Operational thunderstorm nowcasting in the Alpine region using 3Dradar severe weather parameters and

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Operational thunderstorm nowcasting in the Alpine
region using 3D-radar severe weather parameters
and lightning data

• Alessandro Hering1, Urs Germann1, Marco
  Boscacci1, Stéphane Sénési2
• 1 MeteoSwiss, Locarno-Monti, Switzerland
• 2 Météo-France, Toulouse, France.

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Montreux, Lake Geneva, 18.7.2005
Source Webcam Hotel Splendid, Montreux,
Switzerland
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Montreux, Lake Geneva, 18.7.2005
Source Webcam Hotel Splendid, Montreux,
Switzerland
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Montreux, Lake Geneva, 18.7.2005
Source Webcam Hotel Splendid, Montreux,
Switzerland
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TRT (Thunderstorms Radar Tracking)
18.7.2005 (1250-1435)
TRT Cell-based VIL (Vertically Integrated Liquid)
TRT Cell tracking
220 km
40dBZ
13dBZ
25dBZ
55dBZ
Montreux (webcam)
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TRT (Thunderstorms Radar Tracking)
18.7.2005 (1250-1435)
TRT Cell-based VIL (Vertically Integrated Liquid)
TRT Cell tracking
220 km
40dBZ
13dBZ
25dBZ
55dBZ
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TRT (Thunderstorms Radar Tracking)
18.7.2005 (1250-1435)
TRT Cell-based VIL (Vertically Integrated Liquid)
TRT Cell tracking
220 km
40dBZ
13dBZ
25dBZ
55dBZ
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Scan geometry, Orography

• Scan geometry of Swiss radar La Dôle situated on
  a mountain top (1680 m a.s.l.) near Geneva
• Orography roughly in the direction of the hail
  swath on 18 July 2005

Montreux (webcam)
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TRT (Thunderstorms Radar Tracking)

• TRT real-time object-oriented tool for
  thunderstorms nowcasting based on multiple-radar
  composites
• 2003 TRT operational at MeteoSwiss
• Detection Dynamic reflectivity thresholding
  scheme
• cells detected at individual thresholds 36-48
  dBZ
• 2004 Improved cell position extrapolation
• 2005 Lightning data added ? multiple-sensors
  system
• 2006 3D multiple-radar derived storm properties
• cell-based (time series), grid-based (2D
  horizontal fields)
• VIL (Vertically Integrated Liquid)
• EchoTops 15/45 dBZ
• Max storm reflectivity altitude

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Operational view cell-based
attributes VIL, 15/45 EchoTops, storm altitudes

• Cartesian composite 3 C-band Doppler radars
• 20 elevation scan (-0.3 / 40)
• 12 CAPPI between 1 and 12 km
• 5 min
• Lightning data
• CG positive/negative

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The severe hailstorm on 18 July 2005

• One cell, 1100-1500 UTC, developed to a
  supercell hailstorm moving over Lake Geneva to
  western Switzerland
• 250 km track
• hail swath 1200 km2
• 8 people injured
• 15'000 cars damaged
• several vineyards destroyed
• Insured claims gt 70 millions

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Hail swath on 18 July 2005

• Hail crop damage claims (Swiss Hail Insurance)

• Daily maximum grid-VIL

• Daily maximum grid-VIL gt 10 kg/m2

• Squares communities where hail reported at least
  once

540 km
kg/m2
0
20
40
60
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Hail swath on 18 July 2005

• Maximum grid-VIL gt 5 kg/m2 (1030-1700 UTC)
• Hail crop damage locations (Swiss Hail Insurance)
  

100 km
kg/m2
0
20
40
60
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Hail swath on 18 July 2005

• Maximum grid-VIL gt 5 kg/m2 (1030-1700 UTC)
• Hail crop damage locations (Swiss Hail Insurance)
  
• POH (Probability of Hail) Waldvogel et al.
  (1979)

Hail ?H 1.4 km
3850 m
100 km

20
40
60
80
100
0
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Hail swath on 18 July 2005

• Maximum grid-VIL gt 5 kg/m2 (1030-1700 UTC)
• Hail crop damage locations (Swiss Hail Insurance)
  
• POH (Probability of Hail) Waldvogel et al.
  (1979)

Hail ?H 1.4 km
3850 m
VIL
POH
100
20
40
60
80
0
0
20
40
60

kg/m2
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18.7.2005 cell-based attributes
Montreux (F2 tornado, 161 km/h)
Geneva (F1 tornado)
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18.7.2005 max cell-VIL distribution
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Conclusions and outlook

• Reliable operational thunderstorms
  identification, tracking and 3D characterisation
  in Alpine area needs
• high resolution in height / time 20-elev. (-0.3
  / 40) in 5 min
• dynamic reflectivity thresholding scheme TRT
• multiple-radar composites
• Nowcasting in Alpine area
• use 3D storm attibutes VIL, 15/45 EchoTops, max
  storm refl. altitude, CG for assessing the severe
  weather potential of thunderstorms
• combine grid-based 2D-animations and cell-based
  time trends
• Outlook Alpine area
• VIL determine typical values, thresholds for
  occurrence of hail
• explore use of POH!? (Probability of Hail,
  Waldvogel et al.)
• extend time series analysis to forecast
  thunderstorm development (stage in its life cycle)