BoB: Very Severe Cyclonic Storm SIDR

[btangy]

00Z soundings:

VEBS (Bhubaneshwar, India)
http://weather.uwyo.edu/upperair/images ... .skewt.gif

VGTJ (Dhaka, Bangladesh)
http://weather.uwyo.edu/upperair/images ... .skewt.gif

Westerlies are confined above 400mb at Bhubaneshwar (~20N), but over Bangladesh, there are very strong westerlies from about 700mb up, which means there is a very strong (horizontal) shear zone near the coast of Bangladesh. It seem Sidr has been pushing this shear zone further and further north with time, although it is somewhat deceiving as the winds, especially at upper levels, are part of Sidr's outflow. Nevertheless, a very sharp turn toward the NE may be in store. If it happens near the coast, you're talking about a more oblique landfall angle which would be an absolute nightmare as the surge affects a huge part of the coastline. I think the ECMWF was showing this scenario in the 00Z run last night. The 18Z GFS shows this, but to a lesser extent. In any case, this will be something to watch for tomorrow.

Also, given that Sidr is located in right quadrant of a very strong jet entrance region, could have some synoptic scale forcing due to ascent associated with the jet dynamics. Could be helping to give Sidr an extra boost.

[btangy]

Also of interest, dry continental air has been impinging on SIDR for a couple of days now. Pretty impressive gradient between the dry air to the west and the moist air over SIDR. Normally this dry air would get entrained, but the environment is SO condusive for strong convection over the system, that the dry air is simply cannot penetrate the core.

I've been watching this with interest as I thought this would begin to occur earlier today, but it obviously hasn't. If one looks at the sounding from VEBS, there is plenty of dry air to the W, but the flow at these levels is quite meridional so there isn't any means to push this dry air in to the core of Sidr where it would have an impact. I still think this will change as Sidr gets N of of 20N, but by then, it will be hours away from landfall.

[Sanibel]

I think it is probably obvious that Sidr is holding intense form and should be a murderous cyclone at landfall. Probably past the point of no return for major disaster unfolding at this point.

[Crostorm]

[CrazyC83]

15/0230 UTC 18.4N 89.3E T7.0/7.0 SIDR -- Bay of Bengal

Still supports Cat 5.

[Tampa Bay Hurricane]

This is just going to be catastrophic. I mean this is just
horrifying.

I hope my friends and family there have gone to higher
ground. It's prayer time.

[Crostorm]

Is there some doppler radar for that reggion

[f5]

if this trough turns Sidr slightly east i see the eastern eyewall going right up the Ganges river delta and that will be a disaster on a mind boggling scale with not only thousands but deaths in the millions.More inporantly watch the 90 degree line right now its slightly west worst case would be for it to track right up that 90 degree line right into the Ganges river delta and not only that after it gets up in the Mountains were talking about the threat of flash floods and mudslides in the villages up there.

[Ed Mahmoud]

Is there some doppler radar for that reggion

Calcutta Doppler may be having a problem...


IMD doppler radar page

[philnyc]

"The round of intensification yesterday night was both a result of incredible diffluence (strong UL divergence in the right entrance region of a >100 kt upper jet), and SIDR moving over a deep warm pool."

I just wanted to make it clear that the jet stream you guys are speaking about is way north of the cyclone and had no direct interaction with it. It DID carry away upper level air from north of the storm, enhancing the poleward outflow a lot, but that was the only interaction. There was no difluence going on over the storm, just the requisite well positioned anticyclone over it, which removes air in a clockwise fashion from all quadrants of the counterclockwise flow beneath.

here's the definition of difluence from NOAA:
"Difluence
(or diffluence) - A pattern of wind flow in which air moves outward (in a "fan-out" pattern) away from a central axis that is oriented parallel to the general direction of the flow. It is the opposite of confluence.

Difluence in an upper level wind field is considered a favorable condition for severe thunderstorm development (if other parameters are also favorable). But difluence is not the same as divergence. In a difluent flow, winds normally decelerate as they move through the region of difluence, resulting in speed convergence which offsets the apparent diverging effect of the difluent flow."


Having said that, your analyses are great, wxmann_91, and I love reading them.

[Ed Mahmoud]

They do have some good stuff.

[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.

Another unofficial advisory in NHC form, using my estimates:

...POTENTIALLY CATASTROPHIC TROPICAL CYCLONE SIDR CLOSING IN ON THE NORTHERN COAST OF THE BAY OF BENGAL...PREPARATIONS SHOULD BE RUSHED TO COMPLETION...

AT 1030 AM IST...0430Z...THE CENTER OF TROPICAL CYCLONE SIDR WAS LOCATED NEAR LATITUDE 17.9 NORTH...LONGITUDE 89.1 EAST OR ABOUT 320 MILES...530 KM...SOUTH OF KOLKATA INDIA.

SIDR IS MOVING TOWARD THE NORTH NEAR 13 MPH...21 KM/HR...AND THIS MOTION SHOULD CONTINUE UNTIL AFTER LANDFALL.

MAXIMUM SUSTAINED WINDS REMAIN NEAR 165 MPH...270 KM/HR...WITH HIGHER GUSTS. SIDR REMAINS A POTENTIALLY CATASTROPHIC TROPICAL CYCLONE...EQUIVALENT TO A CATEGORY FIVE ON THE SAFFIR-SIMPSON HURRICANE SCALE. SLIGHT WEAKENING IS POSSIBLE BEFORE LANDFALL...HOWEVER...SIDR SHOULD MAKE LANDFALL AS AT LEAST A CATEGORY FOUR-EQUIVALENT STORM.

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 200 MILES...325 KM...FROM THE CENTER.

ESTIMATED MINIMUM CENTRAL PRESSURE IS 901 MB...26.61 INCHES.

STORM TOTAL RAINFALL OF 10 TO 15 INCHES...WITH ISOLATED MAXIMUM AMOUNTS UP TO 25 INCHES IN HIGHLAND AREAS...ARE POSSIBLE ACROSS WEST BENGAL AND BANGLADESH. STORM TOTAL RAINFALL OF 4 TO 8 INCHES ARE POSSIBLE IN PARTS OF WESTERN MYANMAR AND THE REST OF EASTERN INDIA...WITH ISOLATED MAXIMUM AMOUNTS UP TO 15 INCHES. THESE RAINS COULD CAUSE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES.

STORM SURGE FLOODING OF 20 TO 27 FEET IS POSSIBLE ACROSS THE WEST BENGAL AND BANGLADESH COASTS EAST OF THE POINT OF LANDFALL...WITH LOCALLY HIGHER LEVELS UP TO 35 FEET POSSIBLE IN THE GANGES DELTA IF SIDR MAKES LANDFALL NEAR THE WESTERN BORDER OF BANGLADESH. THE FLOODING COULD INUNDATE MUCH OF THE REGION. STORM SURGE FLOODING OF 6 TO 9 FEET IS POSSIBLE IN THE NORTHEASTERN BAY OF BENGAL COAST, PARTICULARLY IN SOUTHWESTERN MYANMAR.

REPEATING THE 1030 AM IST POSITION...17.9 N...89.1 E. MOVEMENT TOWARD...NORTH NEAR 13 MPH. MAXIMUM SUSTAINED WINDS...165 MPH. MINIMUM CENTRAL PRESSURE...901 MB.

$$
FORECASTER CrazyC83

NNNN

[Crostorm]

Is there some doppler radar for that reggion

Calcutta Doppler may be having a problem...


IMD doppler radar page

Thanks Ed Mahmoud

[CrazyC83]

Current Intensity Analysis




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

----- Current Analysis -----
Date : 15 NOV 2007 Time : 033000 UTC
Lat : 18:41:28 N Lon : 89:17:22 E


CI# /Pressure/ Vmax
7.2 / 890.4mb/146.0kt


6hr-Avg T# 3hr-Avg T# Adj T# Raw T#
7.1 7.1 7.1 7.1

Latitude bias adjustment to MSLP : +0.0mb

Estimated radius of max. wind based on IR : 15 km

Center Temp : -21.3C Cloud Region Temp : -80.2C

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 : ON
Rapid Dissipation Flag : OFF

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

Maybe, just maybe, this has peaked?

[WindRunner]

00z RSMC bulletin out . . . STILL 100kts

FKIN20 VIDP 150406

DTG : 20071115/0000Z
TCAC: NEW DELHI
TC : SIDR
NR : 13

PSN : N1730 E08900
MOV : N09KT
C : 956HPA
MAX WIND:100KT GUSTING TO 115KT

FCST PSN+12HRS: 151200 N2000 E08900
MAX WIND+12HRS:120KT
FCST PSN+18HRS: 151800 N2100 E08900
MAX WIND+18HRS:125KT
FCST PSN+24HRS: 160000 N2130 E08900
MAX WIND+24HRS: 130KT

NEXT MSG: 20071115/0600Z

TOO : 15/0800 HRS IST.

[Sanibel]

You don't get the symmetrical radial outflow feathers we saw this morning without a perfect overhead. I need a motion loop, but I would say just east of the India/Bangladesh border for intense landfall. Eastern Sunderbans tiger population should be badly affected. Not to mention a disasterous death toll.

I am having trouble with not having a clear eye. I don't think it is possible to have a high-end intensity cyclone without a clear, sharp eye.

[CrazyC83]

It's looking like maybe another eyewall cycle is getting underway.

[RL3AO]

My guess for motion is around 5 degrees.

[wxmann_91]

You don't get the symmetrical radial outflow feathers we saw this morning without a perfect overhead. I need a motion loop, but I would say just east of the India/Bangladesh border for intense landfall. Eastern Sunderbans tiger population should be badly affected. Not to mention a disasterous death toll.

I am having trouble with not having a clear eye. I don't think it is possible to have a high-end intensity cyclone without a clear, sharp eye.

Opal, which peaked at 150 mph and had a minimum central pressure of 916 mb, never even had an eye and its synoptic setup was not terribly different than this one. Satellite estimates proved to be useless during that storm. This storm has been much more symmetrical and its cloud tops have been nothing to scoff at.

[kd_black]

Guys anybody knows when the SIDR is going to hit the land and where I can get the updated satellite image of this storm?