Sunday, 1 September 2013

Quiet August With Variable Temperatures

     August 2013, similarly to July 2013, was double-faced. We flirted with record lows at times in the first couple weeks of the month, while we flirted, and even broke some warmth records in the last couple weeks. However, what was most noteable in the month was the lack of thunderstorm activity in the Winnipeg area.

     In fact, there were just 2 thunderstorm days at the airport in August. This ties with 1970 and 1971 for second least for the month since 1953. The 1981-2010 normal is 6 or 7 thunderstorm days (6.2 days to be more precise). This August also marks the 3rd consecutive August of below normal thunderstorm activity.

Top least thunderstorm days in August since 1953

Dime-sized hail on Aug 18
     The ONLY decent thunderstorm to strike Winnipeg was on August 18. Hail as large as dimes fell in the city and torrential rains dumped 30-60 mm of rainfall over western and northern parts of the city. The south and east ends of the city were not as lucky, with only about 5-15 mm of rainfall. This was the only large rain event of the month. As a result, I have only received 25.6 mm of rainfall for the entire month of August at my place in south St Vital, the 3rd consecutive drier than normal August both here and at the airport.

     A large factor in the lack of thunderstorm activity in the first half of August was the lack of heat due to a consistent northwest flow behind a very deep trough in the jet stream over northern Ontario. From July 18 to August 14 (a 28-day period), the maximum was just 25.2°C... at a time when it is supposed to be the peak of summer. In fact, normal highs in that period are between 25 and 27°C. Highs in the period averaged 22.4°C and lows 8.9°C, both a good 4 degrees below normal for the period.

     The second half of August salvaged summer. Highs in the last 17 days of the month averaged 29.8°C and lows 15.3°C, both some 4 to 5 degrees ABOVE normal for the period this time. 10 days reached 30°C, above the 1981-2010 normal of 5 days for the month and most 30°C days in August since 2003. Humidity was also quite high on some days, with a maximum humidex of 40.4 on Aug 24, also the yearly maximum so far. Two high daily minimum records were broken in the period; a minimum of 21.4°C on Aug 24 and 19.7°C on Aug 25.

     Thank you for reading! Meteorological summer summary to come tomorrow...

1 comment:

  1. New 1981-2010 normals page for Winnipeg:

    (By the way, SD=standard deviation)

    All the improvements and additions to the record books will be finished either sometime this evening or tomorrow morning.