Topic: Conditions Resulting in Thunderstorms

[Jimmy Deguara]

Mike,

Without photographs it becomes rather difficult to visualise what you mean.

Are you referring to a base structure like this?



or



Regards,

Jimmy Deguara

[Mike]

Is difficult to visualise i know, but i was at work having a break outside.  The cloud formations weren't as the photos.  The best was to describe it would be fairly fat CU with flat blue/grey base, medium sized core with definite 'bubbling' or rising of the tower with what looked like an inflow finger on the left hand side of the base and below a wall cloud (or close to it!) - of a definiative shape, gradually lowered and the base of that fanned out slightly and then rose up into the base once the towers were bent to the left.  It was like a thunderstorm in its early stages before it anvils out and dissipates due to weakening...beats me - it just looked pretty neat considering....

MO

[Shaun Galman]

Hi guys,

Mike: Good to hear your seeing some nice storm structures up there! Do you have the means to keep a small digital camera with you at all (though these days some of the small cameras rival the lager non-SLR versions!) I'm in the same boat as you, as far as not having any means to catch anything interesting that may show up while I'm out at work? I have my Mob. phone camera but it just doesn't cut it lol.

Jimmy: Just a quick question for you- In that first (top) reference picture you've posted, is that lower base cloud structure still class-able as lenticular even though it is under the higher cloud features, anvil, towers and inflow bands and such? Ive seen similar structured cloud under storm bases before and I've always been curious about it?

Cheers and thanks for your time
Shauno

[Mike]

Hey Shauno.  Bit early for storms, but just a bit of convective stuff that puffed up as the transition period is taking its steps towards the buildup period and more instability later down the weeks ahead.  Signs are good for an early wet by what BoM says in their MJO and SOI reports - fingers crossed.

MO

[Jimmy Deguara]

Shaun,

Jimmy: Just a quick question for you- In that first (top) reference picture you've posted, is that lower base cloud structure still class-able as lenticular even though it is under the higher cloud features, anvil, towers and inflow bands and such? Ive seen similar structured cloud under storm bases before and I've always been curious about it?

I would say it is some sort of lenticular or capping type of cloud that has developed under the large cumulus feature.

Regards,

Jimmy Deguara

[Shaun Galman]

Hi guys,

Signs are good for an early wet by what BoM says in their MJO and SOI reports - fingers crossed.

Sounds good Mike! I hope you can get some great shots to share with us this year!

Shaun,
I would say it is some sort of lenticular or capping type of cloud that has developed under the large cumulus feature.
Regards,
Jimmy Deguara

Thanks Jimmy, much appreciated! (It was just one of those weird little curious questions that pop up now and again?)

Cheers and take care.
Shauno

[supercellwish]

Now Thats funny!!! Then again we were all noobies once, Hell (compared to some of these guys (veterans)) i still am lol

QUOTE(2) Jimmy mentioned that LIs less than -6 or lower there would not be much storm potential, yet other forum members said they go by LI of -3 at times?  I don't get it.  Is it the higher the LI the better potential for storm activity, is that it?END QUOTE

If other Variables are in order you can have lighting (hence thunder) -1 or zero even, though unlikly especially in the current climate.

So what im getting at is: You can potentially get Thunderstorms with any negative Value. The more Negative the stronger the updraft. (Up draft is lotsa air going up lol) oh yeh LI is short for Lifted Index. But yeh most people will tell you if its not more negative than say -2 or -3 you prolly shouldnt bother, though -3 is certainly getting there. One day check out the Tornedo ally Lifted index in the US. They must have masive updrafts.

I think maybe it depends where in Aust your chasing too. When I lived in SE qld, during like 2002 to 2004, there were regularly storms that only had LI's of -1, or -2. on the GFS charts

I also find that the more CAPE the more lightning, but im sure I'll be told this is not necasarily the case. You can potentially have lightning with CAPE values of as little as 100. 9if all other variables are good) with 100 CAPE you may get 1 to 5 Strikes per minute. But for as decent lightshow you really need upwards of say 700. With values in the thousands mother nature really tendss to turn it on. The lightning that is.

***NOTE***You shouldnt take what I say too seriosuly as Im very lay indeed with Storm chasing. So just use what I said as a guide a bit.

One day I am going to write a book that shows primary school children how to forecast a thunderstorm. I may even contact the "for dummies" assoc and see if I cant write a "storm Chasing 'for dummies' book. Just ill need to get a little more educated on general meteorology so as not to lead these poor kids astray with crap. Im also a chronic procrastinator, so Unless someone beats me to it, it may never happen by me... hint hint nudge nudge anyone?!?!?  anyone wanna colaborate. Id be a good person to do it with. If I cant understand it no one can lol

[Jimmy Deguara]

Hi Supercellwish,

That quote of mine is now a double misquote or misinterpretation. I recall correcting the last person on that one.

In terms of LI or Surface lifted Index for those browsing this forum for the first time represents a measure of estimating the instability of the atmosphere. Thy are derived from soundings or models but are just a good measure of what potential exists. Obviously, there are other factors in play as well to consider which includes moisture depth that could contaminate some soundings if too shallow, the trigger to set things off in the first place, and heating. The more dynamic the atmosphere, the more potentially severe the storms can get.

I hope this summary places you on the direct path to understanding. Try reading other threads in this forum and you will find out more.

Regards,

Jimmy Deguara

[Mike]

  Hi there Supercellwish.  Long post but i feel some valuable info for you re your book.

Here's a table of what Lifted Index values are:

2 or greater (stable) (+ values)
1 to 0 (almost unstable)
-1 to -4 (troposphere marginally unstable)
-4 to -7 (large instability)
-8 or less (extreme instability)

As I have found out recently you can have massive CAPE and moderate LI numbers but no cloud whatsoever!  There's several elements Mother Nature needs to spark convection properly, without one or the other you'll get zip.

Re your book:

Mr recommendation would be that if your'e writing something for younger folk I would not bother with adding technical stuff  as in LI index numbers as it will only confuse them more - and if you want to keep it in layman's terms use the KISS method - Keep It Simple Stupid (of course not directed personally!).  You can probably use CAPE (Convective Available Potential Energy) as this is the basis for storm type and character.  If you're handy with computer software graphics use simple pics for how storms form - but make your own designs. 

Simple wording without too much technical stuff, but if your book is on storm chasing for dummies you will need to add the techno stuff - it's the fundamentals of storm structure and if you don't include it they'll be missing the point of it all. If your age bracket is aimed at older folk - say 14 upwards you could most likely add the technical stuff because if they're looking to have a career in Met then it would be beneficial. 

Remember to have your book set out in stages, a beginning, a middle and an end.  Keep specific topics within their chapters for ease of reference.  If you use any websites or books as reference make sure you acknowledge them between sentences or on the last credit pages of your book.  Email prospective authors of these resources if you want to use any of their text/graphics - very important you do that because of copyright laws.  I've found that most authors are quite happy to let you do it so long as you ask first.  Because you intend of selling your work for profit it makes it even more important to ask - the best thing is to use your own words and modify references to your own explanations.

The resources within this forum on cloud types, observation are vast so check them out.  You could also visit http://downunderchase.com/storminfo/ which has a comprehensive area on soundings and all the how to's - it's easily worded and is a valuable resource.

Once you get a handle on how things work re storms it will be easy.  Keep things easy for yourself, if you can't undertand it how will anyone else reading your book!  Take your time and make changes.  Read and re-read your work even when you think it's finished, you may have missed something or want to add things.

Printing your book will depend on your budget.  As I'm in the printing game of sorts workwise, go for an A4 sized booklet or smaller. Much like a coffee table type book.  Something that is easy to handle, durable.  The type of paper you decide on, whether you want shiny, matt, gloss.  How many pages?  All these factor in the cost.  Do you want it binded or stapled?  How many photos/graphics? 

First thing you need to do is this:  Make a mock copy of your book with cover, text, photos, graphics and a front/back cover.  Then once you have done take it to a printing business (there's hundreds) and show them what you've done.  They'll work with you re layout, paper, sizing, what they can and can't do and give you a price. What is your market?  Sale price of the book?  Where will you have the book for sale?  Commission prices to those establishments who sell your book - what percentage?  It's not so simple huh!!!!?

 I know I have been quoted to produce my own 30 page photographic storm book in Darwin in A4 size with satin pages for around $3-4,000 with a run of say 5000.  It's not that expensive and you can tailor your book to suit your budget.

Making the book is the easy bit but there's other things to take into account on getting your dream off the ground - but you've started so keep going. You sound like you have a passion so follow it, you won't be dissappointed if you follow through.

If you need a hand with setting the text out i'll give you some assistance with grammar, spelling and the like - as a court typist also it's all i do (boring!!)

Best of luck.

Mike

[supercellwish]

Thank you mike. Jimmy. I really do understand CAPE and LI. I have had it explained quite a few times, a few years back. Also jimmy, I didnt mean to make it look like I was quoating you. Actually I was trying to make it look like I recogocnised the fact that you said no such thing and that it was incorrect. I was actually trying to just add my thoughts and experinces (even if only few) to the topic. I thought maybe one noob would understand another nube beter than a nube would understand a veteran. It would see that not only do noobs not understand veterans, but vets seem to not understand noobs. LOL. So yeh in effect I belive I did not actually quote you, but quoted the person who quoted you. You actually said no such thing. It was a post right before or after yours. And the bloke who miss quoted/understood Just got the nic mixed up because somebody actually did state that you cant get storms unless you got -6 Li which even I know is inccorect to say the least. So I was actually trying to make a bit of a Joke out of it.

Moving along now to Mike, thanks heaps for you tips there. I have copy pasted that into my personal documeants folder on my file/webserver for later when I begin the book. I want to go through another season of chasing first I think before I set about writing the book. So come may 2008 when the weather (I like) has gone. Il begin writing, drawing etc, oh yes and researching. Not a single line will be printed or proposed for printing untill its beeen tripple checked for accuracy by some chasers and Met men respectively. Also it will be for teens upward. Im sure theres plenty of books with pictures and brief descriptions. I want write a handbook, or manual. So yes I would love for you (or anyone else) to help me with spelling and grammar as I am hopless with it. Sometimes though its just because i type faster than I should and end up hitting wrong keys, then out of pure laziness I fail to check or correct my spelling. Though this really is limited to forums and Instant messaging. no excuse I know lol. So thanks again friend

Oh one more thing, Did I get somthing wrong when I was explaining to what his name about CAPE and Li?

Happy Chasing Guys.

Hopefully I will be seing some lightning off of Cape Otway Vic tommorow afternoon/evening /Based on the 06Z GFS Run looking at the 03z image of Vic CAPE and Li. 03Z fri 1000mb CAPE and LiftX
Click on that to see the same image im looking at. That was the lates run at the time of typing this. Im not very good at looking at Skew-t's and understanding them, but from the guides of been reading around here over the years I cant tell they are imperative. So it looks like there is plenty of Windspeed var with heaight but not alot of change in dir. My main dilema is could there be lightning earlier than say 03z , I was thinking (hoping) that because the air is so cold, their might be significant temp variation between the ocean and the air. Am I on the right track? So I though maybe even though the sun has not yet cooked the clouds the o0cean may provide enough energy to throw some sparks my way. I have seen Lightning predominately over the ocean in the last 4 months. Some of which has not even begun firing untill the early hours of the morning. I guess what im really asking is: Is there any difference between the nocturnal cooling mechanisms on land or out to sea?

I dont supose any one knows somebody whos got a boat going 200k off the SW vic coast do they lol, could be real nice out there hehe. But Gee Wiz it wil be cold lol

Thanks heaps fellas, you are all my heroes Happy Chasing!!!

[Antonio (stormboy)]

Going back to the occluded supercells do they also get known as cumulonimbus that develop an anvil and the anvil separates from the main storm and repeats a few times?

storm boy

[Jimmy Deguara]

The occlusion process refers to the gradual separation of an updraft no anvil. As a tornado or mesocyclone wraps rain, it gradually cuts off the warm moist air supply and gradually the updraft shrivels from the mature storm. With cyclic supercells, this process can occur several times as new updrafts dominate and other updrafts separate from the main storm. (I guess this makes supercells a family of the multicell family in some respects although the dynamics and process taking place are different).

Perhaps search the occlusion process.

Regards,

Jimmy Deguara

[Antonio (stormboy)]

Ok thank you for the information Jimmy. By the way what does it mean when you do look at a developing cell and the cumulonimbus or anvil decides to disconnect from the main cell?"

[Jimmy Deguara]

Stormboy,

Storms in their natural process go through stages - the developing stage, the mature stage and the dying stage. A supercell's dynamics is fairly complicated to explain in detail with the lack of time I have because a lot of favourable conditions must come together. I would suggest do a lot of reading on supercells right around the internet and brush up before even attempting to fully comprehend what what processes lead to cut off updrafts and tornadogenesis as well as cyclic mesocyclonic behaviour.

Generally though, it is believed all storms have more than one updraft and they are in different stages of development. In supercells, the most mature stage will have the strong tornadoes and these go through the rope out stage when the updraft occludes or goes through the stage of being cut off from the rest of the storm and eventually shrivels up.

As a case study, take for instance the event on May 12 2004. David Croan and I were top the east of the supercell that exploded and began to produce tornado after tornado - we captured 5 tornadoes including spinups. Three of those tornadoes were quite strong and you can see the sequence in these set of photographs:

http://www.australiasevereweather.com/photography/photos/2004/jd20040512.html

Just for an illustration of what an occlusion looks like, check out tornado 1. You can see the base is ragged and the inflow cut is beginning to separate the tornado and its attached base from the rest of the storm above us.









Also check out the longer lasting tornado 2:















Even though the occlusion process is well under way by this last photgraph of this tornado, this is a better example where you can see the tornado is losing vertical tilt and becoming narrow. It roped out not long after this photograph. Also again you see a higher base and the cut off occurring.



Regards,

Jimmy Deguara

[Antonio (stormboy)]

Those are some nice shot of a tornado above Jimmy. Are they recent? And also are you still chasing in America? Also thank you for the brief description above. I will browse the web and look further into the definitions of the super cells as well as development stages.

Storm boy.