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How does a stormscope/strikefinder actually work?



 
 
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  #21  
Old July 19th 04, 05:57 PM
Andrew Gideon
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Peter Duniho wrote:


A developing storm won't necessarily show rain either. Falling rain
occurs during the mature and dissipating stages of thunderstorm
development, and while water droplets may be present during the developing
stage (being lifted by the updraft), there may not necessarily be enough
to show up on radar as a significant storm.


This I didn't know.

I agree that his statement might have meant what you said, rather than
what
I thought it meant.


Frankly, I'm not sure how your interpretations of what I wrote are
different. I think you've both a pretty good grasp of my concern.

But I still don't see how it would imply 'spherics
devices are inferior for detecting thunderstorms.


I didn't write this. I'm trying to find out just how well they work as
avoidance tools, true, but that doesn't imply that I don't like the device.
I don't know enough yet.

Also, while I'm not
positive, if I recall correctly lightning is present in any thunderstorm
where turbulence and strong updrafts are present, regardless of the stage
of development.


From my reading - light yet, I admit - it sounded like lightening occurred
only after the developing stage is well along. It takes time for the
difference in potential to grow enough that discharges occur, as I've
understand what I read.

Did I misunderstand?

[...]

There are certainly "almost thunderstorms" that it's best to fly around.


No doubt...but I haven't seen anything that would suggest a Stormscope or
Strikefinder wouldn't identify those storms.


Wouldn't a strikefinder, by definition, not see a storm that wasn't yet a
thunderstorm?

I liked your idea, BTW, about trying the strikefinder experimentally. I was
up in poor-but-VFR conditions this weekend, and I was trying to do
something of that sort. Isolated t-storms were predicted, so it seemed a
good opportunity.

Unfortunately, the visibility was sufficiently poor and there were enough
clouds around that I couldn't really see much at a distance. There were
strikes showing, but I couldn't match them with anything visually.

Also, nothing was clustering. There were regions with indicated strikes,
but of no major density. If I had to guess, I'd say that my understanding
about the time it takes for discharges to occur is wrong, and this is a
demonstration of "near t-storms" appearing on the strikefinder. Alas, this
really is just a guess.

I've more reading to do, in the meantime.

- Andrew

  #22  
Old July 19th 04, 05:59 PM
Andrew Gideon
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James M. Knox wrote:

Dumb question time. Why exclude cloud-to-cloud? Wouldn't that type of
lightning also indicate conditions one would wish to avoid?


The official answer is "where would you plot it???"


Azimuth: Where the strike is strongest. Distance: Based upon strength.

Aren't these how strikefinders handle cloud-to-ground strikes?

Some of the newer models have a feature that allows you to temporarily
disable the suppression feature. This was in response to pilot requests
(pilots who got tired of seeing a lot of lightning and NOTHING showing up
on the screen).


Yes, well, that would bug me too laugh!

- Andrew

  #23  
Old July 20th 04, 12:19 AM
Michael
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Andrew Gideon wrote
From my reading - light yet, I admit - it sounded like lightening occurred
only after the developing stage is well along.


Depends on what you mean by well along. In fact, on a day with strong
thermal activity, you can actually detect the static discharges from
thermals. They don't fit the models developed for lightning strikes,
and often a thermal that is close will show up as a strike much
farther away.

It takes time for the
difference in potential to grow enough that discharges occur, as I've
understand what I read.

Did I misunderstand?


No, that part is right. But realize that when the activity is strong,
it doesn't take that much time. Basically, by the time there is
enough liquid water for RADAR to see it, there are static discharges
strong enough for spherics.

Wouldn't a strikefinder, by definition, not see a storm that wasn't yet a
thunderstorm?


Not really. Static discharges need not be lightning to be detectable.

Also, nothing was clustering. There were regions with indicated strikes,
but of no major density. If I had to guess, I'd say that my understanding
about the time it takes for discharges to occur is wrong, and this is a
demonstration of "near t-storms" appearing on the strikefinder.


Exactly.

A spherics device won't keep you dry (since it can't see
non-convective rain) but it will keep you out of severe turbulence.
In fact, I've yet to encounter anything worse than occsional light
turbulence while relying solely on the spherics. Moderate turbulence
in clouds is something I've only ever experienced when allowing a
controller with RADAR to vector me through an area I would not have
entered without RADAR assistance.

Michael
  #24  
Old July 20th 04, 06:02 PM
James M. Knox
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"Peter Duniho" wrote in news:10fnu8jacpfvs32
@corp.supernews.com:

The official answer is "where would you plot it???"


What do you mean? You'd plot it where it happens, just as with
cloud-to-ground strikes.

How could that possibly be an "official" answer?


I would have to look, but I think it was in either the manual or a brochure
(FAQ) that came with my Stormscope.
  #25  
Old July 20th 04, 06:13 PM
Andrew Gideon
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Michael wrote:

Depends on what you mean by well along. In fact, on a day with strong
thermal activity, you can actually detect the static discharges from
thermals. They don't fit the models developed for lightning strikes,
and often a thermal that is close will show up as a strike much
farther away.


Ah ha! This is new to me too.

It takes time for the
difference in potential to grow enough that discharges occur, as I've
understand what I read.

Did I misunderstand?


No, that part is right. But realize that when the activity is strong,
it doesn't take that much time. Basically, by the time there is
enough liquid water for RADAR to see it, there are static discharges
strong enough for spherics.


Hmm. Okay.


[...]

Also, nothing was clustering. There were regions with indicated strikes,
but of no major density. If I had to guess, I'd say that my
understanding about the time it takes for discharges to occur is wrong,
and this is a demonstration of "near t-storms" appearing on the
strikefinder.


Exactly.


So what was I seeing? Static discharges from thermals that could grow into
t-storms?

A spherics device won't keep you dry (since it can't see
non-convective rain) but it will keep you out of severe turbulence.
In fact, I've yet to encounter anything worse than occsional light
turbulence while relying solely on the spherics.


In this case, what are you avoiding? Clusters? Any "strikes"? What's your
threshold for "not that way"?

BTW, when you write "RADAR" in making your comparisons here, are you
referring strictly to ATC RADAR? Or are you including airborn and/or
down/uploaded NEXRAD

- Andrew


  #26  
Old July 21st 04, 05:10 PM
Michael
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Andrew Gideon wrote
So what was I seeing? Static discharges from thermals that could grow into
t-storms?


Yes, pretty much.

In this case, what are you avoiding? Clusters? Any "strikes"? What's your
threshold for "not that way"?


Depends on how much turbulence I'm willing to tolerate. If I avoid
all strikes, I never get anything worse than some light chop and
thermal activity. If I avoid only clusters of strikes, and ignore
individual dots, I've accepted some increase in risk, and also
accepted that I'm going to have light turbulence and some moderate
chop at times.

If I'm going for a weak spot in a line - an area with relatively
little clustering - I know I'm in for it. I won't do this kind of
penetration without some sort of RADAR service - either decent ATC
RADAR or following a RADAR-equipped light aircraft, preferably both.
At that point, I slow to Va-10, ask for a block altitude, and strap
in. At that point, I KNOW I'm in a convective area - I'm just
counting on RADAR to take me around the worst of it. I don't do this
when I can avoid it - it's kind of like flying single engine low IFR.
If everything works it will be OK, but do it long enough...

As a last resort, you can always switch to the short range mode and
steer away from any dots that how up in front of you. It works most
of the time, but realize that if you're doing that, you've already
screwed up.

BTW, when you write "RADAR" in making your comparisons here, are you
referring strictly to ATC RADAR? Or are you including airborn and/or
down/uploaded NEXRAD


Actually, NEXRAD is what ATC has these days, and yes, I'm talking
about airborne RADAR as well. By the time there is enough water being
suspended for airborne RADAR to see it - meaning distinguish it from
the surrounding non-convective light to moderate precip - it will show
up on a Stormscope in an obvious way.

See, the real challenge of using spherics (or RADAR) is not avoiding
weather. That's easy. Simply don't go anywhre you see strikes (or
returns). Unfortunately, that doesn't get you where you are going.
The challenge is to ignore the light/moderate turbulence (or precip)
but avoid the cells. That always requires some amount of judgment and
interpretation. How much clustering is acceptable? Depends on lots
of factors. It's never perfect. Unless you always turn away from the
first indication, you are eventually going to penetrate a cell - the
odds will eventually catch up with you. Of course the same is true of
flying single engine IFR.

Michael
 




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