LIGHTNING STRIKE PROBABILITY
 

Parallax wrote:
(JAXAshby) wrote in message
...
pair of lox, a 5% chance of getting hit = a 95% of NOT getting hit.
snip
I am pleased to see that JAX can multiply. However, my analysis
assumes a LONE sailboat (or other tall object).

JAX multiplying------ what a horrible thought ;-)

LIGHTNING STRIKE PROBABILITY
 

LIGHTNING STRIKE PROBABILITY
 

pair a lox, wanna tell us again about your EE degree in physics? your estimate
does not match up with the math you use to portray your estimate. fine EE you
are, and in physics yet.

btw, if 4% to 20% of all sailboats mooring in the State of Florida get struck
by lightning each year, no insurance company on the planet would insure any
boat in the State of Florida without a HUGE increase in premium as compared to
the State of Georgia or the State of Alabama or the State of Texas of the State
of ...


The Florida Sea Grant Programs paper "Lightning and Sailboats"
estimates that between 4% and 20% of sailboats moored in FL get struck
each yr. Mooring is very close to the case of being a LONE sailbaot I
describe. This is well in accord with my estimates.

Various web sites show the FL strike desnity being 10-30 strikes/km^2.

A LONE tall tree with 5%/yr chance of being struck could live at least
15 yrs having less than 50% chance of being hit. Note that in Central
Florida, there are few tall hills and fewer with lone tall trees.

My analysis appears to be correct.

LIGHTNING STRIKE PROBABILITY
 

LIGHTNING STRIKE PROBABILITY
 

pair of lox, you are stupid beyond words.

tell us again about your double E in physics.



(Parallax)
Date: 7/11/2004 9:00 PM Eastern Daylight Time
Message-id:

(Parallax) wrote in message
.com...
(JAXAshby) wrote in message
...
pair of lox, a 5% chance of getting hit = a 95% of NOT getting hit.

A 5% chance of getting hit = .95 times .95 = a 90% of NOT getting hit
even
once EITHER time in two tries.

a 5% chance of gettting hit = .95 times .95 times .95 times .95 = 81% of
NOT
getting hit even once in FOUR tries.

by 8 tries the chance of NOT getting hit is only about 2 out of 3, by 14
tries
there is a better than even chance of being hit **AT LEAST ONCE**. by 30
tries, the chances of being hit at least once are 4 out of 5. by 50
tries,
chances of being hit at least once are greater than 15 out of 16. by 70
tries,
32 out of 33. by 90 tries, greater than 99 out of a 100.

that oak tree standing on the hill would be toothpicks by the end of the
second
season.

Understand that in central Florida they receive more than 100 electrical
storms
each year. a 5% chance of getting struck would mean central Florida has
never
had trees.



How do you define "effective" area?
Your equation assumes that any lightning within the effective area of
your
boat will strike your boat. If that were the case I'd be very afraid.

"Parallax" wrote in message
om...
Out of curiosity, I did a quick back of the envelope estimate of the
probability of a lone sailboat getting hit by lightning in a
thunderstorm.

...

I found a web site that gave a strike rate of about .5 strikes/km^2/yr
but they did not say where they measured this. However, this means
that a lone sailboat with a mast 17 m tall would have a .35% chance
each yr of getting struck. This is an ideal situation though and may
not address the situation of a sailboat under a thunderstorm where the
strike rate/km^2 is hundreds of times higher. Because I know that the
strike rate in Fl is much higher than average, I'd want to double the
strike rate they give to be about 1/km^2/yr. This gives about a .7%
chance each yr of getting hit. Again, this does NOT address the
situation where you know the strike rate is much higer than average
(sitting under a storm). Based on math and observed strike rate, I
still think my estimate is good.








The Florida Sea Grant Programs paper "Lightning and Sailboats"
estimates that between 4% and 20% of sailboats moored in FL get struck
each yr. Mooring is very close to the case of being a LONE sailbaot I
describe. This is well in accord with my estimates.

Various web sites show the FL strike desnity being 10-30 strikes/km^2.

A LONE tall tree with 5%/yr chance of being struck could live at least
15 yrs having less than 50% chance of being hit. Note that in Central
Florida, there are few tall hills and fewer with lone tall trees.

My analysis appears to be correct.

As an experiment to test whether JAX believes what he says, I propose:

JAX come sailing here in N. Florida in thunderstorms of MY choosing.
He will get a choice of various boats but we remove any grounding
system and replace them with a system where he completes the circuit
across his chest. Prior to sailing (while I remain on shore
videotaping for everyones amusement), he takes out a term life
insurance policy with me as beneficiary for gretaer than the value of
the boat plus $50,000 (I will pay for this policy).
After emerging unscathed from each storm, i will buy him dinner and
pay his hotel bill for the night (we have to have a thunderstorm each
day I pay). After only 11 storms, i will thank him, pay his plane
ticket cost plus $1000 and agree that he is a great sailor. He can
then go back and tell everyone what cowards those Florida rednecks are
and I will agree. Furhtermore, If JAX is worried about sailing in
thunderstorm wind (I am) then he can use a powerboat with a suitably
tall outrigger.

If JAX truly believes what he says, he should jump on this opportunity
to make a fast $1000, get at least 11 days paid for in FL and get to
go sailing for free.

This offer is only good till Sept 10 because then storms start to
taper off in intensity. He must agree to hold me and the boat owner
blameless for any harm that befalls him due to lightning.

So JAX, put up or shut up.

LIGHTNING STRIKE PROBABILITY
 

LIGHTNING STRIKE PROBABILITY
 

On 11 Jul 2004 10:05:27 -0700, (Parallax)
wrote:
... I found a site giving the strike rate for Malaysia and remember
that only two places have a higher strike rate than Central FL,
Equatorial Africa and SE Asia. Malaysia has a strike rate of
25/km^2/yr. I remember that C. FL rate isnt too much smaller than the
highest so I assume 10/km^2/yr and you get (using my effective area)
of a 7% chance/yr of a LONE sailboat getting hit. I find this to be
VERY believable based on experience.
///
I have found web sites calculating strike probability and they all use
a formula similar to mine where effective area goes as the height
squared. However, none i have found specify the factor by wich to
multiply the height to account for electric field modification, they
just qualitatively say it goes as height squared or use empiracaly
derived effective areas.

Here's a possible reason for some lightning estimators using height
squared.

Electric utilities use a cone of protection of 60 degrees included
angle beneath a ground wire.

If one used this 60 degree cone, the surface area "protected" by a
mast, in this case the area at risk, would be pi r squared,
where r is given by mast height X tan 30 degrees = 0.577 X m.h.
so pi r squared is pi X (0.577 X m.h) ^2 = 1.047 X m.h.^2

In other words, mast height squared is a reasonable area at risk
using the assumptions given above.
Then instead of a 7% per annum risk in Tstorms,
the risk is about 0.26% p.a.

Brian Whatcott Altus OK

LIGHTNING STRIKE PROBABILITY
 

pair a lox, you certainly don't let anything let reality interfer with your
proclamations, do you.

pair a lox, wanna tell us again about your EE degree in physics? your
estimate
does not match up with the math you use to portray your estimate. fine EE
you
are, and in physics yet.

btw, if 4% to 20% of all sailboats mooring in the State of Florida get
struck
by lightning each year, no insurance company on the planet would insure any
boat in the State of Florida without a HUGE increase in premium as compared
to
the State of Georgia or the State of Alabama or the State of Texas of the
State
of ...


The Florida Sea Grant Programs paper "Lightning and Sailboats"
estimates that between 4% and 20% of sailboats moored in FL get struck
each yr. Mooring is very close to the case of being a LONE sailbaot I
describe. This is well in accord with my estimates.

Various web sites show the FL strike desnity being 10-30 strikes/km^2.

A LONE tall tree with 5%/yr chance of being struck could live at least
15 yrs having less than 50% chance of being hit. Note that in Central
Florida, there are few tall hills and fewer with lone tall trees.

My analysis appears to be correct.








I am aware that conventional math and physics do not work in JAXWORLD
so will be happy to go over the basic arithematic for anybody.

Concerning insurance, My insurance specifies where I keep my boat.
Long terrm storage on a mooring might nullify it. In N FL, moorings
are not very common. Most boats kept on moorings are lower value
boats so a significant increase in insurance cost isnt likely since a
lightning strike rarely involves any liability considerations. Most
lightning strikes do not sink a boat but they do wipe out electronics.
Experienced boaters in FL normally disconnect their instruments when
they leave their boat for any length of time due to the high
probability of damage from nearby strikes. Statistics show that most
sailboats will eventually get struck or be subjected to a nearby
strike at least once in their lifetime in FL. My own 23' boat once
had its VHF wiped out from a strike on a nearby pine tree, I learned
after that to disconnect the antenna. A review of damage seen by
marine surveyors will show that they commonly see lightning damage on
boats they survey although it is mostly in the form of spiderweb-like
discharge patterns in the glass. The average lightning strike will
produce damage of lower cost than the insurance deductible (remember,
this is only if no ppl involved, ie. at mooring).

LIGHTNING STRIKE PROBABILITY
 

Then instead of a 7% per annum risk in Tstorms,
the risk is about 0.26% p.a.

Brian Whatcott Altus OK


Brian, you confuse pair a lox when you talk rational.

LIGHTNING STRIKE PROBABILITY
 

I'd pay real money to watch that!

--


Keith
__
Giving money and power to government is like giving whiskey and car
keys to teenage boys. --P.J. O'Rourke, Civil Libertarian
" As an experiment to test whether JAX believes what he says, I propose:

JAX come sailing here in N. Florida in thunderstorms of MY choosing.
He will get a choice of various boats but we remove any grounding
system and replace them with a system where he completes the circuit
across his chest. Prior to sailing (while I remain on shore
videotaping for everyones amusement), he takes out a term life
insurance policy with me as beneficiary for gretaer than the value of
the boat plus $50,000 (I will pay for this policy).
After emerging unscathed from each storm, i will buy him dinner and
pay his hotel bill for the night (we have to have a thunderstorm each
day I pay). After only 11 storms, i will thank him, pay his plane
ticket cost plus $1000 and agree that he is a great sailor. He can
then go back and tell everyone what cowards those Florida rednecks are
and I will agree. Furhtermore, If JAX is worried about sailing in
thunderstorm wind (I am) then he can use a powerboat with a suitably
tall outrigger.

If JAX truly believes what he says, he should jump on this opportunity
to make a fast $1000, get at least 11 days paid for in FL and get to
go sailing for free.

This offer is only good till Sept 10 because then storms start to
taper off in intensity. He must agree to hold me and the boat owner
blameless for any harm that befalls him due to lightning.

So JAX, put up or shut up.