Transcript Tornadoes to Torrents

Tornadoes to Torrents
The Southern Ontario Severe
Weather Event of Aug 19, 2005
Social Aspects of the Event
• “Two” F2 Tornadoes…15
Minutes Apart
• Extensive Flooding in the
Greater Toronto Area…
>6 “ Rain in 90 min
• Insured Losses >$400
Million in Toronto
Alone….Most Expensive
in Ontario History
• No Serious Injuries or
Loss of Life
The Journey Across Southern Ontario
“Tornadoes to Torrents”
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Define Two Part Event
Synoptic Set Up
The Tornadoes
Flooding Rains
Interesting Lightning
Features
• Conclusions/Summary
Supercell Track
Flash Flooding
Tornadoes
Fergus
Environment Canada
Lake Nipigon
Lake
Superior
Lake
Huron
Geo
Bay
Lake Ontario
Lake Erie
Environment Canada
Supercell Track
Flash Flooding
Tornadoes
Fergus
CENTER NORMAN OK
0755 AM CDT FRI AUG 19 2005
VALID 191300Z - 201200Z
SPC AC 191255
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION
...LWR GRT LKS...
TSTMS EXPECTED TO FORM IN RESPONSE TO MODEST DIURNAL HEATING AND LOW
LEVEL CONVERGENCE INVOF WARM FRONT CROSSING ERN OH/WRN PA AND WRN
NY. COMBINATION OF INCREASING BOUNDARY LAYER MOISTURE /DEWPOINTS IN
THE UPR 60S TO LOW 70S/ AND 40+ KT DEEP WNW SHEAR SHOULD SUPPORT A
FEW DISCRETE SUPERCELLS. COUPLED WITH ENLARGED LOW LEVEL HODOGRAPHS
INVOF WARM FRONT AND LOW LCLS ASSOCIATED WITH HIGH REGIONAL
PWS...SETUP MAY ALSO SUPPORT A FEW TORNADOES.
WIND PROFILES LIKELY WILL FAVOR STORM MOTION ACROSS THE BOUNDARY
INTO THE COOLER AIR. HOWEVER...PRESENT AND EXPECTED AFTERNOON
SURFACE CONDITIONS SUGGEST THAT A SUFFICIENTLY WIDE CORRIDOR
FAVORABLE FOR SURFACE OR NEAR SURFACE-BASED SUPERCELLS WILL EXIST TO
SUPPORT AN ENHANCED POTENTIAL FOR TORNADOES. THE CONVECTION SHOULD
CONSOLIDATE INTO ONE OR TWO CLUSTERS THAT CONTINUE E AND WEAKEN BY
EARLY EVENING.
MDT
SPC AC 191646
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1146 AM CDT FRI AUG 19 2005
VALID 191630Z - 201200Z
...LOWER GREAT LAKES/UPPER OH VALLEY...
CLOUDS ARE BEGINNING TO THIN ACROSS OH WHERE STRONG HEATING IS NOW
OCCURRING WITH SURFACE TEMPERATURES WARMING INTO THE 80S. THIS
CLEARING IS EXPECTED TO SPREAD EWD INTO WRN PARTS OF NY AND PA
DURING THE AFTERNOON. SURFACE DEW POINTS NEAR 70F COUPLED WITH
WARMING TEMPERATURES WILL CONTRIBUTE TO DIURNAL DESTABILIZATION WITH
MLCAPE INCREASING TO AROUND 1500 J/KG THIS AFTERNOON. DYNAMIC
FORCING ASSOCIATED WITH THE LAKE HURON UPPER LOW AND ASSOCIATED MID
LEVEL JET STREAK ACROSS LOWER MI/SWRN ONTARIO MAY BE STRONGEST OVER
CANADA...HOWEVER WEAK CONVERGENCE ALONG THE COLD FRONT AND BETTER
DEFINED CONVERGENCE NEAR THE WARM FRONT MAY BE SUFFICIENT FOR WIDELY
SCATTERED THUNDERSTORMS TO DEVELOP THIS AFTERNOON AND EVENING.
MODEL GUIDANCE PROVIDES A VARIETY OF SOLUTIONS WITH 12Z ETA
GENERATING LITTLE CONVECTION ACROSS THE REGION...WHEREAS 15Z RUC AND
09Z SREF GUIDANCE ETAKF AND RSM MEMBERS INDICATE GREATER LIKELIHOOD
FOR THUNDERSTORM DEVELOPMENT. SUFFICIENT INSTABILITY AND VEERING
WIND PROFILES IN THE LOWEST 1-2 KM SUGGEST POTENTIAL FOR ROTATING
UPDRAFTS WITH ANY PERSISTENT STORMS THAT CAN DEVELOP...WITH
CONDITIONAL THREAT FOR A FEW SEVERE STORMS INCLUDING A FEW
TORNADOES.
MDT
MDT
WWCN11 CWTO 191650
SEVERE WEATHER BULLET
INISSUED BY ENVIRONMENT CANADA
AT 12:50 PM EDT FRIDAY 19 AUGUST 2005.
-------------------------------------------------------------------WATCHES/WARNINGS IN EFFECT FOR SOUTHERN ONTARIO...
TORNADO WATCH FOR:
=NEW= GODERICH - BLUEWATER - SOUTHERN HURON COUNTY
=NEW= WINGHAM - BLYTH - NORTHERN HURON COUNTY
=NEW= KITCHENER - CAMBRIDGE - REGION OF WATERLOO
=NEW= GUELPH - ERIN - SOUTHERN WELLINGTON COUNTY
=NEW= DUFFERIN - INNISFIL =NEW= GREY - BRUCE
=NEW= BARRIE - COLLINGWOOD - HILLSDALE =
NEW= MIDLAND - COLDWATER - ORR LAKE.
..RISK OF A TORNADO AHEAD OF A COLD FRONT THIS AFTERNOON..
THIS IS AN ALERT TO THE POTENTIAL DEVELOPMENT OF TORNADOES AND
SEVERE THUNDERSTORMS WITH LARGE HAIL AND DAMAGING WINDS.
MONITOR WEATHER CONDITIONS..LISTEN FOR UPDATED STATEMENTS.
IF THREATENING WEATHER APPROACHES..TAKE IMMEDIATE SAFETY
PRECAUTIONS.SEVERE THUNDERSTORM WATCH FOR:
Upgraded from
Sev Tstorm Watch
==DISCUSSION==
A FRONTAL SYSTEM CROSSING THE ABOVE REGIONS WILL COLLIDE WITH AN
INCREASINGLY MOIST AND UNSTABLE AIRMASS TO PRODUCE FAVOURABLE
CONDITIONS FOR SEVERE THUNDERSTORMS AND POSSIBLY TORNADOES THIS
AFTERNOON INTO EARLY THIS EVENING.
RADAR IS CURRENTLY SHOWING TWO LINES OF STRONG THUNDERSTORMS..
THE FIRST FROM SOUTH OF OWEN SOUND TO EXETER AND A SECOND LINE
APPROACHING THE EAST SHORE OF LAKE HURON. SOME OF THESE STORMS
HAVE BEEN EXHIBITING SIGNS OF ROTATION ON DOPPLER RADAR AND THERE
IS POTENTIAL FOR THESE STORMS TO PRODUCE A TORNADO.
AS OF THIS MOMENT THERE HAVE BEEN NO REPORTS OF ACTUAL TORNADOES.
THESE STORMS WILL ALSO BE CAPABLE OF PRODUCING DAMAGING WIND GUSTS
IN EXCESS OF 90 KM/H..LARGE HAIL IN EXCESS OF 2 CENTIMETRES AND LOCALLY
HEAVY RAINFALL IN EXCESS OF 50 MILLIMETRES IN ONE HOUR.
At this time, both the NWS Storm
Prediction Center and the Ontario
,
Storm Prediction Center were composing updated severe weather outlooks.
No severe weather had occurred up to this point.
A coordination call was placed to the Toronto Office from Buffalo….describing
What was being depicted on the KBUF Radar.
Moments later…calls were being received of a tornado on the ground.
WFCN11 CWTO 191735
TORNADO WARNING
ISSUED BY ENVIRONMENT CANADA
AT 1:35 PM EDT FRIDAY 19 AUGUST 2005.
--------------------------------------------------------------------TORNADO WARNING FOR:
=NEW= KITCHENER - CAMBRIDGE - REGION OF WATERLOO
=NEW= GUELPH - ERIN - SOUTHERN WELLINGTON COUNTY
=NEW= MOUNT FOREST - ARTHUR - NORTHERN WELLINGTON COUNTY
=NEW= ORANGEVILLE - GRAND VALLEY - SOUTHERN DUFFERIN COUNTY.
SEVERE THUNDERSTORM WARNING UPGRADED TO TORNADO WARNING FOR:
KITCHENER - CAMBRIDGE - REGION OF WATERLOO
GUELPH - ERIN - SOUTHERN WELLINGTON COUNTY
MOUNT FOREST - ARTHUR - NORTHERN WELLINGTON COUNTY
ORANGEVILLE - GRAND VALLEY - SOUTHERN DUFFERIN COUNTY.
--------------------------------------------------------------------==DISCUSSION==
RADAR IS DETECTING A SEVERE ROTATING STORM NEAR JUST EAST OF CONESTOGO LAKE.
OPP HAVE RECEIVED A REPORT OF A TORNADO WITH THIS STORM. THIS STORM IS MOVING
EASTWARD AT 70 KM/H.
THIS IS A WARNING THAT SEVERE THUNDERSTORMS WITH TORNADOES ARE IMMINENT OR
OCCURRING IN THESE REGIONS. MONITOR WEATHER CONDITIONS.TAKE IMMEDIATE SAFETY
PRECAUTIONS.NOTE..A SUMMARY OF ALL WARNINGS AND WATCHES FOR SOUTHERN ONTARIO
ISAVAILABLE IN THE WWCN11 CWTO BULLETIN ISSUED IMMEDIATELY FOLLOWING THIS BULLETIN.
END/TUGWOOD
Strong
Mesocyclone
Strong
Mesocyclone
But a Funny Thing Happened on
the Way to Toronto…
The Supercell Seemed to
Change ‘Character’
• Tornadic Storm
Evolved into Wind
and Flood Producer
• Mesocyclone (general
circulation) remained
intact
• Marine Layer from
Lake Ontario may
have come into play
Mesocyclone approaching Toronto (20m West YYZ)
Moderate Meso
Storm Reports from Toronto
Brampton…Torrential Rain/Flooding 100mm (4”) Rain
Toronto…Severe Flooding; Golf Ball Sized Hail;
Localized Straight Line Wind Damage
Downsview (EC)…136mm (5.4”) Rain; Flooding
(Partial Evacuation of the Storm Centre)
Toronto…175mm (7”) Rain
Ajax to Oshawa…Torrential Rain; Flash Flooding
Lightning Characteristics
5 Minute Cloud to Ground Lightning Stirkes
300
250
200
Neg LTGCG
Total Strikes 150
Pos LTGCG
100
50
0
1625z
1700z
1730z
1800z
1830z
Two F2 Tornadoes
1900z
1930z
2000z
Flash Flooding
Transition Zone?
Relatively High Strike Count
46% Ave Positive LTGCG
Nearly 60% Positive During 2nd F2
Relatively High Strike Count
22% Ave Positive LTGCG
Studies Worth Citing
The Relationship between Cloud to Ground Lightning Polarity and Surface Equivalent
Potential Temperature during Three Tornadic Outbreaks
(Smith, LaDue, MacGorman 2000)
1512 – Strikes
1225 + Strikes
Southern Ontario
18Z Aug 19, 2005
2490 – Strikes
803 + Strikes
Southern Ontario
20z Aug 19, 2005
Lightning Characteristics
CG Lightning
350
300
# Strikes
250
200
150
100
50
0
Time
F2 Tornadoes
• Ramped up lightning during touchdowns
• High Percentage of Positive Lightning
Strikes…Particularly During ‘Second” F2 Tornado
Studies Worth Citing
Positive CG Lightning Associated with the Spencer F4 Tornado of 30 May 1998
(Carey, Petersen, Rutledge 2000)
Spencer, SD May 30, 1998
Southern Ontario, Aug 19, 2005
Now……
Why did the storm change character?
LI -6
0-3km Helicity 225
SBCape
BRN
Exeter
16z
1560
20
-2.5
200
600
9
Toronto
18z
A Change in Character?
• Did elevation have
anything to do with the
severe weather produced?
• Was the placement of
Theta E Ridge a factor
(other than LTGCG)?
• Did a Lake Ontario marine
layer weaken or change
the storm?
• Was this a ‘normal’
progression in the lifecycle
of a supercell … tornadic
to HP?
1500’
500’
Lessons Learned
• Be aware of the lightning characteristics and
trends within the storm. Watch for significant
changes.
• Make informative calls to surrounding
offices…regardless of how obvious the situation
may seem to be.
• Be flexible enough to change severe weather
modes during a single event.
Special Thanks To:
• Dave Zaff…SOO BUF
• Thomas.Niziol…MIC BUF
• Jim LaDue…WDTB
Developer/Researcher
• Pat King and Dave Sills…
Research Env Canada
• George Kourounis/Keith
Fletcher…Spotters