Saturday, 1 June 2013
An Extreme May
With an average mean 0.3°C below normal, May was the 8th consecutive colder than normal month in Winnipeg. We could still see the consequences of the late start to spring well into the end of the month, most noticeably when it came to thunderstorms and persistent ice cover on the lakes.
The month started wintery. Dauphin reached its all-time coldest May temperature on May 2 at -15.4°C, following a 20-40 cm dump of snow in western Manitoba on April 29-30. Winnipeg nearly broke its low maximum record of 0.2°C in 2011 on May 1 with a high of 0.5°C. At the same time, record snows pummelled the US.
Temperatures for the 2 weeks following were all over the place, alternating between summer and winter values. May 13 saw the biggest jump; Winnipeg's high of 27.5°C was 35 degrees warmer than the low of -7.3°C the day before. Gretna reached a balmy 31.9°C after a low of -4.6°C the previous morning. South of the border, Omaha, Nebraska reached its coldest temperature for so late in the season on May 12 (0°C) and then its hottest temperature for so early in the season 2 days later with a high of 38°C.
2 major rainstorms highlighted the remainder of the month with excessive amounts of rain in parts of southern Manitoba. Areas along the escarpment saw over 100 mm of rain on both events thanks to a consistent upslope flow. Summaries of these storms can be seen by following these links: May long-weekend 4 day-long storm and May 30-31 storm.
For the entire month of May, rainfall amounts varied greatly across southern Manitoba. Well over 180 mm fell along the escarpment, near Deerwood, Miami and Morden, in some cases half the amount of rain they would normal see in an entire year. A maximum of 258 mm was recorded by a cocorahs observer southwest of Miami. In Winnipeg, amounts varied from 68.5 mm at the airport to 88.6 mm in south St Vital. Much lower amounts fell in the Interlake and Parklands, areas that missed out on the heaviest rains of the 2 major rainstorms. Here's a map showing monthly rainfall totals:
The lack of thunderstorms was quite noticeable as well. We are now June 1 and Winnipeg has not had a thunderstorm yet this year. So far this makes it the 4th latest start to the thunderstorm season at Winnipeg airport since these records began in 1953. If we don't get a storm before June 4, then we'll end up at second latest. Latest was June 28, 1958.
As of today, we have now been 281 days without a thunderstorm at Winnipeg airport. So far this is the 2nd longest period wihout a storm. If we don't get a storm by next Friday, this will end up being the longest period on record without a thunderstorm:
This May is also only the 9th since 1953 to not have a thunderstorm and the first since 1995.
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