WeatherTAP.com subscribers can now view Terminal Doppler Weather Radar (TDWR) in both the Radar section of the web site, and WeatherTAP's RadarLab HD feature.
"Terminal Doppler Weather Radars were developed by the FAA and are located near 45 major airports in the U.S.," WeatherTAP's Program Manager Robert Parsons say. "The TDWRs can detect dangerous conditions such as wind shear and have greatly enhanced aviation safety in the country since they were first deployed in 1994."
“The Terminal Doppler Weather Radars offer one more view of precipitation intensity, rainfall rate and echo tops for the user to choose from, plus different tilt angles and doppler velocity of the winds in precipitation areas," says Stacey Simmons of the WeatherTAP team. "Similar to the NEXRAD imagery, there are 16 colors in the short range reflectivity, and we use 120 colors in the long range reflectivity images."
Simmons also pointed out TDWRs offer an option when a nearby NEXRAD site is down for maintenance. Plus, the TDWRs also have similarly derived products such as echo height, vertically integrated liquid data and VAD wind profiles.
The images (also referred to as "products") available with TDWR are similar to the images from the NEXRAD system. In addition to the standard base reflectivity images at three different tilt angles of the radar, there is data for the Doppler velocity of the winds in areas receiving precipitation. With short-range products, the area of high-resolution coverage extends 48 miles from the airport of interest, with 16 colors assigned to the imagery, similar to that of NEXRAD images.
TDWR products also include imagery for storm total precipitation in the standard 16 colors like the NEXRAD system. Echo height, vertically integrated liquid and VAD wind profiles are derived from the same algorithms the NEXRAD system uses, so there is no additional resolution in this imagery.
The TDWR is designed to operate at short range, near the airport of interest, and has a limited area of high-resolution coverage of 48 nautical miles, compared to the 124 nautical miles of the conventional WSR-88Ds. The WSR-88Ds use a 10 cm radar wavelength, but the TDWRs use a much shorter 5 cm wavelength. This shorter wavelength allow the TDWRs to see details as small as 150 meters along the beam, at the radar's regular range of 48 nm. This is nearly twice the resolution of the NEXRAD WSR-88D radars, which see details as small as 250 meters at their close range (out to 124 nm). At longer ranges (48 to 225 nm), the TDWRs have a resolution of 300 meters, which is more than three times better than the 1000 meter resolution WSR-88Ds have at their long range (124 to 248 nm). At distances within 48 nm of the TDWR, these radars can help the user pick out the detailed structure of tornadoes. Using the conventional radar, it is difficult to see the hook-shape of the radar echo, while the TDWR clearly depicts the hook echo, as well as the Rear-Flank Downdraft (RFD) curling into the hook.
An initial question WeatherTAP users are asking is "which site should I click, or use?" The simple answer is both. If a NEXRAD site is down for scheduled maintenance, often a nearby TDWR site will provide the user the necessary imagery. Also, since the TDWRs are designed to alert airports of low-level wind shear, they are the obvious choice for such data. It should be noted the TDWR software is much more aggressive about removing ground clutter than the WSR-88D software, which may result in some precipitation echoes of interest being removed at times, so always check all relevant sites for the complete picture of the weather in the area of interest.
Lead developers for WeatherTAP.com are available for interview about this new feature, or WeatherTAP.com in general. WeatherTAP.com has twice been name "Best of the Web" by Forbes Magazine, and has been known since its inception as "the fastest weather on the Web" as the leader in real-time radar imagery, completely ad-free.
http://www.weathertap.com/media/terminal-data-weather-radar.html
To learn more about TDWR in general, visit the NOAA site.