GCIP/LSA-NW99 Montana's Remote Weather Informational System (RWIS) 
     Miscellaneous Precipitation

     1.0  General Description
     
          The Montana's Remote Weather Informational System (RWIS) 
     Miscellaneous Precipitation 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. 

          Precipitation collected at the MDT RWIS sites is accumulation 
     rainfall amount or snowfall liquid equivalent for the period 
     from midnight GMT to the current time. Every 30 seconds the 
     Remote Processing Unit (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. 

          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 are sample header
     and data lines from the data. Additional 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     Type  Intensity   Accum     Rate
      04/01/99 14:25     Yes     Light   0.7 in.   0.0 iph
      04/01/99 14:35     Yes  Moderate   0.7 in.   0.1 iph
      04/01/99 14:45     Yes  Moderate   0.7 in.   0.1 iph
      04/01/99 14:55     Yes  Moderate   0.7 in.   0.1 iph
      04/01/99 17:03    Snow  Moderate   0.0 in.   0.1 iph


     Parameter                   Definition
     --------------------------------------------------------------------------
     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.