Just what does a 60% chance of rain mean?
dgk
chance of rain falling, or does it mean that there is a 60% chance
that I'm going to get rained on (assumimg that I'm outside)?
I'm not a big fan of biking in the rain, although being around 90F
today I sort of am looking forward to it.
recycled
"dgk" <d...@somewhere.com> wrote in message
news:gvui75pghro1os43j...@4ax.com...
In my experience it means there is a 60% chance that they will change the
forecast just before you leave.
Seriously, it seems every date this summer I penciled in for a ride the
long range forecast switched. I was almost hoping to get thunderstorm
forecasts as I knew by ride time it would have flipped. The only problem was
that the reverse worked too.
Leo Lichtman
"dgk" wrote: (clip) being around 90F
> today I sort of am looking forward to it.
Normal body temp is 98.6F. You may be dying.
Terry Neff
I ran into a story about this a few months back and learned something
new from it.
Apparently it is intended to indicate neither the _percentage of
different locations_ within the named area which are expected to get wet
that day, nor the _percentage of time_ any given location might get wet on
that day. Rather, it is intended to indicate the _percentage of different
days_, each having the same atmospheric conditions, when rain will fall
somewhere within the named area. And apparently then that means that on (100
minus _that percentage of days_) no rain will fall anywhere within that
area.
See:
http://www.sciencedaily.com/releases/2009/04/090414130623.htm
------------ Begin quote from article linked to above:
...new research indicates that only about half the population knows what a
forecast means when it predicts a 20 percent chance of rain, according to
researchers at the University of Washington.
Writing in the Bulletin of the American Meteorological Society, the
researchers said the confusion comes because people don't understand what
the 20 percent chance of rain actually refers to. Many people think it means
that it will rain over 20 percent of the area covered by the forecast or for
20 percent of the time period covered by the forecast, said Susan Joslyn, a
UW cognitive psychologist and senior lecturer.
"When a forecast says there is 20 percent chance of rain tomorrow it
actually means it will rain on 20 percent of the days with exactly the same
atmospheric conditions," she said."
------------ End quote.
dgk
Ok, so all it is telling me is that there is a 60% chance of rain
somewhere in the area. Actually, it has dropped to 40%. I'm very
likely not to get wet, at least by rain.
SMS
What I remember from an explanation I heard a long time ago was that 60%
chance meant that 60% of the area in question would get rain, not that
the entire area had a 60% chance of rain and a 40% chance of no rain.
SMS
> Ok, so all it is telling me is that there is a 60% chance of rain
> somewhere in the area.
No, it means that there is 100% chance of rain in 60% of the area, but
they don't know which 60% that is. So you do have a 60% chance of
getting rained on.
This makes sense if you think about it. Those moving clouds are going to
dump their water somewhere over the area, it's just not clear exactly where.
Frank Krygowski
Frank Krygowski
Wrong.
Frank Krygowski
> Does it mean that somewhere within 100 miles of me there is a 60%
Yes, practically speaking, that's pretty close to it, although the 100
mile radius is too large. Actually, it means 60% of the time the
weather is exactly like this, it's going to rain _somewhere_ in "the
area." I've never found a good definition of "the area" but I'm sure
it's not as big as a 100 mile radius.
> ,,, or does it mean that there is a 60% chance
> that I'm going to get rained on (assumimg that I'm outside)?
Unfortunately, that's not what it means. And it's too bad, because
that information would be a lot more useful!
I've never liked the way they define probability of precipitation.
For one thing, "the area" that a forecast applies to seems poorly
defined, or at least has never been explained to me. What are the
area's boundaries?
For another thing, if (say) the area consisted of one county, and
0.01" of rain fell in only one extreme corner of the county, the
definition allows the weather man to say "See? It rained, just like I
predicted."
- Frank Krygowski
Radey Shouman
> On Wed, 5 Aug 2009 09:17:59 -0700, "Terry Neff"
> <NotARea...@notreal.invalid> wrote:
>
>>"dgk" <d...@somewhere.com> wrote in message
>>news:gvui75pghro1os43j...@4ax.com...
>>> Does it mean that somewhere within 100 miles of me there is a 60%
>>> chance of rain falling, or does it mean that there is a 60% chance
>>> that I'm going to get rained on (assumimg that I'm outside)?
>>>
>>> I'm not a big fan of biking in the rain, although being around 90F
>>> today I sort of am looking forward to it.
>>
>> I ran into a story about this a few months back and learned something
>>new from it.
>>
>> Apparently it is intended to indicate neither the _percentage of
>>different locations_ within the named area which are expected to get wet
>>that day, nor the _percentage of time_ any given location might get wet on
>>that day. Rather, it is intended to indicate the _percentage of different
>>days_, each having the same atmospheric conditions, when rain will fall
>>somewhere within the named area. And apparently then that means that on (100
>>minus _that percentage of days_) no rain will fall anywhere within that
>>area.
[...]
>
> Ok, so all it is telling me is that there is a 60% chance of rain
> somewhere in the area. Actually, it has dropped to 40%. I'm very
> likely not to get wet, at least by rain.
I believe it means that there is a 60% chance of measurable rain at
any given point in the forecast area (it's assumed that the
probability is equal everywhere in the area).
From http://www.srh.noaa.gov/ffc/html/pop.shtml :
The "Probability of Precipitation" (PoP) describes the chance of
precipitation occurring at any point you select in the area.
How do forecasters arrive at this value?
Mathematically, PoP is defined as follows: PoP = C x A where "C" = the
confidence that precipitation will occur somewhere in the forecast
area, and where "A" = the percent of the area that will receive
measureable precipitation, if it occurs at all.
So... in the case of the forecast above, if the forecaster knows
precipitation is sure to occur ( confidence is 100% ), he/she is
expressing how much of the area will receive measurable rain. ( PoP =
"C" x "A" or "1" times ".4" which equals .4 or 40%.)
But, most of the time, the forecaster is expressing a combination of
degree of confidence and areal coverage. If the forecaster is only 50%
sure that precipitation will occur, and expects that, if it does
occur, it will produce measurable rain over about 80 percent of the
area, the PoP (chance of rain) is 40%. ( PoP = .5 x .8 which equals .4
or 40%. )
In either event, the correct way to interpret the forecast is: there
is a 40 percent chance that rain will occur at any given point in the
area.
Fred
"Frank Krygowski" <frkr...@gmail.com> wrote in message
news:b0637054-3578-4c41...@d32g2000yqh.googlegroups.com...
On Aug 5, 8:36 am, dgk <d...@somewhere.com> wrote:
> Does it mean that somewhere within 100 miles of me there is a 60%
> chance of rain falling...
No. It means that after hearing the forecast, there's a 40% chance you'll
stay inside.
Just Plain Burr
"dgk"
>
> I'm not a big fan of biking in the rain, although being around 90F
> today I sort of am looking forward to it.
It could rain on 60% of the road. Thinking from left to right you need to
stay on the right 40% and you should be OK.
Good Luck
Burr
Bill Baka
(F) but if I am riding and hit a cold front and drop to that I can't
ride over 5 MPH. I had to have some bored firefighters pick me up once
when the temperature dropped from 70 to 55 in about 45 minutes and I was
going into hypothermia. I forgot to eat that day and had already done a
lot of miles in the mountains. They just warmed me up, joked with me,
and took me home, no problem since there were no serious calls that night.
Bill Baka
Dan C
> Leo Lichtman wrote:
>> "dgk" wrote: (clip) being around 90F
>>> today I sort of am looking forward to it.
>> ^^^^^^^^^^^^^^^^^^
>> Normal body temp is 98.6F. You may be dying.
>>
>>
> Just for laughs and giggles, I wake up fully functional at 95 degrees
How do you know this, Bill?
> (F) but if I am riding and hit a cold front and drop to that I can't
> ride over 5 MPH. I had to have some bored firefighters pick me up once
> when the temperature dropped from 70 to 55 in about 45 minutes and I was
> going into hypothermia. I forgot to eat that day and had already done a
> lot of miles in the mountains. They just warmed me up, joked with me,
> and took me home, no problem since there were no serious calls that
> night.
Do you *really* expect people to believe bullshit like this? Really?
You actually think you'll go into hypothermia in 55 degrees, while riding
a bicycle?
Quit trying to blow smoke up people's asses, Bill. You're nothing but a
blowhard teller of tall tales, and not even good at it.
--
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Bill Baka
> On Fri, 07 Aug 2009 05:11:29 -0700, Bill Baka wrote:
>
>> Leo Lichtman wrote:
>>> "dgk" wrote: (clip) being around 90F
>>>> today I sort of am looking forward to it.
>>> ^^^^^^^^^^^^^^^^^^
>>> Normal body temp is 98.6F. You may be dying.
>>>
>>>
>> Just for laughs and giggles, I wake up fully functional at 95 degrees
>
> How do you know this, Bill?
I keep a bedside digital thermometer just to see how relaxed I get while
sleeping.
>
>> (F) but if I am riding and hit a cold front and drop to that I can't
>> ride over 5 MPH. I had to have some bored firefighters pick me up once
>> when the temperature dropped from 70 to 55 in about 45 minutes and I was
>> going into hypothermia. I forgot to eat that day and had already done a
>> lot of miles in the mountains. They just warmed me up, joked with me,
>> and took me home, no problem since there were no serious calls that
>> night.
>
> Do you *really* expect people to believe bullshit like this? Really?
> You actually think you'll go into hypothermia in 55 degrees, while riding
> a bicycle?
Yes, moron. I didn't eat that day and was out of useable energy so I was
only barely pedaling at 6 to 8 MPH at 10 P.M. after the sun had left me.
>
> Quit trying to blow smoke up people's asses, Bill. You're nothing but a
> blowhard teller of tall tales, and not even good at it.
>
>
I can't help it you are stupid. Stupid is not curable. Mild hypothermia is.
Bill Baka
D_Frum...@ndersnat.ch
> >> (F) but if I am riding and hit a cold front and drop to that I can't
> >> ride over 5 MPH. I had to have some bored firefighters pick me up once
> >> when the temperature dropped from 70 to 55 in about 45 minutes and I was
> >> going into hypothermia. I forgot to eat that day and had already done a
> >> lot of miles in the mountains. They just warmed me up, joked with me,
> >> and took me home, no problem since there were no serious calls that
> >> night.
> >
> > Do you *really* expect people to believe bullshit like this? Really?
> > You actually think you'll go into hypothermia in 55 degrees, while riding
> > a bicycle?
I've ridden quite a lot at that temperature. I find that 55 is the
point at which I start to need a windbreaker. My particular ride is six
miles, mostly downhill, before sunrise. The couple of times I forgot
the jacket, I found myself shivering by the time I reached my
destination.
> Yes, moron. I didn't eat that day and was out of useable energy so I
was
> only barely pedaling at 6 to 8 MPH at 10 P.M. after the sun had left
me.
If Bill's ride was longer than mine, at a different level of
strenuousness, or maybe the humidity or wind was a little more severe,
or if his metabolism is a little different than mine or had been thrown
out of whack by a lack of ready carbs, I can see how hypothermia could
have ensued.
> > Quit trying to blow smoke up people's asses, Bill. You're nothing but a
> > blowhard teller of tall tales, and not even good at it.
Note to Dan C : If you find Bill Baka's "tall tales" so onerous, I
recommend that you activate your twit filter, or just plain ignore him.
That will free you of the terrible burden of having to endure his posts.
The rest of us will somehow endure without you to police the group for
us.
Personally, I find that most of Bill's posts lie somewhere along a
line between "interesting" and "possibly remembered in an exaggerated
way." Your posts, OTOH, lie squarely on "obnoxious."
Frumious
__o | Profanity and obscenity entitle people who don't
_`\(,_ | want unpleasant information to close their ears
(_)/ (_) | and eyes to you. - Kurt Vonnegut
Mike A Schwab
It means that the forecast location has a 60% chance of getting a
trace of precipitation during the forecast period. Above 55F or so,
getting wet from no salt rain is preferable than sweating from rain
gear.
Tom Keats
dgk <d...@somewhere.com> writes:
> Does it mean that somewhere within 100 miles of me there is a 60%
> chance of rain falling, or does it mean that there is a 60% chance
> that I'm going to get rained on (assumimg that I'm outside)?
It means: if you head out wearing the worst possible
clothing for rain, it's gonna rain. But if you
prepare for rain, it won't.
A 50 % chance means: you stick your head out the door to
check the weather, see that it's raining, and prepare for it.
When you step out, it stops raining. So you go back inside,
prepare for dry weather, step out again, and it's raining again.
Rinse & repeat.
> I'm not a big fan of biking in the rain, although being around 90F
> today I sort of am looking forward to it.
Sometimes folx washing their cars at the curbside are
happily willing to give a rider a refreshing, zesty spritz
from their garden hose, when politely requested to do so.
If there's no lawn-sprinkling ban going on, it can be pleasant
to ride through any sprinkler overspray. Maybe circle back
and do it again. And again.
cheers,
Tom
--
Nothing is safe from me.
I'm really at:
tkeats curlicue vcn dot bc dot ca
Bill Baka
> Bill Baka <bb...@comcast.net> wrote:
>
>>>> (F) but if I am riding and hit a cold front and drop to that I can't
>>>> ride over 5 MPH. I had to have some bored firefighters pick me up once
>>>> when the temperature dropped from 70 to 55 in about 45 minutes and I was
>>>> going into hypothermia. I forgot to eat that day and had already done a
>>>> lot of miles in the mountains. They just warmed me up, joked with me,
>>>> and took me home, no problem since there were no serious calls that
>>>> night.
>>> Do you *really* expect people to believe bullshit like this? Really?
>>> You actually think you'll go into hypothermia in 55 degrees, while riding
>>> a bicycle?
>
> I've ridden quite a lot at that temperature. I find that 55 is the
> point at which I start to need a windbreaker. My particular ride is six
> miles, mostly downhill, before sunrise. The couple of times I forgot
> the jacket, I found myself shivering by the time I reached my
> destination.
If I have food energy left in me I shiver too.
>
>> Yes, moron. I didn't eat that day and was out of useable energy so I
> was
>> only barely pedaling at 6 to 8 MPH at 10 P.M. after the sun had left
> me.
> If Bill's ride was longer than mine, at a different level of
> strenuousness, or maybe the humidity or wind was a little more severe,
> or if his metabolism is a little different than mine or had been thrown
> out of whack by a lack of ready carbs, I can see how hypothermia could
> have ensued.
That is exactly what happened. I forgot to eat breakfast and went for a
long ride with nothing but water. My body was just plain out of reserves
at that point.
>
>>> Quit trying to blow smoke up people's asses, Bill. You're nothing but a
>>> blowhard teller of tall tales, and not even good at it.
>
> Note to Dan C : If you find Bill Baka's "tall tales" so onerous, I
> recommend that you activate your twit filter, or just plain ignore him.
> That will free you of the terrible burden of having to endure his posts.
> The rest of us will somehow endure without you to police the group for
> us.
I post things that did happen to me, and that one was a nearly fatal
hypothermia. I felt like laying in the weeds and going to sleep,
probably never to wake up again.
> Personally, I find that most of Bill's posts lie somewhere along a
> line between "interesting" and "possibly remembered in an exaggerated
> way."
The tricycle at *what felt like 50 MPH* was a child's memory since my
car only coasted down in neutral at 25 MPH. The rest happened in one way
or the other. Climbing the electrical tower I have pictures of with my
Huffy looking like a speck at the bottom. I climbed it merely to take
pictures. I have a few looking down at the million volt wires crackling
around me. At 60 years old and always looking for a new adventure I have
maybe done one of these events per year, which is not a stretch.
Your posts, OTOH, lie squarely on "obnoxious."
Right on the money.
Dan C
Damn the bad luck! Maybe next time.
>
>> Personally, I find that most of Bill's posts lie somewhere along a
>> line between "interesting" and "possibly remembered in an exaggerated
>> way."
>
> The tricycle at *what felt like 50 MPH* was a child's memory since my
> car only coasted down in neutral at 25 MPH. The rest happened in one way
> or the other. Climbing the electrical tower I have pictures of with my
> Huffy looking like a speck at the bottom. I climbed it merely to take
> pictures. I have a few looking down at the million volt wires crackling
> around me. At 60 years old and always looking for a new adventure I have
> maybe done one of these events per year, which is not a stretch.
Let's see the pics, Bill. Post a link to them.
> Your posts, OTOH, lie squarely on "obnoxious."
>
> Right on the money.
>>
>>
>> Frumious
>>
>> __o | Profanity and obscenity entitle people who don't
>> _`\(,_ | want unpleasant information to close their ears
>> (_)/ (_) | and eyes to you. - Kurt Vonnegut
--