Pakistan's Katrina; 94L could develop in Gulf of Mexico

By: Dr. Jeff Masters , 3:23 PM GMT on August 10, 2010

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The monsoon season of 2010 continues to generate havoc in Asia, as lingering rains from the latest monsoon low continue to affect hard-hit Pakistan, China, and India. At least 702 are now reported dead and 1,042 are missing in China's Gansu province, due to torrential monsoon rains that triggered a deadly landslide and extreme flooding on Sunday. At least 137 died in floods and landslides in the neighboring Indian state of Kashmir over the weekend, with 500 people missing. Monsoon flooding and landslides have also killed at least 65 people in Afghanistan in the past two weeks. But no country has suffered more than Pakistan, where monsoon floods have destroyed huge portions of the nation's infrastructure and killed at least 1600 people. The number of people affected or needing assistance has been estimated to be as high as 13 million people--8% of the nation's population. The disaster is the worst natural disaster in Pakistan's history, and is rightfully being called "Pakistan's Katrina."


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.

Monsoons: a primer
In summer, the sun warms up land areas more strongly than ocean areas. This occurs because wind and ocean turbulence mix the ocean's absorbed heat into a "mixed layer" approximately 50 meters deep, whereas on land, the sun's heat penetrates at a slow rate to a limited depth. Furthermore, due to its molecular properties, water has the ability to absorb more heat than the solid materials that make up land. As a result of this summertime differential heating of land and ocean, a low pressure region featuring rising air develops over land areas. Moisture-laden ocean winds blow towards the low pressure region and are drawn upwards once over land. The rising air expands and cools, condensing its moisture into some of the heaviest rains on Earth--the monsoon. Monsoons operate via the same principle as the familiar summer afternoon sea breeze, but on a grand scale. Each summer, monsoons affect every continent on Earth except Antarctica, and are responsible for life-giving rains that sustain the lives of billions of people. In India, home for over 1.1 billion people, the monsoon provides 80% of the annual rainfall. However, monsoons have their dark side as well--hundreds of people in India and surrounding nations die in an average year in floods and landslides triggered by heavy monsoon rains. The most deadly flooding events usually come from monsoon depressions (also known as monsoon lows.) A monsoon depression is similar to (but larger than) a tropical depression. Both are spinning storms hundreds of kilometers in diameter with sustained winds of 50 - 55 kph (30 - 35 mph), nearly calm winds at their center, and generate very heavy rains. Each summer, approximately 6 - 7 monsoon depressions form over the Bay of Bengal and track westwards across India. Four monsoon depressions originated in the Bay of Bengal in the El Niño-weakened monsoon season of 2009. This year's first monsoon depression formed 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 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 second monsoon depression arrived in Pakistan on August 3, and has brought additional heavy rains.

Are the this year's monsoon floods due to global warming?
No single weather event can be attributed to climate change, but a warming climate does load the dice in favor of heavier extreme precipitation events. This occurs because more water vapor can evaporate into a warmer atmosphere, increasing the chances of record heavy downpours. In a study published in Science in 2006, Goswami et al. found that the level of heavy rainfall activity in the monsoon over India had more than doubled in the 50 years since the 1950s, leading to an increased disaster potential from heavy flooding. Moderate and weak rain events decreased over the past 50 years, leaving the total amount of rain deposited by the monsoon roughly constant. The authors commented, "These findings are in tune with model projections and some observations that indicate an increase in heavy rain events and a decrease in weak events under global warming scenarios." We should expect to see an increased number of disastrous monsoon floods in coming decades if the climate continues to warm as expected. Since the population continues to increase at a rapid rate in the region, death tolls from monsoon flooding disasters are likely to climb dramatically in coming decades.

References
Goswami, et al., 2006, " Increasing Trend of Extreme Rain Events Over India in a Warming Environment", Science, 1 December 2006:Vol. 314. no. 5804, pp. 1442 - 1445 DOI: 10.1126/science.1132027

Dave's Landslide blog has some great discussions of the flooding and destruction wrought by the terrible monsoon rains this year in Pakistan, India, Afghanistan, and China.

Donations urgently needed
The massive humanitarian crisis in Pakistan requires a huge response by the international community. Wunderblogger Dr. Ricky Rood, author of our Climate Change Blog, has a friend working in Pakistan who underscored the desperate situation there:

This is the worst natural disaster in the history of Pakistan in terms of number of people and area affected. Although not as many people have been killed as in the 2005 earthquake, we have already nearly 900,000 displaced persons thus far just in Khyber Pakhtunkhwa. Crops are destroyed; shops, hotels, and other business have simply been swept away in Swat, which had just this year been cleared of Taliban and was on the way to recovery; and districts closer to Peshawar and parts of Peshawar district are still, or perhaps again after yesterday/today, under water. After the immediate emergency response, it will be years of rebuilding to replace what has been lost and to start to develop again. I know you have the power to control the weather, so if you cold give us a week or two without more rain at least we could keep the helicopters flying and give people a chance to go to their homes, recover what might still be there, set up tents if we can get enough to them, and start to clean up."

She gave the following recommendations for charities that do work in the flood-ravaged zone, and are effective at getting aid to those who need it the most:

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.

She mentioned that it is better to send money to the organizations doing the relief work than to try to organize shipments of goods.


Figure 2. Morning radar image of 94L from the Key West radar.

94L
A 1010 mb low pressure system (94L) near the Florida Keys is generating disorganized heavy thunderstorms over Florida and the adjacent waters, and could become a tropical or subtropical depression as early as Wednesday. Current Key West radar shows the rotation of the storm, but the thunderstorm activity has not yet organized into low-level spiral bands. A few areas in the Keys and extreme South Florida have seen 1 - 2 inches of rain thus far from 94L. Wind shear is currently a moderate 10 - 20 knots over 94L, and water temperatures are very warm, 30 - 31°C. Water vapor satellite imagery shows that 94L is forming beneath an upper-level low with plenty of dry air, and there is a substantial flow of dry, continental air wrapping into 94L. This dry air is retarding the development of 94L, and may force the storm to organize into a subtropical storm instead of a tropical storm. A subtropical storm typically has a large, cloud free center of circulation, with very heavy thunderstorm activity in a band removed at least 100 miles from the center. The difference between a subtropical storm and a tropical storm is not that important as far as the winds they can generate, but tropical storms generate more rain. There is no such thing as a subtropical hurricane. If a subtropical storm intensifies enough to have hurricane force winds, than it must have become fully tropical. It usually takes at least two days for a subtropical storm to make the transition to a tropical storm.

Forecast for 94L
The latest SHIPS model forecast predicts that wind shear will stay in the moderate range, 10 - 20 knots, over the Gulf of Mexico this week. The storm's main problem will be dry air, and I don't expect 94L to undergo rapid development. Most of the models bring 94L ashore over Louisiana by Thursday, though the GFDL model predicts 94L could stall off the coast and not make landfall until Friday. If 94L does make landfall Thursday, it is unlikely to be a hurricane, due to all the dry air aloft in the Gulf. However, the GFDL model is predicting that the 1-day delay in landfall to Friday will allow 94L enough time to grow fully tropical and intensify into a Category 1 hurricane. I think this solution is unlikely. Storms that get their start underneath a cold, dry, upper-level low very rarely attain hurricane strength in three days. A 40 - 50 mph tropical or subtropical storm at landfall Thursday or Friday is a much more reasonable forecast.

93L
A tropical wave (Invest 93) in the middle Atlantic Ocean is close to tropical depression status. The disturbance has a well-defined surface circulation, but only a limited amount of heavy thunderstorm activity, thanks to dry air and wind shear of 10 - 20 knots affecting it due to a large upper-level low pressure system to the west. Wind shear is expected to stay in the moderate range, 10 - 20 knots, over the next four days, which is low enough that 93L could become a tropical depression at any time during that period. NHC is giving 93L a 60% chance of developing into a tropical depression by Thursday morning. The GFS, GFDL, and HWRF models predict 93L will develop, and the GFDL forecasts that the storm will become a hurricane. A strong trough of low pressure moving across the central Atlantic is recurving 93L to the north, and the system should only be a concern to shipping interests. None of the reliable computer models are forecasting tropical cyclone development in the Atlantic over the next seven days, other than for 93L and 94L.

Moscow hits 99°F again today
Temperatures at Moscow's Domodedovo airport hit 37°C (99°F) today, the 28th day in row that temperatures have exceeded 30°C (86°F) in Moscow. The average high temperature for August 10 is 21°C (69°F). Moscow's high temperature have averaged 15°C (27°F) above average for the first ten days of August--a truly extraordinary anomaly. Smog and smoke from wildfires continued to blanket the city today, with the Russian Meteorological Agency reporting that pollution due to carbon monoxide, nitrogen dioxide, ozone, and hydrocarbons exceeding the safe limit by factors of 1.2 - 2.2. Air pollution levels peaked at 6.5 times the safe level on Saturday. As I reported in yesterday's post, the heat wave has likely killed at least 15,000 people in Russia so far. There is some slight relief in sight--the latest forecast for Moscow calls for high temperatures of 31 - 33°C (88 - 91°F) Wednesday though Sunday--still 20°F above normal, but better than the 27°F above normal so far this month.

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on my blog during the show. You can also email the questions to me today before the show: jmasters@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line. Some topics I'll cover today on the show:

1) Invest 94 and 93
2) A look ahead at the coming two weeks
3) Status of La Niña

Today's show will be about 30 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Jeff Masters

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Quoting StormW:
PGI25L



Thanks, StormW. I look forward to your take on this one. You've got this 5-6 days from the Northern Antilles???
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if 94L becomes a storm what conditions will i experience in Lakewood Ranch, FL?
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Quoting pottery:

This is a Weather Blog.
It is NOT a US weather blog.
Say it ain't so!
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Quoting StormChaser81:
What gives, Did the Doc spend more time looking at overseas weather events and took a glance at 94L which would possibly affect people in the US.

I mean the over seas stuff is still important, but really when we have stuff brewing isnt it more important to look at it.

This blog is getting further away from US weather everyday.

This is a Weather Blog.
It is NOT a US weather blog.
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Definately quite an active day today in the tropics :)
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Quoting Dropsonde:
Sorry, my good computer was hit by lightning a week ago and I have to use a ten year old machine until it is fixed. Paging through that entire blog gobbles up the RAM in no time flat.


Dropsonde, WUMail me the specs on the PC you're using...I might be able to help you tweak more out of it
Member Since: August 2, 2006 Posts: 10 Comments: 9922
From the visible satellite, it even looks as if 94l has moved slightly SW in the past 6hours...
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Quoting StormW:

Do not trust this forecast track on the "predict" website - it has this thing going West for a while and making a 90 deg right hook going North - not really likely! Def see a more WNW movement in to NW Caribbean!!

What say you?
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Storm, can the ULL in the northeastern Gulf have any effect on the position of the high pressure system over the northern Gulf coast? I'm wondering what factors will determine where that high will be located since that will have a very large impact on where 94L goes. Thanks.
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StormW post 67.
Thanks for that.
I dont see any vort. there as yet.
What is your take ?
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Quoting Dropsonde:
Sorry, my good computer was hit by lightning a week ago and I have to use a ten year old machine until it is fixed. Paging through that entire blog gobbles up the RAM in no time flat.


And those posting graphic after graphic that we could easily go pull up ourselves aren't helping matters for you, either.
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Quoting StormW:
StormW What does it mean?It really looks like our new invest
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Quoting StormChaser81:
What gives, Did the Doc spend more time looking at overseas weather events and took a glance at 94L which would possibly affect people in the US.

I mean the over seas stuff is still important, but really when we have stuff brewing isnt it more important to look at it.

This blog is getting further away from US weather everyday.


Didn't you know it's "Web Blog Sweeps Week" in Russia?

Ratings! It's all about the ratings!
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Quoting WeatherfanPR:
95L ?

If I am reading the existing and future Steering for this area, it looks to be trending generally west until it passes the Islands, then NW toward DomRep and Haiti.
?? comments?
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I am no MET. But, from memory, in terms of climate, I think this season best resembles the type of weather we here in the islands had in the David / Allen years.

It was following a couple of years of dry weather, a fairly rainy initial season, much heat, then storms like David / Allen.

For what it is worth, or not.....
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Quoting MiamiHurricanes09:
You aren't seeing it because it isn't happening...what Dr. Masters stated is incorrect.


This is as rare of an occurrence as the "storms that get their start underneath a cold, dry, upper-level low [and] very rarely attain hurricane strength in three days."
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Quoting StormW:


I'm hanging in there! You?

Ditto! Waiting to see what 94L will bring....we could use the rain. But heading to New Orleans this weekend....so, not TOO much rain :)
Member Since: September 5, 2007 Posts: 0 Comments: 3480
95L ?

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What gives, Did the Doc spend more time looking at overseas weather events and took a glance at 94L which would possibly affect people in the US.

I mean the over seas stuff is still important, but really when we have stuff brewing isnt it more important to look at it.

This blog is getting further away from US weather everyday.
Member Since: August 11, 2008 Posts: 0 Comments: 2315
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Member Since: September 2, 2009 Posts: 130 Comments: 21032
Quoting StormW:


To clarify,

94L is a shallow warm core system, and has lost the frontal trof. This would make it a tropical entity.
Oh, I didn't know that. Thanks!
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I see the COC of the surface low roughly located near 25.5N/83.0W. Convection is wrapping around this circulation and TD5 is on the way to development by 5pm EDT today. THe 2pm NHC TWO will have 94L upped to 80-90% and state that a tropical depression is developing and that HH aircraft will be enroute shortly to determine whether or not this is a depression or fully tropical in nature.
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Quoting StormW:
TROPICAL DISTURBANCE INVEST 93L / 94L/ SYNOPSIS ISSUED 10:15 A.M. AUGUST 10, 2010

Thanks for the update Storm! How are ya doing?
Member Since: September 5, 2007 Posts: 0 Comments: 3480
Quoting KennyNebraska:


I do not see this happening in the loop.

What I see is that 94L is insulated from the dry air, and it is the ULL's shearing effects that is having its way with this system right now.

Water Vapor Loop


Thats what I see too... I think Dr. Masters is mistaken.
94L is also not under 10-15 shear, it is under 5-10 shear.
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Quoting divdog:
c neither
Ok? It is evident that 94L is on the verge of becoming a tropical depression...
Member Since: September 2, 2009 Posts: 130 Comments: 21032
Wave at 10N ,53 Wsst is pulling together nicely, showing spin and my bestto benext hurricane, even if not next storm, will it beat 93 or 94?

Danielle, Earl or Fiona?

But, maybe the worst of the three.

This is the one to watch. Should be next Invest and fast become a depression / storm.
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Quoting divdog:
c neither


I guess you wanna be wrong? lol...It is pretty clear 94L is almost, if not developing into a TD as we speak.
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95L ?
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Temperatures at Moscow's Domodedovo airport hit 37°C (99°F) today, the 28th day in row that temperatures have exceeded 30°C (86°F) in Moscow. The average high temperature for August 10 is 21°C (69°F).

Wow. That'd be like northern Maine having a sustained heat wave in the mid to upper 90's.
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Quoting cyclonekid:
Poll!

Which will become a (sub)Tropical system first?

A. 93L
B. 94L
c neither
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What effect, if any, will the ULL near 94L have on the position of the high sitting over the gulf coast region?
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Quoting extreme236:
And I don't think the GFDL is all that unlikely at all. The NAM also agrees with that solution and to me it seems there is a good possibility landfall will not occur until Friday rather than Thursday.
Considering the low moved very little in the last 30 hours I agree 100%.

It's nearly stationary still.
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Hmmmm...Link
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Quoting MiamiHurricanes09:
Current steering layers from CIMSS: Link.

Forecasted steering layers from PSU e-WALL: Link.

Much Obliged.
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Poll!

Which will become a (sub)Tropical system first?

A. 93L
B. 94L
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Quoting KennyNebraska:


I do not see this happening in the loop.

What I see is that 94L is insulated from the dry air, and it is the ULL's shearing effects that is having its way with this system right now.

Water Vapor Loop
You aren't seeing it because it isn't happening...what Dr. Masters stated is incorrect.
Member Since: September 2, 2009 Posts: 130 Comments: 21032

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About JeffMasters

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