Radar

There are a number of radar tools that directly interact with radar data loaded in D-2D, including VR-Shear, Radar Display Controls, and Estimated Actual Velocity.

VR-Shear tool

The VR-Shear tool is used in conjunction with a Radial Velocity (or Storm Relative Mean Radial Velocity Map) product to calculate Rotational Velocity and shear-related quantities. The AWIPS operator positions the two endpoints of the VR-Shear tool over the desired range gates. When positioned, the VR-Shear tool determines the Rotational Velocity (in kts), the distance between end points (in nautical miles), the shear which is the velocity difference divided by the distance between points (in s-1), and it includes the distance from the radar (in nautical miles). Rotational velocity is a very important parameter in warning-decision making, and it is calculated by taking the velocity difference between two gates across azimuths (not necessarily immediately adjacent) at similar ranges and dividing by two (e.g. 40 kt outbound and -40 kt inbound yields a 40kt rotational velocity). Note the VR-Shear tool provides rotational velocity and not velocity difference. Many expert warning forecasters find it faster and easier to sample the peak velocities in a shear signature and mentally subtracting them and dividing by two, but this tool can help you with the math if you are not used to doing that, though it can take some time to get the end points where you want.

Positive shear values measured by the tool indicate cyclonic shear, while negative shear values indicate anticyclonic shear. If either end point is not directly over a range gate with valid velocity data, the phrase “no data” will appear in place of the shear value. Shear values with small signatures over a few azimuths are extremely sensitive to noise in the data and the distance between azimuths, so rotational velocity is usually a more stable parameter in warning decision making.

NOTE: If you pan the main display panel while using the VR-Shear tool to the point where you no longer see the tool endpoints, pressing the Right-Mouse Button in the main display panel will cause the tool to snap to the point where you clicked the button. This feature is common to many of the line tools in AWIPS.

Radar Display Controls tool

The Radar Display Controls tool is a GUI that gives the AWIPS operator control over the appearance of several different radar products. The most common use of Radar Display Controls is to enter a storm motion used in the display of the SRM products to better bring out peak velocities in rotational signatures as a balanced couplet of inbound and outbound velocities.These products are managed in user override files, so the settings will follow the user when logged in to different workstations

• STI (Storm Track)
  • when displaying STI loaded from the radar menu, this filter controls how many storm tracks are shown and whether to plot the past and/or future tracks
• HI (Hail Index)
  • when displaying HI loaded from the radar menu,
    • Probability of Hail (POH) defines the % threshold used in displaying open (default 30%) and filled (default 50%) small triangles (typically superseded by POSH large triangles)
    • Probability of Severe Hail (POSH) defines the % threshold used in displaying open (default 30%) and filled (default 50%) large triangles
• TVS (Tornado Vortex Signature)
  • when displaying TVS loaded from the radar menu, "Show elevated TVS" displays elevated TVSs and is off by default due to higher false alarm rate
• DMD, MD, TVS (Digital Mesocyclone Display, Mesocyclone Display, Tornado Vortex Signature)
  • when displaying DMD, MD, or TVS loaded from the radar menu, "Show extrapolated features" allows the extrapolated features to be displayed (default is off)
• DMD (Digital Mesocyclone Display)
  • when displaying DMD loaded from the radar menu,
    • "Min feature strength" - mesocyclone clutter filter specifies the minimum 3D strength rank use to display a mesocyclone
      • default is 5 (minimal mesocyclone ~ rotational velocity [Vr] 30kts; note 3 (~20 kt Vr), 7 (~40kt Vr), and 9 (~50kt Vr)
    • "Show overlapping Mesos" toggles overlapping mesocyclones (default off)
    • Tracks pullout menu specifies whether to display past and forecast tracks
• MBA (Automated Microburst Detection Algorithm Micro-Burst Alert)
  • when displaying MBA loaded from the radar menu,
    • "Show Wind Shear" lowers the display threshold to include wind shear detections (default off)
      • wind shear 0.5 degree divergence delta-V < 23kts, area < 1.2 miles
      • microburst 0.5 degree divergence delta-V > 23kts, area < 2.5 square miles
      • macroburst 0.5 degree divergence delta-V > 23kts, area > 2.5 square miles
• SRM (Storm-Relative Mean Radial Velocity Map)
  • The motion used in the SRM display is specified in the Radar Display Controls and is displayed on the upper corner of the SRM product. Setting the storm motion subtracts out a constant from the velocities displayed in SRM to better highlight balanced peak inbound and outbound velocities in rotating storms (note that this will not impact divergence and shear calculations which are Galilean Invariant). 
    • Storm Motion from WarnGen Track - user override that applies the motion from that user's last WarnGen track or that user's last Distance Speed Tool track
    • Average Storm Motion from STI - average motion computed each volume scan from the STI product for the radar displaying SRM
    • Custom Storm Motion - user override that applies that user's last custom motion defined in the Custom Storm Motion entry using the slider bars, spin boxes, or typed in text
• SAILS 
  • "Enable SAILS Frame Coordinator"
    • toggle on (default) - keyboard shortcuts change where tilting up from 0.5 degree SAILS tilt will step to the next higher tilt (similar to GR2 Analyst) and Ctrl right arrow will step to the most recent tilt available for any elevation angle
    • toggle off - keyboard shortcuts change where tilting up from 0.5 degree SAILS tilt will not go anywhere (old confusing behavior) and Ctrl right arrow will step to the most recent time of the current tilt
  • For a summary of all-tilts keyboard shortcuts, see the All-Tilts reference page.

Estimated Actual Velocity (EAV) tool

The Estimated Actual Velocity (EAV) tool is a radar analysis tool that allows forecasters to estimate the actual wind speed based on a user defined wind direction, the measured radial velocity, and the intersection angle between the radar beam and wind direction. This tool may be useful to some forecasters during situations where a more exact wind speed is desired to include in a warning, follow-up statement, or other text product when you know the wind direction accurately (say from spotters or from surface observations in widespread damaging wind situations).

When the angle between these two vectors is relatively small (i.e., less than 45 degrees) and the forecaster has a good estimate of the actual wind direction, than this tool’s wind speed values can be more representative of what is actually occurring. When this angle is less than 20 degrees, the wind speeds returned by the tool will be similar to the radial velocity values and provide little additional benefit. When this angle is greater than 45 degrees, the equation used by the EAV tool becomes too sensitive to incremental changes in the angle to reliably determine the actual velocity.

The tool allows users to obtain the actual wind speeds in two different manners. First, the wind speed and direction are listed at either end of the line tool that forecasters use to indicate the wind direction. Second, users can access the EAV estimated velocity at any given point by using sampling which will apply the direction of the EAV tool orientation to the calculation of the velocity estimate at the sampled range gate.

When using the EAV tool, there are some guidelines you should follow:

• You should only use the EAV tool on velocity (V) data
• DO NOT use the EAV tool on Storm-Relative Velocity Map (SRM) product displays
• Only use the EAV tool in well-sampled radial velocity areas and where the wind direction is likely to be unambiguous.

More information on the EAV Tool can be found in WES Exercise 2 D2D Radar-Related Tools Estimated Actual Velocity video.