On Crying “Wolf” A Modest Tirade on Confusing and Inconsistent Weather Radar Displays & A favorite topic – Pireps Aided & Abetted by MIT, FSS, ATC, NWS. Ground based radar depiction provided over data link offers capability to see storms beyond the nearest storms (where X-band airborne radars may be attenuated) plus offers enhanced features (lightning, forecasts, echo tops, …) The different radars may be depicting very different portions of the storm: Airborne radar generally depicts storms near flight altitude Ground based radar depictions can differ greatly depending on how they choose to account for vertical variations in storm reflectivity Users need to understand: Types of thunderstorm and their relative frequency How the radars characterize the various storm types

Storm Depiction Ground radar (data link): Airborne radar: less attenuation enhancements displays differ greatly Airborne radar: storms near flight altitude. Ground based radar depiction provided over data link offers capability to see storms beyond the nearest storms (where X-band airborne radars may be attenuated) plus offers enhanced features (lightning, forecasts, echo tops, …) The different radars may be depicting very different portions of the storm: Airborne radar generally depicts storms near flight altitude Ground based radar depictions can differ greatly depending on how they choose to account for vertical variations in storm reflectivity Users need to understand: Types of thunderstorm and their relative frequency How the radars characterize the various storm types

TSTM types = bad, worse, impossible! Pilot Understanding: TSTM types = bad, worse, impossible! How radars Characterize What does it all mean?.

NEXRAD / WxR Correlation Ground Radar NEXRAD Cell Airborne Radar Rockwell/NASA April 3, 2002.

What Color is your sky? Life is good Bring your umbrella I’m payin’ attention Not this way!! No way, José!!!.

Isolated or “Airmess” Convective Models Radar Data Storm Life Cycle. 5 10 15 20 25 30 35 12 9 6 3 Height (km) Time (min) 20 km "Dissipating" "Mature" "Cumulus" Radar Data Storm Life Cycle. Water Content 0 10 20 30 min Diurnal forcing Short-lived Disorganized

Multi-Cell or “Line” Storms Convective Models Multi-Cell or “Line” Storms 14 12 10 8 6 4 2 –18 –16 –14 –12 –10 –8 –6 –4 –2 Distance Ahead of Outflow Boundary (km) Storm Motion –40°C –20°C –0°C S N Height (km) Really Bad Radar Data Storm Life Cycle Water Content 0 2 4 6 8 hr Large scale forcing Long-lived Organized

Organized v. Unorganized Convective Weather Organized v. Unorganized Embedded Unorganized Cellular Unorganized Convective Complex Linearly Organized Organized

Total Storm Events per ARTCC Convective Weather Relative Frequency Total Storm Events per ARTCC May – Aug 2003 ZBW ZAU ZOB ZID 93 11 119 55 139 42 98 19 ZNY ZDC Unorganized Convective Events 151 59 151 59 167 41 Organized Convective Events 167 41

What Does Radar Measure? Airborne radar at 60 nm measures ± 2-6 km at a/c altitude 5 10 15 20 25 30 35 12 9 6 3 Time (min) "Dissipating" "Mature" "Cumulus" 1 1

What Does Radar Measure? Ground radar measures entire storm profile Time (min) 15 What intensity to report? 1 1

VIL= Vertically Integrated Liquid Squall Line 23 Sept 2003 CIWS VIL ETMS VIL= Vertically Integrated Liquid CIWS Echo Tops Map Choice of maximum reflectivity at any altitude made storms appear very significant, but many aircraft safely flew over the weather Max composite reflectivity Yellow = 30 kft

Other Issues ATC Storm depiction Update rates Major terminal: ASR-9 Smaller: None / composite NEXRAD Enroute: max composite reflectivity from NEXRAD Update rates Airborne: very high Terminal: 30 seconds En route: 1- 5 minutes Data link: Depends. ATC Storm depiction Major terminal: ASR-9 Averages storm vertical profile Smaller terminals: No information or, composite NEXRAD En route: maximum composite reflectivity from NEXRAD Update rates for weather depiction Airborne: very high Terminal: 30 seconds En route: 1- 5 minutes (depends on degree of overlapping coverage) Data link: Depends on product used and product distribution system. Can vary greatly (may be 15 minutes old) Quality of weather depiction Controllers and data link products may have ground clutter contamination Airborne radar may be attenuated “Where IS that update?”

Other Issues Quality of WX depiction Ground clutter ATC ground datalink Attenuation airborne only.

Summary Storm depictions Pilot training needed Ideal product Differ significantly Pilot training needed Storm examples Display differences (airborne, datalink) Ideal product integrated ground based radar plus high quality echo tops plus high quality forecasts Need “consumers report.” Storm depictions on data link can differ significantly from airborne radar due to the vertical reflectivity profile of storms Training for pilots needs to show examples of different types of storms as depicted on airborne radar and data link products Using an integrated ground based precipitation product plus high quality echo tops information plus high quality forecasts probably offers best capability for flight planning making by higher altitude flights Need a “consumers report” for weather radar data link products

Paucity of PIREPs

10,000 Certified!!!!

What does it take? NWS wants Pireps ATC wants Pireps FSS wants Pireps Pilots need Pireps The rules require it !!!!! But…….

Still talking after all these years….. The “System” can be very clumsy. Time availability? Workload? Communications? 77 fatal GA WX accidents in ’00 -01.