ATL: FLORENCE - Post-Tropical - Discussion

[supercane4867]

[ozonepete]

This is why I asked it earlier as to what it does to the track after 72 hours.

For both of you:
What it means is that an approaching trough weakens a ridge as it moves into it. This one will get to the Appalachians by Saturday. Since this is a shortwave trough it won't doesn't extend all the way south to the GOM but the bottom of this U-shaped feature should reach down to near northern GA and AL as it nears the Appalachians. This could weaken the strong blocking ridge enough to allow Florence to move northward inland along the Appalachinas after it has stalled out somewhere over the Carolinas and weakened. It has tremendous impact on how much flooding occurs if it can pick up the remnants and kick them north. Would be less flooding inland, hopefully but highly uncertain at this early point.

Thank you so much - I just watched the 12Z GFS and I assume that is what it is depicting but maybe not as quickly as the NHC is discussing.

You are both welcome. Yes these approaching troughs are sometimes difficult for the models to factor in ahead of time, especially in this very unusual setup with that giant blocking ridge. One of the most unusual setups for a landfalling major hurricane I've ever seen. Unfortunately it looks like the models will continue to have trouble all the way to landfall and beyond. Another factor is that as it weakens the steering currents often change because the steering winds are different in different layers. You can use this CIMSS site to see the current steering winds for different TC strengths.

http://tropic.ssec.wisc.edu/real-time/d ... zoom=&time

[ronyan]

Remember the lines are not part of the forecast, they are just connecting point forecasts.

[tolakram]

https://imgur.com/BLUAuAp

Oooooh, sinister. You have a flare for the dramatic.

I'm not seeing any appreciable speed reduction (mentioned a few posts ago), and while dramatic this is what COD offers. I would also encourage anyone who hasn't left yet to leave now, no sense being anywhere near this thing, landfall or not.

[northjaxpro]

Georgia has announced state of emergency for all counties

https://twitter.com/wsbtv/status/1039917496478965760

This is an ominous sign.

[Zarniwoop]

This like another Hurricane Ike but smaller and with VASTLY more rain.

She can't get her winds together, and I'd be shocked if she lands as a major, but it won't make any difference.

She's going to be pushing so much water and she's going to dump a meter of rain in places.

Even if she landed as a tropical storm there's going to be catastrophic damage from just about every tree in certain areas coming down.

I am not a forecaster and my post should be disregarded by those trying to make decisions. Please refer to the NHC products to make decisions.

[ScottNAtlanta]

Here is the link to current microwave loops

http://tropic.ssec.wisc.edu/real-time/s ... 000&loop=0

[StormPyrate]

So looking at other buoys that have an noticeable increase in wave height, this one up near the cape is up three feet in one hour.
So if I were watching for OBX conditions might be a good one to keep an eye on.
It sits right on the edge of the shelf and normally has 6-7 foot waves, up to over 9 this morning.
https://www.ndbc.noaa.gov/station_page. ... tion=41025

[Nimbus]

The outflow pattern of Florence is the best it has been by far. Pending inner core reconstruction, I believe she will have one more strengthening trend before landfall.

The outflow pattern symmetry occured as an upper level low rolled from west to southwest of Florence. Don't know if that will have any effect on steering such as an earlier bend back to the west? Probably already been factored in.

[meriland29]

https://i.imgur.com/sc0rTas.gif

She looks markedly north of track. Maybe a OBX?

[Bocadude85]

Georgia has announced state of emergency for all counties

https://twitter.com/wsbtv/status/1039917496478965760

This is an ominous sign.

I would assume this is more in response to potential rainfall?

[Vdogg]

This continued March NW is concerning me. If you draw a direct line along it's current direction of motion that's OBX, not Wilmington...

[Bocadude85]

https://i.imgur.com/sc0rTas.gif

She looks markedly north of track. Maybe a OBX?

I have to wonder if the farther northeast track would equate to a stall farther offshore, before the southwest drift.

[Nimbus]

https://i.imgur.com/sc0rTas.gif

She looks markedly north of track. Maybe a OBX?

I have to wonder if the farther northeast track would equate to a stall farther offshore, before the southwest drift.

We have seen storms like Betsy turn almost due north just before the stall or even loop around like some of the GFS runs have shown Florence doing. NHC has to just keep making little track adjustment for consistency so unless we see a dramatic slowdown that should not happen.

[Ken711]

This continued March NW is concerning me. If you draw a direct line along it's current direction of motion that's OBX, not Wilmington...

12Z was slightly west. I'm thinking Morehead City at least have to see the what the Euro shows.

[northjaxpro]

She looks markedly north of track. Maybe a OBX?

I have to wonder if the farther northeast track would equate to a stall farther offshore, before the southwest drift.

We have seen storms like Betsy turn almost due north just before the stall or even loop around like some of the GFS runs have shown Florence doing. NHC has to just keep making little track adjustment for consistency so unless we see a dramatic slowdown that should not happen.

I agree Nimbus.

[Vdogg]

This continued March NW is concerning me. If you draw a direct line along it's current direction of motion that's OBX, not Wilmington...

12Z was slightly west. I'm thinking Morehead City at least have to see the what the Euro shows.

It's always seemed to come back to Moorhead city. Now I'm starting to question if the stall occurs at sea or inland. This makes a big difference in HR. Local Mets have been downplaying all day saying it's going to go south towards SC. This reminds me of Matthew, which came 100 miles further north than forecast and hammered us. We had areas flood that hadn't flooded in a century.

[Michele B]

The problem with the stall is that the storm, even somewhat weaker, will continue to pile water up the rivers and sounds in NC northeast of the eyewall. I hope people evacuated these floodprone areas as the surge may occur over several high tide cycles and current projections are anywhere from 6 to 13 feet above ground. The tidal surge may also occur tens of miles inland of the coast on area rivers.

This is what people need to focus on, and quit looking at only the strength of the storm, or where she will come ashore.

[ronjon]

Dr. Jeff Masters Blog on Florence today:

https://www.wunderground.com/cat6/Florence-Expected-Stall-Near-Coast-Bringing-Extreme-Rain-Surge-and-Wind-Damage

[Michele B]

The shortwave trough over the southern Plains seen in water vapor imagery could end up being a significant factor as it rounds the narrow ridge over the Tennessee Valley and is expected to erode the ridge along the U.S. mid-Atlantic coast on days 3-5.

Does this mean Florence could now turn more west or northwest around the weakened high rather than move SW?

Who was it? Last year, I think, someone kept saying, "'Canes want to go 'poleward'....." Meaning they WANT TO GO northward (Northern Hemisphere speaking!). So any opportunity it gets, it will head that way. When that way is blocked, it looks for the "path of least resistance."

In this case, my understanding is that as soon as that trough moves/weakens, that's the path the storm will take.

Any "experts" want to chime in, please do!