Showers and Thunderstorms, U2, Then More Rain

While the temperatures may not be completely summer-like, today will be a day that indicates a clear shift towards summer weather.  An incoming disturbance will produce widespread convection today with showers and thundershowers covering much of Southern Manitoba.  Pleasant weather should make an appearance for tomorrow’s U2 concert, but Winnipeg will quickly return to rainy weather on Monday as a system that will bring significant challenges to those with housing near the lake moves into the province.

A substantial stacked low pressure system currently positioned just east of Regina is set to move across Southern Manitoba today.  A few factors will combine to produce what could be a fairly interesting afternoon today.  

First, a southerly wind, combined with yesterday’s rain has pushed dewpoints to nearly 10°C throughout the Red River Valley with a relatively deep layer of evidenced by the stratus cloud that has managed to form overnight despite winds of 15-20km/h.  This moisture will provide the fuel needed for thundershowers. 

Secondly, rather cool mid-level temperatures will be in place.  As the low pushes in, temperatures in the mid-levels should drop to -7 to -8°C, which when combined with daytime heating will produce ample instability to get convection initiating.  It is also indicative of fairly low freezing level, which will help in the generation of small hail.

And last but by far not least, the fact that this upper disturbance is stacked on top of a surface low means that there will be significant rotation through the mid and upper levels which will help storms develop rotation.

When these things combine, it’s considered a pretty classic case for cold core funnels.  These funnel clouds do not develop in the classic sense; instead of developing in the rapidly rotating updraft of supercell thunderstorms, they develop through the descent of cold air through a storm that has developed rotation due to significant mid-to-high level spin.  Think of it as a funnel cloud that develops because of how air is coming out of the cloud rather than how air is being ingested into the cloud.

These funnel clouds do have the potential to touch down and become tornadoes.  If they do, they are often extremely short lived (< 1-2 minutes) and are much weaker than the tornadoes that form from supercell thunderstorms.  Any of the storms that could produce a cold core funnel cloud are also extremely likely to be capable of producing hail.

I think that most areas across Southern Manitoba could see hail today, although the threat is biggest in the Red River Valley and east.  Winnipeg and areas south should most likely see pea-sized hail should it develop.  Further east in the Whiteshell and Sprague regions, the potential exists for marginally severe hail (about dime to quarter-sized).

The biggest hindrance to the development of all this is the lack of focus for convection.  With no strong front or trough, convection may simply blow up all over the place instead of in any organized fashion, which will leave all the storms fighting each other for resources.  If this happens, it’s likely that it would quickly blossom into a big area of showers with only the odd lightning strike.

My bet for the Red River Valley is this: low stratus this morning will burn off quickly with the morning sun.  By mid-morning, most areas should be seeing a mix of sun and cloud.  Daytime heating, combined with a weak cap, will initiate the convection earlier than typical, resulting in showers spreading into the Red River Valley around 12-1PM or shortly thereafter.  Any showers that develop in the RRV are just as likely to become thundershowers, and I think there will be numerous funnel clouds today.

As for Sunday and the big U2 concert, it should be quite a pleasant day.  We’ll see a sunny morning give way to a mix of sun and clouds in the afternoon with a daytime highs around 15-17°C.  It will cool off quick in the evening, so make sure to bring a sweater if you’re headed to the concert.

12hr. QPF valid 06Z May 31 from the 06Z May 28 GFS

After that, it looks like a significant low pressure system will track through Southern Manitoba, bringing nothing but headaches and grief for residents on the lakes.  Current indications are for a widespread area receiving 20-40mm of rain with winds potentially as high as 50 gusting to 70 km/h.  This system will do no good for the flood-striken areas near the lakes, and I would suggest that residents in the area should begin to make preparations already as with the strong winds out of the north-east, significant water damming will likely occur on the western to southern beaches.

Deadly Storms Hammer Oklahoma, More Expected Today

I know this isn’t directly related to Southern Manitoba, but the events over the past few days have been so significant I can’t pass up the opportunity to talk about them.  On Sunday, a massive tornado that was recently upgraded to the category EF5 tore through Joplin, MO, killing 125 people and injuring upwards of 750 people.  Over 1500 have been reported missing, however this number is likely inflated as they are preliminary reports mostly from family and some “missing” peoples were simply out of town.  The tornado damaged or destroyed over 800 structures and caused in excess of $1 billion.

Damage Path of the Joplin Tornado
The swath of damage caused by the tornado is easily visible from the sky.

Many thought that this disaster would not be seen for a long time, however mother nature had a completely different opinion yesterday and many, though not all, Kansas, Oklahoma and Texas residents dodged quite a few bullets yesterday.

 Around 3PM yesterday storms started to develop along a dryline pushing eastwards out of Colorado and New Mexico into the Central Plains.  This feature was extremely strong, with some sites going from 29/23 (temperature / dewpoint) to 38/-12 in a matter of a couple hours.  This would be equivalent to going from one of the muggier, more humid days in Southern Manitoba to the Nevada desert over lunchtime.  Normally, this would be a significant enough feature in itself, but there was also a powerful shortwave moving into the area with an associated 90 knot jet streak about 5km off the ground.  This was, for all intents and purposes, a perfect setup for severe storms.

The Storm Prediction Center (SPC) issued a high risk for for the Central Plains yesterday morning, and issued a PDS statement (Particularly Dangerous Situation) near lunchtime when they issued the tornado watch.   By mid-afternoon storms were in full swing.  The northern end of the town of El Reno, OK was hit by a tornado, which killed two people, demolished several houses, and was responsible for a gas explosion.  This picture is a great indicator of how powerful this twister was:

A car pinned against trees that have been significantly de-barked in El Reno, OK.

There was even a weather station on the north end of town that experienced a significant portion of the power of this tornado:

Readings from a weather station in North El Reno.  At the time of the tornado, the station measured a peak wind of 151 m.p.h and a drop in pressure to almost 940mb.

El Reno was not the only town to suffer, though.  The town of Piedmont, OK was hit hard:

(Photo: Reuters / Bill Waugh)

Dozens of homes and businesses were lost in Piedmont.  Two children were killed, a third missing, and their mother is in critical condition.  This repeats itself, unfortunately.  Oklahoma City was put under a tornado warning only for the tornado to dissipate shortly before entering the city.  Instead, debris rained down on the city, enough to make the I40 impassable in at least one spot.  The Norman, OK weather center, home of the SPC was evacuated.  Baseball-sized hail fell at the baseball stadium in Arlington, TX as well as through much of Fort Worth.  More details have yet to emerge, but it sounds as if the town of Denning, AR may have been wiped off the map by a tornado.

It was a tragic day through much of the Central Plains.  The current death toll of 15 is likely to rise as the damage is assessed today and people start to examine and clean up.  At least 4 significant tornadoes occurred yesterday, and several were on the ground through the night.  It was another unfortunate and deadly day in a country that is quickly approaching its deadliest year ever with respect to tornadoes.  And it isn’t over yet.  The SPC has issued another high risk outlook for portions of Arkansas, Tennessee, Indiana, Kentucky, Illinois, and Missouri, with a moderate risk encompassing a much greater area:

It’s an extremely unfortunate year for tornadoes, and at this point it’s hard to imagine that they won’t surpass their deadliest year ever for tornadoes this summer.  If there’s any good that might come out of this, it only emphasizes the importance of having a properly funded forecasting service that is working around the clock to ensure that people and property can be protected as much and realistically as possible.  Good thing those budget cuts to the NWS didn’t go through…

The last thing I wanted to mention, perhaps my whole reason for writing this, is that I know many people who think that these sorts of things “don’t happen in Canada.”  I’m here to say that they do.  More often than one might think.  Tornado alley, a colloquialism used to refer most frequently to the stretch from Oklahoma to South Dakota, actually extends much further than most people think it does.  While tornadoes may be most frequent in those states, it slowly shifts north as summer goes on.  The Dakotas and Minnesota are hotspots for tornadoes.  By mid-to-late summer, tornado alley extends through Southern Manitoba and arcs westwards across Saskatchewan and into Alberta.  One need not look far to see extremely significant tornadoes in Canada’s history:

  • Reeces Corners Tornado (1983); millions of dollars in damages.
  • Southwest Ontario Tornado Outbreak of 1984; 6 confirmed tornadoes, 30 people injured.
  • The “Barrie” Tornado Outbreak of 1985; 13 touchdowns including a F4 tornado in Barrie, ON.  12 killed, 100 injured.  Over 100 buildings destroyed at a cost of over $100 million.  Complete destruction of 300 houses.
  • Mississauga Tornado (July 7, 1985); Injures 10, $400,000 in damages.
  • Saskatoon Tornado (June 1, 1985); 3 weak tornadoes touched down in Saskatoon.  Roofs and windows damaged.
  • “Black Friday” Tornado in Edmonton, AB (July 31, 1987); a strong F4 tornado (possibly F5) hit eastern sections of Edmonton.  27 people died and 253 were injured.  One of Canada’s strongest tornadoes.
  • Medicine Hat, AB Tornado (1988); Tornado caused estimated $50 million in damages.
  • Saskatchewan Outbreak of 1989 (June 19, 1989); 8 tornadoes touch down over central Saskatchewan.
  • Edmonton Tornado (July 27, 1989); Weak tornado in the west end of Edmonton.  2 people injured.  Buildings damaged, trees and power lines uprooted.
  • Mont-Saint-Hilaire tornado (November 16, 1989); An F2 tornado caused $2 million in damage in the community east of Montreal.
  • Sarnia, ON (March 27, 1991); Early season tornado causes an estimated $25 million in damages.
  • Southern Manitoba (June 24, 1992); 5 confirmed tornadoes as well as hail up to the size of tennis balls.
  • Saint-Charles, QC (July 9, 1994); 1 person was killed when a F2 tornado tore through the town.  3 others injured and about 12 homes were damaged.
  • Aylmer, QC Tornado (August 4, 1994); A F3 tornado injures 15 people in Aylmer, QC.  Tornado path was 8km long and caused major damage to a downtown residential subdivision.
  • Turtle Mountain, MB (August 27, 1994); An F4 tornado hits rural farmland with devastation evident at Mayfair Hutterite Colony.  Well over $1 million in damages.
  • Southern Ontario Tornadoes of 1996 (April 20, 1996); Two F3 tornadoes touch down in Grey County, Wellington County and Dufferein County.  Significant property damage, 9 injuries.
  • Saskatchewan (July 4, 1996); 9 tornadoes touch down in the Saskatoon, Maymont and Osler areas in Saskatchewan.  An F3 was measured in the Maymont area.  Homes and property were damaged in Osler.
  • Hull, QC of 1999 (May 8, 1999); A tornado over Hull, QC caused $2 million in damages.
  • Saskatoon Tornadoes of 1999 (May 18, 1999); 3 tornadoes touch down close to the western limits of Saskatoon, SK.
  • Pine Lake, AB Tornado (July 14, 2000); An F3 tornado rips through the Pine Lake campground.  12 people killed.
  • Guelph, ON Tornado (July 17, 2000); An F2 tornado struck the city of Guelph, ON causing around $2 million in damages.
  • Wabamun, AB (August 13, 2003); A tornado touched down on a golf course and lake resort west of Edmonton, AB causing some injuries.
  • May 2004 Tornado Outbreak (May 22, 2004); one strong F2 struck near Mitchell, ON and an F3 in nearby Gad’s Hill.  Extensive property and infrastructure damage.
  • Nipawin (May 23, 2005); A tornado touches down in and around Nipawin, SK.
  • Southern Ontario Tornado Outbreak of 2005 (2005); Widespread damage path from Stratford, ON to Peterborough, ON and along Georgian Bay near Collingwood.  Damages exceeded $500 million.
  • Ontario Outbreak of 2006 (August 2, 2006); 14 confirmed tornadoes rip across southern ontario.
  • Gull Lake Tornado (August 5, 2006); One woman is killed at the Gull Lake campground north of Winnipeg, MB.
  • Eastern Prairie Outbreak of 2007 (June 22-23, 2007); At least 8 tornadoes across southeast SK and southern MB.  The first confirmed F5 tornado in Canada occured at Elie, MB, just west of Winnipeg.  It destroyed 4 homes and heavily damaged a flour mill.  The tornado itself was described as “as bad as they get here in Canada.”  A F3 wedge tornado also touched down near Pipestone, MB and Baldur, MB.
  • Southern Manitoba (May 25, 2008); at least two tornadoes touch down in Southern MB.  One reported near Altona, MB.
  • Niverville Tornado (May 31, 2008); a tornado touches down in Niverville, MB.
  • Southern Manitoba June Tornado Outbreak (June 27, 2008); 5 tornadoes touch down in Manitoba near Gladstone, Neepawa, Arden, Westbourne and MacGregor.
  • Winnipeg Tornado (June 1, 2009); Unconfirmed tornado reported in Winnipeg near the McPhillips Athletic.  Trees toppled on houses and a semi-trailer flipped over on Portage Ave and the Perimeter Highway.
  • Southern Ontario Outbreak of 2009 (August 20, 2009); 18 confirmed tornadoes, the largest outbreak in Canadian history.  They were:
    – F2 tornado from Durham to Markdale; 1 death, many serious injuries.
    – F2 tornado in Carksburg
    – F2 tornado in Vaughan; 3.5 km path through the Woodbridge neighborhood
    – F2 tornado in Vaughan; 2.7 km path through the Maple neighborhood.  This and the previous tornado resulted in hundreds of homes being damaged.
    – F1 tornado in Newmarket
    – F1 tornado in Milton
    – F0 tornado in Moonstone
    – F1 tornado in Ril Lake
    – F0 tornado in Dollars Lake
    – F1 tornado in Gravenhurst
    – F1 tornado from New Lowel to Edenvale; 12.6 km path
    – F1 tornado in Haliburton
    – F1 tornado in Haliburton Forest
    – F0 tornado in Redstone Lake
    – F1 tornado in Arnstein
    – F1 tornado in Carlow/Mayo
    – F1 tornado in Rice Lake
    – F0 tornado in Orono
  • Leamington, ON (June 6, 2010); F2 tornado went from Harrow through Kingsville and Leamington, ON.  No deaths or injuries, but significant damage.

This is by no means a comprehensive list.  Most of this information was gathered from here and I suggest you visit if you want more comprehensive information.  This is to show that tornadoes are quite a common occurrence in Canada and it is important that people are aware of the danger they pose.  Ensure you have a plan for your household on what course of action to take should your life or property be threatened by a tornado.  As the summer heats up in the Prairies, so does the risk that the unfortunate news coming out of the states could be repeated here.

Significant Rains for May Long Weekend

Balmy temperatures will be replaced by rain this long weekend as a significant low pressure system slowly pushes northwards into Southern Manitoba from the U.S. Northern Plains. Read on to find out just how much rain we can expect.

500mb Winds (12Z May 20th GEMREG valid 00Z May 23
500mm Heights & Winds from the 12Z May 20th GEMREG model run valid at 00Z May 23rd.

A powerful low pressure system continues to push northwards towards the Southern Pariries, slowly spreading rain through Southern Saskatchewan today and set to spread rain through Southern Manitoba tomorrow evening. This system is being fed by a frontal wave in the Central Plains, which is feeding moisture northwards into this low. This system is expected to continue to intensify over the next 24-36 hours, intensifying it’s rainfall production as it taps into increased instability and is fed additional heat and moisture from thunderstorms that develop and override the warm front in Nebraska and South Daktoa. Tonight, elevated thunderstorms will stream northwards through the Dakotas as they transform into larger areas of rain with embedded thunderstorms and wrap around the upper low, moving from east to west across Southern Manitoba and Saskatchewan.

This setup has the potential to produce significant amounts of rainfall. While models have been varying slightly in their position and amount of rain, they paint a fairly consistent picture:

24hr. QPF (12Z May 20 GEMREG valid 12Z May 22)
24 hour rainfall totals from the 12Z May 20th GEMREG model run valid at 12Z May 22nd.

24hr. QPF (12Z May 20 NAM valid 12Z May 22)
24 hour rainfall totals from the 12Z May 20th NAM model run valid at 12Z May 22nd.

24hr. QPF (12Z May 20 NAM valid 12Z May 22)
24 hour rainfall totals from the 12Z May 20th NAM model run valid at 12Z May 22nd.

As we can see, although the models all have varying amounts (highly dependent on how it resolves convection), they all paint a significant swath of precipitation heading our way. The GEM-REG keeps the precipitation the furthest south, and without a significant blocking ridge to the north, I’m inclined to think that it’s keeping things too far south. The current general agreement would be a swath of 0.75 to 1.5 inches of rain from Shaunovan/Swift Current through Brandon, Winnipeg and the Whiteshell.

For Southern Manitoba, we will likely see some showers or thunderstorms develop along the ND/MN border tomorrow morning and push northwards into Southern Manitoba by the early afternoon. This area of rain will slow as it approaches Winnipeg and begin to intensify into an area of rain. By late afternoon, it will likely be raining over most of Southern Manitoba and will last through most of the night. The Red River Valley will likely see a break late overnight into early Sunday morning before the rain starts again with wrap-around precipitation moving through. Winnipeg and the RRV will see approximately 20-30mm of rain if current guidance pans out, with strong east/north-easterly winds of 40km/h gusting to 60km/h.

Monday will see much cooler temperatures, with daytime highs for Winnipeg a mere 13° or 14°C under clearing skies. Next week looks cooler than this week, but we we should see plenty of sunny skies with temperatures quickly rebounding into the high teens/low twenties by the middle of the week.

Summer is Here!

As Manitobans in the Southwest corner of the province continue their battle against the swollen Assiniboine river, mother nature has granted us tremendous weather.  Clear skies and warm temperatures have spread throughout much of the province, giving us a reprieve from the cool and cloudy conditions that we seemed to be entrenched in for…well a long time.  But will it last?

An “omega block” set up across the Prairies late last week, with the jet stream rounding the base of an upper low off the coast of California and then heading up to the Northern Prairies, arching over an upper high that had built into the central Prairies and then heading south and exiting the continent around the bottom of an upper low off the east coast.  This allowed a large-scale southerly flow to develop and warmer air to push northwards into Canada.  As a side note, this is called an “omega block” because the jet stream curves in the shape of the Greek character omega, and it’s a fairly stable pattern that doesn’t move very quickly, hence it’s a blocking pattern.

Over the past few days, a shortwave has pushed into Alberta and the blocking pattern has begun to shift.  Instead of completely collapsing, it seems to have rotated such that the block is now aligned northwest-southeast instead of north-south.  This will allow cooler air to push into the western Prairies (as is seen today with cooler temps and rain through southwest Saskatchewan) while building the warm air over the eastern Prairies.

Stormier weather is brewing to our south, though.  A significant shortwave is expected to eject northeast out of a stationary long-wave trough on the upper-west coast on Thursday night, moving into the Dakotas by Saturday.  This feature has a lot of uncertainty attached to it at the moment, but the models have been pushing the precipitation envelope further north with each successive run, which puts Winnipeg increasingly into the risk of some rain ruining our lovely weather.

12 Hour QPF valid 06Z Sun 22 May from the GFS Model

I’ll provide some further details about this system in a couple days when it’s beginning to resolve a bit better.  It looks likely that areas south of Morris in the Red River Valley will likely see some accumulating rain this weekend, but first we get to enjoy several more days of hot, sunny weather.  Get out there and enjoy it!