Presentación realizada en la 3rd European Nowcasting Conference, celebrada en la sede central de AEMET en Madrid del 24 al 26 de abril de 2019

Germann, Urs

Hamann, U.

Hering, Alessandro

Nisi, L.

English

Nisi, Luca

Hamann, Ulrich

Agencia Estatal de Meteorología

Federal Department of Home Affairs FDHAFederal Office of Meteorology and Climatology  MeteoSwissLightning-jumps in convective cells tracked by radar as a nowcasting tool in complex orographyAlessandro M. Hering, Luca Nisi, Ulrich Hamann and Urs GermannMeteoSwiss, Locarno-Monti, Switzerland3rd European Nowcasting Conference (ENC), 24-26 April 2019, Madrid, SpainLightning Jump• Lightning Jumps (LJ): sudden increase in total lightning (CG+IC) flash rate within thunderstorm cells• LJ based on trends in total lightning as a bulk thunderstorm property• LJ associated with rapid intensification of the updraft, increasing number of ice particle collisions, greater charge separation and lightning number• LJ can occur from few minutes to tens of minutes before the onset of severe weather (hail, heavy rain, wind gusts,…)• Last decade: several publications LJ detection algorithms (e.g.)  USA: Williams et al. (1999), Schultz et al. (2009-2017), Darden et al. (2010), Gatlin and Goodman (2010), Chronis et al. (2015),… EU: Farnell et al. (2017, 2018), Wapler (2017),…• Goals Real-time implementation of LJ algorithm:  since summer 2018 Assess the nwc potential in case of real-time, operational useSouthern Switzerland, Lake Lugano, near Radar Monte Lema Photo: Andreas HostettlerLightning Jumps vs. hail storms (2014-2017)(total lightning: CG + IC;   cell duration ≥30min)LJ before hail initiation (POH ≥ 80%) or MaxEcho (ordinary storms)(35673)   (3512)   (1254)    (685)     (133)stormsnumber:frequencyordinary POH≥80%MESHS≥2cmMESHS≥4cmMESHS≥6cm0.00.10.20.30.50.60.70.80.90.4Nisi et al. (in preparation)LJ algorithm: Schultz et al., 2009, modified(LightningRatemin: 15 flashes / 5 min;  Sigma-level = 1)Preliminary:POD: 45%   FAR: 29% LeadTime: ~18 min 3%43%Lightning Jump: real-time algorithm (1)• LJ algo originally built/tested to run on 3D Lightning Mapping Arrays• Main sources of total lightning data for LJ algorithms (literature):  LMAs (Lightning Mapping Arrays);   3D, acc. <100 m  GOES-R GLM (Geostationary Lightning Mapper); acc. <10 km1) Total Lightning Detection Network: METEORAGE / EUCLID VLF/LF, CG+IC, triangulation+time-of-arrival resolution: 30 sec, acc. <1 km 2) Thunderstorm cells by TRT (Thunderstorms Radar Tracking) 5 radars, dual-pol, C-Band, 20 elevations (-0.2°/40°)  standard resolution: 5 min, 1kmMeteoSwiss(operational)Lightning Jump: real-time algorithm (2)Modified 2σ Lightning Jump algorithm (Schultz et al. 2009-2017): computeincrease in total flash rate relative to standard deviation of last 15min• Approximate TRT cells by an ellipse (last 15min)• Interpolate                    between two 5min ellipses         2.5min time resolution• Every 2.5min: compute total flash rate (flashes min-1) of each storm • Activation threshold Lightning Jump algorithm: ≥10 flashes min-1 (current cell)   Compute for last 15 min: time rate of change of tot. flash rate (DFRDT) every 2.5min Compute standard deviation σ of DFRDT (t-2.5 - t-15) Lightning Jump: DFRDTt0≥ 2σ/extrapolateLightning Jump: real-time application15.06.2017, 13:50-16:35 UTCTRT operational view: time series up to current time, automatically computed from 3D cell footprint, every 5 minRadar-based severity parametersH il par m ters and lightning parametersVIL / VILD ET45 / ET15 max HHail Size (MESHS) Hail Prob. (POH) Freezing levelRANK / IR 10.8µm MSGPrecip 1h-accuLtot / IC / CG Area Det. / AREA 45dBZ MaxEcho Velocity / DirectionMaxEchoHail Prob. (POH)VIL / VILD max HHail Size (MESHS) Freezing levelRANK / IR 10.8µm MSGPrecip 1h-accuLtot / IC / CG Area Det. / AREA 45dBZ Velocity / Directiontotal Lightning / IC / CGLightningJump14:47 15:25 15:47 algo15.06.2017, 13:50-16:35 UTCET45 / ET15max HAIL size (MESHS) Treloar (1998)HAIL prob. (POH) Waldvogel (1979)14:4714:47 15:25 15:4715:25 15:47Δt = 2.5 minSigma-level/Flash-rate (>= 10/min)LJ warning: Δ15 June 2017 14:15-16:25 UTCΔt = 2.5 min100 km>9              7               5              3               1Total lightning density [#/km2] SwitzerlandSigma-level/Flash-rate (>= 10/min)LJ warning: ΔTotal lightning density [#/km2] >9              7               5              3               115 June 2017 14:15-16:25 UTCΔt = 2.5 min100 kmDaily maximum POH90             70             50             30            10Probability of Hail   [%]15 June 2017 14:15-16:25 UTCΔt = 2.5 min100 km90             70             50             30            10Probability of Hail   [%]Daily maximum POHLJ warning: Δ 15 June 2017 14:15-16:25 UTCΔt = 2.5 min100 km90             70             50             30            10Probability of Hail   [%]15 June 2017 10:00-21:00 UTCΔt = 2.5 minDaily maximum POHLJ warning: Δ 100 kmSummary and conclusions• Modified 2σ Lightning Jump Algorithm implemented, real-time (summer 2018)• Time resolution: 2.5min; 1km• Real-time Lightning Jump Algorithm: also works with a conventional VLF/LF Total Lightning detection network promising performance, can be used as complementary nwc tool for severe weather (e.g. hailstorms) also in complex orography can help to increase lead time of real-time TS warnings caveat: LJ can occur also during/after hail occurrence (no lead time) and in sub-severe storms (no hail) so far only few feedback from forecasters, comprehensive evaluation of the real-time algorithm is still pending• Outlook: integrate LJA in the convection nowcasting and warning systems already in use at MeteoSwiss such as TRT, COALITION, NowPAL, NowPrecip and INCA explore large LJ data archive

Lightning-jumps in convective cells tracked by radar as a nowcasting tool in complex orography

https://repositorio.aemet.es/bitstream/20.500.11765/10619/1/NTSP6_Hering_3ENC2019.pdf

Lightning-jumps in convective cells tracked by radar as a nowcasting tool in complex orography

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