Automation of the Waterspout Nomogram
CMOS/AMS Congress 2012
Montreal May 28 – June 01
Wade Szilagyi and Kwok K Chung Meteorological Service of Canada Environment Canada Introduction
Purpose • To develop an algorithm that generates a waterspout prognostic field for the Great Lakes
Advantages • Dramatically reduces diagnosis time of waterspout potential
• More efficient coordination between forecast offices
• Precursor upstream forecast events viewable (a better spatial sense) Waterspout Climatology over the Great Lakes Development History of the Waterspout Nomogram
• 1994 – Intensive investigation initiated into waterspout activity over the Great Lakes
• 1996 – Waterspout Nomogram
• 2004 – Szilagyi Waterspout Index (-10 to +10)
• 2011 – Experimental Waterspout Prognostic System Waterspout Nomogram
• An empirical technique to forecast waterspouts Waterspout Nomogram Wade Szilagyi, Meteorological Service of Canada (updated 2010) 50000 • Based on 207 events over the 45000 Severe Weather Associated 40000 Great Lakes from 1988 to 2011 Waterspouts 35000
30000 Upper Low Waterspouts No Waterspouts • Predictors: 25000 20000 Land Breeze Waterspouts 15000
10000 Waterspouts Not Likely
1. Water-850 mb temperature (ft) LCL) - (EL Depth Cloud Convective 5000 Winter Waterspouts difference (ΔT) 0 0 5 10 15 20 25 30 35 40 Water - 850 mb Temperature Difference (C) 2. Convective cloud depth (EL - Additional criterion: 850 mb Wind ≤ 35 kts LCL = ΔZ)
3. 850 mb wind speed (U850 )
Szilagyi Waterspout Index (SWI)
• Quantifies the likelihood of waterspout formation Szilagyi Waterspout Index (SWI) Favorable Waterspout Conditions for SWI ≥ 0 • Based on the Waterspout 50000 Wade Szilagyi, Meteorological Service of Canada (updated 2010) Nomogram 45000 40000
35000 • A set of dimensionless SWI values 30000
(ft) 25000
(from -10 to +10) is plotted on the 20000 Waterspout Nomogram 15000 10000 Convective Cloud Depth (EL - LCL) LCL) - (EL Depth Cloud Convective 5000
0 • Waterspouts are likely to occur 0 5 10 15 20 25 30 35 40 Water - 850 mb Temperature Difference (C) when SWI ≥ 0. The larger the Additional criterion: 850 mb Wind ≤ 35 kts SWI the higher the potential
• SWI is a function of both ΔT and ΔZ
A New Waterspout Prognostic System An Overview of the Waterspout Prognostic System
CMC OR CMC GemReg GemLam Output Output
Gridded Water Temp Sounding Profile Central Command PGSM Surface data Sort (at every grid point) Program [CMC] Upper air data
NinJo
Output display Parcel_trajectory SWI (parameters required output fields for the index)
SWI lookup table Website (derived from nomogram) Output display Example
Case 1
August 21, 2011 – The Goderich Tornado Event
GEMREG model output for 500 mb height and surface analysis 18Z Aug 21, 2011
500 mb Height / Vorticity Surface analysis Valid 18Z 2011/08/21 Valid 18Z 2011/08/21 Upstream signals for Goderich waterspout. Also, several waterspouts reported over Erie
Waterspout Index at 15Z Aug 21, 2011
SWI Color Scale 1645Z: 1 waterspout
Upstream signals for Goderich tornado 1530Z: 1 waterspout
1659Z: svrl waterspouts
1604Z: 1 waterspout 1655Z: 5 waterspouts Waterspout spotted at ~1930-1955Z northwest of Goderich
Waterspout Index at 18Z, Aug 21, 2011
1745Z: 1 waterspout
SWI works very well for this event.
http://www.ctv.ca/gallery/html/goderich-tornado/index_.html Hook echo were clearly seen from radar at 1950 and 2000Z as the storm cell moves from water to land Cold air advection behind front à increasing area of waterspout potential
Waterspout Index at 21Z, Aug 21, 2011 Cold air continues to advect south à area of waterspout potential more extensive
Waterspout Index at 00Z, Aug 22, 2011 Conclusion
• The new waterspout prognostic system speeds up the process for diagnosing waterspout potential
• The applicability of the algorithm has been demonstrated positively through a number of case studies
• The Goderich case showed that the SWI field could be used as a precursor signal for tornados downstream Future Plans • Adopt a higher resolution grid (0.1 lat x 0.125 long)
•Distinguish between “tornadic” vs “non-tornadic” waterspouts
•Include surface convergent fields (GemReg/GemLam) to Refine the risk area
•Automated output 24/7 this July on OSPC website (http://ospcweb/)
•Expand to other marine areas: Atlantic/Pacific coasts, globally (www.icwr.ca)
•Relate SWI to landspouts Conversion of the Nomogram to SWI Look Up Table
•Each (ΔT,ΔZ) pair has an associated SWI value SWI Lookup Table
ΔT Cloud Depth (ΔZ) SWI Conversion of nomogram to SWI . through a lookup table . -1 54000 55000 8.5 -1 55000 56000 9 -1 56000 57000 9.5 -1 57000 58000 10 . . 0 3000 4000 -8.5 0 4000 5000 -8 Szilagyi Waterspout Index (SWI) 0 5000 6000 -7.5 Favorable Waterspout Conditions for SWI ≥ 0 50000 Wade Szilagyi, Meteorological Service of Canada (updated 2010) 0 6000 7000 -7 45000 . 40000 . 35000 1 9000 10000 -6 30000 1 10000 11000 -5.5 (ft) 25000 1 11000 12000 -5.5 20000 . 15000 . 10000 Convective Cloud Depth (EL - LCL) LCL) - (EL Depth Cloud Convective 6 33000 34000 3.5 5000 6 35000 36000 4.5 0 0 5 10 15 20 25 30 35 40 Water - 850 mb Temperature Difference (C) 6 36000 37000 5 Additional criterion: 850 mb Wind ≤ 35 kts 6 38000 39000 6 . .