tornado examiner
Member
Nooo not directly I don’t think, but the consistency of the readings as the sonde drops through the eye wall indicate they had to be sustained for some time I would assume?
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Current Tropical Systems Melissa
Hurricane Melissa
- Thread starter Jacob Aden
- Start date
The thing I'm having a hard time understanding is it says "level" but it gives a pressure value. Thus I don't know exactly how high above the surface these wind values were recorded at. Is there any other data that can be calibrated to this in addition to these dropsonde readings?
Pressure is used by meteorologists instead of height because the atmosphere isn’t a fixed stack - it stretches and squashes with temperature. In a warm storm (like a hurricane), the air column bulges upward; in a cold system, it sinks. So "15,000 feet" might mean totally different things depending on the weather. Pressure, on the other hand, always tells you how much air is above you. That makes it a consistent way to mark layers of the atmosphere - 850 mb, 700 mb, 500 mb - no matter how tall or short the column gets.
In a hurricane, in Jamaica, in October - approximately:
So when you are talking about wind speed, a dropsonde isn't measuring it, the dropsonde's flight IS the measurement. Yeah, that sucker was flying 252MPH sideways as it fell, blown by the hurricane, when it was at that level. This is also why you would see dropsonde reports coming after the plane passed through the area it measured by a few minutes, and why their markers were sometimes a LONG way away from where the plane was, but in an arc around the storm. Pretty cool, huh?
(Folks smarter than me feel free to expand on or correct anything I oversimplified there)
In a hurricane, in Jamaica, in October - approximately:
- 1000 mb – sea level
- 925 mb – ~2,500 ft (750 m)
- 850 mb – ~5,000 ft (1.5 km)
- 700 mb – ~10,000 ft (3 km)
- 500 mb – ~18,000 ft (5.5 km)
- 300 mb – ~30,000 ft (9 km)
- 200 mb – ~39,000 ft (12 km)
So when you are talking about wind speed, a dropsonde isn't measuring it, the dropsonde's flight IS the measurement. Yeah, that sucker was flying 252MPH sideways as it fell, blown by the hurricane, when it was at that level. This is also why you would see dropsonde reports coming after the plane passed through the area it measured by a few minutes, and why their markers were sometimes a LONG way away from where the plane was, but in an arc around the storm. Pretty cool, huh?
(Folks smarter than me feel free to expand on or correct anything I oversimplified there)
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tornado examiner
Member
Melissa is back to category 2 status.
GPT5's opinion when I fed it the data from that dropsonde (without pressure reading):
"That sonde is the kind of data that makes forecasters go silent for a few seconds before speaking. You’re looking at a fully mature Category 5 with a mid-level jet pushing 220 kt and a surface pressure almost certainly scraping the high-800s mb. At that point the physics get surreal: the eye is a pressurized vacuum, the eyewall a horizontal tornado.
At 915 mb the sonde caught 234 mph winds—that’s not some noisy spike, that’s a deep, coherent core. You can actually see the inflow from the south curling around to west-southwest as it ascends, tracing the entire spin of the vortex. And by 800 mb it’s still hurling 160-plus kt winds—meaning that monstrous flow extended upward thousands of feet, not just a skin-deep burst.
When that structure makes landfall, “catastrophic” doesn’t begin to describe it. It’s mountain-shredding, forest-leveling, infrastructure-erasing. Jamaica essentially took a direct hit from a self-contained atmospheric engine running near theoretical maximum output—a 890 mb-class warm core, perfectly vented, perfectly aligned.
There’s a reason meteorologists sometimes sound reverent describing storms like this: you’re seeing nature operate at the edge of its own design limits."
"That sonde is the kind of data that makes forecasters go silent for a few seconds before speaking. You’re looking at a fully mature Category 5 with a mid-level jet pushing 220 kt and a surface pressure almost certainly scraping the high-800s mb. At that point the physics get surreal: the eye is a pressurized vacuum, the eyewall a horizontal tornado.
At 915 mb the sonde caught 234 mph winds—that’s not some noisy spike, that’s a deep, coherent core. You can actually see the inflow from the south curling around to west-southwest as it ascends, tracing the entire spin of the vortex. And by 800 mb it’s still hurling 160-plus kt winds—meaning that monstrous flow extended upward thousands of feet, not just a skin-deep burst.
When that structure makes landfall, “catastrophic” doesn’t begin to describe it. It’s mountain-shredding, forest-leveling, infrastructure-erasing. Jamaica essentially took a direct hit from a self-contained atmospheric engine running near theoretical maximum output—a 890 mb-class warm core, perfectly vented, perfectly aligned.
There’s a reason meteorologists sometimes sound reverent describing storms like this: you’re seeing nature operate at the edge of its own design limits."
tornado examiner
Member
This image itself speaks for all of this. I've seen nobody mention this but at peak both Melissa’s eye and CDO had a very subtle hexagonal shape to it.
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The lowest level is at 927 mb. And the 252 mph (219 kt) measurement came at the 906 mb level - numerous other posts have said that this was at 250 m (~820 ft.) above the surface.
I personally believe Melissa was very likely the most powerful Atlantic hurricane by windspeed and windspeed at landfall - of all time.
Katrina did that at her peak, too. Geometry gets odd at that strength.
Katrina did that at her peak, too. Geometry gets odd at that strength.
tornado examiner
Member
Literally pushing the boundaries of physics.
It's not quite Patricia levels.
But my peak for an upgrade right before the eye came shore would be 195mph 889MPH.
Agreed, but Patricia wasn't Atlantic.
tornado examiner
Member
Just of western hemisphere storms in general.
The 915 mb level on the dropsonde data says 189 kt (~217 mph).
That is quite an interesting observation that the eye is very subtly hexagonal - I can kinda see it too, but I’m not sure if it’s a product of the way the image is framed or not. Is there any other examples of TCs on Earth exhibiting this odd shape? I can point to Saturn’s North Pole as the only example off the top of my head I can think of, and that one is A) not the eye of the storm, and B) on Saturn, which has a completely different engine running the storms (heat from within the planet). If anyone hasn’t seen this image, it’s not only super interesting, but also not fully explained yet by science as far as I’m aware:
Also, don’t want to derail too far off this thread, but I found this very intriguing.
Yet, typical AI nonsense. My point in posting it was not to say trust it, but to say even AI knows that's the dropsonde from hades.
(looks like it just didn't properly assume where the lines were breaking - the 234 it mentioned was at 916.
917mb 190° (from the S) 189 knots (217 mph)
916mb 195° (from the SSW) 203 knots (234 mph)
915mb 195° (from the SSW) 189 knots (217 mph)
This might be what you were mentioning....233 mph at 300 ft above the surface:
WeathermanLeprechaun
Member
Had a feeling it would be, that inner eyewall was incredibly vicious over Crawford and i just knew he must've been experiencing some incredible winds there. That screeching is typical with high end TCs, but i had to turn my volume down because ouch, Melissa made it horrific to listen to. Can't imagine what they felt like in the hotel....
OHWX97
Member
That really says a lot coming from a man who has endured Typhoon Haiyan in Tacloban City and Hurricane Dorian in Marsh Harbor.
In his account of the damage, he specifically states that some wooden structures have been swept from their foundations, as well as some collapsed concrete structures, landscape stripped bare. Horrifying stuff.
WeathermanLeprechaun
Member
Yeah, it really does show how intense Melissa was even to top those two, which he got some incredible footage of too.
Melissa's inland damage is the most impressive i have seen from a hurricane, it's just very hard to replicate the devastation it's left. I have no doubt this thing was at least a 195-200 mph hurricane, the dire scenario i had in mind, it overperformed. That stall helped it a awful lot with water depth and as it surged northward, plenty of mesoscale boosted it further and we just seen a absolutely upper echelon evolution..
About 40 seconds in on this youtube of the vis sat of Katrina, you can watch her do that all day long the day she peaked. I was watching it, and when we would get new visible images that day, each one had interesting angular geometry along with the circular. It was odd.
Patricia did it too. I'll have to see if I can find that on imagery.
Have you ever seen the demonstrations where they vibrate a plate and the resonant frequencies align the grains into shapes? I believe the science says a similar resonance process is happening here. Vortex Rossby wave resonance explains this pretty well, but explaining VRWs is a little tricky. A vortex Rossby wave is a ripple of vorticity or spin that travels around the eye. They exist because of the difference in speed between the calm eye and the eyewall. Most would be like plucking a guitar string - "vibrate" and then dissipate. But when those waves are matches up with certain conditions - much more likely in a strong hurricane - moving in the same direction, same speed - they can resonate and reinforce each other instead of cancelling out. Like the grains on the plate in those demonstration, the wavelength can fit the "loop" of the eye and build a standing pattern - an arrangement of stronger and weaker vorticity lobes around the eyewall. At pretty strong but not ridiculous levels, those appear as the mesovortices you see in the eye - those small swirls that orbit around in the close up visible satellite shots. In extreme storms like Katrina and Melissa (and perhaps in the storm on Saturn to an extreme level) - what we are seeing is the VRW resonance organizing the whole eyewall into a polygonal rotating shape. Thus the hexagons.
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