BoB: AMPHAN - Post-Tropical

[doomhaMwx]

 https://twitter.com/mcbbsr/status/1263009304442855426



Digha is west of the expected of the landfall location.

[doomhaMwx]

 https://twitter.com/timesofindia/status/1262982045413699584



 https://twitter.com/timesofindia/status/1262998887985344512

[doomhaMwx]

Satellite and radar images as of 09Z (2:30pm IST) suggest that the eye/center of Amphan is/was about to move onto West Bengal's Sagar island. Storm surges are probably occurring now along the banks of the Hooghly River and neighboring coasts.

[Hayabusa]

I wonder why JTWC does this sometimes, like when a TC is having an eyewall replacement cycle they either bump the intensity forecast (in this case for Amphan to 150 kt), or maintain the intensity like during Yutu, there was one warning maintaining 155 kt for the next 3 warnings but they didn't pan out...

[Shell Mound]

While it is a bit of a relief the wind has dropped(but maybe trying to reintensify slightly judging by the latest radar and satellite) the winds are the secondary impact, and the major winds will be localized. Thete still will likely be widespread wind damage.

The primary concern is the storm surge. This area is arguably the most vulnerable region in the world for storm surge because of geography and population. Right now it appears the Sundarban refuge will get the brunt of the surge which is not the worst case scenerio, it will still be high and widespread enough to cause extensive damage.

I really hope those in low lying areas have got the warning and have headed to higher ground.

I think people are focusing too much on the MSW rather than the large wind field. The widespread fetch and low pressure, along with the bathymetry, topography, and angle of approach, guarantee a devastating storm surge, regardless of the MSW. Katrina (2005) and Ike (2008) are actually good comparisons in terms of size, pressure, and demographics, along with the shallow shelf waters. Expect a storm surge of twenty to thirty feet, at least locally. If that transpires, then anticipate tens of thousands of casualties, if not more, depending on local political realities.

[1900hurricane]

Don't know who dropped the wind radii way down with the 06Z advisory at JTWC, but an ASCAT bull's eye jived very nicely with previous wind radii estimates. Previous wind radii resulted in IKE of near 90 TJ and Surge Destruction Potential (SDP, which is supposed to emulate the SSHWS for surge impacts) of 4.5.



 https://twitter.com/1900hurricane/status/1263087433824043010

[Abdullah]

The air pressure in Kolkata right now has fallen below the estimated minimum central pressure of Amphan at the 12Z Best Track, and stands at 961.7 millibars.

https://www.wunderground.com/dashboard/pws/INEWTO3

[mrbagyo]

Footage of Kachuberia Jetty at Hooghly River


Edit: I was victimized by Fani's old footage deym.

[doomhaMwx]

Sunset

[Abdullah]

The air pressure in Kolkata right now has fallen below the estimated minimum central pressure of Amphan at the 12Z Best Track, and stands at 961.7 millibars.

https://www.wunderground.com/dashboard/pws/INEWTO3

About half an hour later, and the pressure's down to an insane 952.3 millibars.

[shah83]

The air pressure in Kolkata right now has fallen below the estimated minimum central pressure of Amphan at the 12Z Best Track, and stands at 961.7 millibars.

https://www.wunderground.com/dashboard/pws/INEWTO3

About half an hour later, and the pressure's down to an insane 952.3 millibars.

That's the landfall pressure of Hurricane Ike. Does feel like this is going to be similar to impact as Ike.

[doomhaMwx]

Center has moved past Kolkata now.

[BYG Jacob]

The death toll will be terrible.

[Jr0d]

The death toll will be terrible.

I hope not. Hopefully the warnings got out.

I am concerned that the Hooghly River had significant surge. It is tought to tell if the storm was far enough east for offshore winds(and much lower surge) there.

[ColdMiser123]

The air pressure in Kolkata right now has fallen below the estimated minimum central pressure of Amphan at the 12Z Best Track, and stands at 961.7 millibars.

https://www.wunderground.com/dashboard/pws/INEWTO3

About half an hour later, and the pressure's down to an insane 952.3 millibars.

Bottomed out at 951.9 mb, significantly lower than the JWTC best track estimate at 12z, suggesting pressure may have been even lower at landfall south of Kolkata. Underscores just how essential in situ recon observations are for gathering accurate intensity estimates for significant cyclones prior to landfall.

[aspen]

The air pressure in Kolkata right now has fallen below the estimated minimum central pressure of Amphan at the 12Z Best Track, and stands at 961.7 millibars.

https://www.wunderground.com/dashboard/pws/INEWTO3

About half an hour later, and the pressure's down to an insane 952.3 millibars.

Bottomed out at 951.9 mb, significantly lower than the JWTC best track estimate at 12z, suggesting pressure may have been even lower at landfall south of Kolkata. Underscores just how essential in situ recon observations are for gathering accurate intensity estimates for significant cyclones prior to landfall.

With that pressure, could it have been in the range of 100-110 kt at landfall?

[ColdMiser123]

About half an hour later, and the pressure's down to an insane 952.3 millibars.

Bottomed out at 951.9 mb, significantly lower than the JWTC best track estimate at 12z, suggesting pressure may have been even lower at landfall south of Kolkata. Underscores just how essential in situ recon observations are for gathering accurate intensity estimates for significant cyclones prior to landfall.

With that pressure, could it have been in the range of 100-110 kt at landfall?

Tough to gauge a wind speed intensity based off of minimum pressure alone, since that also depends on how broad the wind field is. A storm can have a very low pressure, but if the wind field is broad enough, could still have wind speeds in the Category 2 range. Hurricane Ike made landfall as a Category 2 with pressure of 950 hPa, more typical of a Category 3. Hurricane Sandy had a secondary peak as a Category 2 before becoming post-tropical at landfall, with pressure at 945 hPa.

Also depends on how low the base pressure is, since the deviation from that base pressure is what matters more for gauging storm intensity. Pressures are naturally lower in the west Pacific compared to the Atlantic.

[mrbagyo]

Finally found a decent video showing the strong wind of Amphan.

 https://twitter.com/sayon_96/status/1263089738795253760




Can't find any reliable news from Sagar island.

[doomhaMwx]

Kolkata

 https://twitter.com/i/status/1263156890894102528



 https://twitter.com/i/status/1263113888775540742

[FireRat]

 https://twitter.com/simpliguru1/status/1263069092522553345




What a wallop! There are lots of reports of wind damage across a large portion of the affected area including Kolkata. No word on Storm Surge damage yet. 20 dead thus far.