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Extremely dangerous Cyclone Sidr bears down on Bangladesh and India

By: Dr. Jeff Masters, 2:43 PM GMT on November 14, 2007

Tropical Cyclone Sidr, a powerful Category 4 storm with 140 mph winds, is bearing down on the densely populated coasts of Bangladesh and India. Landfall is expected along a low-lying stretch of coast just east of Calcutta (Kolkata), India in just 36 hours. Sidr (the Arabic word for the the jujube tree) is only the second major (Category 3 or higher) tropical cyclone to affect the Bay of Bengal this decade. The other was Tropical Cyclone Mala, which hit Myanmar as a Category 3 storm on April 28, 2006, killing 22 people.

Figure 1. Image of Tropical Cyclone Sidr as a Category 4 storm (933 mb) taken at 2:47am EST 11/14/07. Image credit: Navy Research Lab.

Sidr weakened briefly yesterday, as its inner eyewall collapsed and was replaced by a new outer eyewall with a larger diameter. Now that this process is complete, Sidr has taken advantage of the low wind shear and high heat content oceanic waters it find itself over, and was intensified. As the storm continues northwards over the next 24 hours, the storm should be able to maintain its intensity. However, in the 12 hours prior to landfall, there will be a sharp increase in wind shear associated with a trough of low pressure. Ocean heat content will be on the decline as well, and the best guess is that Sidr will be a Category 1 or 2 cyclone when it hits land.

Figure 2.Deadliest tropical cyclones of world history.

A Category 1 or 2 cyclone hitting the low-lying, densely populated coasts of Bangladesh could still be devastating. The triangular shape of the Bay of Bengal acts to funnel storm surge waters into Bangladesh, and the very shallow bottom of the bay allows the surge to pile up to very high heights. A list of the 13 deadliest cyclones in world history (Figure 2) shows that nine of these have occurred in the Bay of Bengal. The big killer in all of these cyclones was the storm surge. The only known cyclone of Category 5 strength to hit Bangladesh, the April 1991 cyclone, brought a 30 foot storm surge to the coast near Chittagong. Surge height up to 41 feet are possible along some regions of the coast (Figure 3).

Figure 3.Maximum surge height along Bangladesh's Bay of Bengal coast as computed by Islam (2006).

The big question is, how much of the storm surge that Sidr is currently piling up with its Category 4 winds will make it to the coast, if the expected weakening occurs? We know from our experience with Hurricane Katrina that a weakened Category 3 hurricane at landfall can still push a storm surge characteristic of a Category 5 storm to the coast. This occurs because once a hurricane sets a large mass of water spinning, the angular momentum of that spinning water takes a long time to relax. The ocean carries the memory of how strong a hurricane was to the coast, in the form of a higher storm surge. Thus, I would expect a storm surge at least one category higher than what one might expect based on its landfall strength. One positive note is that Sidr is a much smaller storm than Katrina. Hurricane force winds extend outwards about 60 miles from Sidr's center, which is half of what Katrina's winds did. Thus, Katrina's hurricane force winds blew over an area of ocean four times greater than Sidr's.

methaz.org is currently predicting that a storm surge of 12-15 feet will affect the Bangladesh coast.

Links to watch:
Calcutta (Kolkata), India
Barisal, Bangladesh
Cox's Bazaar, Bangladesh


Islam, T., "Integrated Approach to Cyclone Wind Analysis and disaster planning for the Bangladesh coast," Ph.D. Dissertation, Texas Tech University, December 2006.

I'll have an update Thursday.

Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.

Reader Comments

It appears so

Thanks. I know that it (dry air) probably won't have any affect on land fall, but maybe it will help to tear it apart once it hits land. My prayers go out to all affected!
From the JointTyphoonWarningCenter for November15 0900Zulu (9:00amUTC)
Tropical Cyclone 06C (Sidr) Warning Number 012

Center Position at November15 0600Zulu (6:00amUTC) near 19.3N 89.3E
Movement Past Six Hours - 5 degrees at 15knots (17miles per hour / 28kilometres per hour)

Maximum Sustained Winds - 135knots (155miles per hour / 250kilometres per hour)
Gusts - 165knots (190miles per hour / 305kilometres per hour)

Radius of 64 Knot Winds (74miles per hour / 118kilometres per hour) :
NorthEast Quadrant - 60NauticalMiles (69miles/111kilometres)
SouthEast Quadrant - 60NauticalMiles (69miles/111kilometres)
SouthWest Quadrant - 50NauticalMiles (58miles/93kilometres)
NorthWest Quadrant - 55NauticalMiles (63miles/102kilometres)

Radius of 50 Knot Winds (58miles per hour / 93kilometres per hour) :
NorthEast Quadrant - 85NauticalMiles (98miles/157kilometres]
SouthEast Quadrant - 85NauticalMiles (98miles/157kilometres)
SouthWest Quadrant - 75NauticalMiles (86miles/139kilometres)
NorthWest Quadrant - 75NauticalMiles [86miles/139kilometres]

Radius of 34 Knot Winds [39miles per hour / 63kilometres per hour] :
NorthEast Quadrant - 140NauticalMiles (161miles/259kilometres)
SouthEast Quadrant - 140NauticalMiles (161miles/259kilometres]
SouthWest Quadrant - 125NauticalMiles (144miles/231kilometres)
NorthWest Quadrant - 125NauticalMiles (144miles/231kilometres)
An excellent satellite composite area map of the affected region.
Dacca,Bangladesh is in the center. And Kolkata,India (Calcutta) is to the far bottom&left.
You can grab&move the map by holding down your mouse's left click to see the southern coast.
The light blue along the coastline is extremely shallow water (sunlight reflecting off the bottom).
(Partial repost and update of a late post on Dr. M's last blog)
The movement of TC Sidr north into the Bay of Bengal is a potential disaster of immense proportions unfolding before our eyes. So far the news media seems to have taken little notice; I did find these news links (many more reports today, updated):
Storm lashes Bangladesh island, thousands evacuated
Super Cyclone "Sidr" Headed For W Bengal-Bangladesh Coast
India, Bangladesh Order Evacuations as Cyclone Nears
Cyclone Sidr to Make Category 4 Landfall
Cyclone Sidr Aims for the Worst Spot a Hurricane Could Hit
Cyclonic storm spares Orissa, likely to cross Sagar Island

The Bay of Bengal is a very low-lying and densely populated area, consisting of extensive mangrove swamps and many river deltas including those of the large Ganges, Meghna, and Brahmaputra rivers. Its funnel-shape and extensive shallow bathymetry help contribute to the potential for large storm surges. Since we are past new moon the tides at the time of landfall will be past their extremes, but as this tidal chart for Sagar Island shows, tidal variation is will still be close to 3 meters near the predicted point of landfall, so the precise time of landfall and speed of the storm may be a critical issue. Besides being the home of at least 160,000 people, Sagar Island is also the site of one of the most revered temples in the Hindu religion, where "On the 14th of January every year pilgrims come from all over India, quarter million people on the average but sometimes one million or more" (Pilgrimage on the ocean - development of Sagar island, Bay of Bengal). Not unlike many areas in the Mississippi Delta, the Ganges Delta has been an area that has lost much of its natural defenses from storms due to human development and mismanagement. According to a recent study,

"Morphological changes on Sagar Island are occurring at an alarming rate due to both natural and anthropogenic activities. The eastern part of the island is rapidly eroding due to destabilization and growth of tidal flats in the Muriganga estuary and the gradual shifting of water current towards the island. Over the last four years (1996-1999), the rate of coastal erosion has been much higher (11.35 km 2 ) than accretion (2.65 km 2 ), compared with the conditions prior to 1996.[...](Coastal geomorphological and land-use and land-cover study of Sagar Island, Bay of Bengal (India) using remotely sensed data).

According to the Weather Quality Reporter, the location of Sagar Island Station 42903 is imprecisely reported. A satellite map of Sagar Island and the surrounding region can be found on their site, here (Zoom out from initial view).

Seemingly in the crosshairs of Sidr's wrath is the large Sunderbans National Park, home to many endangered species including the Royal Bengal Tiger. This area is dotted with numerous islands and include the much-reported inhabited former islands of Suparibhanga and Lohacharra that have disappeared into the sea leaving 10,000 homeless (Rising sea levels engulfing Indian world heritage islands). Regarding the Sunderban's National Park, Suhrid Sankar Chattopadhyay writes:

"An ecosystem in peril - ONE of the largest mangrove forests in the world and a unique tiger habitat, the Sunderbans in West Bengal is facing a serious threat to its ecosystem from poaching and rampant felling of trees. Situated at the mouth of the Bay of Bengal in the Ganga-Brahmaputra delta, the Sunderbans covers an area of around 10,000 sq km. Of this, 4,262 sq km is in India and the rest is in Bangladesh. Of the 60 varieties of mangroves and mangrove associates that are found in India, the Sunderbans accounts for 50, many of which are rare. Known for its biodiversity, the region has been identified as a World Heritage Site by the International Union for the Conservation of Nature" (Full Article here).
Is Sidr ALready making landfall?

Sidr Latest
decimus785 - Sidr's CDO is clearly (partially)overland, with its outflow being routed around to the east of the southern extent of the Himalayas that are visible in the image link you provided. But I don't think that the center is making landfall yet. (Edit - Could be wrong about that though, looking for updates).
WWIN40 DEMS 150300

IWB 15TH NOV 2007 MNG :

JTWC Tropical Cyclone 06B (Sidr) Warning #12 Issued at 15/0900Z
JTWC - Multispectral Satellite Imagery from 15/0530Z
Earth Observatory- Natural Hazards (Includes Hi-Res satellite images of Sidr).
Sidr's flooding will be the biggest danger, not winds so much. Seeing 1 death after hurricane was too much. I feel horrible for those people over there. They are trying to eek out a living by farming and aside from loss of life, their livelihoods are about to be wiped out.
Ivansrvivr - Agreed, the surge is going to affect millions of people, probably more like tens of millions. In the one article I linked to it says that the Sunderbans National Park itself is home to something like 4* million people. I fear this may be a catastrophe that dwarfs even the Sumatra/Indian Ocean tsunami. I very much hope that fear is wrong. Since the area is so impoverished and remote, I wonder if we will ever even know.

*Erratum: Estimated population of the Sundarban is 4 million people, not 40 million as originally stated in this post.
Bad things happen to good people everyday. India will do all it can to protect the lives there.
But the poorest will be the ones devastated..The quick response after the storm passes will be paramount in keeping the Life lost to a Minimum.
Anyone having a problem seeing the image below? Or with distortion?
The latitude and longitude lines should form a square.

Maximum Sustained Wind at 130knots / 150miles per hour / 241kilometres per hour.
Minimum Air Pressure of 926mb
Position of Sidr's center at 20.9North 89.5East
Equivalent to a very strong Cat.4 hurricane, nearing Cat.5
I almost don't want to know. I know that those are people over there with lives like you and me. I wish that those countries could employ some kind of means to prevent so many from possibly dying.
the ecosystem in that area has seen landfalling tropical systems throughout history. Naure has an amazing way of recovering from what appears to total devastation.
513. Patrap 1:15 PM GMT on November 15, 2007
"Bad things happen to good people everyday. India will do all it can to protect the lives there.
But the poorest will be the ones devastated..The quick response after the storm passes will be paramount in keeping the Life lost to a Minimum.

Patrap - You are exactly right that a fast and massive response will save many from starvation and disease. I hope this event receives the coverage it deserves in the news media to garner that support, even though no posh tourist resorts are in the path of the destruction.

Son almost late for school, BBL.
Morning all, good to see ya pat, guygee, Ivan, and everyone else.

Thoughts going out to the folks in Bangladesh.
thanks stormw,going to be a wild day up here in the northeast.
Howdy folks...guygee, I noted something very interesting in one of the articles you linked above; the comments section had an entry from 11-15, late in their day, saying that no mention had been made on their local television as yet; that was about 14 hours ago. While the outlets are saying that they are evacuating thousands, how widespread can the evacs be if the local news sources aren't blaring the warning from every television and radio in west Bengal?
one can only hope and pray they are getting everyone away from the coast as far as possible,but you get the feeling word is not getting to a lot of people in that area.
Not long now...

Thanks, Storm, I have been availing myself of those resources
Half the system and all the Huge right side surge is inundating the lowlands. The event is well under way...under darkness now.
Into the fray goes a region..against Natures Cyclone,a most powerful one.
Issued by the Bureau of Meteorology, Brisbane
Issued at 10:59pm on Thursday the 15th of November 2007

The Cyclone WATCH for coastal and island communities between Thursday Island and
Cape Flattery has been cancelled.

At 10:00 pm EST Tropical Cyclone Guba Category 1 with central pressure 990
hectopascals was centred near latitude 10.8 south and longitude 146.0 east which
is 365 kilometres northeast of Lockhart River.

The cyclone has moved only slowly in the past 24 hours.

Tropical Cyclone Guba is expected to remain slow moving, drifting to the south
for the next 2 days.

Gales are not expected to affect coastal communities in the next 48 hours.

Details of Tropical Cyclone Guba Category 1, for 10:00 pm EST
Central Pressure : 990 hectopascals
Location of Centre : within 75 kilometres of
: latitude 10.8 degrees south
: longitude 146.0 degrees east
: which is 365 kilometres northeast of Lockhart River
Recent Movement : south at 4 kilometres per hour
Maximum wind gusts : 100 kilometres per hour

My Heart goes out to everyone in the Path of Cyclone Sidr.
Cheers AussieStorm
High Wind and Seas Warnings
521. Floodman 1:51 PM GMT on November 15, 2007
"...guygee, I noted something very interesting in one of the articles you linked above; the comments section had an entry from 11-15, late in their day, saying that no mention had been made on their local television as yet; that was about 14 hours ago. While the outlets are saying that they are evacuating thousands, how widespread can the evacs be if the local news sources aren't blaring the warning from every television and radio in west Bengal?"

Hi Floodman - It really makes you wonder, doesn't it? Even if they are evacuating thousands, that is just a drop in the bucket. I would guess that the vast majority of people in the deltas and mangrove swamps have poor communications infrastructure and even worse transportation infrastructure. Most people are simply stranded with no hope of evacuation. I am also guessing that politics has a big part in this. Firstly the respective national governments probably do not want to advertise their impotence in the face of this disaster. Also, the region has been a hotbed of political strife, religious animosity and war for a long time. The people most in danger are a neglected people. As hard as this is to say, like the Maya who suffered through Dean and the Moskito who took the brunt of Felix, it may be that the central governments do not much care what happens to many of these people, and possibly even regard parts of the population there as a threat to their own nationalistic interests.

Race, politics and religion do not affect the weather, only how we respond to weather-related disasters.
morning, folks! My thoughts and prayers are with those who face their own mortality today.

Here's a warning issued by the RSMC New Delhi:
this was posted on the New Delhi weather site as The expected devastation and course of sction to take:

Category: Super Cyclonic Storm

T.No.: T6.5 and above

Wind Speed: 120 Knots and above (222 Kmph and above)

Structures: Extensive damage to non-concrete residential and industrial buildings.

Structural damage to concrete structures. Air full of large projectiles

Road/Rail: Extensive damage to kutcha roads and some damage to poorly repaired pucca roads. Large scale submerging of coastal roads due to flooding and sea water inundation. Total disruption of railway and road traffic due to major damages to bridges, signals and railway tracks. Washing away of rail/road links at several places.

Communications: Uprooting of communication and power poles. Total disruption of communications and power supply.

Agriculture: Total destruction of standing crops/ orchards, uprooting of large trees and
blowing away of palm and coconut crowns, stripping of tree barks.

Marine Interests: Phenomenal seas with wave heights of more than 14 m. All shipping activity unsafe.

Coastal Zone: Extensive damage to port installations. Storm surge more than 5m.
Inundation upto 40 km in specific areas and extensive beach erosion. All ships torn from their moorings. Flooding of escape routes.

Overall Damage Category: Catastrophic

Suggested Actions: Fishermen not to venture into sea. Large scale evacuations needed.

Total stoppage of rail and road traffic needed in vulnerable areas.


My question is directed towards Dr. Masters or I guess if anyone else that can answer that.

But where did you retrieve the surge map for india?

Moring ya guys
GM Baja
Mornin NE (thanks)

Looks like the hurricane force winds would already be affecting the coastal area... a 'say a prayer for folks' day :(
Looks like it HAS made landfall....

http://www.nrlmry.navy.mil/tc-bin/tc_home2.cgi?ACTIVES=07-SHEM-02P.GUBA,07-SHEM-03S.LEE,07-IO-06B.SID R,07-WPAC-91W.INVEST,07-SHEM-98P.INVEST,07-SHEM-98S.INVEST&PHOT=yes&NAV=tc&ATCF_BASIN=io&ATCF_YR=200 7&ATCF_FILE=/data/www/atcf_web/public_html/image_archives/2007/io062007.07111506.gif&CURRENT=2007111 5.1500.meteo7.x.ir1km_bw.06BSIDR.130kts-926mb-209N-895E.100pc.jpg&AGE=Latest&CURRENT_ATCF=io062007.0 7111506.gif&ATCF_NAME=io062007&ATCF_DIR=/data/www/atcf_web/public_html/image_archives/2007&YEAR=2007 &YR=07&ARCHIVE=active&MO=NOV&BASIN=IO&STORM_NAME=06B.SIDR&STYLE=tables&AREA=atlantic/tropics&AID_DIR =/data/www/indian/southern/microvap/dmsp&DIR=/TC/tc07/IO/06B.SIDR/ir/geo/1km_bw&TYPE=ir&PRODUCT=ir&S UB_PROD=geo&SUB_SUB_PROD=1km_bw&PROD=geo
Good morning to the people which it is morning,

I am afraid that there will be others that its becoming nightfall that are not so fortunate. I am not going to elaborate on the death toll that Sidr will cause and its a shame in this day and time that such a thing will happen. Today, in another part of the world, a massive disaster will happen that we know is coming and nothing can be done to stop it. Everyone needs to count their blessing everyday! Excuse me for saying this.......5 digit death toll is a real possibility.........We all need to pray for these people......peace
544. mobal
Wow, This really looks bad!
I didn't see this answered in the last page or two.......

What is the expected alignment of surge and tides? With 3m tide, 7m surge, and 10m waves, the damage would be catastropic if well-aligned.

Am I correct that the worst will hit at night (next few hours)?

looks like the eyewall replacement is about to go underway. Maybe this will help to deintensify the storm more rapidly.
SIDR makes landfall in Sundarbans
Posted on Thursday, November 15th, 2007 at 8:25 pm

Hurricane SIDR hit the coastal areas of Sundarbands this evening and expected to make landfall in Khulna-Barisal belt crossing the Baleshwar river between 9:00pm to 10:00pm tonight, a Met Office bulletin said.

The powerful hurricane with 160 to 180 kph wind speed hit Hiron Point, Khepupara and Dublarchar coastlines in Sundarbans at about 5:00pm, the Met bulletin added.

It is now centred 150 km off the Mongla Port.

Meanwhile, coastal areas of Mongla, Barisal and Khulna are experiencing storms accompanied with heavy downpours as a prelude to the impending natural calamity. Over1000 fishermen went missing after 300 fishing trawlers sank in the Bay during the storms.

A latest Met Office special bulletin said great danger signal number 10 was advised to hoist for Mongla seaport while great danger signal number 9 for Chittagong and Cox’s Bazar seaports.

The hurricane intensity was centred at about 385 kms south-southwest of Chittagong port, 345 kms southwest of Cox’s Bazar port and 265 kms south of Mongla port this afternoon.

Emergency cabinet meeting is going on to find a way out to minimise the possible damage that is expected to cause as the hurricane began lashing the country’s coastlines.

Thousands of people were evacuated from the vulnerable coastal areas including Chittagong and Cox’s Bazar, visualising the incoming ravaging picture of the powerful cyclone.

Under the influence of the hurricane, the whole country including the capital is experiencing drizzling with gusty winds.

Leave of the government officials and employees in coastal districts has been cancelled. The government ordered them to remain at their respective stations and joined hands with the emergency operations to evacuate people from coastal localities to safer places.

Waterway communications across the country is also suspended following the calamity.

Met office warned that the coastal areas may face tidal surge 20-25 feet high above normal astronomical tide.

Coastguard and patrol police were directed to ensure security of the people taking shelter at different shelter centres.

The air force has been asked to aid rescue operations and airdrop relief supplies by their helicopters.

The coastal districts of Bhola, Barisal, Patuakhali, Barguna, Pirojpur, Jhalakati, Bagerhat, Khulna, Satkhira, Jessore and their offshore islands and chars will remain under the great danger signal No 10.

Besides, the coastal districts of Cox’s Bazar, Chittagong, Noakhali, Feni, Laxmipur, Chandpur and their offshore islands and chars will remain under the great signal No 9.

Inland river ports of the districts of Cox’s Bazar, Chittagong, Noakhali, Feni, Laxmipur, Bhola, Barisal, Patuakhali, Barguna, Chandpur, Pirojpur, Jhalakati, Bagerhat, Khulna, Jessore and Satkhira have been advised to keep hoisted riverine great danger signal No 4.

All fishing-boats and trawlers over the north Bay must remain in shelter till further notice, the bulletin added.

tried to put an image...then a link...somethigns goofy with this blog.
I had a problem with it not posting a link also, Lake. *shrugs*
tempermental blog gods.
Nice of India to make the upgrade to a SuperCyclone warning during landfall. /sarcasm

From the Navy's 3:00pmUTC photograph, Sidr made landfall around 9:00pmBangladeshStandardTime (UTC 6hours) while the tide is falling to it's low at 10:34BDT.
Not sure whether the previous high tide was allowed to slide back out past Sidr's storm surge, or whether the storm surge has been pushing that high tide inland.

Still no coverage by the US television networks as far as I can tell.
You'd think that Anderson Cooper would be all over this.
555. IKE
There's a new Dr. Masters blog.
Zaphod - Indian Standard Time (IST) is GMT+5:30. From this tide chart for Sagar Island, the next high tide is at 12:25 IST or 17:55 GMT.

Sagar Island 2007-11-16 12:25 AM IST 4.42 meters High Tide

I was just reading about the population in Bangladesh The Divisions of the country along the coast,Barisal and Khulna, have a population of almost 38 million people. On top of that,most parts of Bangladesh are less that 39 feet above sea level and 50 percent of the land would flood with a rise of 3 feet in the seal level. This would be kind of scary for the people that live in the area. Where would they evacuate too? Lets all keep our thoughts for them.