**  An explanation of some of the Weather Station Parameters  **

NOAA Reports

NOAA is the National Oceanic and Atmospheric Administration, an American Organisation dedicated to all things to do with climate and the oceans. The reports are tabulated in a standard used by NOAA.

Heat Index

The Heat Index uses the temperature and the relative humidity to deter mine how hot the air actually "feels." When humidity is low, the apparent temperature will be lower than the air temperature, since perspiration evaporates rapidly to cool the body. However, when humidity is high (i.e., the air is saturated with water vapor) the apparent temperature "feels" higher than the actual air temperature, because perspiration evaporates more slowly.

Moon Phase

Shows the current moon phase. The sequence shown is for Northern Hemisphere. The sequence of the icons is reversed in the Southern Hemisphere.

Beaufort Scale

The Beaufort Scale is an empirical measure for describing wind speed which ranks wind speeds in classes.

Temperature

The Inegrated Sensor Suite houses the outside Temperature and Humidity sensors in a white vented and shielded enclosure that minimizes solar radiation-induced temperature error.

Humidity

Humidity itself simply refers to the amount of water vapor in the air. However, the total amount of water vapor that the air can contain varies with air temperature and pressure.
Relative humidity takes into account these factors and offers a humidity reading which reflects the amount of water vapor in the air as a percentage of the amount the air is capable of holding. Relative humidity, therefore, is not actually a measure of the amount of water vapor in the air, but a ratio of the air’s water vapor content to its capacity. When we use the term humidity in the manual and on the screen, we mean relative humidity.
It is important to realize that relative humidity changes with temperature, pressure, and water vapor content. If a parcel of air with a capacity for 10 g of water vapor contains 4 g of water vapor, the relative humidity would be 40%. Adding 2 g more water vapor (for a total of 6 g) would change the humidity to 60%. If that same parcel of air is then warmed so that it has a capacity for 20 g of water vapor, the relative humidity drops to 30% even though water vapor
content does not change.
Relative humidity is an important factor in determining the amount of evaporation from plants and wet surfaces since warm air with low humidity has a large capacity to absorb extra water vapor.

Wind Chill

Wind chill takes into account how the speed of the wind affects our perception of the air temperature. Our bodies warm the surrounding air molecules by transferring heat from the skin. If there is no air movement, this insulating layer of warm air molecules stays next to the body and offers some protection from cooler air molecules. However, wind sweeps away that warm air surrounding the body. The faster the wind blows, the faster heat is carried away and
the colder you feel. Wind has a warming effect at higher temperatures.

Note: There is no windchill when the air temperature is at or above 93° F (34° C).

Rain Guage - How it works.

     

Rain Storm

Rain Storm displays the rain total of the last rain event. It takes two rain clicks (0.4 mm) to begin a storm event and a full 24 hours without rain to end a storm event.

Temperature Humidity Wind (THW) Index

The THW Index uses humidity, temperature and wind to calculate an apparent temperature that incorporates the cooling effects of wind on our perception of temperature. 

Dew Point

Dew-point is the temperature to which air must be cooled for saturation (100% relative humidity) to occur, providing there is no change in water content. The dew-point is an important measurement used to predict the formation of dew, frost, and fog. If dew-point and temperature are close together in the late after noon when the air begins to turn colder, fog is likely during the night. Dew-point is also a good indicator of the air’s actual water vapor content, unlike relative humidity, which takes the air’s temperature into account. High dew-point indicates high vapor content; low dew-point indicates low vapor content. In addition a high dew-point indicates a better chance of rain and severe thunder storms. You can even use dew-point to predict the minimum overnight temperature. Provided no new fronts are expected overnight and the afternoon Relative Humidity 50%, the afternoon’s dew-point gives you an idea of what minimum temperature to expect overnight, since the air is not likely to get colder than the dew-point anytime during the night.

Dew point is not stored in archive memory or the database. Dew point is calculated whenever it is displayed. If you edit the temperature or humidity value, the dew point will change as well.

Air Density

Air Density (the weight of 1 cubic foot or 1 cubic meter of air ) is a valuable tool for racing enthusiasts, because it helps determine the optimal jetting under current weather conditions.

Internal combustion engines operate at their peak efficiency (producing the most power or using the least fuel) when the correct ratio of oxygen and fuel are introduced into the combustion chamber. The carburetor jets (or fuel injector setting) control the ratio of how much fuel is introduced into a given airflow. Carburetors do not automatically compensate for changes in the amount of oxygen in that airflow and therefore changes in oxygen concentrations can result in inefficient operation. Changes in the oxygen content of air result from changes in the weather (barometric pressure, temperature, and humidity).

Measuring oxygen concentration in air is difficult; other measures are commonly used to estimate oxygen content. For example, determining changes in the density of the air (i.e., how much a given volume of air weighs) can produce a reasonable estimate of changes in oxygen concentration.

Barometric Pressure

The weight of the air that makes up our atmosphere exerts a pressure on the surface of the earth. This pressure is known as atmospheric pressure. Generally, the more air above an area, the higher the atmospheric pressure. This, in turn, means that atmospheric pressure changes with altitude. For example, atmospheric pressure is greater at sea-level than on a mountaintop. To compensate for this difference in pressure at different elevations, and to facilitate comparison between locations with different altitudes, meteorologists adjust atmospheric pressure so that it reflects what the pressure would be if measured at sea-level. This adjusted pressure is known as barometric pressure.

Barometric pressure changes with local weather conditions, making barometric pressure an important and useful weather forecasting tool. High pressure zones are generally associated with fair weather, while low pressure zones are generally associated with poor weather. For forecasting purposes, the absolute barometric pressure value is generally less important than the change in barometric pressure. In general, rising pressure indicates improving weather conditions, while falling pressure indicates deteriorating weather conditions.

Barometric Trend

The Bar Trend shows the direction of change (higher, lower, steady) of the barometric pressure over the last three hours.

  • The Bar Trend is updated every 15 minutes.

  • Rapid rise is indicated if the pressure increases >= 0.06" Hg ( >= 2 mb)

  • Slow rise is indicated if the pressure increases >= 0.02" and < 0.06" Hg ( >= 0.67 mb and < 2 mb)

  • Steady is indicated if the pressure changes < 0.02" Hg ( < 0.67 mb )

  • Slow fall is indicated if the pressure decreases >= 0.02" and < 0.06" Hg ( >= 0.67 mb and < 2 mb)

  • Rapid fall is indicated when the pressure decreases >= 0.06" Hg ( >= 2mb )

Wind Run

Wind run is measurement of the "amount" of wind passing the station during a given period of time, expressed in either "miles of wind" or "kilometers of wind". WeatherLink calculates wind run by multiplying the average wind speed for each archive record by the archive interval.

For Example:

Average Wind Speed = 5 mph

Archive Interval = 30 minutes (0.5 hours)

Wind Run = 5 mph x 0.5 hours = 2.5 miles of wind

  • If you are using mph to measure wind speed, wind run will be reported in miles.

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