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Comment by jrockway | Hacker News Reader

That's too bad. I always liked the raw radar imagery. (OK, not really raw, but the same images that real forecasters get.) The Weather Channel is too mainstream; all their imagery is editorialized and dumbed down for an audience that just wants to know if it's going to rain today.

I guess I will have to write a quick perl script to generate my own images now.

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>The Weather Channel is too mainstream; all their imagery is editorialized and dumbed down for an audience that just wants to know if it's going to rain today.

Not to mention that their forecasts are presented in a way that is statistically incoherent. Look at their hourly forecasts, then click to break down by 15 minute intervals. It is common to see things like "rain during 2:00-3:00 = 30%", and then also have something like 50% during one of the 15 minute intervals within that time range. I have yet to come up with a hypothesis for what those percentages could mean, and have that scenario be possible.

Purely speculating, but it may be the expected duration of rain. So 30% in one hour means on the average it will rain 18 minutes within that hour and 50% of 15 mins would be 7.5 rainy minutes.

My real guess is that they have independent models for different time resolutions.

30% chance of rain actually means 30% of the area is projected to have rain covering it rather than there being a 30% chance you will be rained on.

An unlikely, but theoretically possible way to get 50% inside of 15 minute interval but 20% over an hour would be if the model prodicted very widespread rain in a band moving over an area and time weighted the percentage.

> 30% chance of rain actually means 30% of the area is projected to have rain covering it

Common misconception. The Chance of precipitation is actually stating that historically, given these conditions x% of days produced precipitation. It is a statement of the odds that it will rain at all.

http://www.straightdope.com/columns/read/854/what-does-it-me...

That site you provide (or cite) is the only one I can find that describes it that way. Every other source describes the otherway which I still think is correct:

NOAA: http://www.srh.noaa.gov/ffc/?n=pop

http://www.usatoday.com/weather/resources/askjack/wadefine.h...

http://en.wikipedia.org/wiki/Probability_of_precipitation

Even those links state the PoP is a measure of the chance that it will happen at all. That is the historical measurement.

No, that is the simplified explanation of how the average person should think about it. We are talking about the definition and a possible way to get the odd results the OP mentioned observing.

My understanding is that this would mean that ~30% of the computer models predict rain between 2:00-3:00. I doubt they would stake everything on a singular model, but I could be wrong.

If you're an OS X or iOS user, check out RadarScope: http://www.basevelocity.com/RadarScope/ - it's a prosumer weather radar app, and it's got what you're looking for. I'm not affiliated with them in any way, just a happy user.

> I guess I will have to write a quick perl script to generate my own images now.

a few years from now: sells to Facebook for $1B ;)

You might be interested in http://lug.rose-hulman.edu/proj/aweather

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