The Huntsville Area Weather Network (HAWN) is primarily comprised of Amateur Radio stations using the Automated Position Reporting System (APRS) into APRSWXNET and Citizen Weather Observer Program (CWOP) [http://www.wxqa.com] sites, which augment the existing National Weather Service (NWS), Federal Aviation Administration (FAA), United States Department of Agriculture (USDA), etc. weather observation sites across the region. This fine scale weather network has been developed by utilizing existing weather stations as well as through development and placement of stations at strategic locations. It is being developed to aid the Huntsville [Alabama] (HUN) National Weather Service forecast office to provide more accurate forecasts to their County Warning Area (CWA). It also provides amateur radio operators with real-time data accessible from home or mobile stations. At the beginning of 2003, there were three amateur stations operating in North Alabama and two citizen weather sites. In April 2004, there were 16 amateur sites and 7 citizen weather sites operational.

The Huntsville CWA is outlined in red in the image and covers fourteen counties. Red dots indicate amateur radio weather stations, while purple dots represent NWS and FAA automated sites, dark gray dots are citizen weather sites and light green dots are planned amateur sites. Amateur stations report their observations at 3, 5, 10 minute or 1 hour intervals via the APRS protocol developed by Bob Bruninga (WA4APR). Many stations report temperature, relative humidity, rainfall, barometric pressure and wind speed and direction.  A few stations report a subset of these parameters. These data are principally transmitted on 144.39 MHz through a digital repeater (digipeater) network to internet gateways or directly via internet connections.

The additional weather stations were primarily located at digipeater sites. Two digipeater sites were also added to the network and had weather stations incorporated with them. The weather stations are mainly comprised of Davis Instruments units (http://www.davisnet.com) as well as Peet Brothers (http://www.peetbros.com) Ultimeter stations. The Davis units must be interfaced to a computer in order to create a data packet for APRS. The Peet Brothers stations have built-in output modes that allow them to interface directly with a terminal node controller (TNC). Unfortunately, this data is typically in a hexadecimal format that does not lend itself to translation by packet ready radios, in particular Kenwood HT-D7A and TM-D7 radios. Options are being explored to translate this data stream to the APRS positionless weather report. Some recently installed  Peet Brothers stations are utilizing  a Byonics WXTrak (http://www.byonics.com) that translates the Peet information into a human readable form and also acts as a dumb TNC.

The HAWN amateur and citizen weather stations are also used by the National Weather Service at their Forecast Systems Laboratory (http://www-frd.fsl.noaa.gov/mesonet/ ) and incorporated into their Meteorological Assimilation Data Ingest System (MADIS) data set which is used by local forecast offices around the country. More importantly, they perform quality control checks on the amateur and citizen weather data and use this quality-controlled data to initialize weather forecast models. These observations help to improve the daily forecasts by the weather service. Within its short life the HAWN observations have allowed the HUN forecasters to better understand the local environment and on one occasion have allowed them to not issue warnings, saving untold dollars for counties since they did not have to deploy crews and equipment for a storm that did not produce frozen precipitation in their county.

Link to

North Alabama APRS Weather Stations

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