[wxqc] Rain Forecast

[Chris Proulx]

>
> I did a lot of searching around the NOAA website, and it looks like their
> numbers are not entered by computer, but are entered by people. The
> numbers
> seem to be forecast probabilities for the covered time periods. The time
> periods I looked at seemed to be three hours. This seems to be confirmed
> by
> the chart given at the following URL (I really like this chart, by the
> way):


I would question whether this is an actual probability that is subject to
the type of statistical analysis you are performing, or is it rather the
forecaster's confidence in the precipitation forecast.

In other words, when the forecast is a "30% chance of rain" is the
forecaster actually saying, "My confidence is low that: some location in the
zone (area) for which this forecast is being prepared will receive .01 of
rain in the forecast time period."

A true probablilty would require the forecaster to have a historical data
set of conditions that match or closely similar to the forecast conditions
from which he/she could derive the probability.  Seems unlikely. (Which is
why the POP is entered by a human and not derived by a computer.)
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