ATL: DORIAN - Post-Tropical - Discussion

[supercane4867]

The whole neighborhood turned into a pile of twisted garbage. This is surreal

 https://twitter.com/leahmcelrath/status/1168979029162110976

[Raebie]

I just can't wrap my mind around the level of devastation.

[socplay02]

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.

Thanks for the explanation!

"Warm-core" vs "cold-core", etc. Never knew that before!

As far as "updraft (suction) vortices....." I've experienced what I THOUGHT was that phenomena when all the water is sucked out of a toilet when the eye wall of a hurricane is directly overhead.

Yes off topic a bit, but this is important for us living in hurricane prone areas to understand why we prepare our homes the way we do for a hurricane.

So I'm a psych major turned into a self taught data analyst/aspiring data scientist, so I have no clue what I'm talking about here (though I loved physics in high school). I learn by trying to make analogies and understanding how my assumptions are wrong.

Hurricanes have updraft too though don't they? Would it be more accurate to say that a tornado is very similar to a hurricane in many ways, but on a significantly smaller scale? In a hurricane, the same constant forces are measured in miles, but with a tornado, those same variations might be measured in feet.

Ah, but re-reading, the cold core system is interesting and key, because tornados are typically surrounded by warm environments right? If that's the case, they are almost reacting/bouncing off every warm spot they encounter (sort of like a top spinning on a non smooth surface, where a hurricane is a top on a smooth surface). This leads to all sorts of random force being applied to a surface in all sorts of different directions (kind of like the Tahoma narrows bridge, but ironic that was caused by constant wind forces, but allowed the resonance to produce waves that eventually piled on one another enough to overlap in a way a tornado might apply overlapping forces to a surface and destroy the bridge).

Other than the higher wind speeds, is that why going through the eye wall is so damaging? You have a piece of wood on a house, and the part in the eye is stationary, while the piece in the eye wall is getting slammed by wind?

[ronjon]

Something to note - many models have a NW jog as Dorian approaches the Cape early morning tomorrow morning. Radar showing an increasingly strong eyewall structure returning. Heavy continuous mass of convection (and likely tropical storm force winds) just offshore now.

https://www.wunderground.com/radar/us/fl/key-west/mlb

[aperson]

Really hard to tell due to pressure dropouts on last recon pass but looks like it's sitting somewhere around 960mb now.

[gailwarning]

Reading the arguments of cat 5 winds vs tornado winds, but they appear to not include the "fists of God". Now I personally have not experienced them, I have seen thier aftermath. Imagine if you will, a subdivision of the same model homes, hundreds of them. Then, in the middle of them. 2 or 3 houses completely flattened, and you see this all over.

Fist of God have been explained to me by those that have experienced them as first hearing an F16 fighter jet approaching, then BOOM, an explosion like effect, and just like thsy, it's over. These are tornados within a hurricane. I'm sure a pro met can explain it better, but the assumption that the houses with the worst damage were not properly built may be a fallacy, especially during a cat 5 hurricane.

We experienced something like that near Melbourne during Irma, to a lesser degree. That first rain band had so many areas of rotation that the TV Mets couldn't announce them fast enough. We were watching the window glass breathing in and out, wondering how much tension they could take without shattering. This was despite the roll-down shutters. We briefly heard that frightful freight train sound and then heard shingles flying off the roof and striking the sides of the house and the shutters. Our neighbors across the street watched as about a third of the water was sucked straight up out of their pool and then slammed back in. Our house, theirs, and those immediately around them lost bunches of shingles, while those a half block away were fine. Our next door neighbor's roof was only about 6 months old but large swaths were bare right down to the plywood.

[Aric Dunn]

Convection right now is doing fairly well and recon showing pressure is likely not rising ... or at least that fast..

Check out the NAM... 18z.. we can possibly expect some pretty large wobbles..

https://www.tropicaltidbits.com/analysi ... 0318&fh=48

[supercane4867]

High definition aerial video posted by LSM. The magnitude of damage is among the worst ever seen worldwide.

[youtube]https://youtu.be/8QoqtB6HPMY[/youtube]

[robbielyn]

Interesting change in the flow over NC and Tennessee looks like some mid to upper level ridging has developed as well as a little south into SC... could be what the EURO caught onto..

https://imgshare.io/images/2019/09/03/5.gif

looks like Dorian is plowing through that trough like get out of my way i headed towards the carolinas.

[webke]

Convection right now is doing fairly well and recon showing pressure is likely not rising ... or at least that fast..

Check out the NAM... 18z.. we can possibly expect some pretty large wobbles..

https://www.tropicaltidbits.com/analysi ... 0318&fh=48

Look at the difference in the track between the 12K and 3K NAMS

[aperson]

FL/SFMR winds from recon are indicating a cat 1 storm with possibly higher winds in the upper atmosphere waiting to mix down. FL winds were barely hurricane force in the NW quad after accounting for 15% reduction but were in the high 95kt range in the SE quad

[Nimbus]

Ring of deep convection growing and edging closer to the Florida coastline. Would not be shocked to see hurricane conditions affect the warning area. NHC made a good call on this.

Hurricane warnings up for St. Lucie cty

Don't know where else, just interested in that, since my 93-y/o dad lives there.

Warnings up for most of the peninsula and SC coast.



https://www.nhc.noaa.gov/storm_graphics ... d_wind.png

40 or 50 knots tops in St Lucie but that is still enough to take out power lines for hours to days. Power outage and possibly surge will be the main hassle in Florida. Beginning at SC and north some of the models show 10m winds above 52 knots so could be more problems there. If Dorian stalls he might just get taken out by the next front but we will have to wait to see.

[NDG]

https://twitter.com/LiveStormsMedia/status/1168956931152723971

The waves at the end of the video were gigantic.

[TeamPlayersBlue]

Reading the arguments of cat 5 winds vs tornado winds, but they appear to not include the "fists of God". Now I personally have not experienced them, I have seen thier aftermath. Imagine if you will, a subdivision of the same model homes, hundreds of them. Then, in the middle of them. 2 or 3 houses completely flattened, and you see this all over.

Fist of God have been explained to me by those that have experienced them as first hearing an F16 fighter jet approaching, then BOOM, an explosion like effect, and just like thsy, it's over. These are tornados within a hurricane. I'm sure a pro met can explain it better, but the assumption that the houses with the worst damage were not properly built may be a fallacy, especially during a cat 5 hurricane.

'Fist of God' there was a good bit of research done after Andrew because of this phenomena - and that was the conclusion reached (at least at that time) by the researchers - that there were tornados occurring within the hurricane.

Ive seen videos on the net, i think it was icyclones video from Maria, where inside the eyewall, there would be gusts to around 150 mph, then suddenly, the winds would be going in the opposite direction within seconds. It was wild

[aperson]

1800z steering

[socplay02]

I live in ft lauderdale, but have an antena (cord cutter) and I get West Palm Beach news. Hopefully this stays out as far from the coast as possible, because they are getting some serious surf, and some erosion (high tide isn't until midnight. Vero Beach especially looks like the road might collapse (they said it did during Michael).

I can't imagine if this had hit fort lauderdale. Up north they have tall dunes with a ton of sea grapes, and most of the beaches I've seen are lower than all the condos and other structures. In Ft Lauderdale, everything near the beach is basically beach level one side and inter costal on the other.

[Airboy]

Product: Air Force Vortex Message (URNT12 KNHC)
Transmitted: 3rd day of the month at 20:41Z
Agency: United States Air Force
Aircraft: Lockheed WC-130J Hercules with reg. number AF99-5309
Storm Number & Year: 05 in 2019
Storm Name: Dorian (flight in the North Atlantic basin)
Mission Number: 40
Observation Number: 05

A. Time of Center Fix: 3rd day of the month at 20:14:20Z
B. Center Fix Coordinates: 27.69N 78.59W
B. Center Fix Location: 113 statute miles (182 km) to the NE (53°) from West Palm Beach, FL, USA.
C. Minimum Height at Standard Level: 2,725m (8,940ft) at 700mb
D. Minimum Sea Level Pressure: 958mb (28.29 inHg)
E. Dropsonde Surface Wind at Center: From 205° at 6kts (From the SSW at 7mph)
F. Eye Character: Open in the southeast
G. Eye Shape & Diameter: Circular with a diameter of 22 nautical miles (25 statute miles)
H. Estimated (by SFMR or visually) Maximum Surface Wind Inbound: 68kts (78.3mph)
I. Location & Time of the Estimated Maximum Surface Wind Inbound: 41 nautical miles (47 statute miles) to the WNW (293°) of center fix at 20:02:30Z
J. Maximum Flight Level Wind Inbound: From 19° at 78kts (From the NNE at 89.8mph)
K. Location & Time of the Maximum Flight Level Wind Inbound: 24 nautical miles (28 statute miles) to the WNW (283°) of center fix at 20:07:30Z
L. Estimated (by SFMR or visually) Maximum Surface Wind Outbound: 62kts (71.3mph)
M. Location & Time of the Estimated Maximum Surface Wind Outbound: 55 nautical miles (63 statute miles) to the SE (131°) of center fix at 20:32:00Z
N. Maximum Flight Level Wind Outbound: From 219° at 99kts (From the SW at 113.9mph)
O. Location & Time of the Maximum Flight Level Wind Outbound: 25 nautical miles (29 statute miles) to the SE (128°) of center fix at 20:22:30Z
P. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 12°C (54°F) at a pressure alt. of 3,046m (9,993ft)
Q. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 13°C (55°F) at a pressure alt. of 3,048m (10,000ft)
R. Dewpoint Temp (collected at same location as temp inside eye): 13°C (55°F)
R. Sea Surface Temp (collected at same location as temp inside eye): Not Available
S. Fix Determined By: Penetration, Radar, Wind and Pressure
S. Fix Levels (surface & flight level centers within 5nm of each other): Surface and 700mb
T. Navigational Fix Accuracy: 0.02 nautical miles
T. Meteorological Accuracy: 1 nautical mile

Remarks Section:

Maximum Flight Level Wind: 99kts (~ 113.9mph) which was observed 25 nautical miles (29 statute miles) to the SE (128°) from the flight level center at 20:22:30Z

[TeamPlayersBlue]

This devastation reminds me of Ike hitting Bolivar Peninsula. Most of the damage came from the surge in Ike. 110 MPH at landfall but Ike was arguably the most mature hurricane in the ATL basin.

[Aric Dunn]

EURo, ICON 18z, NAM. showing a good bend back to the nw more over the next 18 to 24 hours.

[tallywx]

Center is east of 11am forecast track (and model guidance).