Friday, August 13, 2010

Torrential early morning thunderstorm swamps Winnipeg

After 5 days of heat and humidity, Mother Nature unloaded over Winnipeg early this morning with a torrential thunderstorm that swamped the city with heavy rainfall. The storm moved in over the southwest part of the city by 5:40 am, and within 30 minutes had dropped about 40 mm of rain over much of the city. The heavy rainfall caused numerous problems in the city with traffic light outages, flooded underpasses and manhole covers being blown off by the tremendous rainfall rates.

The photo here (from Mike O'Flaherty to CJOB) shows the storm approaching the city from the west before 6 am. At my weather station in Charleswood, I recorded 33 mm of rain between 5:40 and 6 am, with a total of 41 mm by 6:40 am. Winnipeg airport recorded 43 mm of rain while the Forks had 40 mm downtown. The University of Winnipeg weather station recorded 57 mm between 5:50 and 6:50 am. Lesser amounts of 20-30 mm were recorded over the southern parts of the city. (click here for city of Winnipeg rainfall map) The thunderstorms signaled an upcoming change in the weather pattern, with cooler weather moving in for the weekend into next week.

Radar image from 6 am showing
intense cell over Winnipeg.


  1. Only recorded 6mm in NE Transcona this morning...sounds like the West end got hit much harder!

  2. Slept right through it.

  3. It was part of that impressive MCV that formed over western N Dakota overnite and tracked NNE ahead of the main upper trough. It seemed to be associated with an elevated moisture pool at or above 700 hPa.

    Rotating area of convection continues off to our west evolving into more stratiform precip. Looks as though the rain may wrap back in over the next few hours while a dry intrusion and clearing affect areas off to our east and N east.

  4. Unfortunately Winnipeg drivers and underpasses weren't the only victims of that MCV. A St. Brieux Saskatchewan resident driving just south of the Border on Hwy 52 at Bowbells ND was also a tornado victim.
    See Saskatoon Star Phoenix
    or CBC NEWS

  5. Periods of rain and high of only 14C on Sunday!!!
    It's gonna feel like fall!

    Oh and 150 mm of rain for the interlake by Sunday could spell a disaster for farmers!

  6. Rob!

    I see that you are at 100 mm of rain for the month!!!

    How much more rain this weekend do YOU see the city getting this weekend!
    How about strong could the winds get????

  7. Great graphic and links Rob.
    I was waiting from 5:30am til 6 after a lot of lightning and thunder and rec'd just a mild shower here.(St Vital park) Lots of hit and nearby misses with that storm. St Francis X 1mm and Breezy Bend .4mm had very little while 3 km east 27mm at Headingley, and 43mm in Charleswood.

    The Southwest corner of Lake Winnipeg from Matlock to Gimli also missed this and everything else this week although Tuelon 20Kn west had 40mm and Balmoral 57mm today.

  8. daniel..

    yeah.. 100 mm for the month, and 65 of that has fallen in less than 2 hours!

    As for how much more rain over Winnipeg this weekend.. still a tough call depending on what model you believe, and even then, models have been having a terrible time getting precip amounts and placement right. Canadian GEM brings wrap around rain over us Saturday afternoon through Saturday night into Sunday morning with about 10-20 mm. NAM shows most of the pcpn staying north of us through the Interlake Saturday and Saturday night before some rain moves down Sunday. Based on the expected upper pattern and surface features, I would expect some showers moving into Winnipeg Saturday afternoon, with periods of rain Saturday night into Sunday. Overall rainfall amounts over the weekend very uncertain but a rough guess is 10-20 mm for Winnipeg, with higher amounts north of the city. Gusty northwest winds by Saturday evening with gusts to 60 or 70 km/h. Cool fall like temperatures with highs only in the mid teens over the weekend.

    In addition gale warnings are out for the MB lakes for Saturday into Sunday. NW gales of 35-40 knots possible Saturday afternoon into Sunday morning. This will produce pounding waves on the southeast shores of Lake Winnipeg and Lake Manitoba. Not a good weekend for a Grand Beach outing.. (unless you're a windsurfer!)

  9. By the way, city of Winnipeg has posted a map of today's rainfall amounts. Click on my name for image. North end got hit the hardest this time with over 50 mm, much of it between 6 and 6:30 am.

  10. Another tornado has gone through Steinbach (apparently). Unfortunately I didn't witness this event so I can't confirm or deny it. However, if the pictures in the article area the worst damage to be found, the idea that this was a tornado is laughable.

    Click my name for details

  11. wow, looks like a dramatic cooldown coming for us in winnipeg. to add to that looks like it will stick with us for almost the whole week. dont tell me that summer is over, that would be too short for my likings.

  12. Its at least another month til our average first frost date.
    Isn't it Sept 22?

  13. Rob
    Is the forecast overly enthusiastic about those daily Hi-Temps until thursday. Upper Mid teens?

  14. don.. current forecast calls for highs in the mid teens until Thursday which looks reasonable.. The highs of 28-29C for Thursday and Friday however look way too optimistic. Maybe low 20s Thursday then 25C by Friday with a chance of showers and thunderstorms by next weekend as another low tracks through the Dakotas according to the GFS..

    The last two days of the forecast (day 6-7) are based on the Canadian ensemble forecast system, which has been showing a signifacnt warm and dry bias with Winnipeg forecasts over the past few weeks. I would knock a good 5 degrees off these forecasts until this warm bias can be corrected.

    Note that the forecast for Day 6-7 uses a different model output than what is used for the Day 3-5 forecasts (GLB model output) That is why there is sometimes a large discrepancy between the Day 5 and 6forecasts.

  15. Rob
    Thanks for the City Rain Link.

    Although your station recorded 42mms yesterday, the city appears to be reporting 25 to 30 for Charleswood.

    Is this a new location anomaly or the spottiness of the downpour?

  16. Don

    I have a manual rain gauge in my backyard to cross check the values from my Davis station that are posted online.. usually they're within one or two mm of each other in big events, so my Davis station is pretty well calibrated. In Friday's case, my Davis station recorded 40.9 mm in that downpour, and my manual gauge had 41.6 mm so virtually identical. The rain was coming down hard with a gusty west wind, so it's possible my rain gauges overcaught rainfall being blown off my roof. Ideally, rain gauges should be located in an open area at a distance 4 times the height of the nearest tall object (trees, houses, etc). This criteria however is difficult to achieve in a typical residential setting. Overall though, I have found that my values usually fit in very well with the city network.

  17. It's cold out there today!!
    I had to put on my winter parka and mitts......

  18. Quite a bit more rain in the north end today compared to the south.. generally 15-20 mm recorded along the north perimeter to 10 mm downtown to 5 mm in the south today. Looks like amounts in the north end were enhanced by a narrow band of embedded lake effect rain off Lake Manitoba oriented down Highway 6 into the city.

    Rain moves off tonight and we should be drier tomorrow.. some lake effect showers persisting off Lake Winnipeg to our northeast, but drier west. Next clipper comes in Tuesday with another area of showers through southern MB Tuesday afternoon/night into Wednesday morning. We then dry out for Wednesday afternoon through the rest of the week, with models now showing a nice warmup for the weekend with highs back to 30C. Hope that forecast sticks.. I'm not ready to give up on summer just yet!

  19. Skies have cleared.
    Winds are light (NW)
    Unless some clouds move in Winnipeg airport could get quite cool tonight!!

    Say.... 7 C!!