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How to Effectively Use Weather Radar

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How to Effectively Use Weather Radar How to Effectively Use Weather Radar Presented by: Robert Reale Company: Who Am I? What is WeatherWorks? • WeatherWorks • Private weather consulting firm located in Hackettstown, NJ • Over 30 years in the snow and ice industry • We are the best at interpreting and communicating weather data • Robert Reale • Rutgers University graduate • Director of Education, Assistant Operations Manager • Main research areas include: - Improve forecasting of snow & ice - Radar Meteorology Session Overview • What is RADAR? How Does it Work? • Regional vs Doppler Radar • Doppler Radar Intricacies • Classic Radar Signatures of Various Weather Events • Snow and Ice Manager: How to Better Radar What is RADAR? • RADAR is an acronym for “RAdio Detection And Ranging”. • RADAR works by sending electromagnetic waves and “listening” for the return signals. • Radar is calibrated to help detect mainly atmospheric moisture (rain, snow, sleet, hail). How Does RADAR Work? How Do You Radar? • NOAA (National Weather Service) • Local news or television station • Weather Channel • Internet: (WUnderground, Intellicast, etc) • Phone Apps • Social media outlets • Private weather service How Do You Radar? 4AM - 9AM National Composite Regional Composite Local Doppler Airport Tower Radar (TDWR) How Do You Radar? 730AM - 9AM National Composite Regional Composite Local Doppler Airport Tower Radar (TDWR) How Do You Radar? 8AM - 9AM National Composite Regional Composite Local Doppler Airport Tower Radar (TDWR) How Do You Radar? 8AM - 9AM National Composite Regional Composite Local Doppler Airport Tower Radar Composite Radars • Can be regional or national views. • Created using an algorithm to combine all of the local Doppler radars together. • Useful to get the “big picture” of what is happening. • However, composite radars can be a bit deceiving, and often over-estimate the coverage of precipitation. Many news stations and apps show “composite radars” Composite Radars Notice how widespread the showers look on the regional compared to the local! Doppler Radars • Uses the Doppler Effect to measure the distance of a meteorological target, and its approaching or receding velocity towards the Doppler Radar site. • Radar locations: • Over 140 in the US • Over 30 in Canada • Doppler radars may struggle to detect: • Precipitation far away from the radar location • Precipitation obstructed by mountains • Very light precipitation, such as flurries or drizzle NWS Local Doppler Radars Airport Tower Radars (TDWRs) Canadian Radars How far can Doppler Radars reach? • Local Doppler radars most effectively detect precipitation within 50 miles, but can reach over 100 miles away. • The radars are orientated slightly upward, which means the beams gradually increase in elevation the farther they travel from the radar. Radar Site So the Radar Tilted Upward Means…? • Radar is NOT detecting what is occurring at the ground, but rather at an angle above it. • The base angle is 0.5° • Close to the radar is representative of nearly the ground, but further away is NOT. WeatherWorks Trenton 5000 ft 1500 ft Radar Site Trenton WeatherWorks Radar 20mi 65mi Why is That Not Falling? Virga • Virga is observable My radar shows precipitation falling from a snow, but nothing cloud, but evaporates is falling. What do I before reaching the ground. do with my crews? • Virga can happen at any time of the year, but it is most common during the winter when the air is drier. Why is That Not Falling? Virga Loop time: 725AM – 855AM Most of this is NOT reaching the ground Classic Winter Virga Example: Feb 16, 2015: 9 - 10PM Classic Winter Virga Example Feb 16, 2015: 10PM Classic Winter Virga Example Feb 16, 2015: 10 - 11PM Classic Winter Virga Example Feb 16, 2015: 11PM Classic Winter Virga Example Feb 16, 2015: 11PM - 12AM Classic Winter Virga Example - TDWR Feb 16, 2015: 11PM - 12AM Further Understanding Doppler Radar 1. Clear Air Mode 2. Precipitation Mode • Mode when little or no • Mode used when actual precipitation is detected precipitation is detected in area • Scale ranges from • Scale ranges from -28 dBz to 28 dBz 5 dBz to 75 dBz or greater • Very sensitive • Most common mode seen by > can detect, birds, smoke, dust public on television / internet • Useful for detecting very light • Useful in determining intensity precipitation (flurries, drizzle, etc) of precipitation • Updated every 10 minutes • Updated every 5 minutes, or less Radar Deceptions Any guess as Why does the radar to what this is? look like this? Hint: It’s not a shower Let’s Talk P-Type Rain or Snow? Where is the Mixing Line? • As mentioned, regional composite radars are useful, but can be misleading and appear overdone. • Winter precipitation type radars are also nice and “pleasing to look at”, but they are just radar algorithms. That means it’s not necessarily what is happening, and again can often be wrong. A Better Way to Rain vs Snow: Dual-Pol • A few years ago, NOAA developed new radar technology, allowing the radar to send beams in two directions (horizontal and vertical). • This enables the RADAR to detect both size AND shape of precipitation. • This is incredibly useful, especially for determining precipitation type Correlation Coefficient: This shows how “similar” precipitation particles during the winter. are to each other. The lower the number, the more “different” the particles are from each other. Low CC is usually indicative of hail or wintry mix. In this case, the strip of yellowish colors indicate the change over line from snow to rain. Blizzard of 17’: From a Radar Perspective • March Blizzard of 2017 was a very challenging storm throughout the Northeast, with snow to significant sleet. • This “snuck” up on some, however as the storm was progressing, radar clearly showed the mixing line moving north. • Dual-pol was essential in determining this. Identifying Weather Events on Radar • Major Winter Storms • Banding • Snow Showers • Additional Water-Enhanced Snow • Severe Thunderstorms • Detecting Boundaries • Hurricanes Classic Major Midwest Snow Storm February 1-2, 2011: Ground Hog’s Day Blizzard Classic Major Nor’Easter December 26, 2010: Boxing Day Blizzard Classic Lake Effect Snow Showers March 18, 2015 (8 - 9AM) Classic Lake Effect Snow Showers March 18, 2015 (8 - 9AM) Classic Lake Effect Snow Showers March 18, 2015 (8 - 9AM) Other Water-Enhanced Snow Showers January 5, 2016 Detecting Severe Weather May 22, 2014 Detecting Boundaries September 5, 2012 Hurricane - Isaac August 29, 2012 How Does WeatherWorks Use Radar? • Obviously there is a lot more that goes into interpreting and understanding radar than just looking at it. • We constantly combine our radar knowledge with actual ground truth to verify precipitation type, intensity, and impacts to various surfaces. • This is done through additional resources, including: • Airport observations • Mesonets • Trained Spotters • Webcams • Additional TDWR radars How Can YOU Better Radar? • Use composite (regional) radars for the “big picture”, but use Doppler (local) radars for better detail and accuracy. • Learn where the nearest Doppler Radar site is located, as well as surrounding ones • Understand the radar is detecting reflectivity ABOVE the ground, and how high varies based on distance from the radar site. - Be aware of virga - Radar may “over-shoot” low level snow showers • For more accurate rain / snow lines, use dual-pol and be aware of radar algorithms How Can YOU Better Radar? • Combine radar with actual ground truth. • Sources of ground truth include: - Airport observations (METARs) http://aviationweather.gov/metar - Webcams https://weather.weatherbug.com/weather-camera/ - Weather Forums / Social Media - … Looking outside Recommended Radar Sources Desktop: Phone App: - NOAA - RadarScope https://www.weather.gov/Radar - WeatherTap - WeatherTap Mobile http://www.weathertap.com/ - GR2Analyst http://www.grlevelx.com/gr2analyst/ Questions? Contact Information: Robert Reale 908-850-8600.
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