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Temperature at which the air becomes saturated as it cools. If the road or runway temperature drops to or below the dew point, moisture may develop on the surface. The form the moisture takes depends on the surface temperature and the amount of chemical present.

Relative Humidity

Percent of moisture in the air. A relative humidity of 0% shows that the air contains no moisture and 100% shows that the air is completely saturated and cannot absorb more moisture.

Wind Speed

SpdAvg

Average speed of the wind during a one minute period.

Wind Direction

DirAvg

Average wind direction during a one minute period. Wind direction can be displayed in two formats: cardinal points or degrees. Cardinal format has 8 possible headings. Degree format displays wind direction in values ranging from 001 to 360.

Direction	Cardinal Format	Degree Range
North	N	338 - 22
Northeast	NE	23 - 68
East	E	69 - 112
Southeast	SE	113 - 158
South	S	159 - 202
Southwest	SW	203 - 248
West	W	249 - 292
Northwest	NW	293 - 337

Gust

SpdGst

Maximum wind speed measured during a one minute period. The RPU averages the wind speed every four seconds and collects 15 four-second averages in one minute. The largest of these 15 values is the gust value.

Precipitation Type

Precip

Type of precipitation detected by a precipitation sensor, if one is available. Certain types of precipitation sensors can only detect the presence or absence of precipitation and will display Yes or No. Other types of precipitation sensors, such as the Weather Identifier and Visibility Sensor (WIVIS) or Optical Weather Identifier (OWI), can classify the type of precipitation and will report a specific type of precipitation. The WIVIS and OWI precipitation sensors may report Yes at the onset of precipitation until sufficient time has elapsed to classify the precipitation type.

Precipitation Rate

Rate

Average precipitation rate computed every minute. Snowfall is converted to water equivalent and the rate represents the rate of liquid equivalent.

Precipitation Intensity

Intens

Intensity of the precipitation as derived from the precipitation rate. The National Weather Service defines the following intensity classes: light, moderate, or heavy.

Precipitation Accumulation

Accum

Rainfall amount or snowfall liquid equivalent for the period from midnight GMT to the current time. Every 30 seconds the RPU computes the amount of water that accumulated during the previous 30 seconds based upon the precipitation rate. The RPU adds that amount to the previous total accumulation, keeping a running total. At midnight GMT the total accumulation is stored in the history file and the counter is reset to zero.

Visibility

Vis

Average distance that you can see, both day and night, computed every three minutes.

Pavement Temperature

Temperature range of the pavement sensor roughly 3 mm (1/8 inch) below the surface of the sensor.

Glossary

Air Temperature:

Air temperature at the RPU.

Dew Point Temperature:

GMT:

A time standard which uses the local time of Greenwich, England known as Greenwich Mean Time. It is one of the time standards used in meteorology, and it is 4 hours ahead of EDT (5 hours ahead of EST) - 00:GMT is equal to 8 pm EDT (5 pm PDT), 12:GMT is 8 am EDT (5 am PDT). You might also see GMT listed as Z, Zulu time, or UTC, Universal Coordinated Time.

Gust :

Precipitation:

Accumulation Rainfall amount or snowfall liquid equivalent for the period from midnight GMT to the current time. Every 30 seconds the RPU computes the amount of water that accumulated during the previous 30 seconds based upon the precipitation rate. The RPU adds that amount to the previous total accumulation, keeping a running total. At midnight GMT the total accumulation is stored in the history file and the counter is reset to zero.

Precipitation Intensity:

Intensity of the precipitation as derived from the precipitation rate. The National Weather Service defines the following intensity classes: light, moderate, or heavy. Precipitation Rate Average precipitation rate computed every minute. Snowfall is converted to water equivalent and the rate represents the rate of liquid equivalent.

Precipitation Type:

Relative Humidity:

Percent of moisture in the air. A relative humidity of 0% shows that the air contains no moisture and 100% shows that the air is completely saturated and cannot absorb more moisture.

RWIS:

Road and Runway Weather Information System

Visibility:

Average distance that you can see, both day and night, computed every three minutes.

Wind Direction:

Wind Speed:

Average speed of the wind during a one minute period.