SEVERE WEATHER 101: New Generation of NEXRAD

nexrad2As we told you last week, NEXRAD in the Quad Cities was getting a major upgrade.  After a weeks worth of work, the radar is again operational, but work continues on the new technology.  It’s called Dual-Polarization Radar, or Dual-Pol.  In the future, the radar will still be known as NEXRAD.

As of this posting, all the new features of the radar are not accessible.  And I can tell you that the new features will likely not be available to the average person.  But websites that offer premium radar data, along with broadcast media, will have access to the new scans and the benefits that come with them.

In this post, I hope to educate you about the benefits of Dual-Pol radar and what the new products mean.  First things first, Dual-Polarization radar scans three dimensionally.  Unlike a normal radar that can only scan horizontally, Dual-Pol scans both horizontally AND vertically.  That produces a 3-D image of the storm and better understanding of what is going on.

When it comes to the basic scans, precipitation intensity and wind velocity, little has changed.  But what the 3-D scanning produces is new information that will give forecasters a better understanding of what exactly is happening beyond wind and rain.

Correlation Coefficient

4panel_branson_textThe correlation coefficient scan focuses on objects detected by radar.  orange and yellows (where thunderstorms are located) can indicate hail potential, or hail mixing with rain.  But the most powerful feature of this scan is its ability to detect debris.  This gives meteorologists a better indication whether an area of rotation has, in fact, produced a tornado.  This ability was put on display during a late February tornado outbreak.  A dual pol radar captured the image to the right of debris in the air as a tornado ripped through Branson, MO. 

Besides hail and debris, this scan will also detect non-storm related things such as a flock of birds.  While that doesn’t sound exciting, the actions of animals can sometimes give forecasters an indication of the air patterns that could impact thunderstorm development.


Hydrometeor Classification Algorithm

This particular scan will be most beneficial any time of the year for forecasters.   With this scan, a Dual-Pol radar won’t just show you the estimated intensity of the rainfall, it can show you what type of precipitation is falling.  Current NEXRAD technology only detects reflectivity.  The heavier the rain the higher the reflectivity.  In cases of extremely high reflectivity rates, a meteorologist would speculate that it could be, in fact, hail falling instead of rain.

But with the HCA scan, the radar will be able to tell whether it’s rain, hail, sleet, snow, etc.  By telling the difference, and eliminating the guess work, estimated rainfall rates and detection of other, more dangerous forms of precipitation will improve dramatically.  This will create better rainfall estimates, snowfall estimates, hail prediction and, as a result, better more accurate warnings.

There are other new scans that will also improve the detail we within a threatening storm.  But I feel these two are the most important.  This is the biggest upgrade to the NEXRAD radar system since it’s creation more than 20 years ago.  First designed in 1988, there is hope that NEXRAD is reaching the end of its successful run.  Pending budget approval, the National Severe Storm Laboratory is continuing research on the radar that should replace NEXRAD in the next 10-15 years. 

It’s called Phased Array radar.  The potential benefits of this technology are still not completely known, but something to look forward to as weather forecasting and weather detection continue to improve – and save lives.

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