1. 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

2. 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

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

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

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

6. 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
min
Diurnal forcing
Short-lived
Disorganized

7. 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 hr
Large scale forcing
Long-lived
Organized

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

9. 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

10. 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

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

12. 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

13. 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?”

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

15. 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

16. Paucity of PIREPs

17. 10,000 Certified!!!!

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

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