Monday, 31 December 2012

#9 - Top Ten Weather Events of 2012 in the Winnipeg Area

May's Wild Thunderstorms

     In southern Manitoba, May was quite a month for thunderstorm-lovers with many convective events; most notably on May 14, 18, 22/23 and 27.

Little rain, just blowing dust. By BobLedoux near Ft Whyte
     A cold front moving across southern Manitoba in the evening on May 14 sparked off thunderstorms, despite a great lack of humidity. This lack of humidity, with surface dewpoints generally in the low single digits, was the perfect recipe for a severe wind event thanks to ''evaporative cooling''. (Definition of evaporative cooling here)

     The thunderstorms dropped very little rain, but brought severe gusts of wind and interesting cloud formations. Sudden gusts of 80 to 100 km/h were common across the RRV, with a maximum of 85 km/h at Winnipeg airport with the first cell to move through the city. Some regions were hit repeatedly as several cells formed one after another. In addition, they actually formed a bit ahead of the main front, meaning we had to contend with another round of severe wind with the front itself later in the evening. Winnipeg airport recorded a gust of 93 km/h with the front, after the storms. Some trees and even semi-trailers were toppled, and there were numerous power outages in many communities throughout southern Manitoba. Most outages were restored quickly, except for a few regions north of Portage such as St. Ambroise, which lost power for several hours after the storms. The winds were also blamed for a wall collapse at the construction site of Winnipeg's new football stadium.

Photo by Hannah Shiffman via CBC Manitoba
     Thanks to very dry soil conditions, the winds also produced dust storms, a rarity in southern Manitoba. Near zero-visibility in blowing clouds of dust was seen locally in rural areas. According to The Weather Network, some callers to their storm line said they had to pull over as visibility reached near zero in blowing dust and dirt. The following day, some farmers even woke up to ''dirt drifts'' in their fields. Within Winnipeg, blowing dust was mainly seen in open areas and northern parts of the city.

     These storms claimed one life on Lake Manitoba. Two men were out fishing on the lake when the wind hit with little warning. The strong winds and heavy waves overturned their boat. One man made it to shore, while the second was swept away by the waves. Searchers combed the area for several days afterwards for his body, finding it on May 23, 11 km away from the location of the capsize.

     (*Here's a list of videos I find give a great idea of the conditions felt on May 14: Video 1, Video 2, Video 3*)

     On the evening of May 18, a retreating warm front was the cause of another thunderstorm outbreak in the RRV and southeastern Manitoba. Of note, there was a very tight temperature gradient with this front. At 5 PM, while it was only 15°C in Minot, it was 35°C in Fargo.

Storm resembled flying saucer. By Rebecca Schleicher
     Lines of thunderstorms formed just west and southwest of Winnipeg by 7:30 PM and swept through the city between 8 and 9:15 PM. The storms trained over western, central and northern sections of the city, giving long-lasting torrential downpours. A swath of 25-35 mm of rainfall fell through these parts, while only 5 to 10 mm fell in east, southeast and extreme northwest sections of the city. A peak rainfall rate of 133 mm per hour was recorded in Charleswood at 8:11 PM. In addition, hail as large as quarters fell in central and northern parts of the city, and lasted long enough to accumulate locally. Lightning was frequent, and the heavy rain flooded a few streets. The rain was blamed for an apartment roof collapse at the corner of Aikins Street and Atlantic Avenue. Residents were evacuated and there were no injuries. Some traffic and street lights lost power as well. These storms however were a blessing to the fire situation in southern Manitoba.

     (*Here's a list of my favourite videos of the thunderstorms on May 18: Video 1, Video 2, Video 3, Video 4*)

Photo by John Kristalovich
     More strong thunderstorms made their appearance late on May 22 and early May 23. This time, the main story was the magnificent display of lightning in the RRV late evening and early overnight; definitely not something we see every May. Lightning was almost constant at times and there were many cloud-to-ground strokes. Rain in Winnipeg was not impressive with only a general 2 to 6 mm across the city. Heavier amounts of 10 to 20 mm fell to the east and northeast of the city, with locally higher amounts.

     (*Some awesome videos of the lightning May 22/23: Video 1, Video 2, Video 3*)

     Yet another round of storms drenched the Winnipeg area on May 27. A line of heavy elevated thunderstorms swept through the city near 6:30 PM, locally dumping a good 10 to 15 mm of rainfall in as little as 10 minutes. Lightning was not frequent. Storms continued on and off through the evening until about 9:30 PM. By the end of the day, in addition to showers earlier in the day, as much as 20 to 35 mm of rainfall had fallen in southern and northern parts of the city.

     All these storms along with some rain events in between brought monthly totals as high as 130 mm in parts of northern and western Winnipeg. This is more than double the normal of 57.4 mm for the month of May. However, amounts were lower in other parts of the city with as low as 85 mm in parts of the southern and eastern ends; areas that missed out on heavy rains on May 18 and 28. The 98.0 mm at the airport made it the 21st wettest May on record.

Flooding in Winnipeg May 18, by Charmaine Straker
 This post contains information, photos or videos from the following sources:

City of Winnipeg water and sewage department rainfall reports
CTV Winnipeg
CBC Manitoba
The Weather Network
Rob's Blog
Environment Canada Weatheroffice

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