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

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

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

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 5.1°? 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!

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

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.

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”

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

How Does SAILS Work? For VCP12

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

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

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

Summary Operating in VCP 12, SAILS will add 10-18 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)

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