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ASSESSMENT OF THE NEW GREAT LAKES WATERSPOUT FORECAST SYSTEM
2013 Great Lakes Operational Meteorology Workshop
Victor Chung & Wade Szilagyi
Meteorological Service of Canada
April 9, 2013
Page 2 – April 21, 2023
Introduction – The Great Lakes Waterspout Forecast System (GLWFS)
• Experimental tool → potential for waterspouts over the Great Lakes
• Output → Szilagyi Waterspout Index (SWI), 0-48 hrs
• Automation of the Waterspout Nomogram
• Used for the first time in 2012 at the OSPC
Page 3 – April 21, 2023
Verification - Methodology
Page 4 – April 21, 2023
Verification Considerations -Seasonal Period
• Peak of waterspout season (August - September) chosen
Page 5 – April 21, 2023
Verification Considerations - Diurnal Time Period
• Daytime only (12-18Z, 18-24Z)
Page 6 – April 21, 2023
Verification Considerations – Areal Coverage
• Half lake resolution (marine forecast sub-zones)
Page 7 – April 21, 2023
Verification - Database
• 13,180 entries
Page 8 – April 21, 2023
Verification - Database
• Date (Aug. – Sept.)
• Time (12-18Z, 18-24Z)
• Location (i.e. western Lake Erie)
• Forecast/Observed/Possible Waterspouts (Yes/No)
• Forecast SWI (<0, 0, 1,…,10)
• SWI Percent Coverage (0, 25, 50, 75,100%)
• Forecast/Observation Location Correlation (Yes/No)
• Lead Time (0-48 hrs)
Page 9 – April 21, 2023
Verification - Results
• N = 1,318
Page 10 – April 21, 2023
Verification - Results
Page 11 – April 21, 2023
Verification - Results
• Average Lead Time = 36 hrs!
• Forecast/Observation Location Correlation = 92%
• Forecast SWI value-waterspout events most frequently associated with forecast SWI
≥ 7
• SWI Percent Coverage-over half of the events occurred when coverage was ≥ 75% →
SWI areal coverage is a factor to consider when forecasting waterspouts
Page 12 – April 21, 2023
Case Study –Waterspout Outbreak (Aug. 9-13, 2012)
Page 13 – April 21, 2023
1500Z, Aug 09, 2012
1604z
1601z
1542zA fewwaterspouts
Page 14 – April 21, 2023
1800Z, Aug 09, 2012
1700z
1710zFunnels and 2 waterspouts
1700zA few waterspouts
1710-1735zMultiplewaterspouts 1926z
Page 15 – April 21, 2023
2100Z, Aug 09, 2012
2145z
2137zMultiplewaterspouts
Page 16 – April 21, 2023
0600Z, Aug 10, 2012
0524z
Page 17 – April 21, 2023
1200Z, Aug 10, 2012
1242-1248z2 waterspouts
Page 18 – April 21, 2023
0000Z, Aug 11, 2012
Early evening2 funnels
Page 19 – April 21, 2023
1200Z, Aug 11, 2012
1330z
Page 20 – April 21, 2023
1500Z, Aug 11, 2012
1630z
Page 21 – April 21, 2023
2100Z, Aug 11, 2012
2000z
Page 22 – April 21, 2023
0000Z, Aug 12, 2012
2325z
Page 23 – April 21, 2023
1200Z, Aug 12, 2012
1510-1525z2+ waterspouts
1506z
Page 24 – April 21, 2023
Conclusion
1.Has a very good lead time
2.Has excellent rare event skill score
3.Has good non-rare event skill scores
The Waterspout Forecast System:
Page 25 – April 21, 2023
Future Work• Include surface convergence (SWI → ESWI)
• Higher resolution model output (horizontal and vertical)
• Distinguish between “Severe Wx” vs “Fair Wx” waterspouts
• Expand to other marine areas: Atlantic/Pacific coasts, globally
• Experimental → Operational
• Investigate use as a landspout forecast tool