How to Effectively Use Weather Radar. Presented by: Robert Reale Company:

Transcription

1 How to Effectively Use Weather Radar Presented by: Robert Reale Company:

2 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

3 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

4 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).

5 How Does RADAR Work?

6 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

7 How Do You Radar? 4AM - 9AM National Composite Regional Composite Local Doppler Airport Tower Radar (TDWR)

8 How Do You Radar? 730AM - 9AM National Composite Regional Composite Local Doppler Airport Tower Radar (TDWR)

9 How Do You Radar? 8AM - 9AM National Composite Regional Composite Local Doppler Airport Tower Radar (TDWR)

10 How Do You Radar? 8AM - 9AM National Composite Regional Composite Local Doppler Airport Tower Radar

11 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

12 Composite Radars Notice how widespread the showers look on the regional compared to the local!

13 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

14 NWS Local Doppler Radars

15 Airport Tower Radars (TDWRs)

16 Canadian Radars

17 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

18 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 Radar Site 1500 ft Trenton 5000 ft WeatherWorks Radar 20mi 65mi

19 Why is That Not Falling? Virga Virga is observable precipitation falling from a cloud, but evaporates before reaching the ground. Virga can happen at any time of the year, but it is most common during the winter when the air is drier. My radar shows snow, but nothing is falling. What do I do with my crews?

20 Why is That Not Falling? Virga Loop time: 725AM 855AM Most of this is NOT reaching the ground

21 Classic Winter Virga Example: Feb 16, 2015: 9-10PM

22 Classic Winter Virga Example Feb 16, 2015: 10PM

23 Classic Winter Virga Example Feb 16, 2015: 10-11PM

24 Classic Winter Virga Example Feb 16, 2015: 11PM

25 Classic Winter Virga Example Feb 16, 2015: 11PM - 12AM

26 Classic Winter Virga Example - TDWR Feb 16, 2015: 11PM - 12AM

27 Further Understanding Doppler Radar 1. Clear Air Mode Mode when little or no precipitation is detected Scale ranges from -28 dbz to 28 dbz Very sensitive > can detect, birds, smoke, dust Useful for detecting very light precipitation (flurries, drizzle, etc) Updated every 10 minutes 2. Precipitation Mode Mode used when actual precipitation is detected in area Scale ranges from 5 dbz to 75 dbz or greater Most common mode seen by public on television / internet Useful in determining intensity of precipitation Updated every 5 minutes, or less

28 Radar Deceptions Why does the radar look like this? Any guess as to what this is? Hint: It s not a shower

29 Let s Talk P-Type

30 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.

31 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 during the winter. Correlation Coefficient: This shows how similar precipitation particles 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.

32 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.

33 Identifying Weather Events on Radar Major Winter Storms Banding Snow Showers Additional Water-Enhanced Snow Severe Thunderstorms Detecting Boundaries Hurricanes

34 Classic Major Midwest Snow Storm February 1-2, 2011: Ground Hog s Day Blizzard

35 Classic Major Nor Easter December 26, 2010: Boxing Day Blizzard

36 Classic Lake Effect Snow Showers March 18, 2015 (8-9AM)

37 Classic Lake Effect Snow Showers March 18, 2015 (8-9AM)

38 Classic Lake Effect Snow Showers March 18, 2015 (8-9AM)

39 Other Water-Enhanced Snow Showers January 5, 2016

40 Detecting Severe Weather May 22, 2014

41 Detecting Boundaries September 5, 2012

42 Hurricane - Isaac August 29, 2012

43 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

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45 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

46 How Can YOU Better Radar? Combine radar with actual ground truth. Sources of ground truth include: - Airport observations (METARs) - Webcams - Weather Forums / Social Media - Looking outside

47 Recommended Radar Sources Desktop: - NOAA - WeatherTap Phone App: - RadarScope - WeatherTap Mobile - GR2Analyst

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49 Questions? Contact Information: Robert Reale