Please note that as of Jan 1st, I am now using 1981-2010 normals for Winnipeg monthly temperatures. When referring to monthly "normal" temperatures, a 30 year average is used as the standard for defining "normal". These 30 year averages are generally updated every decade (1951-1980, 1961-1990, 1971-2000, etc) based on EC weather monitoring stations. In Winnipeg's case, these are based on temperature readings from YWG airport.
When looking at the "new" 1981-2010 normals, we see some interesting changes from the previous 1971-2000 normals that we've been using over the last decade (see table below) The most notable difference is how much warmer our winters have become, especially January which now has a "normal" monthly temperature that is 1.4C warmer than the previous 1971-2000 normal. In other words, a "normal" January last decade would now be considered 1.4C below normal using the new 1981-2010 normals.
MONTH ......... 1981-2010 ....... 1971- 2000 ...... difference
normal normal
JAN ................. -16.4C .............. -17.8C ............ +1.4C
FEB ................ -13.5C .............. -13.6C ............ +0.1C
MAR ............... - 5.8C .............. - 6.1C ............ +0.3C
APR ............... 4.5C .............. 4.0C ............ +0.5C
MAY ............... 11.4C .............. 12.0C ............ -0.6C
JUN ................ 16.9C .............. 17.0C ............. -0.1C
JUL ................. 19.6C .............. 19.5C ............ +0.1C
AUG ................ 18.7C .............. 18.5C ............ +0.2C
SEP ................. 12.9C .............. 12.3C ............ +0.6C
OCT ................ 5.1C ............... 5.3C ............ -0.2C
NOV ................ - 4.6C ............... -5.3C ............. +0.7C
DEC ................ -13.5C .............. -14.4C ........... +0.9C
ANNUAL .......... +2.9C ............. +2.6C ............ +0.3C
9 out of 12 months now have "warmer" normals than the previous 1971-2000 values. This has resulted in an annual average that is now 0.3C warmer than the previous annual average. Only May saw a notable decrease (-0.6C) in average monthly temperatures compared to 1971-2000 values.
EC continues to use 1971-2000 normals but plans to move to the new 1981-2010 normals sometime this year (the US has been using them for a couple years now). I don't have the new normals for 1981-2010 precipitation values yet, but will post those as soon as I get them.
It's weird how much the month of May has actually been cooling down the past 2 decades. Just looking at the 21st century (2000-2012) the average mean for May was a measly 10.6°C.. Not sure what would explain such a significant cool down for one single month of the year.
ReplyDeleteI notice that there was a period of very warm Mays in the 70's and 80's so I suppose by losing those years in our normals may explain the ''cool down''...? But it in the past 20 years, not one single May was in the top 30 warmest Mays.. Intriguing.
There's also been more snowfall in May lately, so I expect the normal May snowfall to increase quite a bit in the 1981-2010 normals.
Anonymous..
ReplyDeleteYeah, the cold and snowy Mays of 2002 and 2004 certainly killed the May average over the past decade. As you said, losing some of those warm Mays of the 70s (including 1977 - Winnipeg's warmest May on record) could explain the cooler average.