I once asked on one of thees two newsgroups what a 40% chance of rain
really meant, and I got good answers.

Today almost by accident I came across
http://en.wikipedia.org/wiki/Chance_of_rain which actually points to
Probability of Precipitation, for people who have more syllables than
they know what to do with.

Anyhow, it's a good clear answer. (although so were the answers I got
here.)

Sorry, put ngs in subject field. But it does explain chanie of rain.



On Sat, 08 Jun 2013 23:35:23 -0400, micky
wrote:

I once asked on one of thees two newsgroups what a 40% chance of rain
really meant, and I got good answers.

Today almost by accident I came across
http://en.wikipedia.org/wiki/Chance_of_rain which actually points to
Probability of Precipitation, for people who have more syllables than
they know what to do with.

Anyhow, it's a good clear answer. (although so were the answers I got
here.)

Here's my answer, before I look at your explanation.

A "40% chance of rain" means that, whenever the current set of meteorological
conditions occurs, it will rain 40% of the time.

--------------------------

I'm not sure I liked the explanation. "For instance, if there is a 100%
probability of rain covering one side of a city, and a 0% probability of rain
on the other side of the city, the POP would be 50%."

This makes no sense whatever. A person about to be precipitated on /has/ to be
on one side of the city or the other. You can't average the rainfall
probabilities, any more than you can average his position (unless he were
small enough to be under the influence of quantum mechanics).

On Sun, 9 Jun 2013 06:21:42 -0700, "William Sommerwerck"
wrote:

Here's my answer, before I look at your explanation.

A "40% chance of rain" means that, whenever the current set of meteorological
conditions occurs, it will rain 40% of the time.

--------------------------

I'm not sure I liked the explanation. "For instance, if there is a 100%
probability of rain covering one side of a city, and a 0% probability of rain
on the other side of the city, the POP would be 50%."

This makes no sense whatever. A person about to be precipitated on /has/ to be
on one side of the city or the other. You can't average the rainfall
probabilities, any more than you can average his position (unless he were
small enough to be under the influence of quantum mechanics).

It's probably spam, spew, or whatever, but I'm bored so...

These might help:
http://www.srh.noaa.gov/ffc/?n=pop
http://weather.aol.com/2013/02/22/what-does-a-40-percent-chance-of-rain-actually-mean/

Note that if the weather forecaster predicts that tomorrows weather
will be about the same as todays weather, they have about a 50% chance
of getting it right as most days are within +/- 3 degrees of the
previous day. That's the generally consider accuracy requirement:
http://www.forecastadvisor.com/docs/accuracy/
Rain is a bit more complexicated:
http://www.forecastadvisor.com/blog/2006/06/02/precipitation-accuracy/

Plug in your zip code and check the accuracy of the weather
forecasting services for your area:
http://www.forecastadvisor.com
If you're seriously into forecasting:
http://www.forecas****ch.com


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sun, 9 Jun 2013 06:21:42 -0700, "William Sommerwerck"
wrote:

Here's my answer, before I look at your explanation.

A "40% chance of rain" means that, whenever the current set of meteorological
conditions occurs, it will rain 40% of the time.

--------------------------

I'm not sure I liked the explanation. "For instance, if there is a 100%
probability of rain covering one side of a city, and a 0% probability of rain
on the other side of the city, the POP would be 50%."

This makes no sense whatever. A person about to be precipitated on /has/ to be
on one side of the city or the other. You can't average the rainfall
probabilities, any more than you can average his position (unless he were
small enough to be under the influence of quantum mechanics).

I haven't linked at Jeff's links yet, but in reply to you. You're
right, except the weather bureau isn't going to give percentages just
for me. They might give for the whole town, and that it ends up
raining on one side of town and not the other does not in itself mean
they were wrong. In fact, in the example above, when they say 50%,
they mean it WILL rain in half the city and won't in the other half.

If you had your own private weather report, as Cape Canaveral has on
the days it might launch a rocket, it will cover a smaller area. But
even if it's only an acre, it might rain on one half and not on the
other half.

The same sort of consideration was imposed on me when trying to decide
whether to get a shingles vaccination. They say 1/3 of people
(Americans?) will get shingles. But am in in the 1/3 or the other
2/rds? I have twice as much chance of being in the 2/3rds, and I
can't be in both. What to do?

If this is actually how they calculate percentage, aren't we stuck
with it?

On Sun, 09 Jun 2013 15:28:42 -0400, micky
wrote:

I haven't linked at Jeff's links yet,

Sniff... I just hate being ignored.

If you had your own private weather report, as Cape Canaveral has on
the days it might launch a rocket, it will cover a smaller area. But
even if it's only an acre, it might rain on one half and not on the
other half.

Ah, but you can have your very own personal local weather report and
forecast with the NWS "Point Forecast". For example:
http://forecast.weather.gov/MapClick.php?textField1=37.081275&textField2=-122.09458699999999#.UbVHONgVRSk
is the forecast for about 4 square miles surrounding my location.
http://www.weather.gov
Just inscribe your address in the search box and click on "get
detailed info. I've been using it for about a year. It works better
than the area type forecasts, mostly because the nearest official
weather station is at the airport, about 20 miles away.

However, there has been one minor change. "Chance of precipitation"
has morphed into "precipitation potential". Don't let it bother you
as they mean the same thing.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sun, 09 Jun 2013 20:34:09 -0700, Jeff Liebermann
wrote:

On Sun, 09 Jun 2013 15:28:42 -0400, micky
wrote:

I haven't linked at Jeff's links yet,

Sniff... I just hate being ignored.

I'm sorrry. I looked at them since I posted and they say the same
thing my link did.

If you had your own private weather report, as Cape Canaveral has on
the days it might launch a rocket, it will cover a smaller area. But
even if it's only an acre, it might rain on one half and not on the
other half.

Ah, but you can have your very own personal local weather report and
forecast with the NWS "Point Forecast". For example:
http://forecast.weather.gov/MapClick.php?textField1=37.081275&textField2=-122.09458699999999#.UbVHONgVRSk

Sleepy now. I'll have to try this later.

is the forecast for about 4 square miles surrounding my location.
http://www.weather.gov
Just inscribe your address in the search box and click on "get
detailed info. I've been using it for about a year. It works better
than the area type forecasts, mostly because the nearest official
weather station is at the airport, about 20 miles away.

However, there has been one minor change. "Chance of precipitation"
has morphed into "precipitation potential". Don't let it bother you
as they mean the same thing.

I hope so. I get upset when there are too many syllables.

Another common practice to be questioned is: what's the difference between
using the expression partly cloudy, as opposed to partly sunny?

--
Cheers,
WB
..............


"micky" wrote in message
news
I once asked on one of thees two newsgroups what a 40% chance of rain
really meant, and I got good answers.

Today almost by accident I came across
http://en.wikipedia.org/wiki/Chance_of_rain which actually points to
Probability of Precipitation, for people who have more syllables than
they know what to do with.

Anyhow, it's a good clear answer. (although so were the answers I got
here.)

On Mon, 10 Jun 2013 11:07:25 -0400, "Wild_Bill"
wrote:

Another common practice to be questioned is: what's the difference between
using the expression partly cloudy, as opposed to partly sunny?

I guess people would say that one is used by an optimist and the other
by a pessimist.

I'm more acquainted with a glass of water half full or half empty.
They always say half full is used by the optimist who looks at the
good part of things, and half empty by the pessimist who looks at the
bad.

But I think it's the other way around. The optimist expects the glass
to be full and notices that it is half empty. The pessimist starts
with the assumption it will be empty and notices that it is half full.

I feel the same about cloudy.

On Sun, 09 Jun 2013 20:34:09 -0700, Jeff Liebermann
wrote:

On Sun, 09 Jun 2013 15:28:42 -0400, micky
wrote:

I haven't linked at Jeff's links yet,

Sniff... I just hate being ignored.

If you had your own private weather report, as Cape Canaveral has on
the days it might launch a rocket, it will cover a smaller area. But
even if it's only an acre, it might rain on one half and not on the
other half.

Ah, but you can have your very own personal local weather report and
forecast with the NWS "Point Forecast". For example:
http://forecast.weather.gov/MapClick.php?textField1=37.081275&textField2=-122.09458699999999#.UbVHONgVRSk
is the forecast for about 4 square miles surrounding my location.
http://www.weather.gov
Just inscribe your address in the search box and click on "get
detailed info. I've been using it for about a year. It works better
than the area type forecasts, mostly because the nearest official
weather station is at the airport, about 20 miles away.

I'm not sure it makes a difference for me. I can enter my zipcode, or
another that is probably closer to me (taking the integral of all the
distances to me from places in that zipcode) , and even though there
is no airport in either of these zipcodes, I think some place reports
weather info (a public school, maybe?) . I can use weather.com,
yahoo.weather.com, and maybe wunderground.com One of these zipcodes
is longer than 4 miles and I'm not sure about the other.

What I often need is the average monthly temperatures, highs and lows,
somewhere in the world where and when I want to take a vacation. Do
you have any resource good for that.?

However, there has been one minor change. "Chance of precipitation"
has morphed into "precipitation potential". Don't let it bother you
as they mean the same thing.

I hope so. I get upset when there are too many syllables.

On Mon, 10 Jun 2013 18:24:11 -0400, micky
wrote:

http://www.weather.gov
(...)
I'm not sure it makes a difference for me. I can enter my zipcode, or
another that is probably closer to me (taking the integral of all the
distances to me from places in that zipcode) , and even though there
is no airport in either of these zipcodes, I think some place reports
weather info (a public school, maybe?) . I can use weather.com,
yahoo.weather.com, and maybe wunderground.com One of these zipcodes
is longer than 4 miles and I'm not sure about the other.

In the distant past, NWS only used their own weather stations and
reports from weather observers. Today, they use CWOP, MADIS, and
possibly some of the amateur weather data collection systems, such was
WeatherUnderground.
http://wxqa.com
http://madis.noaa.gov
The result is a much finer grain forecast is possible, such as the NWS
point forecast.

What I often need is the average monthly temperatures, highs and lows,
somewhere in the world where and when I want to take a vacation. Do
you have any resource good for that.?

Sure, but you'll have to analyze it yourself.
http://www.wunderground.com/history/
http://weather.org/weatherorg_records_and_averages.htm
http://www.weather.com/outlook/travel/vacationplanner/vacationclimatology/monthly/USCA1020
etc... Google for "weather history".

I also have some marginal history on the wx stations I maintain. For
example, for AR779 in Bonny Dune, CA:
http://bd-wx.k6hju.com/BonnyDoon.htm (current conditions)
http://www.findu.com/cgi-bin/wxpage.cgi?k6hju-2
http://aprs.fi/weather/K6HJU-2
http://db.aprsworld.net/datamart/gnuplot/weather-plot.php?call=K6HJU-2
http://weather.gladstonefamily.net/site/AR779
http://raws.wrh.noaa.gov/cgi-bin/roman/raws_ca_monitor.cgi?state=MTR&rawsflag=290&timeobs =12&orderby=n&type=0
http://raws.wrh.noaa.gov/cgi-bin/roman/meso_base.cgi?stn=AR779
All the above sites have history, but in varying formats and time
spans.

However, there has been one minor change. "Chance of precipitation"
has morphed into "precipitation potential". Don't let it bother you
as they mean the same thing.

I hope so. I get upset when there are too many syllables.

The chance of rain forecast is primarily a measure of how many people
wash their cars. It will only rain upon the washed cars. It will
also rain only on outdoor barbeques, baseball games, roofing projects,
road repair, and other activities directly impacted by rain. You can
probably produce an effective rain forecast by collecting statistics
on such activities, and assuming the worst will happen.



--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

micky wrote:

I'm more acquainted with a glass of water half full or half empty.
They always say half full is used by the optimist who looks at the
good part of things, and half empty by the pessimist who looks at the
bad.


An engineer says that the glass is twice the size it should be, and
was grossly over engineered.

On Mon, 10 Jun 2013 18:24:11 -0400, micky
wrote:

On Sun, 09 Jun 2013 20:34:09 -0700, Jeff Liebermann
wrote:

On Sun, 09 Jun 2013 15:28:42 -0400, micky
wrote:

I haven't linked at Jeff's links yet,

Sniff... I just hate being ignored.

If you had your own private weather report, as Cape Canaveral has on
the days it might launch a rocket, it will cover a smaller area. But
even if it's only an acre, it might rain on one half and not on the
other half.

Ah, but you can have your very own personal local weather report and
forecast with the NWS "Point Forecast". For example:
http://forecast.weather.gov/MapClick.php?textField1=37.081275&textField2=-122.09458699999999#.UbVHONgVRSk
is the forecast for about 4 square miles surrounding my location.
http://www.weather.gov

But after looking at these two urls, they only allowed one to put in
the city and state, or zip code. Where is the "much finer grain
forecast is possible, such as the NWS point forecast." that you
referred to in Monday's post?

Or by "finer grain" do you mean there is more data for the same area?

Since we had been talking about the formula for POP, I thought you
meant you could narrow down the area one was looking at.

Just inscribe your address in the search box and click on "get

By address, do you mean city and state, or do you mean something more
specific, like street address?


detailed info. I've been using it for about a year. It works better
than the area type forecasts, mostly because the nearest official
weather station is at the airport, about 20 miles away.

I'm not sure it makes a difference for me. I can enter my zipcode, or
another that is probably closer to me (taking the integral of all the
distances to me from places in that zipcode) , and even though there
is no airport in either of these zipcodes, I think some place reports
weather info (a public school, maybe?) . I can use weather.com,
yahoo.weather.com, and maybe wunderground.com One of these zipcodes
is longer than 4 miles and I'm not sure about the other.

What I often need is the average monthly temperatures, highs and lows,
somewhere in the world where and when I want to take a vacation. Do
you have any resource good for that.?

However, there has been one minor change. "Chance of precipitation"
has morphed into "precipitation potential". Don't let it bother you
as they mean the same thing.

I hope so. I get upset when there are too many syllables.

On Thu, 13 Jun 2013 05:30:23 -0400, micky
wrote:

Ah, but you can have your very own personal local weather report and
forecast with the NWS "Point Forecast". For example:
http://forecast.weather.gov/MapClick.php?textField1=37.081275&textField2=-122.09458699999999#.UbVHONgVRSk
is the forecast for about 4 square miles surrounding my location.
http://www.weather.gov

But after looking at these two urls, they only allowed one to put in
the city and state, or zip code. Where is the "much finer grain
forecast is possible, such as the NWS point forecast." that you
referred to in Monday's post?

Or by "finer grain" do you mean there is more data for the same area?

Weather.gov allows the full address. I just tried various addresses.
It correctly built a small box on the map surrounding the location.
Try it again, using the recommended address or lat-long formats as
found in:
http://www.weather.gov/ForecastSearchHelp.html
If Google Maps can't find your location, then either you were
insufficiently specific, or you don't exist. Failure to exist is an
existential proposition and may require the assistance of a
philosopher to rectify.

By address, do you mean city and state, or do you mean something more
specific, like street address?

Something more specific, like your exact address. See that help at:
http://www.weather.gov/ForecastSearchHelp.html
If there are too many syllables, perhaps an abrev or concat will work.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Tue, 11 Jun 2013 13:10:40 -0400, "Michael A. Terrell"
wrote:


micky wrote:

I'm more acquainted with a glass of water half full or half empty.
They always say half full is used by the optimist who looks at the
good part of things, and half empty by the pessimist who looks at the
bad.


An engineer says that the glass is twice the size it should be, and
was grossly over engineered.

NO! NO! NO! That is what the cost cutting bean counter says. It is
engineered correctly (proper reserve capacity).

?-)

josephkk wrote:

On Tue, 11 Jun 2013 13:10:40 -0400, "Michael A. Terrell"
wrote:


micky wrote:

I'm more acquainted with a glass of water half full or half empty.
They always say half full is used by the optimist who looks at the
good part of things, and half empty by the pessimist who looks at the
bad.


An engineer says that the glass is twice the size it should be, and
was grossly over engineered.

NO! NO! NO! That is what the cost cutting bean counter says. It is
engineered correctly (proper reserve capacity).


Not if it keeps falling out of the cupholder. ;-)