ATL: MICHAEL - Post-Tropical - Discussion

[Blow_Hard]

Now it comes down to wobbles whether downtown Panama City gets the storm surge or not. Mexico Beach, Port St. Joe and Apalachicola is not looking good.

Hey PTW...are you guys still in Bay County or did you evacuate. My wife and I are with her elderly parents in the Bylsma Manor subdivision. Just waiting, watching and praying.

[Buck]

I saw someone post a chart that details the offshore slopes of the Gulf Coast and it illuminated why storm surges can get up to 24 feet in Mississippi but why that's more unlikely for, say, Port St. Joe, FL. I've googled it but I'm mostly just getting seafloor or oil rig maps. Does anyone have it handy? Much appreciated.

[Hurricane Andrew]

I saw someone post a chart that details the offshore slopes of the Gulf Coast and it illuminated why storm surges can get up to 24 feet in Mississippi but why that's more unlikely for, say, Port St. Joe, FL. I've googled it but I'm mostly just getting seafloor or oil rig maps. Does anyone have it handy? Much appreciated.

That would be wxman57's chart. It has to do with proximity of deep water to the coast.

[Hurricane Andrew]

The difference is amazing between max (Cat 3) surge near Panama City vs. Apalachca Bay. Didn't realize there'd be that much of a difference. In addition to the shallower waters further east, I suppose there's also the fact that a greater forcing of water "pile-up" would exist to the east, whereas further west along the Panhandle the increased storm surge can at least spread out a greater distance perpendicular to the coastline?

One key factor in storm surge calculations is called the "Shoaling Factor". The shoaling factor relates to the distance offshore to the 10-fathom depth (60 ft). The closer to the coast that 10-fathom depth, the less the storm surge threat. Note that for Pensacola to Panama City, the multiplier in the storm surge calculation is only about 0.4. Compare that to 1.8 in Vermilion Bay or 1.75 on the Mississippi Coast (or the 1.1 to 1.2 in Apalachee Bay). The shoaling factor is one of the more significant factors in storm surge height.

Here's a graphic I made from a similar chart in my old (very old) Mariner's Shore Protection Manual. The calculation methods in that manual still work well today.

http://wxman57.com/images/shoaling.JPG

This is for the user who asked about it above

[MGC]

I'm speechless....could this possibly reach high end cat 4? Yup, could even flirt with Cat-5. Things are looking grave for PCB to Port St. Joe. Would not want to be under that eyewall. Sadly many are going to perish this afternoon somewhere along the coast. Sad..sad..sad.....MGC

[cycloneye]

Pressure seems to be leveling off at least for now. That's good news

No sign of an EWRC?

[ColdMiser123]

Pressure seems to be leveling off at least for now. That's good news

NOAA2 had an extrapolated pressure near 932 this pass, down 2 mb from the previous pass an hour ago.

[tropicwatch]

Now it comes down to wobbles whether downtown Panama City gets the storm surge or not. Mexico Beach, Port St. Joe and Apalachicola is not looking good.

Hey PTW...are you guys still in Bay County or did you evacuate. My wife and I are with her elderly parents in the Bylsma Manor subdivision. Just waiting, watching and praying.

Was able to convince them that discretion was the better part of valor. We got out!

[xironman]

@MikeWDross — Recon dropsonde measuring incredible winds aloft in the eye-wall. 176 MPH around 1k feet. 181 mph around 3k feet.

You don't want to be around when one of those mesovortices brings that down to the surface.

[tolakram]

Pressure seems to be leveling off at least for now. That's good news

Not sure about that. I would hope it's not falling as fast, but still falling.

[chaser1]

Somehow the satellite appearance has improved quite a bit in the last 30 minutes.

You have got to be kidding - I feel like I just woke up in Fiji..... on a very bad day! So, having just woke up and trying to catch up, absorb, and make sense of the latest satellite appearance and official updates along with the fragments of sporadic wind & pressure reports still being reported.

In a nutshell, what is the latest recon reported pressure and max wind speed as things stand now?

[Miami Storm Tracker]

Good Morning,

waking up to an even more impressive storm than last night. Wishing all of you up there the best stay safe.

[USTropics]

Pressure seems to be leveling off at least for now. That's good news

No sign of an EWRC?

No sign of an EWRC. Current eyewall has been open and closed throughout the night/morning. It's been closed for ~2 hours now according to VDM messages.

[tolakram]

 https://twitter.com/philklotzbach/status/1050002818386415616

[supercane4867]

[tolakram]

 https://twitter.com/EricBlake12/status/1050002656494804992

[otowntiger]

I fear that portions of the gulf coast around Panama City will look like Homestead back in '92.

[supercane4867]

Eye drop has 936mb with 64kt winds. That indicates actual central pressure of 930mb

[NDG]

Dropsonde from the AF recon at 12z in the eastern eyewall measured 179 mph winds just around 750 feet above the surface, incredible.

[Buck]

The difference is amazing between max (Cat 3) surge near Panama City vs. Apalachca Bay. Didn't realize there'd be that much of a difference. In addition to the shallower waters further east, I suppose there's also the fact that a greater forcing of water "pile-up" would exist to the east, whereas further west along the Panhandle the increased storm surge can at least spread out a greater distance perpendicular to the coastline?

One key factor in storm surge calculations is called the "Shoaling Factor". The shoaling factor relates to the distance offshore to the 10-fathom depth (60 ft). The closer to the coast that 10-fathom depth, the less the storm surge threat. Note that for Pensacola to Panama City, the multiplier in the storm surge calculation is only about 0.4. Compare that to 1.8 in Vermilion Bay or 1.75 on the Mississippi Coast (or the 1.1 to 1.2 in Apalachee Bay). The shoaling factor is one of the more significant factors in storm surge height.

Here's a graphic I made from a similar chart in my old (very old) Mariner's Shore Protection Manual. The calculation methods in that manual still work well today.

http://wxman57.com/images/shoaling.JPG

This is for the user who asked about it above

THANK YOU!