ATL: DORIAN - Post-Tropical - Discussion

[Michele B]

https://twitter.com/TravisCC/status/1168935463526309892

Every time I go to say "that looks like tornado damage!" I remind myself that Dorian was as strong as an F3 tornado (158–206 mph), but lasted for almost an entire day. So no surprise that many buildings are stripped to the slab, really.

Horrifying.

So true. By the way, as I pour over most of the photo and especially video links that you guys are posting here, I just wanted to put out a broad "THANK YOU" for posting them here. As hard as they are to look at and watch, they're equally mesmerizing in terms of the real-world impact and damage that was inflicted. It's easy to get lost in data, maps, and models but some of these video's depicting conditions during and immediately after the storm really bring to light what a Catagory 5 hurricane stalled over in the Bahamas did to those islands and the community there.

I know we are saying "They are poor, their homes not well-built, blah, blah..."

But truth be told, would WE fare any better if a CAT 5 storm SAT over our area for 24+ hours?!?!?

This whole thing is too terrible to even contemplate. I'm just about reduced to tears every time I think about that. I think I would go insane.

[jhpigott]

Juno Pier reported a wind gust of 58mph earlier today. Highest report I could find on FL east coast so far. Imagine that may change

[Vdogg]

I just don't see a strengthening system here atm like other people are reporting. Its eye keeps growing as it sheds its angular momentum out into rainbands. It keeps entraining dry air and opening its eye. MIMIC-TPW2 is showing much drier air than yesterday being entrained from its west. It continues to have stacked vorts all the way up to 200mb with excellent lower convergence and strong upper divergence in its anticyclone, but it cannot get the fuel to pump itself back up.

It's already broadened and flattened its wind field out to such a degree that it's not going to instantly ramp back up once conditions are more favorable like those small compact-core systems. I really agree with the previous posters that mentioned that this system reminds them of Ike.

I don’t think anyone is calling for RI, but with cloud tops cooling and the eye coming back, some slight restrengthening is definitely underway. I think this can easily make it back to low end Cat 3. It hasn’t even reached the Gulf Stream yet.

[txwatcher91]

2 outflow channels in place

Dorian throws another loop.


https://i.imgur.com/Iu7YVeh.gif

This is why models show it strengthening some as it heads north. The outflow channels and warmer waters should help maintain if not increase the strength as it heads northwest. I don't foresee this becoming a naked swirl in the next 24 hours...

[Raebie]

there was a shantytown in the Marsh Harbour area home to Haitian immigrants, that appears to have been obliterated.

I hope all those poeple evacuated....

to where?

A concrete shelter.

[Bunkertor]

It could be my eyes but it seems on radar the eye is moving closer to the Florida coast and I say tho because if it goes north west it may get really close to cape canaveral. Like I said maybe it’s me.

Hi Stormy !

[EquusStorm]

You've also got to factor in not only the massive vertical component of tornadic winds lifting and carrying things, but also their rapid acceleration producing such a spike in wind loads that most structural elements can be overwhelmed. Long duration straight line winds are destructive but the lack of vertical component and the capacity to create a spiraling blender of debris tends to make hurricane winds of a similar speed less destructive, though much longer duration that may eventually cause structural fatigue.

But hurricanes have storm surge on their side which is a whole new horror altogether

[hurricaneCW]

2 outflow channels in place

Dorian throws another loop.


https://i.imgur.com/Iu7YVeh.gif

This is why models show it strengthening some as it heads north. The outflow channels and warmer waters should help maintain if not increase the strength as it heads northwest. I don't foresee this becoming a naked swirl in the next 24 hours...

Euro remains quite strong with it even near the Carolinas, and if it can repair its inner core then a Cat 3 is possible. The storm isn't overly large like an Ike where it would take a long time to reorganize.

[Michele B]

Not really. Hurricane winds and torandic winds are not the same, and comparing them directly is inadvisable. FWIW you're also using the old Fujita scale -- 185mph winds on the new scale would be high end EF4.

I used the old scale on purpose, because the Enhanced Fujita scale is based on damage, not wind speed. The wind speeds on the EF scale are approximate and do not related to how the scale is assigned.

Would actually be interested in learning how hurricane and tornado winds differ. Do you have an article I could read?

So was the old Fujita Scale. The wind speeds assigned were just his best estimates of those needed to cause the damage associated with each category. The EF-scale is just an update of that to incorporate more recent research. Of course, it has many of the same flaws, but I digress...

That said, that aerial image is by far the most tornado-like hurricane damage image I've seen to date, one-upping anything from Michael. Difficult to tell how much of that was wind vs. surge, though.

Remember, too, it's "apples vs oranges" comparing storms where tides/storm surge is a factor - like Michael and Dorian - on a low-lying coast. Comparing to a storm where it is inland....The tides, oceans, etc. coming ashore definitely add to the destruction. Water is a potent foe.

I delivered supplies to Michael survivors. I SAW the destruction. That entire neighborhood where EVERYTHING IS FLAT, and not a house is left standing (well, there IS one....I'm sure by now everyone knows how he built it!).

[aperson]

You've also got to factor in not only the massive vertical component of tornadic winds lifting and carrying things, but also their rapid acceleration producing such a spike in wind loads that most structural elements can be overwhelmed. Long duration straight line winds are destructive but the lack of vertical component and the capacity to create a spiraling blender of debris tends to make hurricane winds of a similar speed less destructive, though much longer duration that may eventually cause structural fatigue.

But hurricanes have storm surge on their side which is a whole new horror altogether

Thanks a ton for the wisdom here. Can't wait to see updates on tree damage from Dorian once all is said and done here!

[GCANE]

 https://twitter.com/jpetramala/status/1168952817752694786

[CryHavoc]

Every time I go to say "that looks like tornado damage!" I remind myself that Dorian was as strong as an F3 tornado (158–206 mph), but lasted for almost an entire day. So no surprise that many buildings are stripped to the slab, really.

Horrifying.

Not really. Hurricane winds and torandic winds are not the same, and comparing them directly is inadvisable. FWIW you're also using the old Fujita scale -- 185mph winds on the new scale would be high end EF4.

In what ways is it wrong to compare hurricane and tornadic winds? How are they different?

Serious question.

To elaborate a bit on what aperson stated:

Tornadic winds and hurricane winds are very different animals. Hurricanes are warm core systems and are actually fairly stable with regard to changes in speed and altitude -- this is why hurricane hunter aircraft can fly through even cat4/5 hurricanes fairly safely.

Tornadoes form from cold core systems and as such one of their primary methods of wind movement is actually vertical -- this makes sense, considering that mature tornadoes are connected directly to the parent cloud/supercell. When a hurricane hits your house (assuming that it doesn't do so with an embedded spin up tornado!), the wind damage is caused by straight-line winds. In coastal cities more damage often occurs from storm surge than from actual winds. In strong/violent tornadoes, they (often) develop small circulation centers within the parent tornado that have extremely strong updraft components in the form of suction vortices -- some of these have wind speeds of 300+ mph, and they can actually lift the roof off of the house to drastically increase the rate of structural failure for the rest of the building. Once wind has a "grip" on a building (i.e., a part of the building fails that allows wind to channel to more areas rather than just the outside), the forces exerted by the wind speed increase tremendously.

Sorry for the OT explanation -- just thought it was important in light of the comments comparing Dorian to a tornado. They are both beasts, but beasts of a different sort. That said, the damage here does look incredible, and heart-breaking.

[hurricaneCW]

You've also got to factor in not only the massive vertical component of tornadic winds lifting and carrying things, but also their rapid acceleration producing such a spike in wind loads that most structural elements can be overwhelmed. Long duration straight line winds are destructive but the lack of vertical component and the capacity to create a spiraling blender of debris tends to make hurricane winds of a similar speed less destructive, though much longer duration that may eventually cause structural fatigue.

But hurricanes have storm surge on their side which is a whole new horror altogether

Very true.

That being said there's no other weather phenomenon as widely destructive or costly as a hurricane. The combination of flooding, surge, and wind impacts over 100s if not 1000s of miles is unmatched.

[Meteorcane]

Not really. Hurricane winds and torandic winds are not the same, and comparing them directly is inadvisable. FWIW you're also using the old Fujita scale -- 185mph winds on the new scale would be high end EF4.

In what ways is it wrong to compare hurricane and tornadic winds? How are they different?

Serious question.

Tornadic winds are shorter duration and are much more turbulent. Winds in a mature hurricane are typically more geostrophically balanced so there is less short-term turbulence but more long-term constant wind from a uniform direction.

There is much more to wind than just its speed.

Yes this is correct, tornadoes also tend to be associated with quite a bit of vertically-directed forces/accelerations which can exceed the gravitational force. Hence you tend to have more objecst propelled upward as well as blown horizontally. This article is outdated (from the pre EF scale era) but if you want to go into more detail see pages 7-11 in https://training.weather.gov/wdtd/courses/EF-scale/lesson2/FinalNWSF-scaleAssessmentGuide.pdf

[Jr0d]

There is a meeting tomorrow at the Key West City Hall to coordinate relief efforts. They are going to need a lot of help.

https://www.miamiherald.com/news/weathe ... 35717.html

[EquusStorm]

Yeah the tree damage is going to be on a scale rarely witnessed... easily at or above Irma/Maria levels and I'm afraid we may have practically no surviving trees across Grand Bahama given the duration. I did an intense landfalling TC tree damage comparison a while back before even Michael and Dorian may easily top the list in the Atlantic; only a south Pacific storm or two may seriously rival it. EF3-4 tornado tree damage levels here with debarking.

[chaser1]

Not really. Hurricane winds and torandic winds are not the same, and comparing them directly is inadvisable. FWIW you're also using the old Fujita scale -- 185mph winds on the new scale would be high end EF4.

In what ways is it wrong to compare hurricane and tornadic winds? How are they different?

Serious question.

Tornadic winds are shorter duration and are much more turbulent. Winds in a mature hurricane are typically more geostrophically balanced so there is less short-term turbulence but more long-term constant wind from a uniform direction.

There is much more to wind than just its speed.

Much has to do with the physical force and stress of such severe winds while adding the very sudden twisting and torquing occurring at the same time. This is a pretty bad anology and am sure someone else here may better exhibit, but imagine a skinny 4' sapling tree. Now, imagine exerting a considerable force against it by pushing the top part in one direction. It'll bend a good deal and with enough force, probably break. Now imagine in another experiment that you simply grabbed the top and violently shook it back and forth and in every direction. Two things would likely occur -
1) The back and forth physical stress would likely cause it to twist and break faster.... 2) Neighbors peering out their windows will have thought that you've lost your mind and may report you to some Arbor Cruelty organization

[Jevo]

12z Euro showing the NW turn possibly coming.. getting very close to the NE florida coast and very very clsoe to GA/SC

Happy belated birthday, fella

[plasticup]

Yeah the tree damage is going to be on a scale rarely witnessed... easily at or above Irma/Maria levels and I'm afraid we may have practically no surviving trees across Grand Bahama given the duration. I did an intense landfalling TC tree damage comparison a while back before even Michael and Dorian may easily top the list in the Atlantic; only a south Pacific storm or two may seriously rival it. EF3-4 tornado tree damage levels here with debarking.

Would that have long-term effects on erosion? I know that in some low-lying places the loss of foliage can lead to loss of land in the coming months/years.

[Michele B]

there was a shantytown in the Marsh Harbour area home to Haitian immigrants, that appears to have been obliterated.

I hope all those poeple evacuated....

to where?

Stronger buildings. I see a few that aren't c ompletely obliterated.