View source for Southern Ontario tornado outbreak of 2005

{{Short description|Series of thunderstorms in Southern Ontario in 2005}}
{{Use mdy dates|date=August 2018}}
{{Infobox storm
 | name                 = Southern Ontario Tornado Outbreak of 2005
 | image                = 1903_hookdb_smooth_toronto_supercell.png
 | alt                  = 
 | caption              = Supercell thunderstorm hitting Toronto and the surrounding suburbs
 | type                 = Tornado outbreak
 | active               = August 19, 2005 
 | lowest pressure      = 
 | lowest temperature   = 
 | tornadoes            = 3 confirmed, 1 unconfirmed
 | fujitascale          = F2
 | tornado duration     = 3 hours, 10 minutes
 | highest winds        = 
 | hail                 = 
 | gusts                = 
 | maximum snow         = 
 | power outages        = 
 | total fatalities     = None
 | damages              = in excess of $500 million [[Canadian dollar|CAD]]
 | affected             = [[Ontario|Southern Ontario]]
 | current advisories   = 
 | enhanced             = 
 | notes                = 
}}
The '''Southern Ontario tornado outbreak of 2005''' was a series of thunderstorms on the afternoon of August 19, 2005, that spawned tornadoes damaging homes in the [[Conestogo Lake|Conestoga Lake]], [[Fergus, Ontario|Fergus]], and [[East Zorra-Tavistock, Ontario|Tavistock]] areas. A tornado was reported within the Toronto city limits, although this was never officially confirmed by the [[Meteorological Service of Canada]]. The storms morphed into heavy rain cells when reaching Toronto. The [[Insurance Bureau of Canada]] has estimated that insured losses were the highest in the province's history, exceeding 500 million [[Canadian dollar]]s, two and a half times that of Ontario's losses during the [[North American ice storm of 1998|1998 ice storm]] and the second largest loss event in Canadian history<ref name=SMC>{{Cite web |url=http://www.ec.gc.ca/meteo-weather/default.asp?lang=En&n=B0F843F5-1 |title=Ontario's Most Expensive Weather Disaster |work=Canada's Top Ten Weather Stories For 2005 |author=[[Meteorological Service of Canada]] |publisher=[[Environment Canada]] |date=November 27, 2009 |accessdate=June 13, 2010 |archive-date=June 11, 2011 |archive-url=https://web.archive.org/web/20110611121146/http://www.ec.gc.ca/meteo-weather/default.asp?lang=En&n=B0F843F5-1 |url-status=dead }}</ref> until another event of torrential rain of July 8, 2013 (1 billion CAD).<ref>{{cite web |url=http://www.ec.gc.ca/meteo-weather/default.asp?lang=En&n=5BA5EAFC-1&offset=3&toc=show |title=2. Toronto's Torrent |author=[[Meteorological Service of Canada]] |date=April 17, 2014 |publisher=[[Environment Canada]] |work=Canada's Top Ten Weather Stories for 2013 |accessdate=December 21, 2015 |archive-date=December 23, 2015 |archive-url=https://web.archive.org/web/20151223002744/http://www.ec.gc.ca/meteo-weather/default.asp?lang=En&n=5BA5EAFC-1&offset=3&toc=show |url-status=live }}</ref>

== Meteorological events ==
[[File:Southern Ontario weather map 2005-08-19 at 12 GMT.png|thumb|left|Composite weather map on the morning of August 19, 2005]]
[[File:Damages path 2005-08-19 Southern Ontario.png|thumb|left|Tornadoes and downpour cells tracks with time shown in local time and their motion speed in yellow]]
On the early morning of August 19, a low-pressure area was sitting over Northern [[Michigan]] with a cold front southwestward. This same system had been causing an [[August 2005 Wisconsin tornado outbreak|outbreak of tornadoes over Wisconsin]] the day before. As shown in the map to the left, there was up to {{convert|abbr=on|50|mm}} of [[precipitable water]] in the warm air mass invading Southern Ontario with a strong southwesterly [[Jet-stream#Low level jets|low level jet]] parallel to the cold front and the presence of an upper [[jet-stream]]. All of these were very favorable for the development of severe thunderstorms. Furthermore, the [[wind shear]] in the lower troposphere was creating a large [[Hydrodynamical helicity|helicity]] value conducive to a tornado potential.<ref name=cstar>{{Cite web |url=http://cstar.cestm.albany.edu/nrow/nrow7/Hamilton%5CTornadoes%20to%20Torrents.ppt |title=The Southern Ontario Severe Weather Event of Aug 19, 2005 |author1=Collaborative Science, Technology |author2=Applied Research Program |name-list-style=amp |publisher=State University of New York at Albany |accessdate=June 15, 2010 |archive-date=February 17, 2016 |archive-url=https://web.archive.org/web/20160217174119/http://cstar.cestm.albany.edu/nrow/nrow7/Hamilton/Tornadoes%20to%20Torrents.ppt |url-status=live }}</ref>

With the advancing cold front, two lines of thunderstorms developed. The first one was near [[Stratford, Ontario]] ({{convert|abbr=on|20|km}} west of [[Kitchener, Ontario|Kitchener]]), and spread as far north as [[Georgian Bay]] near [[Collingwood, Ontario]] while the second one was following behind near the shores of [[Lake Huron]].<ref name=cstar/> They tracked eastward and reached as far as Oshawa during the afternoon.<ref name=SMC/> Dozens of storm cells populated the line, two of them developing into tornadic [[supercell]]s. At their worst, the tornadoes reached the [[Fujita scale|F2]] level, with gusts between {{convert|abbr=on|180|and|250|km/h|mph}}.<ref name=SMC/> [[Severe thunderstorm warning]]s were sent, mentioning the possibility of tornadoes in view of the radar output and the potential analysis.<ref name=cstar/>

The main storm, later dubbed the ''Toronto Supercell'', spawned a first tornado tracking through [[Milverton, Ontario|Milverton]] ({{Coord|43|34|00|N|80|56|00|W|region:CA-ON_type:city|name=Milverton}}) to [[Conestogo Lake]] ({{Coord|43|41|10|N|80|43|50|W|name=Conestoga Lake}}) (west of [[Elmira, Ontario|Elmira]]) from 12:40 to 1:20 pm local time. A second twister moved from [[Salem, Wellington County|Salem]] ({{Coord|43|41|36|N|80|26|49|W|name=Salem}}) to Lake Belwood ({{coord|43|46|05|N|80|20|08|W|name=Lake Belwood}}) (north of [[Guelph]]), passing just to the north of [[Fergus, Ontario|Fergus]] 10 minutes later.<ref name=SMC/> When the storm came close to the [[Greater Toronto Area]], a [[tornado warning]] was issued, but the storm changed its characteristics. It produced winds of well over {{convert|abbr=on|100|km/h}}, golf ball sized [[hail]], but mostly heavy rain flooding many parts of the city between 2 and 4 pm.<ref name=SMC/>

Finally, another severe storm passing Southeast of [[Stratford, Ontario|Stratford]], in the [[East Zorra-Tavistock, Ontario|Tavistock]] area ({{coord|43|12|45|N|80|50|51|W}}), gave an F1 tornado with winds between {{convert|120|and|150|km/h}} by 3:20 pm.<ref>{{cite web |url=http://www.on.ec.gc.ca/announce.cfm?ID=738&Lang=e |title=Ontario Weather Review – August 2005 (section Severe Weather) |author=Jack Saunders |date=September 1, 2005 |archiveurl=https://web.archive.org/web/20110928121145/http://www.on.ec.gc.ca/announce.cfm?ID=738&Lang=e |archivedate=September 28, 2011 |publisher=[[Environment Canada]] |accessdate=June 18, 2010}}
</ref>

== Storm's characteristics ==

The Toronto Supercell maintained all the characteristics of a tornado producer as it approached the city. [[Convective storm detection]] showed on [[weather radar]]s a [[hook echo]], a [[Bounded weak echo region|BWER]] and a strong [[mesocyclone]] but the vortex left the ground after the second tornado.<ref name=cstar/> Studies were made to try to explain the change in behavior to an extremely high producer of rain. One area of [[Thornhill, Ontario|Thornhill]], just north of the Toronto City limits recorded {{convert|175|mm|in|0}} of rain in less than one hour.<ref name=SMC/><ref name=cstar/>

Toronto is situated by [[Lake Ontario]] and a [[Sea breeze|lake breeze]] often develops during the day. This wind brings cooler air at the surface and causes a marine [[temperature inversion]] which could have been enough to keep the rotation aloft.<ref name=cstar/> To the west of the city, there is the [[Niagara Escarpment]], reaching {{convert|1,500|ft|m}} above sea level (ASL), while the shores of Lake Ontario are just {{convert|250|ft|m}} ASL. This drop could equally have cut off the rotation from the surface.<ref name=cstar/>

The lightning shows that there was a strong peak during the F2 tornadoes, dominated by the [[Lightning#Positive and negative lightning|positive cloud-to-ground strikes]]. Studies have shown that this is often the case in tornadic storms. It was followed by a sharp drop and then another peak, but this one dominated by negative lightning during the flooding phase of the storm.<ref name=cstar/>

== Impacts ==
[[File:Keele and Jane concord ontario damage from the supercell which struck august 19 2005.jpg|thumb|left|Flood waters washed away a portion of a parking lot near Keele St. and Highway 7 in Vaughan.]]
The twisters uprooted hundreds of trees, chewed the limbs off of countless others, downed power lines, tossed cars and trucks aside, and ripped into several homes, cottages and barns.<ref name=SMC/> In [[Guelph]] and [[Orangeville, Ontario|Orangeville]], 10,000 residents were left without power.<ref name=CTV>{{Cite web |url=http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/1124477195313_2/?hub=TopStories|archive-url= https://web.archive.org/web/20060427021701/http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/1124477195313_2/?hub=TopStories|url-status= dead|archive-date= April 27, 2006 |title=Ontario endures severe storms, tornado warnings |author=CTV News Channel |publisher=[[CTV Television Network|CTV]] |date=August 19, 2005 |accessdate=June 16, 2010 |authorlink=CTV News Channel (Canada)}}</ref> No deaths or injuries were reported.<ref name=SMC/>

In Toronto, {{convert|abbr=on|103|mm}} of rain fell in one hour in [[North York]] and surrounding area, double the amount left by [[Hurricane Hazel]] in 1954 (the heaviest rain from Hazel fell over Etobicoke and the Airport area). At the [[Meteorological Service of Canada]] (MSC) [[Downsview, Toronto|Downsview]] headquarters, {{convert|abbr=on|130|mm}} of rain fell, {{convert|abbr=on|100|mm}} of which occurred in less than an hour, a record for any storm in Toronto.<ref name=SMC/> A block or two to the north in [[Thornhill, Ontario|Thornhill]], a weather watcher emptied her rain gauge at {{convert|abbr=on|175|mm}}.<ref name=SMC/> Rainfall totals from the storm exceeded {{convert|abbr=on|140|mm}} in parts in [[Vaughan, Ontario|Vaughan]]. A volunteer storm spotter reported a tornado in the north part of the city but it was not confirmed by [[Environment Canada]].<ref name=CTV/>

The rain washed out a portion of [[Finch Avenue]] near Sentinel Ave in North York. It overflowed storm drains which caused severe basement flooding to many thousands of homes and two floors of the MSC building. Around Toronto, torrential rains snarled traffic and stranded drivers. Fire services responded to more than 1,000 calls. Marine services personnel rescued four people who fell into the fast-moving currents of the [[Don River (Ontario)|Don River]].<ref name=SMC/>

== See also ==

* {{annotated link|Heat wave of 2006 derecho series}} 
* {{annotated link|Southern Ontario Tornado Outbreak of 2009}} 
* {{annotated link|1985 United States–Canada tornado outbreak}}

== References ==

<references/>

==External links==
* [https://web.archive.org/web/20151222130351/http://www.ontarioweather.com/SPECIALS/stormchasing/2005/fergustornado.asp Report on the Fergus tornado] by Dave Patrick, a storm chaser, with pictures of the damages
* [http://ontario.hazards.ca/maps/intro5-e.html Weather hazard statictics] in Ontario by Environment Canada

{{Commons category}}
{{2005 tornado outbreaks}}

{{DEFAULTSORT:2005-08-19 Southern Ontario Tornado Outbreak}}
[[Category:History of Toronto]]
[[Category:2005 meteorology|Tornado, Southern Ontario]]
[[Category:2005 in Ontario|Tornado, 08]]
[[Category:Tornadoes in Ontario|2005-08, Southern Ontario]]
[[Category:Tornadoes of 2005|08, Southern Ontario]]
[[Category:August 2005 in Canada|Tornado, Southern Ontario]]