Extremely dangerous Cyclone Sidr bears down on Bangladesh and India

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

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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

References:

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

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557. lawntonlookers
3:48 PM GMT on November 15, 2007
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.
Member Since: March 22, 2006 Posts: 9 Comments: 1570
556. guygee
3:44 PM GMT on November 15, 2007
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


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555. IKE
3:40 PM GMT on November 15, 2007
There's a new Dr. Masters blog.
Member Since: June 9, 2005 Posts: 23 Comments: 37858
554. LakeShadow
3:38 PM GMT on November 15, 2007
You'd think that Anderson Cooper would be all over this.
Member Since: August 10, 2007 Posts: 3 Comments: 2134
553. aspectre
3:36 PM GMT on November 15, 2007
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.
Member Since: August 21, 2007 Posts: 0 Comments: 4860
552. LakeShadow
3:33 PM GMT on November 15, 2007
tempermental blog gods.
Member Since: August 10, 2007 Posts: 3 Comments: 2134
551. BajaALemt
3:32 PM GMT on November 15, 2007
I had a problem with it not posting a link also, Lake. *shrugs*
Member Since: September 25, 2007 Posts: 53 Comments: 8533
550. LakeShadow
3:30 PM GMT on November 15, 2007
tried to put an image...then a link...somethigns goofy with this blog.
Member Since: August 10, 2007 Posts: 3 Comments: 2134
548. LakeShadow
3:27 PM GMT on November 15, 2007
looks like the eyewall replacement is about to go underway. Maybe this will help to deintensify the storm more rapidly.
Link
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547. guygee
3:24 PM GMT on November 15, 2007
Link: Regional Meteorological Center Kolkata
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546. BajaALemt
3:23 PM GMT on November 15, 2007
Member Since: September 25, 2007 Posts: 53 Comments: 8533
545. Zaphod
3:23 PM GMT on November 15, 2007
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)?

Thanks,
Zap
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544. mobal
3:23 PM GMT on November 15, 2007
Wow, This really looks bad!
Member Since: August 3, 2005 Posts: 482 Comments: 5332
543. LakeShadow
3:16 PM GMT on November 15, 2007

Member Since: August 10, 2007 Posts: 3 Comments: 2134
542. weatherboyfsu
3:14 PM GMT on November 15, 2007
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
Member Since: July 17, 2005 Posts: 0 Comments: 1025
541. BajaALemt
3:14 PM GMT on November 15, 2007
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
Member Since: September 25, 2007 Posts: 53 Comments: 8533
540. BajaALemt
3:12 PM GMT on November 15, 2007
Looks like it HAS made landfall....


Link
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539. BajaALemt
3:06 PM GMT on November 15, 2007
Mornin NE (thanks)


Looks like the hurricane force winds would already be affecting the coastal area... a 'say a prayer for folks' day :(
Member Since: September 25, 2007 Posts: 53 Comments: 8533
538. NEwxguy
3:03 PM GMT on November 15, 2007
GM Baja
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537. BajaALemt
3:02 PM GMT on November 15, 2007
oops..........Annnnnnnnnnnd....

Moring ya guys
Member Since: September 25, 2007 Posts: 53 Comments: 8533
536. Spetrm
3:02 PM GMT on November 15, 2007
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?
Member Since: June 9, 2007 Posts: 409 Comments: 9857
535. BajaALemt
3:01 PM GMT on November 15, 2007
Close

Link
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534. LakeShadow
2:59 PM GMT on November 15, 2007
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.

Member Since: August 10, 2007 Posts: 3 Comments: 2134
533. LakeShadow
2:47 PM GMT on November 15, 2007
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:
Link
Member Since: August 10, 2007 Posts: 3 Comments: 2134
532. guygee
2:31 PM GMT on November 15, 2007
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.
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531. decimus785
2:18 PM GMT on November 15, 2007
High Wind and Seas Warnings
Link
529. AussieStorm
2:06 PM GMT on November 15, 2007
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
Member Since: September 30, 2007 Posts: 9 Comments: 15935
528. Patrap
2:05 PM GMT on November 15, 2007
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.
Member Since: July 3, 2005 Posts: 424 Comments: 128259
527. Floodman
2:01 PM GMT on November 15, 2007
Thanks, Storm, I have been availing myself of those resources
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526. Floodman
2:00 PM GMT on November 15, 2007
Not long now...

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523. decimus785
1:53 PM GMT on November 15, 2007
522. NEwxguy
1:52 PM GMT on November 15, 2007
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.
Member Since: September 6, 2007 Posts: 878 Comments: 15734
521. Floodman
1:51 PM GMT on November 15, 2007
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?
Member Since: August 2, 2006 Posts: 10 Comments: 9922
520. NEwxguy
1:50 PM GMT on November 15, 2007
thanks stormw,going to be a wild day up here in the northeast.
Member Since: September 6, 2007 Posts: 878 Comments: 15734
518. StormJunkie
1:34 PM GMT on November 15, 2007
Morning all, good to see ya pat, guygee, Ivan, and everyone else.

Thoughts going out to the folks in Bangladesh.
Member Since: August 17, 2005 Posts: 26 Comments: 16519
517. guygee
1:27 PM GMT on November 15, 2007
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.
Member Since: September 16, 2005 Posts: 0 Comments: 3167
516. Ivansrvivr
1:22 PM GMT on November 15, 2007
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.
515. Ivansrvivr
1:19 PM GMT on November 15, 2007
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.
514. aspectre
1:17 PM GMT on November 15, 2007
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
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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.
Member Since: July 3, 2005 Posts: 424 Comments: 128259
512. guygee
1:13 PM GMT on November 15, 2007
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.
Member Since: September 16, 2005 Posts: 0 Comments: 3167
511. Ivansrvivr
1:00 PM GMT on November 15, 2007
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.
510. guygee
12:59 PM GMT on November 15, 2007
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).
Member Since: September 16, 2005 Posts: 0 Comments: 3167
509. guygee
12:48 PM GMT on November 15, 2007
WWIN40 DEMS 150300

IWB 15TH NOV 2007 MNG :
=======================

THE VERY SEVERE CYCLONIC STORM (SIDR) OVER EC-BAY AND ADJOINING WC-BAY OF BENGAL MOVED NORTHWARDS AND LAY CENTRED AT 0300 UTC OF 15TH NOV 2007 OVER EC AND ADJ WC AND N-BAY WITHIN HALF A DEGREE OF LAT 18.0 DEG N / LONG 89.0 DEG E ABOUT 530 KMS SOUTH OF KOLKATA(.) SYSTEM IS LIKELY TO INTENSIFY FURTHER AND MOVE IN A NORTHERLY DIRN AND CROSS WEST BENGAL-BANGLADESH COASTS EAST OF SAGAR ISLAND NEAR LONG 89.0 DEG E BY AROUND MIDNIGHT OF TODAY THE 15TH NOVEMBER 2007(.)
[...]
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508. guygee
12:36 PM GMT on November 15, 2007
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).
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507. decimus785
12:29 PM GMT on November 15, 2007
Is Sidr ALready making landfall?


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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.