| Indicators |
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English |
Description |
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Hour Temperature |
The average actual temperature forecast for this hour, over minutely instances. |
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Hour Feels Like Temperature |
The average temperature forecast for this hour which may feel different to the actual temperature due to factors such as wind and humidity, over minutely instances. In winter it may feel colder, in summer it may feel warmer. |
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Day High Temperature |
The average actual high temperature forecast for this day, over hourly instances (hourly highs), which are forecast over minutely instances (minutely highs). |
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Day Low Temperature |
The average actual low temperature forecast for this day, over hourly instances (hourly lows), which are forecast over minutely instances (minutely lows). |
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Day-Day Feels Like Temperature |
The average temperature forecast for the day-hours of this day which may feel different to the actual temperature due to factors such as wind and humidity, over day-hourly instances, which are forecast over day-minutely instances. |
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Day-Night Feels Like Temperature |
The average temperature forecast for the night-hours of this day which may feel different to the actual temperature due to factors such as wind and humidity, over night-hourly instances, which are forecast over night-minutely instances. |
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Precipitation Chance |
Known as ‘probability of precipitation’, it is a measure of the likelihood that the minimum amount of precipitation will occur from the capacity of the forecast clouds. |
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Wind Speed @ Direction |
The resulting quantity from air moving from high to low pressure. Often measured in meters-per-second (m/s), miles-per-hour (mph), or knots (the number of nautical miles traveled in one hour). This value is relative to the angle at which the wind is ‘coming from’. Yes Kenny, wind direction is the direction in which the wind comes from. We haven’t forgotten. |
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Wind Gust Speed |
The resulting impulse quantity from air moving from high to low pressure in more irregular patterns. These are usually observed in twenty-or-less-second periods. |
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Sunrise |
The time of day at which 0° on our sun’s apparent position creates a tangent with the observable horizon upon its emergence, from a point of observation. Due to atmospheric refraction, the sun’s apparent position at this time is greater than its actual position. Therefore when this record is taken, the sun’s upper limb has not yet created the tangent meaning the actual event will take place after the observed event. The sun’s angular radius + atmospheric refraction will equate to the sun’s actual angle below the horizon at sunrise and sunset. |
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Sunset |
The time of day at which 0° on our sun’s apparent position creates a tangent with the observable horizon upon its disappearance, from a point of observation. Due to atmospheric refraction, the sun’s apparent position at this time is greater than its actual position. Therefore when this record is taken, the sun’s upper limb has already passed the tangent meaning the actual event takes place before the observed event. The sun’s angular radius + atmospheric refraction will equate to the sun’s actual angle below the horizon at sunrise and sunset. Additionally as the sun experiences a transitional disappearance (not a ‘lights out’ scenario), there are multiple stages of post-sunset called ‘twilight’. This begins after the period ‘day’, at sunset when the observable sun moves from sunset (horizon) to civil dusk (moving a total of 6° relative to the horizon). This period is called ‘civil twilight’. The second instance sees the observable sun move from civil dusk to nautical dusk (moving a total of 12° relative to the horizon). This period is called ‘nautical twilight’. The third instance sees the observable sun move from nautical dusk to astronomical dusk (moving a total of 18° relative to the horizon). This period is called ‘astronomical twilight’. This is the final twilight instance before the period ‘night’. |
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Pressure (p) |
The weight of air molecules pressing on the surface of the earth.
$${
P_h=P_0e^{\frac{-mgh}{kT}}
}$$
$${
\mathrm{Where:}\\
P_h=\mathrm{Pressure\ at\ Height}\ h\\
P_0=\mathrm{Pressure\ at\ Sea\ Level}\\
g=\mathrm{Acceleration\ Due\ to\ Gravity}\\
k=\mathrm{Boltzmanns\ Constant}\\
T=\mathrm{Absolute\ Temperature}\\
m=\mathrm{Mass\ of\ One\ Air\ Molecule}
}$$
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Humidity (h) |
The concentration of water vapor in the air.
$${
AH=\frac{m_{H_{2}O}}{V_{net}}
}$$
$${
\mathrm{Where:}\\
AH=\mathrm{Absolute\ Humidity}\\
m_{H_{2}O}=\mathrm{Mass\ of\ the\ Water\ Vapor}\\
V_{net}=\mathrm{Volume\ of\ the\ Air\ and\ Water\ Vapor\ Mixture}
}$$
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Dew Point (dp) |
The temperature at which air must idle, at a constant pressure, in order to achieve humidity of 100%. That is, where the air cannot retain any more water in vapor (gas) form. |
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Visibility (vb) |
The horizontal opacity of the atmosphere from the point of observation to the point of dissipation. It’s often expressed in [visible] distance or as a percentage of pure transparency. To the human eye, a relevant way of testing this is by observing the prominence of a distant object against a(n ideally) clear sky. Visibility does not have anything to do with cloud cover. It could be cloudy but visibility could be 99%. |
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UV Index (UV) |
This stands for ‘ultraviolet index’ which is a universal standard for rating ultraviolet radiation from our sun against the likelihood of sunburn. In place, at a time. A lower value implies less likelihood of sunburn. |
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