For Storm Rel Velocity only…Use the Composite storm table for the storm motion to enter. Either use table value for particular storm if looks good, or average several storm motions to arrive at a value to enter. TOR warning also an option, look at code at bottom of warning. Do this first before clicking on SRV.
Stormlab/Interwarn computer configuration 1 PC 2 PC 3 PC * * * Interwarn * * * Composite Reflectivity+Table * * * SPC Mesoanalysis * * * Precipitation * * * VAD Winds L 2 L 2 * Storm Relative Velocity L 2 L 2 * Velocity L 2 L 2 * Reflectivity #1 #2 #3 #1 #2 #1
Doppler Weather Radar Concepts <ul><li>Radar beam increases in altitude with distance from radar. </li></ul><ul><li>Radar beam increases in size with distance from radar. </li></ul><ul><li>Radar takes 4-5 minutes to complete full scan when in storm/precip mode. </li></ul><ul><li>Reliable doppler wind data limited to about 60-70 nm. </li></ul><ul><li>Radar velocity 100% when parallel, 0% when perpendicular to beam direction. </li></ul>
.96 Degree Beam Resolution If R = 60 NM 120 NM 180 NM 240 NM D = 1 NM 2 NM 3 NM 4 NM D D = Beam Width Radar resolution with respect to beam width / range
The Zero Isodop “Problem” When the wind velocity is parallel to the radial, the full component of the wind is measured When the radial is perpendicular to the the wind, the radar displays zero velocity - This “zero zone” is called the “Zero Isodop”. What percentage of actual wind will the radar detect? 0 0 = 100% - Parallel 15 0 = 97% 30 0 = 87% 45 0 = 71% 60 0 = 50% 75 0 = 26% 90 0 = 0% - Perpendicular
Azimuth Resolution Considerations Weak inbound, weak outbound Rotation too small to be resolved Stronger inbound than outbound Strong inbound, strong outbound Azimuth 3 Azimuth 2 Azimuth 1 Enlarged image along a radial. Individual “blocks” represent one sample volume. This graphically shows the radar resolution. Rotational couplet identification can be affected by azimuth resolution. As the diagram shows, the closer a rotation is to the radar the more likely it will be identified correctly. If the rotation is smaller than the 1 0 beam width (possible at long ranges) then the rotation will be diluted or averaged by all the velocities in that sample volume. This may cause the couplet to go unidentified until it gets closer to the radar.
How to evaluate a storm report <ul><li>Take no report at face value, always question the source of the report </li></ul><ul><li>The more accurate, reliable, and timely the report, the better the NWS does with its warnings, and the better local communities do with managing their alert and siren systems. Make sure the report is not a recycled one from a few minutes ago. </li></ul><ul><li>Every false alert/warning/siren sounding just leads to public inaction on the next storm. </li></ul><ul><li>If a storm report is received, try to verify as best as possible: </li></ul><ul><li>The exact time and location </li></ul><ul><li>If estimated or measured (how) </li></ul><ul><li>If building damage…type of building (structure) and exact damage </li></ul><ul><li>If tree damage….size of tree and/or branches…type of tree if known </li></ul><ul><li>If reporting rotation…is it clearly visible and not just clouds moving around </li></ul><ul><li>If tornado…is there clear ground contact and a connection to the cloud above </li></ul>If it don’t spin, don’t turn it in!
Tornadic Supercell “Ingredients” <ul><li>Instability (varies, usually CAPE > 1000 J/Kg) </li></ul><ul><li>Deep layer shear (0-6km) bulk shear > 35kt </li></ul><ul><li>Low level shear (0-1km) SRH > 150 m 2 /s 2 or </li></ul><ul><li> pre-existing boundary) </li></ul><ul><li>Relatively high RH values (in BL and aloft) </li></ul><ul><ul><ul><li>Sfc Td depressions <12°F </li></ul></ul></ul>
Tornadogenesis: Three ingredients Development of a persistent, rotating updraft 1 Ingestion of enhanced SRH (occasionally, large-scale SRH is sufficient) and development of strong low-level rotation 2 Development of a downdraft partially embedded in the rotation that aids in the transport of rotation to the ground, followed by focusing of that rotation through convergence if the downdraft reaches the ground with some very uncommon properties 3
TDWR WSR-88D Left over old hook “ eye” New hook developing
Suggested Tornado Siren guideline <ul><li>Your community is in a NWS tornado warning polygon (extreme e fringe?) </li></ul><ul><li>… .OR…. </li></ul><ul><li>You have a reliable/verified report of a tornado approaching/in your community or a verified funnel cloud (not cold air type) and </li></ul><ul><li>You have used Stormlab to verify the report. (rotation at 0.5/1.5/2.5) </li></ul>
Summary of How to Use Stormlab <ul><li>Use to verify incoming storm report: does it match radar? Sirens? </li></ul><ul><li>Use to position or update spotters </li></ul><ul><li>Use to time incoming weather: pathcast </li></ul><ul><li>Use to see what the radar is detecting : hail, high winds, meso, TVS </li></ul><ul><li>Use to monitor potential: flash flooding, cell mergers, strength </li></ul><ul><li>Use to know when threat has ended: rain, wind </li></ul><ul><li>Use to see visual display of the: warning polygon </li></ul><ul><li>Use to monitor weather during festivals: When to shut down? </li></ul><ul><li>Be sure to go to SPC meso page to have an idea what to expect </li></ul><ul><li>Use Interwarn to monitor: warnings, statements, storm reports </li></ul>