Monday, July 09, 2007

What does that mean?

Ever wonder what the weather man really means by scattered clouds? I found at the National Weather Service site...

PRECIPITATION
Technically, the Probability of Precipitation (often referred to as a "POP") is defined as the likelihood of occurrence (in percent) of a measurable amount of liquid precipitation (or water equivalent of frozen precipitation) during a specified period of time at any given point in the forecast area.

The following are precipitation probabilities used by the National Weather Service.

POP Percentage Expression/Uncertainty Areal Qualifiers
0 Percent None None
10 Percent ISOLATED or None ISOLATED or None
20 Percent SLIGHT CHANCE ISOLATED
30-50 Percent CHANCE SCATTERED
60-70 Percent LIKELY NUMEROUS
80-100 Percent (none) OCCASIONAL or
PERIODS OF

SKY CONDITION
Forecasts normally include a sky condition unless it is implied from another part of the forecast. Below are terms we use to describe the sky condition:

Descriptive Term Predominant or Average Cloud Cover
CLEAR or SUNNY No clouds
MOSTLY SUNNY or MOSTLY CLEAR 1/8 to 2/8 clouds
PARTLY CLOUDY or PARTLY SUNNY 3/8 to 5/8 clouds
MOSTLY CLOUDY (sometimes CONSIDERABLE CLOUDINESS) 6/8 to 7/8 clouds
CLOUDY 8/8 clouds
Also used:
INCREASING CLOUDS
DECREASING CLOUDS

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