Tuesday, September 23, 2008

Strong thunderstorms bring heavy rain, high winds

The first official day of fall was marked by strong thunderstorms last night that brought a swath of heavy rain over the Red River valley, as well as some severe wind gusts along the US border. Thunderstorms developed over northern North Dakota late Monday, and pushed into southern MB during the evening. As the storms crossed the border into Manitoba, they produced torrential rain and wind gusts to 106 km/h (57 knots) at Emerson at 10:43 pm, and an unverified gust of 165 km/h (89 knots) at Gretna at 10:42 pm. Although possible, the Gretna gust seems suspiciously high since there would have been damage reported with such wind gusts, and no reports of damage have been received so far. The storms were accompanied by 29 mm of rain within one hour at Gretna, and 34 mm of rain within one hour at Emerson between 10 and 11 pm.

The storms continued to move to the northeast through the night bringing a swath of heavy rain mainly from the Gretna/Emerson areas through Letellier/Dominion City to St Pierre up to the Landmark area just east of Winnipeg. Rainfall in this swath totalled 50-90 mm from overnight thunderstorms. The heavy rain area just clipped the east side of Winnipeg with Deacons Corners (Hwy 1/Perimeter) reporting 46 mm of rain since midnight, while the west end of the city only had 15-20 mm including Winnipeg airport and my site in Charleswood.

Some rainfall amounts recorded since late yesterday include.

Dominion City… 91 mm (spotter report)
Landmark………78 mm (including 44 mm 9 pm - midnight)
St Pierre………..72 mm (MB Ag-wx)
Emerson………. 65 mm (EC)
Morris…………. 62 mm (MB Ag-wx)
Winkler………… 58 mm (MB Ag-Wx)
Dugald………….53 mm (MB Ag-Wx)
Steinbach………46 mm (MB Ag-Wx)
Gretna…………..46 mm (EC)
Wpg - Deacons Corners…46 mm (CWB)

Winnipeg Forks…. 22 mm (EC)
Winnipeg Arpt….. 17 mm (EC)


  1. Well last night really surprised me!
    I maybe expecting a couple rumbles of thunder.
    Well was I ever wrong.
    That strong winds gusts over 100 km/h really shocked me!
    I did not know the set up was there for damaging winds!
    Still can anyone speculate where those strong winds came from???
    A microburst???
    A gust front?
    A derecho??

  2. Those storms were pretty energetic.. feeding on 18C dewpoints with very good dynamics to get organized cells. That all added up to some intense thunderstorms with CAPES near 1500 which can easily give you downburst wind gusts of 100 km/h or more. If that Gretna gust to 165 km/h is true, it must have been very localized and not widespread enough to cause significant damage.

    I'm a little surprised there wasn't more large hail reported.. I guess freezing levels were too high.

  3. Rob the day before (Sunday) here in Regina, that system did drop some significant hail around Regina. I had to replace my anemometer cups as 2 of 3 were broke off by nickel to quarter sized hail that made the grass white.

    Dean - NWR Weather

  4. Hi Dean.. Too bad about the hail damage. Did you have a backup anemometer? I see your station is measuring wind speed again.

    By the way, picked up another 15 mm of rain last night.. a lot more than I thought we'd get last night. That makes a total of about 40 mm for the past 2 days.

  5. I have had 68.2mm since Sept. 22.

    That is way too much for me, and now everything is soaking wet, never mind the mosquitoes.

  6. Well Scott...it looks high and dry for the next 5 days.....
    that's if Environment Canada forecast is correct!

  7. Most forecasts going with a liklihood of showers for Sunday with an upper low moving across southern MB and an inverted trof at the surface. So I wouldn't count on a completely dry weekend coming up. Hopefully EC's forecast is right and the precip misses us. But hey, it's a weekend.. what are the odds of THAT happening?!

  8. Unfortunately I think that much rain will not dry up before the weather turns.

    This could be a bad situation for the RRV in Spring. If we get more rain in September, and into October we could saturate the ground, prime for flooding. If we have a snowy winter, look out!

  9. Any bets on what the winter will be like. I'm hoping for lots of snow.

  10. I'm hoping for lots of snow too!

    After watching the forecast for the summer, here is my theory.

    Look at the winter forecast, and assume it will be the exact opposite! That is how the summer forecast was, and how it usually ends up!

  11. Without a strong ENSO signal (we're in a neutral ENSO phase right now, i.e. no El Nino or La Nina.. "La Nada" as Dave Phillips likes to say), it's impossible to predict what kind of winter we'll have. Seasonal outlooks are dicey at the best of times.. and only have appreciable skill when there's a strong ENSO signal that correlates with certain climatic patterns in certain parts of the country. This is especially true with winter outlooks. This year however, we don't have that correlation to work with.

    The last time we had a neutral ENSO pattern was the fall/winter of 2001-02. That year, we had a mild fall and mild winter in southern MB. But before that, another neutral ENSO episode in 1996 led to a cold fall and cold snowy winter (followed by the Great Flood of 1997)

    So, as much as we'd like to know and predict what kind of winter to expect, there are times that confidence levels are too low to warrant a specific forecast.

  12. looks like we got TS KYLE on our hands.

  13. Kyle is forecast to hit Nova Scotia as a weak Hurricane (barely Cat 1).

    Rob is definitely right when it comes to seasonal forecasts. You basically won't know until we get there.