1. Balanced or Slightly Shear Dominant Regions of the QLCS Line Normal 0-3 km Bulk Shear ≥ 30 Knots Surge or Bow in the Line 1 1.Define the Updraft Downdraft Convergence Zone (UDCZ): Convergence zone coincident with gust front 2.Along UDCZ, look for: Deep, nearly vertical updraft Tight reflectivity gradient Trailing stratiform, also possibly thin leading stratiform Inflection point Solve for component of 0-3 km bulk shear that is perpendicular to the UDCZ Look for values ≥ 30 knots A rear inflow jet or enhanced outflow are likely candidates to cause a surge or bowing When all three ingredients are co-located in a QLCS, there is an increased likelihood for mesovortex genesis and intensification, along with increased tornado potential. 2 3 (1) Enhanced Surge - Tip of local surge is displaced more than 5 nm from the rest of the line OR larger bow is accelerating. - Located where the UDCZ curls from the leading edge back into the precipitation. - FIN on front & often northern side of surge. RIN location is typically directly behind FIN, but depends on trajectory of the RIJ/outflow. 1. Enhanced Surge 2. Inflection Point 3. Paired Front & Rear Inflow Notch (FIN/RIN) Michael Mathews NOAA/NWS Bismarck, ND (2) Inflection Point (3) FIN (3) RIN - Synoptic front or convective outflow ingested by surge. Front is typically stationary. 4. Boundary Interaction - May be variation of coupled FIN/RIN and local surge. - Low level Vr ≥ 25 kts. 8. TDS 5. Front End “Nub” 6. Contracting Bookend Vortex with Increasing Rotational Velocity 7. Tight & Strong Mesovortex [5] “Nub” UDC Z [6] Bookend Vortex Any one of the 8 scenarios met with the 3 ingredients is often worthy of a Tornado Warning. Multiple scenarios should further confidence. 1. Reflectivity Tag About to Intersect Surge - Often ahead of line and may only be viewable at higher slices. 2. 0-3 km ML CAPE ≥ 40 J/kg 4. History of TDS’s 3. Reflectivity Spiking Up Near Surge Nudgers are secondary, and should add confidence to a Tornado Warning when one of the scenarios and the three ingredients are present. michael.mathews@noaa.gov Jason Schaumann NOAA/NWS Springfield, MO jason.schaumann@noaa.gov 2240 UTC 2351 UTC 2311 UTC 2255 UTC Balanced or slightly shear dominant 0-3 km line normal bulk shear ≥ 30 kts RIJ or enhanced outflow causing surge in line Balanced or slightly shear dominant 0-3 km line normal bulk shear ≥ 30 kts RIJ or enhanced outflow causing surge in line X Balanced or slightly shear dominant 0-3 km line normal bulk shear ≥ 30 kts RIJ or enhanced outflow causing surge in line Balanced or slightly shear dominant 0-3 km line normal bulk shear ≥ 30 kts RIJ or enhanced outflow causing surge in line Balanced or slightly shear dominant 0-3 km line normal bulk shear ≥ 30 kts RIJ or enhanced outflow causing surge in line Balanced or slightly shear dominant 0-3 km line normal bulk shear ≥ 30 kts RIJ or enhanced outflow causing surge in line Balanced or slightly shear dominant 0-3 km line normal bulk shear ≥ 30 kts RIJ or enhanced outflow causing surge in line Balanced or slightly shear dominant 0-3 km line normal bulk shear ≥ 30 kts RIJ or enhanced outflow causing surge in line X QLCS forming…cold pool has yet to fully conglomerate. 35 kts 0-3 km bulk shear X X QLCS formed…RIJ impacting line from southwest. Marginal North side of surge is close to fulfilling three ingredients. Report: 80 mph winds flipped pontoon and snapped trees. Reports: Over the following 30 minutes this section of the QLCS produced multiple wind gusts from 65 to 90 mph. Inflection Point Null Event for a Central North Dakota QLCS on 7/21/2014 More on the three ingredients, scenarios, and nudgers at the NWS Springfield, MO office Google Site. This includes one pagers and a brief training video. Courtesy Doug Cramer WFO SGF Courtesy Doug Cramer WFO SGFBenefits Can be used at long ranges from the radar where developing mesovortices are not visible Improved lead time and probability of detection of tornadoes (Stanford et al, 2013) Marginal Marginal