Friday, 6 January 2012

Top 10 Weather Events of 2011 - #3

#3 October Rumbles
     Although thunderstorms have occurred in October in the past, often they are weak and infrequent. That is why this year’s October thunderstorms were so spectacular. The frequency and intensity of the storms was anything but normal. With 4 or 5 thunderstorm events, there were more thunderstorms in October than there were in July and August combined. The intensity of some of storms was mind-boggling, some being just as spectacular as mid-summer storms. The following are summaries of each thunderstorm event this October. Don’t be fooled, the pictures were taken this October, not July!! :P

     Oct 7 – A cold front sweeping through southern Manitoba triggered an extensive area of isolated thunderstorms. The storms were moving very quickly, therefore were short-lived. One cell popped up right over the city bringing brief downpours to central and northern areas, and lots of thunder. Storms were strongest in the Interlake where very heavy downpours were accompanied by frequent lightning, and pea to marble sized hail.
Winnipeg : My pics

Visible Satellite of Oct 7 storms

     Oct 12 (1) – Area of storms pushed in from North Dakota near midnight and overnight in the southeast. Stayed mostly south east of Winnipeg. Brought impressive lightning, and locally heavy rain.
     Oct 12 (2) – Clusters of strong non-severe storms popped up throughout the south and south east late afternoon. Slow moving, they dumped impressive amounts of rain and small hail. Lightning was also once again frequent. Generally, in the city around 5 mm of rain fell in the west end, and 5-15 mm in central, eastern and northern areas. South St-Vital was spared the heavy rain, therefore only received a trace of rainfall.

Visible Satellite of Oct 12 storms

     Oct 22 – This thunderstorm event took the big prize. Just a week before Halloween, a storm of this calibre was very unexpected and possibly even a once in a lifetime event.
From Theweathernetwork
     What began as a line of showers over south western and southern Manitoba quickly evolved into an impressive line of strong non-severe storms by early evening. What followed was absolutely startling. Frequent cloud-to-ground and cloud-to-air strikes lit up the sky near sundown, a display typically reserved to the summer months. As for rainfall, it wasn’t particularly special, with moderate rain and local downpours. Generally, only about 2-5 mm of rain fell over the city. Thunder and lightning was easily the biggest highlight.
     The storms kept marching east, even after sunset. Decent instability and sustained lift along the front kept things going (13-15 C with 7-9 C dewpoints). Although rare, it is important to keep in mind that the atmosphere only cares about how one layer compares with another. A sharp decline in temperature with height, along with decent moisture and lift is all that is needed for thunderstorms. It wasn’t overly warm on the surface that day, with highs in the low to mid teens, although it was very cold above the ground. This difference created an unstable atmosphere.

Here are some links of videos of Oct 22:

     Oct 26 – Widely scattered thunderstorms popped up once again in southern Manitoba in the afternoon. One developed right over the city, with central areas generally hardest hit. Small pea sized hail fell in many areas, covering the ground. It was cool enough that not all the hail had melted by the next morning. The lingering moisture caused extensive thick fog the next morning.

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