ATL: LORENZO - Post-Tropical - Discussion

[sponger]

Long period 20 second ground swell showing up on the St Augustine buoy. Amazing long period swell from 2000 miles away!


https://www.ndbc.noaa.gov/station_page. ... tion=41117

Drier air and some shear impinging the Southern circulation?

https://www.tropicaltidbits.com/sat/sat ... product=ir

[Highteeld]

For me, the fact that recon did not pass through Lorenzo at either of its two peaks makes it impossible for me to conclude if ADT was running hot or not, especially regarding the NHC upgrade.

On a second note, the outer eyewall is pretty stout. Having that many 100 kt flight level obs in the NE quadrant at such a broad radius is very impressive. Tighten that up and you could probably get ~ 150 kt flight level. There is a considerable amount of angular momentum in that outer eyewall.

Now here's what would be fascinating; if we could calculate what the FL winds would be in the Outer eyewall at this time with last night's eyewall size given its current intensity and size. Conservation of angular momentum would suggest a major increase, but could it support a cat 5 at the sfc?

[1900hurricane]

Pressure gradient is blown way up. First pass only supports about 80 kt. Pressure above 950 mb. ATMS may have been on to something.

I don't think so, rather I think Lorenzo has rapidly weakened over the past few hours due to a combination of a significant EWRC, dry air, and shear. The satellite presentation isn't even half as impressive as it was overnight.

Very possible. I think the rate of change observed with later passes of pressure falls in particular may help, but even then, data is still rather incomplete unfortunately.

[1900hurricane]

Center dropsonde worth about 950 mb.

[Highteeld]

Looks like a moat to me

[Hypercane_Kyle]

Pressure gradient is blown way up. First pass only supports about 80 kt. Pressure above 950 mb. ATMS may have been on to something.

I don't think so, rather I think Lorenzo has rapidly weakened over the past few hours due to a combination of a significant EWRC, dry air, and shear. The satellite presentation isn't even half as impressive as it was overnight.

Very possible. I think the rate of change observed with later passes of pressure falls in particular may help, but even then, data is still rather incomplete unfortunately.

Keep in mind that it's definitely possible for a Cat 5 to weaken this much that quickly. Katrina went from 175mph to 125mph in the span of like eight hours IIRC. 160 to 115-110mph is pretty drastic but we're in completely unprecedented territory here, so we don't have any way to gauge how quickly a storm of this magnitude can unravel. I vaguely remember Julia unraveling pretty quickly too.

But last night we had recon in that showed that Lorenzo had rapidly intensifying to a Cat 4 and that ADT estimates also (IIRC) supported Cat 4. That explosive intensification continued throughout the night, with ADT estimates going to >=7.0. This strongly supports that Lorenzo reached 140 knots, if only for a few hours around 02-03z.

[CyclonicFury]

I have some doubts Lorenzo ever reached Category 5. The recon data from yesterday afternoon barely supported an intensity of 115 kt, and today, it barely supports 85 kt. The pressure was not significantly dropping during yesterday's research mission, and it would have had to drop 25 mb in 5 hours, and then rise back up to 950 mb today for NHC's 925 mb estimate to be correct. Not to mention, 140 kt is above the MPI in this region. The downgrade in the best track makes me wonder.

Dorian was no doubt a Category 5, though.

[NotoSans]

 https://twitter.com/philipslau681/status/1178381370558574593

[1900hurricane]

Looks like both planes are flying at constant altitude at about the same pattern. One is at about 2400 m and the other is at 3000 m.

*Edit: nevermind, their patterns have diverged slightly.

[Ubuntwo]

I have some doubts Lorenzo ever reached Category 5. The recon data from yesterday afternoon barely supported an intensity of 115 kt, and today, it barely supports 85 kt. The pressure was not significantly dropping during yesterday's research mission, and it would have had to drop 25 mb in 5 hours, and then rise back up to 950 mb today for NHC's 925 mb estimate to be correct. Not to mention, 140 kt is above the MPI in this region. The downgrade in the best track makes me wonder.

Dorian was no doubt a Category 5, though.

During both flights the pressures measured were essentially in-line with or slightly below Dvorak estimates. The flight yesterday showed steadily dropping pressures, and a couple hours after the flight left the storm quickly saw a dramatic increase in satellite presentation. We only have two data points, but if that's anything to go off of the storm did reach a pressure in the 920's or so. Of course now with dry air and an outer eyewall choking off the inner winds will decline significantly but broaden. I personally do not believe it reached category 5 intensity because the storm's size means such a pressure would equate more to 130 or 135kt, and that peak was very short lived.

[StruThiO]

 https://twitter.com/webberweather/status/1178122851062308864

[NotoSans]

Recon data support at most 80-85 knots. Looks like a mismatch with the central pressure of around 950mb due to the ongoing ERC.

[1900hurricane]

 https://twitter.com/1900hurricane/status/1178390972608200705

[galaxy401]

Even if they initially estimated Lorenzo's intensity at 155 mph, people would claim that it should have been upgraded to a Category 5 anyways. No matter what the peak strength was between 155-160 mph, there would have been debates going on.

[NotoSans]

 https://twitter.com/philipslau681/status/1178420933712703493

[Kazmit]

I made an overlay comparing the size of Dorian and Lorenzo. The difference is insane.

[storm_in_a_teacup]

I made an overlay comparing the size of Dorian and Lorenzo. The difference is insane.

https://i.imgur.com/hic3PvJ.jpg

“Bruh, do you even isentropic lift?”...

[TallyTracker]

I made an overlay comparing the size of Dorian and Lorenzo. The difference is insane.

https://i.imgur.com/hic3PvJ.jpg

Those blocks are 10 degrees square and Lorenzo is larger than one of those blocks! That’s insane!

[Chris_in_Tampa]

This image shows all of the Atlantic tracks from 1851 through 2019 where a storm had 1-minute sustained winds of category 4 or 5 strength. (130 mph or more; 113 knots or more) Full path of Lorenzo, from best track data, is shown as a white line and is through 8pm AST on Sunday.


Higher quality PNG image: https://i.imgur.com/WPQ2Yh1.png

[Chris_in_Tampa]

Below is the best track path through 8pm AST Sunday and the winds swaths from best track data as of 8pm AST Sunday. (Best track data at that time had the winds at 95 knots, category 2 strength, which is why the icon says 2) The NHC track point and cone were as of 5pm AST Sunday.

The islands of Flores and Corvo in the Azores are noted. The labels aren't exactly lined up, but Corvo is the smaller dot slightly north of Flores.

https://en.wikipedia.org/wiki/Flores_Island_(Azores)
https://en.wikipedia.org/wiki/Corvo_Island



And for the detailed information on those wind swaths, with radius in nautical miles:

34 Knot Wind Radii

Northeast: 210nm
Southeast: 220nm
Southwest: 150nm
Northwest: 180nm

50 Knot Wind Radii

Northeast: 110nm
Southeast: 100nm
Southwest: 100nm
Northwest: 110nm

64 Knot Wind Radii

Northeast: 80nm
Southeast: 70nm
Southwest: 70nm
Northwest: 80nm