BoB: Very Severe Cyclonic Storm SIDR

[CrazyC83]

TPIO10 PGTW 141801

A. TROPICAL CYCLONE 06B (SIDR)

B. 14/1730Z

C. 16.6N/3

D. 89.3E/0

E. ONE/MET7

F. T7.0/7.0/D1.0/24HRS STT: S0.0/00HRS (14/1730Z)

G. IR/EIR LLCC

05A/PBO IRREG EYE/ANMTN. 20NM DG EYE SURR BY CMG
CONVECTIVE RING YIELDS A DT OF 7.0. MET AND PT AGREE.
DBO DT.

SCANLIN

T7.0 supports a Cat 5 storm...

[CrazyC83]

UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 7.2.1
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 14 NOV 2007 Time : 173000 UTC
Lat : 16:31:01 N Lon : 89:20:24 E

CI# /Pressure/ Vmax
6.9 / 901.2mb/137.4kt

6hr-Avg T# 3hr-Avg T# Adj T# Raw T#
6.8 6.9 6.9 6.9

Latitude bias adjustment to MSLP : +0.0mb

Estimated radius of max. wind based on IR :N/A km

Center Temp : -41.2C Cloud Region Temp : -81.9C

Scene Type : EYE

Positioning Method : RING/SPIRAL COMBINATION

Ocean Basin : INDIAN
Dvorak CI > MSLP Conversion Used : PACIFIC

Tno/CI Rules : Constraint Limits : NO LIMIT
Weakening Flag : OFF
Rapid Dissipation Flag : OFF

****************************************************

CIMSS now at the upper maximum of Cat 4 and with a 901mb pressure...

[Derek Ortt]

actually, CIMSS is cat 3. 137.4KT is above the cat 5 threshhold

[wxman57]

Dhaka, Bangladesh weather forecast not mentioning much. Just cloudy with a 70% chance of Rain Friday with winds between 4-8 mph.

http://www.wunderground.com/global/stations/41923.html

Here's another Dhaka forecast - light showers and NE wind at 9 mph:

http://www.bbc.co.uk/weather/5day.shtml?world=2156

The Weather Channel's forecast actually does indicate some bad weather - ENE wind 45 mph with rain and thunder:

http://www.weather.com/outlook/travel/businesstraveler/wxdetail/BGXX0003?dayNum=2&par=netvibes&site=netvibes&cm_ven=bd_select&cm_cat=netvibes&cm_pla=netvibes&cm_ite=CityPage

Of course, most of these free online forecasts are generated automatically from model data. No meteorologist looks at them.

Current TAF for Dhaka:
TAF VGZR 141600Z 141818 16008/15KT 4000 SCT012 BKN100 TEMPO 1806 16025G35KT 2000 RA BKN007 FEW025 CB OVC080=

Temporary conditions of wind 160/25kts gusting 35kts from 18Z to 06Z. Should pass through after 18Z tomorrow.

[Derek Ortt]

a good weather forecast for Dkaha

Winds initially out of the east at 50-60 mph with gusts approaching 80-90 mph. Switching to SW in the afternoon hours. 100 percent chance of rain. Accumulations likely will exceed 10-15 inches, producing serious river flooding

[btangy]

Sidr is very near its potential intensity and just passed over an area of higher than normal ocean heat content. There is some subtle evidence from that the deepest convection is now shifting downshear indicating that the shear is increasing from the S. CIMSS diagnoses the shear at 11m/s from 190 degrees, but the actual shear the storm is experiencing is most likely much less. One can only hope the change in convective signature is the start of a weakening trend.

[CrazyC83]

The following post is NOT an official forecast and should not be used as such. It is just the opinion of the poster and may or may not be backed by sound meteorological data. It is NOT endorsed by any professional institution including storm2k.org For Official Information please refer to the NHC and NWS products.

I decided to write up an advisory in NHC form myself, using our standards and my estimated numbers, to see what it would look like:

...POTENTIALLY CATASTROPHIC TROPICAL CYCLONE SIDR TRACKING NORTHWARD IN THE BAY OF BENGAL...STILL INTENSIFYING...

AT 1230 AM IST...1800Z...THE CENTER OF TROPICAL CYCLONE SIDR WAS LOCATED NEAR LATITUDE 16.4 NORTH...LONGITUDE 89.4 EAST OR ABOUT 420 MILES...680 KM...SOUTH OF KOLKATA INDIA.

SIDR IS MOVING TOWARD THE NORTH NEAR 9 MPH...15 KM/HR...AND A GRADUAL INCREASE IN FORWARD SPEED IS EXPECTED OVER THE NEXT 24 HOURS.

MAXIMUM 1-MINUTE SUSTAINED WINDS ARE NEAR 160 MPH...260 KM/HR...WITH HIGHER GUSTS. SIDR REMAINS A POTENTIALLY CATASTROPHIC TROPICAL CYCLONE...EQUIVALENT TO A CATEGORY FIVE ON THE SAFFIR-SIMPSON HURRICANE SCALE. FLUCTUATIONS IN STRENGTH ARE EXPECTED OVER THE NEXT 12 TO 24 HOURS...FOLLOWED BY STEADY WEAKENING BEFORE LANDFALL. NONETHELESS, SIDR SHOULD BE AN EXTREMELY DANGEROUS TROPICAL CYCLONE WHEN IT REACHES EASTERN INDIA OR BANGLADESH...AT LEAST CATEGORY THREE.

HURRICANE FORCE WINDS OF AT LEAST 75 MPH EXTEND OUTWARD UP TO 80 MILES...130 KM...FROM THE CENTER...AND WINDS OF AT LEAST 40 MPH EXTEND OUTWARD UP TO 150 MILES...245 KM.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 908 MB...26.85 INCHES.

STORM TOTAL RAINFALL OF 8 TO 15 INCHES - WITH LOCAL MAXIMUM AMOUNTS UP TO 24 INCHES IN HIGHLAND AREAS - ARE POSSIBLE ACROSS EASTERN INDIA AND BANGLADESH. STORM TOTAL RAINFALL OF 3 TO 6 INCHES ARE POSSIBLE IN PARTS OF WESTERN MYANMAR. THESE RAINS COULD CAUSE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES.

STORM SURGE FLOODING OF 18 TO 25 FEET IS POSSIBLE ACROSS THE WEST BENGAL AND BANGLADESH COASTS...WITH LOCALLY HIGHER LEVELS UP TO 32 FEET POSSIBLE IN THE GANGES DELTA IF SIDR MAKES LANDFALL NEAR THE WESTERN BORDER OF BANGLADESH. STORM SURGE FLOODING OF 5 TO 7 FEET IS POSSIBLE IN THE NORTHEASTERN BAY OF BENGAL COAST, PARTICULARLY IN SOUTHWESTERN MYANMAR.

REPEATING THE 1230 AM IST POSITION...16.4 N...89.4 E. MOVEMENT TOWARD...NORTH NEAR 9 MPH. MAXIMUM SUSTAINED WINDS...160 MPH. MINIMUM CENTRAL PRESSURE...908 MB.

$$
FORECASTER CrazyC83

NNNN

[wxman57]

Sidr is very near its potential intensity and just passed over an area of higher than normal ocean heat content. There is some subtle evidence from that the deepest convection is now shifting downshear indicating that the shear is increasing from the S. CIMSS diagnoses the shear at 11m/s from 190 degrees, but the actual shear the storm is experiencing is most likely much less. One can only hope the change in convective signature is the start of a weakening trend.

One problem is that a weakening of the peak wind may not reduce the surge threat. What we've observed time after time is that an intense hurricane that weakens rapidly will retain much of its kinetic energy. Though the peak wind may drop significantly, the wind field expands to compensate. This happened with Katrina and Rita prior to landfall. The resulting expansion in the wind field could mean that the devastating storm surge would cover a larger area. Such a retention of kinetic energy was observed mostly following hurricanes that interacted with land (Wilma near the Yucatan, Katrina passing over Florida) or during eyewall replacement cycles. Weakening due to strong shear may also disrupt the surface wind field, reducing the surge.

In the case of Sidr, it's looking like almost a worst-case scenario. Surge could be in the 20-30 foot range in an area as flat as south Louisiana but with many millions more people.

[Ed Mahmoud]

TPIO10 PGTW 141801

A. TROPICAL CYCLONE 06B (SIDR)

B. 14/1730Z

C. 16.6N/3

D. 89.3E/0

E. ONE/MET7

F. T7.0/7.0/D1.0/24HRS STT: S0.0/00HRS (14/1730Z)

G. IR/EIR LLCC

05A/PBO IRREG EYE/ANMTN. 20NM DG EYE SURR BY CMG
CONVECTIVE RING YIELDS A DT OF 7.0. MET AND PT AGREE.
DBO DT.

SCANLIN

what agency is that?

[P.K.]

PGTW is the JTWC.

Does anyone have a link to the BMD that is actually current? The one listed by the WMO has the forecast from 15/12/2000 on it! http://www.bangladeshonline.com/bmd/

[CrazyC83]

http://www.imd.ernet.in/section/nhac/dynamic/rsmc.htm Latest IMD forecast (official but completely bogus)

As for Bangladesh, being such a poor country, I don't know if they have a website for their department.

[Squarethecircle]

If it weren't for the fact that I'm not paranoid, I'd say they're all gonna die.

[CrazyC83]

If it weren't for the fact that I'm not paranoid, I'd say they're all gonna die.

Hopefully they are evacuating as we speak...since they need lots of time to do that as it is primarily by foot...

[Squarethecircle]

If it weren't for the fact that I'm not paranoid, I'd say they're all gonna die.

Hopefully they are evacuating as we speak...since they need lots of time to do that as it is primarily by foot...

They're not going to evacuate for "rain and light winds." Unless they get the word out NOW, the IMD is going to be responsible for a LOT of deaths. Is it unprecedented to get two storms of this intensity in one season?

[CrazyC83]

If it weren't for the fact that I'm not paranoid, I'd say they're all gonna die.

Hopefully they are evacuating as we speak...since they need lots of time to do that as it is primarily by foot...

They're not going to evacuate for "rain and light winds." Unless they get the word out NOW, the IMD is going to be responsible for a LOT of deaths. Is it unprecedented to get two storms of this intensity in one season?

I'm not sure if it is unprecedented as there isn't much history available that I know of from that region. I agree this could be a global tragedy with the IMD responsible. A global inquiry should be initiated if there is an extremely high death toll due to poor warning. Most of the many millions of people there live in poor housing that is no match to wind and water. It would be like trying to ride out a Category 5 hurricane in a FEMA trailer...

[wxman57]

Jeff Masters sent out a link to a very good Masters Thesis on tropical cyclones in the Bangladesh area. Good reading:

http://etd.lib.ttu.edu/theses/available/etd-11052006-145639/unrestricted/tanveer_dissertation.pdf

[Coredesat]

The problem with Bangladesh is that there is simply nowhere to evacuate to - unlike developed countries, there are no good roadways in and out of the forecast landfall area, and the Ganges delta is so large that it would require evacuating millions of people several hundred miles away, which is a very difficult venture this close to landfall.

Bangladesh does have designated storm shelters, but they are likely to be in major disrepair (as they are the same ones used during the 1991 cyclone that still killed 138,000 despite there being any shelters at all).

[P.K.]

I'm not sure if it is unprecedented as there isn't much history available that I know of from that region.

Finding information on past cyclonic storms is not easy. If you want the best track data you would have to write to an address in India I was told by the IMD.

[Coredesat]

http://www.imd.ernet.in/section/nhac/dynamic/rsmc.htm Latest IMD forecast (official but completely bogus)

As for Bangladesh, being such a poor country, I don't know if they have a website for their department.

Bangladesh is poorer than Papua New Guinea, which doesn't have a website at all.

[HURAKAN]

Looking really impressive.