Iowa DOT Weatherview

What type of information is available

What type of RWIS weather information is available?
Iowa's winter weather brings an average of 34 inches of snow annually. The Iowa Department of Transportation's Maintenance Division is responsible for snow and ice control on 10,500 miles of Interstate and primary highways. When you consider all the lanes of multiple-lane highways, that is the equivalent of 25,800 miles of single-lane highway. The RWIS network of weather sensors provides the decision makers responsible for snow and ice control and other maintenance activities at the Iowa Department of Transportation with weather information specifically related to the roadway.

The first RWIS site was installed in the Des Moines area in 1989. The value of weather information specifically targeted for surface transportation was quickly discovered, and the system has grown to a network of 58 sites throughout the state. There are three types of information the RWIS sites provide.

·         Surface Temperature is a measurement of the actual temperature of the roadway or bridge surface.  The surface temperature governs what will happen to a highway or bridge when precipitation occurs in the winter more than air temperature.  These sensors literally provide the temperature "where the rubber meets the road.

·         Subsurface Temperature is the temperature approximately 18 inches below the roadway surface.

·         Atmospheric Weather Data is the information normally thought of as weather information. Weather instruments collect air temperature, relative humidity, wind speed, wind direction, and precipitation information.

What type of AWOS weather information is available?
Iowa has 113 public use airports. Of these, the 41 airports with AWOS towers fulfill approximately 270,000 aircraft landings and takeoffs every year. An AWOS tower at the airport provides pilots with more informed flight planning information, as well as for a safer descent to a lower legal altitude for landing approaches.

Collection of AWOS weather information?
The AWOS data is Atmospheric Weather Data and includes temperature, dew point, barometric pressure, wind speed, wind direction, wind speed, peak gusts, altimeter setting, density altitude, visibility, and cloud height. The stations operate 24 hours a day and the weather data is updated every minute.

How else can I get AWOS weather information?
A computer-synthesized voice broadcasts the weather data that can be received either by ground-to-air radio or by telephone. The weather information can also be accessed through the computer network. The computer network is a statewide network that uses dedicated phone lines to connect all of the AWOSs to a host computer via personal computers located at each AWOS site. The personal computer at each site can be used to access AWOS weather information form all of the other AWOS sites that are in the network. It is also programmed to access the Federal Aviation Administration's Direct Access Terminal (DUAT) system to receive national weather information and file flight plans.

The computer at an airport site may be called from any personal computer to access weather observations. A communications program such as HyperTerminal® for Microsoft Windows® or comparable program must be used to access the airport computer. The computer must also have a Hayes-compatible modem with a transmission rate between 1,200 and 56,000 bps (56k). The modem setting should be 8 data bits, 1 stop bit and no parity. After successfully calling one of the airport sites, the information on the computer screen will have instructions for the viewer to follow to acquire the desired weather data. In addition to the 41 AWOS locations, 14 modems have been installed at 13 other airport sites as part of the statewide AWOS computer network.

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Weather Data Disclaimer: The weather data provided here by the Iowa Department of Transportation only reflects conditions at the specified site. Because of Iowa weather patterns, conditions can vary greatly in a small area; i.e., weather conditions a few miles away from the sensor could be completely different. In addition, failure of the sensors, or the equipment processing the information, may occur and produce unreliable information. Therefore, this information should not be used as the only factor in determining whether to travel in a particular area. The Iowa DOT recommends you check a number of sources, including media weather reports, in making your travel plans.

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