GCIP/LSA-NW99 Surface Montana's Remote Weather Informational System (RWIS) Dataset 1.0 General Description The Montana's Remote Weather Informational System (RWIS) surface dataset is one of several datasets provided in the GEWEX Continental-Scale International Project (GCIP) Large Scale Area-North West (LSA-NW) Enhanced Annual Observing Period (EAOP) 1999. Data from this source are provided as is in their original format and were not quality controlled by UCAR/JOSS. This dataset contains the available data for the GCIP LSA-NW EAOP-99 domain and time period (01 April 1999 through 31 March 2000). The GCIP LSA-NW EAOP-99 domain is approximately 90W to 115W longitude and 36N to 51N latitude. 2.0 Detailed Data Description The Montana's Remote Weather Informational System (RWIS) consists of 59 sites across the state. Remote weather informational systems provide real time information via standard communication tools (phone lines and computer network) statewide. These sites are located in strategic locations to provide accurate real time weather information. This information allows Montana Department of Transportation (MDT) personnel to schedule personnel and equipment based on current weather and pavement surface conditions. Real time weather information improves response time, increases winter maintenance efficiency and minimizes the traveling public's exposure to hazardous weather related roadway conditions. More information can be found at the following MDT RWIS web sites: http://www.mdt.state.mt.us/departments/maintenance/rwis/mdtrwis.html and http://www.mdt.state.mt.us/ . To view the real time weather station information visit the MDT RWIS site at http://rwis.mdt.state.mt.us/ . 2.1 Detailed Format Description The Montana's Remote Weather Informational System (RWIS) data format is provided in each data file. Below is a sample header line from the data and parameter definitions. Data parameter definitions can be found in the MDT RWIS web site's glossary at http://rwis.mdt.state.mt.us/scanweb/glossary.htm#DataDef . Date/Time Sub Sfc Temp RH DP SpdAvg SpdGust Dir Type Intensity 03/01/01 00:30 28.6F 33F 30.6F 49% 14F 14 mph 17 mph SW None -9999 Parameter Definition -------------------------------------------------------------------------- Surface Temperature (Sfc) Temperature of the pavement sensor roughly 3 mm (1/8 inch) below the surface of the sensor. Subsurface Temperature (Sub) Typically, the temperature approximately 43 cm (17 inches) below the top of the pavement. You can place additional subsurface sensors at different depths to monitor frost depth. Relative Humidity (RH) 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. 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 Remote Processing Unit (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. Probability of Precipitation (Prob) Likelyhood of precipitation during a forecasted period. 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. 3.0 Quality Control Processing No quality control was done on this dataset. 4.0 References None.