ROC
National Division
Clik Here for more informationBuilding on concept of SAILS, the Multiple Elevation Scan Option for SAILS allows the operator to select either one, two or three supplemental low-level elevation scans (verses only one supplemental scan allowed in the initial SAILS implementation) per VCP (ONLY available with VCP 12 and VCP 212).
MESO-SAILS_Intial_Description_v02_Feb_2014.pdf
MESO-SAILS_Description_Briefing_Jan_2014.pdf
MESO-SAILS_Test_Report_July_2013_for_ROC_Web_Page.pdf
Dynamic Scanning - VCP duration and product availablilty comparisons underscore the advantages of using AVSET and SAILS during severe weather events
Severe Weather VCP Duration: This table lists the average VCP duration based on AVSET termination angle (VCP 12 and 212 include SAILS).
Product Availability Comparison: This table compares the number of products available per hour with and without AVSET and SAILS executing.
Storm-Based AUTO PRF
The Auto PRF algorithm has been in the WSR-88D since the beginning. This algorithm works well but it simply selects the Doppler PRF that results in the least amount of range folded (purple) data for the entire area within a 230 km radius of the radar without consideration for the importance of any individual storm. To address this limitation, the ROC is working on a Storm-Based AUTO PRF function to augment the legacy AUTO PRF algorithm.
Storm_Based_Auto_PRF_Details_v2.pdf
Storm-Based_Auto_PRF_Presentation_Aug_2011.pdf
Storm_Based_Auto_PRF_ Investigation_Report.pdf
AUTO PRF for SZ-2 VCPs
To accommodate the requirement for SZ-2 to have 64 pulses per radial, the PRFs for all SZ-2 VCPs are hard coded. The hard coded PRFs result in the second trip clutter induced range folding bins to always be at a constant range for each VCP. While in most circumstances this is a manageable issue, under some conditions the inability to change the location of the second trip clutter induced range folded data can have a detrimental impact on the forecast and warning process. To address this deficiency, the ROC is implementing an automated PRF selection capability for the three SZ-2 VCPs (VCP 212, VCP 211 and VCP 221). This new SZ-2 Auto PRF Function determines the optimum PRF (Storm-Based or Legacy, as selected by the operator) and modifies the antenna rotation rate to maintain the 64 pulses per radial requirement.
We are encouraged by early testing of testing the SZ-2 Auto PRF function. Please check back later for more detailed information.
A scanning method to reduce the elapsed time between 0.5° elevation scans.
How Does SAILS Work?
In the example illustrated by the three figures to the right, the radar is operating in VCP 12 with a termination angle of 19.5° (AVSET is not active or AVSET is active and there are stomrs near the RDA). In this scenario, 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.
When SAILS is active:
SAILS may not be recommended for every radar due to existing bandwidth limitations.
Level II Data (PDF) (New as of 1/23/13)
General Description (PDF) *Updated 01/13
SAILS Presentation (PDF) *Updated 01/13
SAILS FAQ (PDF)
The Enhanced Velocity Azimuth Display Wind Profile (EVWP) function is designed to improve the availability and accuracy of VWP wind estimates.
General Description
The Velocity Azimuth Display (VAD) algorithm computes wind speed and direction for the heights required by the VWP product. The VAD algorithm uses a slant range parameter (default = 30 km) to guide the selection of the elevation angle for each required height. For any particular height, the elevation angle that is closest to the slant range is used to compute the wind.
The VAD wind estimate for each individual height is based on the data from a single elevation/range pair. This assumes that adequate return is available using the single elevation/slant range pair to calculate a representative wind estimate for the particular height. Several cases have demonstrated that, in many meteorological situations, the assumption that adequate valid return exists at a single range/elevation pair is not valid.
The Enhanced Velocity Azimuth Display Wind Profile (EVWP) function is designed to improve the availability and accuracy of VWP wind estimates. The concept behind the EVWP function is the fact that each VWP height is achieved at different slant ranges, depending on the elevation. Therefore, in additional to the execution of the Original VAD, the EVWP function generates multiple supplemental VAD wind estimates using different elevation/slant range pairs for each required height. Then, the EVWP function selects the �best� wind estimate for inclusion on the VWP product.
More Detailed Information
In additional to the execution of the Original VAD algorithm, generate multiple supplemental VAD wind estimates using different elevation/slant range pairs for each height. For any elevation, slant ranges are limited to the interval between 10 and 20km. As each elevation is scanned, the EVWP function passes these additional slant ranges to the VAD algorithm to process. The VAD algorithm computes a wind estimate for each height (identified slant range) intersected by the elevation scan. Each wind estimate is passed to the EVWP function for validation. The following describes this process:
Adaptable Parameters for EVWP
The following are the adaptable parameters for EVWP. The LOCA for these parameters has not been established.
Example Testing Results
KOHX_Feb_6_2008_Squal Line, shows the results of a long-period convective event from KOHX and was presented to the DQ Group on Feb 11, 2011. (PDF)
KLWX_May11_12_2006_Convective_Event, shows the results of a long-period severe convective event from KLWX. (PDF)
KGWX_May_2-3_2008_VWP-EVWP_Comparison, shows the results of a long-period convective event from KGWX. (PDF)
