
Member Since: Posts: Comments:
Ah, yes... another miss by WindSat
I sure miss QuikScat



edited oops on image
Member Since: Posts: Comments:
Here's today's 26.C (78.8F) isotherm map of the Atlantic. (Note that the blues hugging the Atlantic and Gulf coasts don't mean the water is cold below, say, 30m/100 feet; they mean that the water is no deeper than that in those areas.) Of special interest to note is that in the Caribbean and stretching into the Atlantic are thousands of square miles of ocean where the 26.C water extends in places lower than 400' below the surface, and some places to 500'. Even the majority of the Gulf has cyclone fuel down to 200' below the surface.

It's gettin' hot in h-e-e-r-e

(Image source)

Meanwhile, here's today's SST map of the same area: Note the 26.C line; there's not a whole lot of non-land area in the image that can't support a cyclone. (Pay special attention to the areas around Florida and the Bahamas where the water is a bath-like 90.F plus.)

It's gettin' hot in h-e-e-r-e

(Image source)
Member Since: Posts: Comments:
Quoting nrtiwlnvragn:
Does the NHC throw a curve ball and initiate closer to the location in the TWD...stay tuned.


Strike 1
Member Since: Posts: Comments:
Quoting gordydunnot:
As opposed to oblong,elliptical.
The non-invest is looking more symmetrical.
Member Since: Posts: Comments:
1226. Levi32
Quoting bappit:


Hmmmmm, could warm SST's lead to larger waves which in turn lead to less favorable conditions for tropical storm development?


Warmer SSTs in the Atlantic have little to do with generating large, amplified tropical waves. Those are created over Africa by a stronger than normal African Easterly Jet and an ITCZ located farther north than normal.

They are correct that large waves extending far to the north end up embedded in dry air and entrain a stable airmass, which can prevent development in the eastern Atlantic, however, that makes them a big threat farther west because such waves can remain well-defined for a long time and then blow up convection when they encounter the TUTT near the Caribbean. Bonnie this year was the classic example of this. She was a massive, naked wave in the eastern Atlantic embedded in dry air to the north but then she blew up north of the Caribbean once she got west of 50-60W.
Member Since: Posts: Comments:
As opposed to oblong,elliptical.
Member Since: Posts: Comments:
Just remember, 40% chance of development means there's a 60% chance of no development. That's called downcasting I might add.
Member Since: Posts: Comments:
Does the NHC throw a curve ball and initiate closer to the location in the TWD...stay tuned.
Member Since: Posts: Comments:
A possibly significant role for hydrodynamically stable waves in this context is counter-intuitive: one might be tempted to think that large-scale instability implies a more vigorous sequence of events that would lead to genesis more readily than what might be triggered by a neutral or slowly decaying wave. But we must be willing to entertain less intuitive ideas in order to understand the possible preference for neutral or slowly decaying modes in TC genesis. (i) These modes are maintained by diabatic heating (H3) in addition to their %u201Cdry%u201D maintenance (compact spectral content). (ii) Genesis is an interactive multi-scale process and not simply a consequence of moist hydrodynamic instability. If the quasi-mode configuration as described above favors mesoscale development, then it may actually be more favorable for genesis than a more vigorous unstable wave. Oddly enough, the fact that the instability paradigm in reality applies only to a minority of cases seems to support such counter-intuitive thinking.


Member Since: Posts: Comments:
1221. Levi32
Quoting StormSurgeon:
Oh by the way Levi.....Circular Circulation? LOL


Lol...yup.
Member Since: Posts: Comments:
Quoting stormhank:
When will that area marked 40% be re classified??

I would think most likely early tommorrow moring if it holds together
Member Since: Posts: Comments:

Viewing: 1270 - 1220

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 | 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 | 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Mostly Cloudy
63 °F
Mostly Cloudy