Dual-polarization is the most significant enhancement made to the nation’s federal weather radar system since Doppler technology was first installed in the early 1990s. Dual-pol radar sends and receives both horizontal and vertical pulses, which produces a much more informative picture of the size and shape of the objects in the sky. This provides meteorologists the ability to distinguish between rain, snow, hail and non-weather items like wildfire smoke plumes, birds and insects. Conventional Doppler radar only has a one-dimensional view making it difficult to tell the type of precipitation or object in the sky.

“This achievement is the result of years of research, development and continued investment that’s helping us become a more weather-ready nation,” said Dr. Louis Uccellini, director, NOAA’s National Weather Service. “It is amazing what we can see with dual-pol technology. This game-changing technology has already helped forecasters issue more accurate and timely warnings to the public and has saved lives.”

Dual-pol is credited with providing improved detection of heavy rainfall, which can increase warning time for flash floods. During winter storms, forecasters use dual-pol information to monitor a transition from snow to sleet and freezing rain, which allows for a more accurate forecast. Dual-pol can also spot airborne debris giving forecasters the ability to confirm a tornado on the ground, even in the dark or when hidden by heavy rain. The new technology has also been used to help detect hazards to aircraft, such as volcanic ash plumes, icing conditions and birds.

“I am committed to supporting the National Weather Service’s critical mission of forecasting and warning about severe weather, and supporting the men and women who work every day to fulfill that mission”, said Senator Barbara A. Mikulski, chairwoman of the Appropriations subcommittee that funds NOAA, “We owe it to our communities — to the coastal states that depend on accurate hurricane forecasts, and to the interior states that depend on timely tornado warnings — to make sure our weather offices are fit for duty. These new state-of-the-art radars will ensure our forecasters have the tools and technology they need to protect lives and livelihoods.”

The National Weather Service has used dual-pol to develop 14 new radar products that have improved the speed, understanding, and accuracy of the information it provides about extreme weather. Forecasters now have more confidence to accurately assess weather events and be more descriptive in weather warnings, which helps improve public response to the warnings.

The nationwide dual-pol upgrade began in Sept. 2011 and the public has been benefiting from the new technology every day since. Here are a few successes:

• On Feb. 10, 2013, NWS weather forecasters in Jackson, Miss., used the new radar technology to confirm a powerful tornado (EF-4) was moving across Southern Mississippi’s Lamar County toward the populated city of Hattiesburg. Forecasters warned the public using detailed, descriptive language about the tornado’s size and path, resulting in no fatalities. On the same day, dual-pol information helped the Jackson forecasters recognize thunderstorms with particularly heavy rainfall rates, enabling them to issue flash flood warnings more than an hour before flash flooding started.

• Dual-pol technology can also identify non-weather targets such as bugs, bats or debris from a tornado producing damage on the ground.

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  On Nov. 7-8, 2012, NWS meteorologists at the Boston forecast office relied on dual-pol radar information to help locate the rain/snow line as a nor’easter traversed the area. During the afternoon and evening, a storm formed across Rhode Island and eastern Massachusetts. Snow fell to the west of the boundary where temperatures dipped into the 30s, while rain fell to the east where temperatures held in the 40s. Using dual-pol information, forecasters were able to accurately track the slow progress of the rain-snow line and provide short term forecasts which helped department of transportation officials focus their snow removal assets and for the media to highlight the hazardous routes to the traveling public.
• The NWS forecast office in Phoenix relied on dual-pol technology to successfully warn for a very large dust storm that moved across the metro area during the early evening of July 5, 2011. There were widespread reports of near-zero visibility and winds gusting more than 50 mph. Dual-pol radar data estimated this dust storm reached a peak height of at least 5,000 to 6,000 feet, with a leading edge stretching close to 100 miles and traveling at least 150 miles. Forecasters collaborated with emergency management and media partners, providing details on potential impacts as the dust approached from the southeast.  Dust storm warnings described the large size of the dust area and the potential for widespread low visibilities of less than a quarter mile.  Safety tips in the warnings and updating warning statements helped people in the storm's path make fast and smart decisions.

In addition to the 122 NWS-owned radars, the full nationwide radar network includes another 37 radar sites owned by the FAA and Defense Department, which will be completely upgraded to dual-pol technology this summer. NOAA’s NEXRAD radar program is a tri-agency effort with NOAA, the Federal Aviation Administration, and the United States Air Force.

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