A New Great Lakes Waterspout A New Great Lakes Waterspout Prognostic System Prognostic System

(Automation of the Waterspout Nomogram)(Automation of the Waterspout Nomogram)

Wade Szilagyi and Victor ChungPresented by: David Rodgers

Meteorological Service of Canada

20th U.S. – CanadianGreat Lakes Operational Meteorology Workshop

March 14-16th

2012

IntroductionPurposeTo develop an algorithm that produces a

waterspout prognostic field for the Great Lakes

AdvantagesDramatically reduces diagnosis timeMore efficient coordination between forecast

offices Precursor upstream forecast events viewable

Waterspout Climatology over the Great Lakes

Development History1994 – Intensive investigation initiated

into waterspout activity over the Great Lakes

1996 – Waterspout Nomogram

2004 – Szilagyi Waterspout Index

2011 – Experimental Waterspout Prognostic System

Waterspout NomogramAn empirical technique to

forecast waterspouts

Based on 207 events over the Great Lakes from 1988 to 2011

Predictors:

1. Water-850 mb temperature difference (ΔT)

2. Convective cloud depth (EL-LCL = ΔZ)

3. 850 mb wind speed (W850 )

Waterspout Nomogram Wade Szilagyi, Meteorological Service of Canada (updated 2010)

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0 5 10 15 20 25 30 35 40Water - 850 mb Temperature Difference (C)Additional criterion: 850 mb Wind ≤ 35 kts

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Severe Weather AssociatedWaterspouts

Upper Low Waterspouts

Land BreezeWaterspouts

Winter Waterspouts

Waterspouts Not Likely

No Waterspouts

Szilagyi Waterspout Index (SWI)Quantifies the likelihood of

waterspout formation

A set of dimensionless SWI values (from -10 to +10) are plotted on the Waterspout Nomogram

Waterspouts are likely to occur when SWI ≥ 0. The larger the SWI the greater the potential

SWI is a function of both ΔT and ΔZ

Szilagyi Waterspout Index (SWI) Favorable Waterspout Conditions for SWI ≥ 0

Wade Szilagyi, Meteorological Service of Canada (updated 2010)

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An Overview of the Waterspout Algorithm

PGSM[CMC]

CMCGemRegOutput

GriddedWater TempSurface data

Upper Air data

Parcel trajectory(parameters required

for the index)

SWIlookup table

(derived from nomogram)

SortSounding Profile

(at every grid)

SWIoutput fields

Central CommandProgram

NinJo

Web

Output display

CMCGemLamOutput

OR

Output display

Conversion of Nomogram to SWI

Szilagyi Waterspout Index (SWI) Favorable Waterspout Conditions for SWI ≥ 0

Wade Szilagyi, Meteorological Service of Canada (updated 2010)

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0 5 10 15 20 25 30 35 40Water - 850 mb Temperature Difference (C)Additional criterion: 850 mb Wind ≤ 35 kts

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(ft)

ΔT Cloud Depth (ΔZ) SWI ..-1 54000 55000 8.5-1 55000 56000 9-1 56000 57000 9.5-1 57000 58000 10 . .0 3000 4000 -8.50 4000 5000 -80 5000 6000 -7.50 6000 7000 -7..1 9000 10000 -61 10000 11000 -5.51 11000 12000 -5.5..6 33000 34000 3.56 35000 36000 4.56 36000 37000 56 38000 39000 6..

SWI Lookup Table

Conversion of nomogram to SWI through a lookup table

•Each (ΔT,ΔZ) pair has an associated SWI value

Two Cases

1. August 21, 2011 – The Goderich Tornado Event

2. September 24, 2011 – The Lake Michigan Outbreak

August 21, 2011 – The Goderich Tornado Event

GEMREG Model Output for 12Z Aug 21 and 00Z Aug 22, 2011

500 mb Height / Vorticity12Z, Aug 21, 2011

500 mb Height / Vorticity00Z, Aug 22, 2011

Waterspout Index at 15Z Aug 21, 2011

1645Z: 1 waterspout 2.5 km off of Massassauga Provincial Park

Upstream signals for Goderich waterspout

SWI ColorScale

Hook Echo evident from 1930-1955Z northwest of Goderich

http://www.ctv.ca/gallery/html/goderich-tornado/index_.html

SWI worked very well for this event.

Waterspout Index at 18Z, Aug 21, 2011

Hook echo was evident at 1950 and 2000Z as the storm cell moved onshore

Cold air advection behind front increasing area of waterspout potential

Waterspout Index at 21Z, Aug 21, 2011

Cold air continues to advect south area of waterspout potential more extensive

Waterspout Index at 00Z, Aug 22, 2011

September 24, 2011 – Waterspout outbreak over Lake Michigan

Upper Low near Chicago, 12Z September 24

1200Z: 4+ waterspouts distant east of LI pier in Chicago

Waterspout Index at 12Z, Sept 24, 2011

1200Z: 1 waterspout 2 miles east of Waukegan

1430-1545Z:4 waterspouts off Fort Sheridan

1445-1520Z: 1 waterspout 3-4 miles east of Chicago

18Z September 24

Waterspout Index at 18Z, Sept 24, 2011

1625Z: 1 waterspout 2 miles northeast of Chicago

1510-1545Z: 7 waterspouts off of Milwaukee

21Z September 24

Waterspout Index at 21Z, Sept 24, 2011

2015Z: 1 waterspout 1 mile southeast Kenosha

00Z September 25

Waterspout Index at 00Z, Sept 25, 2011

0010Z: 1 waterspout 2 miles east of Kenosha

ConclusionThe 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 of tornados downstream

Future Adopt a higher resolution grid (0.1 lat x 0.125 long) and

use GemLam

Distinguish between “tornadic” vs “non-tornadic” waterspouts

Include surface convergent fields (GemReg/GemLam) Refine risk area

Automated output 24/7

Expand to other marine areas: Atlantic/Pacific coasts, globally

Relate SWI to landspouts