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Fire Weather
Parameters
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CLOUD COVER Predominant cloud condition (e.g., cloudy, pcldy, clear)
PRECIP TYPE Type of precipitation expected to occur such as rain, showers, thunderstorms.
TEMP (24H TREND) Forecasted maximum or minimum temperatures in Fahrenheit with a 24-hour trend noted in parenthesis.
RH % (24H TREND) Forecasted maximum or minimum relative humidity with a 24-hour trend noted in parenthesis.
20FT WIND (MPH)
20-foot wind speed (mph) and direction (eight compass points).
PRECIP AMOUNT Amount of liquid precipitation expected to the nearest hundredth (0.01).
PRECIP DURATION How many hours are measurable precipitation expected to last?
MIXING HGT (M - MSL)
and
MIXING HGT (FT - MSL)
A projected height in meters or feet above mean sea level through which vigorous mixing will take place based on the maximum temperature on a given day. It is the height at which smoke will lose its buoyancy and stop rising. It is valid for the afternoon hours when temperature nears the predicted maximum.
TRANSPORT WND (M/S)
and
TRANSPORT WND (MPH)
The predicted average wind in meters per second or miles per hour in the layer below the mixing height near the predicted maximum (usually in the afternoon).
VENT INDEX The Ventilation Index parameter is obtained by multiplying the mixing height in meters times the wind speed in meters per second.
CAT DAY The Vent Index corresponds to a Category Day
<2000
1
2000-3999
2
4000-7999
3
8000-16000
4
>16000
5
MIX HGT 500 The temperature in Fahrenheit needed to achieve a mixing height of 500 meters. If expected high temperature is cooler than the 500 meter mixing height temperature, then the mixing height parameter above will be less than 500 meters.
STABILITY CLASS The stability class based on wind, incoming solar radiation (sun angle), and cloud cover. The more unstable the forecasted stability class, the more readily a pollutant is dispersed.
Stability Class Description
A
Extremely Unstable
B
Unstable
C
Slightly Unstable
D
Neutral
E
Slightly Stable
F
Stable

 


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