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Old 06-16-2019, 11:55 AM   #25366
Fabri91
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A fine day for a bike ride.
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Old 06-16-2019, 03:49 PM   #25367
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Another day to prove: Tornadoes are created on the surface, not in the clouds.

We have a beautiful funnel cloud moving through the region in almost calm air today.

https://www.news38.de/braunschweig/a...OL6zsH9SmBPqZc

The cause is a stationary front passing through the region, it is just a few kilometers south of my place.
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Old 06-18-2019, 02:23 PM   #25368
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Yep, it's been a few wild days for severe weather in Central Europe. Normally, the one forming due to a stationary front would be of the landspout variety, but yes...while I wouldn't go as far as saying they form from the ground up, it's almost always stuff in the lower-most inflow layers in surface-based storms that kicks up the feedback loops leading to tornadic formation. I've been a storm spotter for over 10 years now, seen a few funnels, but I still find it hard to wrap my head around the whole thing.

Even with supercells, having a deep rotating updraft and the RFD kicking in surely helps, but even so, not all produce even if all the conditions are met. Packs of more buoyant air, as well as local air currents producing low level shear due to the topography might form the initial vortex, which then gets picked up and stretched, or integrated, in the bigger circulation.
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Old 06-18-2019, 04:43 PM   #25369
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Quote:
Originally Posted by steph View Post
 Yep, it's been a few wild days for severe weather in Central Europe. Normally, the one forming due to a stationary front would be of the landspout variety, but yes...while I wouldn't go as far as saying they form from the ground up, it's almost always stuff in the lower-most inflow layers in surface-based storms that kicks up the feedback loops leading to tornadic formation. I've been a storm spotter for over 10 years now, seen a few funnels, but I still find it hard to wrap my head around the whole thing.

Even with supercells, having a deep rotating updraft and the RFD kicking in surely helps, but even so, not all produce even if all the conditions are met. Packs of more buoyant air, as well as local air currents producing low level shear due to the topography might form the initial vortex, which then gets picked up and stretched, or integrated, in the bigger circulation.

I think this recent research is very impressive, especially since the problems of creating a tornado in a simulation show that the mechanism must be some kind of chain reaction. Even just compiling the simulation code again with a different version of the same math library is enough to switch a simulation run from EF4 to nothing. At a 30m grid the trigger for a tornado must be something taking place at the least-significant bits of a floating point number.



http://orf.media/


Especially, he speaks my language as a CFD kind of guy - those things like vorticity and procession of vortices makes sense to me and I can point at them in thunderstorms.


In his most recent presentation, he also shows with simulation data, how the tornado is triggered on the ground, showing a sudden increase in vortex stretching (dw/dz) low on the ground.



And it seems like the RFD isn't really as important for the tornado as classic tornado research claims. Things look different if you can make the invisible wind visible.
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Old 06-22-2019, 08:48 PM   #25370
Matias Saibene
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Question I can't login in to Orbit Hangar Mods

Hello everyone. I have not used Orbiter (and Orbiter-Forum) for a long time and that's why I'm a bit confused. Is there a problem with Orbit Hangar Mods? I can not log in with my Orbiter Forum account. The site also has an unknown error shown at the top of the page.


My browser is Opera 60.0.3255.151, OS Manjaro GNU/Linux and Windows 7.


I did not want to start a new topic for such a short question, so I posted it here.

Greetings to all.
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Old 06-22-2019, 09:09 PM   #25371
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Quote:
Originally Posted by Matias Saibene View Post
 I can not log in with my Orbiter Forum account.
Your Forum account is not supposed to work for the Orbiter Hanger as well. My account certainly does not work either as I would expect.
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Old 06-22-2019, 09:15 PM   #25372
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Quote:
Originally Posted by Matias Saibene View Post
 Hello everyone. I have not used Orbiter (and Orbiter-Forum) for a long time and that's why I'm a bit confused. Is there a problem with Orbit Hangar Mods? I can not log in with my Orbiter Forum account. The site also has an unknown error shown at the top of the page.


My browser is Opera 60.0.3255.151, OS Manjaro GNU/Linux and Windows 7.


I did not want to start a new topic for such a short question, so I posted it here.

Greetings to all.

No, this should work - but the Hangar is struggling a bit due to some recent essential maintenance works.


I'm looking into it.


Quote:
Originally Posted by Marjin
 Your Forum account is not supposed to work for the Orbiter Hanger as well. My account certainly does not work either as I would expect.

It should do - Vash linked them some years back, so you would log in with a Forum account. You can still log in with older accounts on the Hangar from before the link, but you can't register a new one.
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Old 06-22-2019, 09:35 PM   #25373
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Ok, thanks for making that clear.
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Old 06-22-2019, 10:24 PM   #25374
Matias Saibene
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Thumbs up

I also want to comment that sometimes Orbiter-Forum tells me Error 500 when I try to access my user profile (https://www.orbiter-forum.com/member.php?u=9882).

Quote:
Originally Posted by Xyon View Post
 No, this should work - but the Hangar is struggling a bit due to some recent essential maintenance works.


I'm looking into it.





It should do - Vash linked them some years back, so you would log in with a Forum account. You can still log in with older accounts on the Hangar from before the link, but you can't register a new one.
Thank you for your quick response, I can imagine that maintain a server and two web pages can't be easy, so your work is appreciated keeping everything running for many years. I known O-F since 2012 and it is excellent.

Greetings.
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Old 06-24-2019, 07:05 AM   #25375
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A WW2 bomb just exploded in a field near Limburg last night, at 4 AM local time. Created a 10m wide and 4 m deep crater and caused a magnitude 1.7 earthquake
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Old 06-24-2019, 07:45 AM   #25376
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In a way, it's amazing that the chemicals powering the reaction haven't leaked/degraded in all this time. Makes me think of the few broken arrow incident (and sunken subs) where they haven't recovered the nukes. But then again, the complexity of a nuke should also mean that an impact would screw up the mechanism enough that you get at most a fizzle. It would only be logical that the classical ones are designed to blow pretty much no matter what (hence the late detonations) and a nuke only has a very specific chain of triggers that could make it go off.

Edit: shouldn't the natural decay of the uranium render them incapable of criticality after a few decades?

Last edited by steph; 06-24-2019 at 08:02 AM.
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Old 06-24-2019, 10:28 AM   #25377
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Quote:
Originally Posted by steph View Post
 In a way, it's amazing that the chemicals powering the reaction haven't leaked/degraded in all this time. Makes me think of the few broken arrow incident (and sunken subs) where they haven't recovered the nukes. But then again, the complexity of a nuke should also mean that an impact would screw up the mechanism enough that you get at most a fizzle. It would only be logical that the classical ones are designed to blow pretty much no matter what (hence the late detonations) and a nuke only has a very specific chain of triggers that could make it go off.

Edit: shouldn't the natural decay of the uranium render them incapable of criticality after a few decades?
Nope. The primary isotopes used in nukes are U235, which has a half life in the hundreds of millions of years, and Pu239, with a half life around 24,000 years. Neither will be significantly depleted by decay within decades. It takes about 300 years for Pu239 to be depleted by even 1%. For U235, that will take 10 million years.

---------- Post added at 10:28 ---------- Previous post was at 10:19 ----------

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Originally Posted by Urwumpe View Post
 A WW2 bomb just exploded in a field near Limburg last night, at 4 AM local time. Created a 10m wide and 4 m deep crater and caused a magnitude 1.7 earthquake
Not a controlled detonation of a known bomb? Farmer Hans is just minding his own business, and then his wheat field gives him an abrupt 4 AM wakeup call?
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Old 06-24-2019, 11:54 AM   #25378
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Quote:
Originally Posted by Linguofreak View Post
  Not a controlled detonation of a known bomb? Farmer Hans is just minding his own business, and then his wheat field gives him an abrupt 4 AM wakeup call?

As long as you ignore the bag of blasting caps in his back pocket. I mean, less faffing around if it goes off 'by itself' at 4 in the morning.
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Old 06-24-2019, 01:45 PM   #25379
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Quote:
Originally Posted by Linguofreak View Post
 Not a controlled detonation of a known bomb? Farmer Hans is just minding his own business, and then his wheat field gives him an abrupt 4 AM wakeup call?
No, it was not even known that there was still a bomb left. It simply exploded.

https://www.fnp.de/lokales/limburg-w...-12660945.html

About 500 lb heavy, according to experts. It exploded not far away from the main road in that region, I already drove by the location a few times.

And now we also have two Eurofighters that collided midair over Mecklenburg-Vorpommern. One ejected pilot found, the other is still missing. The crash sites are 10 km apart.

https://www.tagesschau.de/inland/eur...sturz-101.html
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Old 06-24-2019, 02:46 PM   #25380
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Are there many of these "spontaneous" explosions?
Any idea what it was aimed at, any airfields or factories nearby?

N.
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