1. WSR‐88D Dynamic Scanning
- SAILS and AVSET
Fred H. Glass

2. Supplemental Adaptive Intra-Volume Low-Level Scan (SAILS)
Automated Volume Scan Evaluation and
Termination (AVSET)
Dynamic scanning techniques designed to:
shorten volume scan times
increase frequency of lowest-level scan
Benefits are more frequent volume scan updates/data and more low-level “looks”
AVSET has been in operation since Spring 2010
SAILS will be implemented in late April-May 2014, and is intended only to support severe weather operations

3. Automated Volume Scan Evaluation and Termination (AVSET)
Operator selectable method to make each volume scan “dynamic”
The number of angles/elevations scanned is dependent on the sampled meteorological return
Terminates volume scan once returns fall below thresholds of dBZ and areal coverage
Shortens time between product updates when no significant data exists on higher elevation tilts
VCP31/32 not impacted by AVSET

6. How AVSET Works Only analyzes data above 5°
To terminate, each condition must be met:
≥18 dBZ over < 80 km²
≥ 30 dBZ over < 30 km²
areal coverage ≥18 dBZ has not increased by 12 km² or more since the last volume scan
If all three conditions are met…
AVSET terminates the volume scan after completion of the next higher elevation
VCP 212 Example:
Below thresholds at °? Will terminate after 6.4°
Now for some details on AVSET’s execution. AVSET only analyzes data above 5°, which means that VCPs 31 and 32, the Clear Air Mode VCPs, are not impacted.
For each elevation above 5°, AVSET checks the total areal coverage of returns above both 18 and 30 dBZ. To terminate the volume scan, there are three conditions and all three of them must be met.
The coverage at or above 18 dBZ must be less than 80 km2.
The coverage at or above 30 dBZ must be less than 30 km2.
The coverage at or above 18 dBZ has not increased by 12 km2 or more since the last volume scan.
If these three conditions exist, the next slide tells you what AVSET will do!

7. How Short Can We Go? VCP 12 full volume scan time 4 min, 18 sec
AVSET shortest update 3 min, 10 sec
You may be wondering how much AVSET could potentially shorten a VCP. Since AVSET begins checking the data for the first elevation above 5.0°, it could be that the returns are below the thresholds on that first elevation. If so, AVSET will terminate the volume scan after the next higher elevation is complete. Examples for VCP 11 and 12 are presented here, with a complete volume scan and the shortest possible termination with AVSET. All the times will vary slightly from site to site.
VCP 212 full volume scan time 4 min, 36 sec
AVSET shortest update 3 min, 30 sec

8. AVSET and Range to Weather
AVSET with storms at far range
Only relevant elevations above 5° used
AVSET with storms at close range
Entire VCP used
The number of elevations not sampled for any given VCP is completely dependent on the range and height of relevant weather features. When there is deep convection at close range, as with the storm on the left side of the graphic, the entire VCP will be used. As the range of storms increases or the height of weather features decreases, AVSET will dynamically control the number of scanned elevations, which will shorten the VCP update time as appropriate. As storms approach or grow, AVSET dynamically adds elevations to ensure complete coverage.

9. Supplemental Adaptive Intra‐Volume Low‐Level Scan (SAILS)
A new dynamic scanning method which is operator selectable
Inserts a new low-level scan (0.5°) into the “middle” of the volume scan (wrt time)
The goal is to evenly space, as close as possible, the time interval between low-level data updates
Only functional in the existing severe weather VCPs 12 and 212
Z, V, SW and Dual Pol variables will be generated and distributed (Level 2)
Known as the “Sails Scan”

10. How Does SAILS Work?
Figure 1
In this example, the radar is operating in VCP 12 with a termination angle of 19.5°. The “middle” of the volume scan is ~140 seconds which results in collecting the Supplemental Low‐Level scan after completion of the 3.1° elevation cut.
Figure 2
When SAILS is active:
the radar scans up through the middle of the volume scan, 3.1° elevation cut in this example (Figure 1)
transitions down to collect the supplemental 0.5° split cut data (Figure 2) then
elevates to 4.0°, in this example (Figure 3), to resume collecting data to complete the volume scan.
Figure 3

11. How Does SAILS Work?
For VCP12

12. SAILS Implementation
To collect the supplemental 0.5° scan adds approximately 35 seconds to the volume scan duration
SAILS 0.5° Update Rate: Every ~140 seconds (~105 seconds w/ AVSET)
shortens low-level scan update to < 3 minutes; < 2 minutes with AVSET
In VCP 12, volume scan completion times range from as short as 225 sec with AVSET (termination after 6.4°) to 285 sec for a full volume scan

13. VCP 12 with SAILS Insertion Points
AVSET
Termination Angle = 15.6
AVSET
Termination Angle = 12.5
AVSET
Termination Angle = 10.0
AVSET
Termination Angle = 8.0
AVSET
Termination Angle = 6.4
Elevation Angles (VCP 12)
VCP 12 Elevation Duration
Termination Angle = 19.5
0.5°
31 Sec
31 Sec
31 Sec
31 Sec
31 Sec
31 Sec
31 Sec
0.9°
31 Sec
31 Sec
31 Sec
31 Sec
31 Sec
31 Sec
31 Sec
1.3°
31 Sec
31 Sec
31 Sec
31 Sec
31 Sec
31 Sec
31 Sec
1.8°
15 Sec
15 Sec
15 Sec
15 Sec
15 Sec
15 Sec
15 Sec
0.5°
31 Sec
31 Sec
2.4°
14 Sec
14 Sec
14 Sec
14 Sec
14 Sec
14 Sec
14 Sec
0.5°
31 Sec
31 Sec
3.1°
14 Sec
14 Sec
14 Sec
14 Sec
14 Sec
14 Sec
14 Sec
0.5°
31 Sec
31 Sec
4.0°
14 Sec
14 Sec
14 Sec
14 Sec
14 Sec
14 Sec
14 Sec
5.1°
14 Sec
14 Sec
14 Sec
14 Sec
14 Sec
14 Sec
14 Sec
6.4°
14 Sec
14 Sec
14 Sec
14 Sec
14 Sec
14 Sec
14 Sec
8.0°
13 Sec
13 Sec
13 Sec
13 Sec
13 Sec
13 Sec
10.0°
13 Sec
13 Sec
13 Sec
13 Sec
13 Sec
12.5°
13 Sec
13 Sec
13 Sec
13 Sec
15.6°
13 Sec
13 Sec
13 Sec
19.5°
13 Sec
13 Sec
Duration
243 Sec
274 Sec
261 Sec
248 Sec
235 Sec
222 Sec
209 Sec
0.5 Elevation Update Times
243 Sec *
136 Sec and 138Sec *
136 Sec and 125 Sec *
122 Sec and 126 Sec *
122 Sec and 113 Sec *
108 Sec and 114 Sec *
108 Sec and 101 Sec *
* Plus Retrace Time

14. Benefits of SAILS
Significantly reduces low‐level scan update interval, especially for more distant storms
Provides more low‐level “looks” during severe weather operations
VCP 12
Number of 0.5° Product Updates per Hour
Volumetric Product Updates per Hour
Standard Operation 14
AVSET
14 ‐ 19
SAILS 24 12
SAILS and AVSET
24 ‐ 32
12 ‐ 16
VCP 212
Number of 0.5° Product Updates per Hour
Volumetric Product Updates per Hour
Standard Operation 13
AVSET
13 ‐ 17
SAILS 22 11
SAILS and AVSET
22 ‐ 28
11 ‐ 14

15. Summary
Operating in VCP 12, SAILS will add additional 0.5° elevation scans per hour
During severe weather operations, the frequent low‐level “looks” provided by SAILS will significantly enhance WSR‐88D forecast and warning support, while not impacting WSR‐88D data quality or hardware operations
AVSET will be enabled by default with the arrival of SAILS
Extend SAILS to result in 2-4 low-elevation scans per volume in Build 16 (April 2015)

16. Questions
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