What a difference a year makes...

JANUARY SNOWCOVER - 2012 (LEFT) VS 2013 (RIGHT)
Top image shows satellite image of snow cover
Bottom image shows webcam image from Emerson

 

 

The  images above show the stark contrast in snowcover over the southern Prairies and northern plains this year compared to last year.  Last year saw very mild conditions through December and early January, along with well below normal snowfall. In fact, up to Jan 1st, Winnipeg had received only 27 cm of total snowfall for the season, with only 5 cm all of December.  The lack of snow was quite evident from satellite images which showed a notable lack of snowcover into early January over much of southern SK, southern MB, and the northern plain states. The lack of snowcover allowed temperatures to soar to record high values in early January, including +6.7C in Winnipeg on the 5th, 11.5C in Gretna, and an all time January high of 13C in Fargo ND.

This year it's been a lot different, but certainly more typical for winter in this part of the world. Winnipeg has seen 75 cm of snow through Jan 1st, about 3 times the amount from last year, and almost twice the normal up to this point.  Snowcover is much more widespread across the Prairies, with much of the area covered in a blanket of white (see satellite image above)  Snowcover has been greater throughout much of the US as well, with about 65% of the country snowcovered compared to only 23% at the same point last winter. Snowcover is a very efficient heat deflector, as incoming solar radiation reflects off the bright snow surface back into space, making it more difficult for the earth's surface to warm up. The result is colder temperatures, which we've been seeing this winter compared to last winter.

Winnipeg as seen from international space station

Winnipeg as seen from ISS space station
taken by Chris Hadfield - Jan 3 2013

Commander Chris Hadfield took a superb shot of Winnipeg today from the international space station (ISS) orbiting above the earth. Chris posted this image via a tweet sent today.  The image clearly shows the built up urban areas of Winnipeg (dark areas) surrounded by snow covered fields around the city. The Red River is clearly visible cutting through the city as is the Red River floodway to the east of the city. The YWG airport runways are also clearly visible to the west.

Chris Hadfield has been posting many unique and stunning images of Canada from the ISS as it orbits the earth. Several of these images were posted in this National Post article.  Far out!

Milder start to the new year

A strong upper ridge of high pressure over the western Prairies is allowing a surge of milder Pacific air to push across the Prairies over the next few days. The bulk of the mild air will be confined over Alberta and southern  Saskatchewan, however above normal temperatures are forecast over southern Manitoba into next week as the upper flow becomes more zonal (westerly)  This will allow temperatures in Winnipeg to climb to the minus 5C mark or higher at times tomorrow into next week.  Long range guidance is indicating that the spell of above normal temperatures is expected to persist into mid to late next week before a return to colder conditions.       

Rob's Obs now using 1981-2010 normals

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.  

December to finish colder and snowier than normal..

December 2012 will finish colder and snowier than normal in Winnipeg, capping off what had been a record warm year through the fall.  December will finish with an average monthly temperature of -14.7C at YWG airport, or about 1.2C colder than the normal* December average of -13.5C (1981-2010 normal - see note at bottom of post)  Two cold spells around the 7th-13th and over the Christmas holidays brought the monthly average below normal, the third straight month with below normal temperatures. December snowfall of 32 cm (as measured at my site) was above the December mean of 19.8 cm, and brought the seasonal snowfall total so far up to 75 cm in the city.. almost matching last winter's entire snowfall total (80 cm) Normal seasonal snowfall in Winnipeg is around 110 cm.

For the year, 2012 will end up with an annual average of +4.6C in Winnipeg, some 1.7C above normal* and the 5th warmest calendar year on record since complete records began in 1873.  2012 was on pace to be the warmest calendar year through October, but a colder than normal finish dropped the year down to 5th place honours.

Top 5 warmest calendar years in Winnipeg (since 1873)  

1.  1987 ........... +5.4C
2.  1931 ........... +5.3C
3.  1878 ........... +4.7C
4.  1998 ........... +4.7C
5.  2012 ........... +4.6C

Normal* ........... +2.9C (based on 1981-2010 average)
normal annual temperature over entire period of record is 2.2C (1873-2012)

*NOTE:  Rob's Obs will be using 1981-2010 normals from now on. These are the updated 30 year normals that  replace the "old" normals which used the 1971-2000 averages. EC is still using the 1971-2000 normals, but plans to move to the updated 1981-2010 values soon.  I will have more details on this in a later post.