Regarding CAPE

[Spinosaurus75DinosaurFan]

Brought up before here by Graf, but not a lot of people responded.

How exactly do we decide what instability to use for CAPE? As a calc group member myself, I do not understand how to choose the instability at all up to now. What exactly shows that the cloud has weak, moderate or strong instability? What value should we use? I think it is pretty confusing for users, as I see most calcs just randomly assume a "reasonable" value.

 

[DMUA]

sees this thread

if this is another forking revision-

it's fine

Oh

Well, I don't think there's much to say honestly. But, generally, a weak storm shows no sign of thundering, but it does make the sky dark and maybe rains. Moderate storms do have some lightning, but it's few and far between. Strong storms have frequent thunder and are quite violent.

That's my general understanding.

 

[Antoniofer]

Welp, I do not tend to make storm calc that much, the only cases are for thunderstorm, rain with lightning, but nothing beyond that, in wicj it was suggested to me to use 4k J/kg

 

[Spinosaurus75DinosaurFan]

So we just assume strong instability? Also what the heck are those 2 values for the tornado outbreaks? When are they used?

 

[DMUA]

Well, usually you'll use strong because the storms are rather severe, but, if it's not nearly as severe, it's more fitting to use a lower value.

Also, the tornado outbreaks are for when it's so unstable it creates a tornado.

 

[Spinosaurus75DinosaurFan]

So...

Low instability = a dark cloud and some rain

Moderate instability = some lighting

Strong instability = a lot of thunder

That should be included on the page if that is the case.

 

[DMUA]

Yeah, probably.

 

[Antoniofer]

So we just assume strong instability? Also what the heck are those 2 values for the tornado outbreaks? When are they used?

I didn't assume it, but the times I used the method I worked with that value. if I'm not mistaken, there's a few references in the CAPE (or its equivalent) page.

 

[Amelia_Lonelyheart]

I don't know any formal method, I just try to go for education, conservative guesses and see if others are fine with my assumption, but my answer is more or less the one Spino posted above.

 

[Spinosaurus75DinosaurFan]

If what DMUA said is correct, I believe that should be put in the standard storm calculation page.

 

[Therefir]

Yeah, this should be mentioned somewhere in the storm page.

 

[Mr. Bambu]

Generally one just eyeballs it. Personally...

• If it is just a normal storm with nothing particularly violent about it, I use Weak Instability (1 kJ/kg)

• If it is a somewhat typical storm but presents lightning or other more dangerous effects (such as high-speed winds or visibility-reducing rains or whatever), I use Moderate Instability (2.5 kJ/kg)

• If it has a clearly violent nature, with monsoon-level winds or similar, damage to buildings, multiple lightning strikes at once, or something similar, I use Strong Instability (4 kJ/kg)

• If the storm has spawned after effects such as tornadoes, hurricanes, tsunamis, etc, then I use the value for the Tornado Outbreak (5.89 kJ/kg)

• If the storm is stated to be stronger than most known storms or has feats of simply leaving behind paths of destruction, I will use the Plainfield Tornado Instability (8 kJ/kg)

 

[Antvasima]

What do the rest of you think about Mr. Bambu's rule of thumb? Should we write it down somewhere?

 

[TataHakai]

Mr.Bambu's looks good and should probably be added to the storms page.

 

[Antvasima]

Okay. Thank you for the evaluation.

 

[Spinosaurus75DinosaurFan]

Bambu's look good.

 

[Antvasima]

Okay. Thanks.