Additional Heavy Rain and Flooding Concerns in Central Texas; Tropical Storm Chantal to Impact the Coastal Carolinas

Heavy rainfall and flooding concerns remain for today across Central Texas and the Hill Country, with scattered thunderstorms expected this afternoon and evening. Tropical Storm Chantal has formed and will bring heavy rainfall and flooding concerns to portions of the coastal Carolinas. Life-threatening surf and rip currents are expected from the Southeast to Mid-Atlantic. Read More >

A Bit About Dual Polarized Radar Technology

Dual Polarization (or "dual-pol") technology added an additional 14 products to the suite of data already previously available to NWS forecasters. These tools are currently assisting forecasters in the warning and forecast process.

How is Dual Polarization Radar Data Different?

It compares the power and timing of energy returned to the radar from both horizontal and vertical pulses, gleaning information such as the size, shape, and composition of precipitation particles.

Previous radars only measured energy returned from particles in the air from a radar beam sent at an anlge horizontally from a radar.

What are the Potential Benefits of Dual-Pol?

Better estimation of total precipitation
Better estimation of the size distribution of hydrometeors (precipitation particles)
Improved ability to identify areas of heavy rainfall (flash flooding potential)
Improved detection and mitigation of non-weather echoes
Easier identification of the melting layer (helpful for identifying snow levels in higher terrain)
Ability to classify precipitation type
New severe thunderstorm signatures

What is polarization?

A radio wave is a set of oscillating electric and magnetic fields, oriented 90 degrees to each other. Polarization of the wave is the direction, or orientation, of the electric field.

Horizontal Polarization

The electric field is oriented horizontally, along the x-axis.

Vertical Polarization

The electric field is oriented vertically, along the y-axis.

"Old" NWS Doppler Radar (horizontally-polarized only) versus "Dual Polarized" Radar

The old Doppler radar capability transmits and receives only horizontally polarized radio wave pulses. Therefore, they measure only the horizontal dimension of cloud and precipitation particles. New dual-pol capability will allow the transmit and receipt of both horizontally and vertically polarized radio wave pulses. Therefore, they measure both the horizontal and vertical dimension of cloud and precipitation particles.

More Information

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Additional Heavy Rain and Flooding Concerns in Central Texas; Tropical Storm Chantal to Impact the Coastal Carolinas

Dual Polarization Technology