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POPS
You hear or read the latest
weather forecast and it says "it's going to rain," and you want to
know when, where, and how much; but instead, you are just given a probability
of precipitation, a POP. What is this percentage? What does it mean?
POP is described as the
probability that measurable precipitation, amounts greater than 0.01",
will occur at a specific point, or rain gauge, in a specific period of time.
For example, the meteorologist
says there is a 60% chance of rain today. According to National Weather Service
policy, it means at any given point in the forecast area, including your backyard;
there is a 60% chance that rain will occur. Another way of looking at it is,
out of 100 days identical to today, on 60 of them, rain will occur.
Sometimes, more descriptive
wording is used to lend additional meaning to the probability of precipitation
in the forecasts. This wording explains the uncertainty and areal qualifiers,
respectively. For example, a 10-20% chance of showers means there is a SLIGHT
CHANCE of showers, or the showers would be isolated or widely scattered. Now,
a 30-50% chance of showers means there is a CHANCE of showers, or the showers
would be scattered. A 60-70% chance of showers means showers are LIKELY, or
the showers would be numerous. While, a 80-100% chance of showers means it is
current or very likely to happen. POPs do not necessary pertain to the intensity
of the precipitation.
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