December Smashes 1914 Rain Record – 2013 Second Driest Overall and Warm

Records Fall

With 1041 mm at the Airport, 2013 should be officially recorded as the 2nd driest year since records began in 1896. Only 1985 was drier at the official stations. The month of December 2013 was the driest ever recorded.

Dry Dry Everywhere:

No matter where you look in the Alberni Valley it has been a dry December, and a dry year. Since records began there have only been 4 other years where the historic Port Alberni weather stations have received less than 1250 mm of rain. 1911(BVCR 1117.2 mm), 1922 (CPA 1150 mm), 1929 (BVCR/CPA 1105 mm/1155 mm), 1985 (PASA/RCRK 1016 mm/1169 mm), and now 2013 (ABW/PAAP 1033 mm/1041 mm).

After scanning the historic stations of Beaver Creek, Port Alberni (City), Lupsi Cupsi, Robertson Creek, Port Alberni “A”, and Alberni Airport records, I could only find one December that registered under 100 mm. That was the Beaver Creek station in 1914 at 63 mm. We smashed even that record with the 39.6 mm measured at the Airport. The next driest is 108 mm nearly 50 mm, or one really good rain storm, more. The top three driest Decembers in all Alberni records are now:

2013: 39.6 mm Port Alberni Airport (AUT)
1914: 63.8 mm Beaver Creek
1948: 108.5 mm Port Alberni (City)

This caps off an extremely dry end to 2013. With October, November, and December all breaking records or very dry.

Comparing to “Normal”, the historic Port Alberni “A” Somass station normal rainfall for December is 255 mm (1971-2000) to 275 mm (1981-2010). So Alberniweather received 15% of those normals. The Airport tally is incomplete, since it is missing the 23rd and 31st, but this should not greatly affect the total. Compared to the Robertson Creek Hatchery station nearby the normal is between 336.9 mm and 344.6 mm. That leaves the 39.6 mm as 11.7% of normal. For 2013 our total precipitation at Alberniweather was 1032.8 mm, or 54% of the normal 1910 mm to 1907 mm at the Port Alberni “A” Somass station. The 1041 mm total at the Airport was 48% of the normal 2134 mm to 2153 mm at the Robertson Creek Hatchery Station.

How Abnormal?

After some encouragement from Bruce in the comments I’ve done some more data work and come up with this:

What you see is all of the annual rainfall values from the major overlapping stations in the Valley since 1895. The middle line is the average. The shaded area is one Standard Deviation… the 2nd dotted line above and below the average is 2SD and the limits of the graph 3SD.

This is a mathematical way of figuring out how infrequently something might happen. As you can see, this years values are just beyond the 2nd Standard Deviation line on the low end, which means it should only ever happen about 5% of the time. So it’s rare, but not unheard of. If it had fallen beyond the confines of this graph, and so beyond 3 sigma, then that would have about a 0.3% chance of happening, or, a 1-300 year event.

Here is the same treatment for December:

Snowpack taking a hit.

This late year dryness is having serious repercussions on the snow pack. The BC River Forecast Centre shows the sorry state of the snowpack at the Jump Creek measuring site south of Mt. Arrowsmith.

The dark blue line hugging zero is this year. The red is the ‘minimum’ recorded in past years. That means we’re in record low snow pack for the South Island. The hourly data up to today (January 2nd) shows the rain today had basically no effect.

The North Island snow pack is somewhat better, and did rise today, but it is not great and could easily end up very low by spring if conditions do not improve.

Temperatures cool for December and warm for Year.

Temperatures were generally at or slightly below normal for the month of December. Which is to be expected given how dry it was and the resulting lack of southerly winds and rain, and the clear cool days.

Regardless of this, for the year, average temperatures were warmer than the 1981-2010 normal for mean and minimum and exactly normal for maximums. In terms of minimums, they were significantly warmer, both at the Airport, with 0.42° C increase, and in the City, with a large 1.89° C difference above normal.

If you’re thinking ‘global warming’, remember these are comparisons to the most recent 30 year trend not to the much more broad 50 year 1850-1899 that total past warming is relative to when using IPCC estimates. Records that early don’t exist in Port Alberni. If we were to do a similar study of ‘total’ global warming, we’d have to use the earliest possible records from Beaver Creek and Port Alberni (City) for the 50 years from 1900-1949. Unfortunately, we don’t have a corrected dataset to use…. but I may find the time one day to figure out how to do it anyway. 🙂 As it stands though, rest assured, the further back you look, the higher the rise in temperatures gets.

Monthly Timelapse:

Stats and Analysis for the Year 2013

Changes for 2014 and onwards:
We are using only 1981-2010 ‘normals’ and ‘averages’
We are grouping the official “Airport” records with Robertson Creek “normals” and my and other city stations with the old “A” station because of significant differences in values and locations.

Also note, in its future projections of warming, the IPCC is using averages from 1980-1999. So if you are asking yourself whether ‘their projections’ match ‘our weather’ you can generally do so with the data provided here.

Finally, Islandweather.ca does not provide overall annual averages for their stations, so can’t include them. Hopefully when they do, I’ll update this post to include them like I do for the monthly reports.

Average Daily Temperature for 2013:
City Station Ave. Difference from Somass 1981-2010 normal: +0.57° C
Official (Airport) Difference from Robertson Creek 1981-2010 normal: +0.21° C
Environment Canada Airport: 9.8° C
Alberniweather:10.3° C
Alberni Elementary:NA
Maquinna: NA
Neptune Canada: NA
Overall City Average: 10.3° C
1981-2000 Environment Canada Normal (A – Somass): 9.73° C
1981-2010 Environment Canada Normal (Robertson Creek): 9.59° C

Average Minimum Daily Temperature for 2013:
City Station Ave. Difference from Somass 1981-2010 normal: +1.89° C
Official (Airport) Difference from Robertson Creek 1981-2010 normal: +0.42° C
EC: 4.9° C
Alberniweather: 6.6° C
AES: NA
MAQ: NA
NEP: NA
Overall City Average: 6.6° C
1981-2000 Environment Canada Normal (A – Somass): 4.71° C
1981-2010 Environment Canada Normal (Robertson Creek): 4.48° C

Average Maximum Daily Temperature for 2013:
City Station Ave. Difference from Somass 1981-2010 normal: +0.29° C
Official (Airport) Difference from Robertson Creek 1981-2010 normal: -0.04° C
EC: 14.6° C
Alberniweather: 15.0° C
AES: NA
MAQ: NA
NEP: NA
Overall City Average: 15.0° C
1981-2000 Environment Canada Normal (A – Somass): 14.71° C
1981-2010 Environment Canada Normal (Robertson Creek): 14.64° C

Average Precipitation for 2013:
City Station Ave. Difference from Somass 1981-2010 normal: -874.52 mm
Official (Airport) Difference from Robertson Creek 1981-2010 normal: -1112.59 mm
EC: 1041.0 mm
Alberniweather: 1032.8 mm
AES: NA
MAQ: NA
NEP: NA (not measured)
Overall City Average: 37.5 mm
1981-2000 Environment Canada Normal (A – Somass): 1907.32 mm
1981-2010 Environment Canada Normal (Robertson Creek): 2153.59 mm

Stats and Analysis for the Month of December 2013
Changes for 2014 and onwards:
We are using only 1981-2010 ‘normals’ and ‘averages’
We are grouping the official “Airport” records with Robertson Creek “normals” and my and other city stations with the old “A” station because of significant differences in values and locations.

Average Daily Temperature for December:
City Station Ave. Difference from Somass 1981-2010 normal: -0.23° C
Official (Airport) Difference from Robertson Creek 1981-2010 normal: -0.88° C
Environment Canada Airport: 0.9° C
Alberniweather:2.3° C
Alberni Elementary:2.2° C
Maquinna: 1.9° C
Neptune Canada: 2.4° C
Overall City Average: 2.2° C
1981-2000 Environment Canada Normal (A – Somass): 2.43° C
1981-2010 Environment Canada Normal (Robertson Creek): 1.78° C

Average Minimum Daily Temperature for December:
City Station Ave. Difference from Somass 1981-2010 normal: -0.07° C
Official (Airport) Difference from Robertson Creek 1981-2010 normal: -1.84° C
EC: -2.1° C
Alberniweather: 0.1° C
AES: -0.1° C
MAQ: -0.1° C
NEP: 0.4° C
Overall City Average: 0.3° C
1981-2000 Environment Canada Normal (A – Somass): 0.37° C
1981-2010 Environment Canada Normal (Robertson Creek): -0.26° C

Average Maximum Daily Temperature for December:
City Station Ave. Difference from Somass 1981-2010 normal: +0.39° C
Official (Airport) Difference from Robertson Creek 1981-2010 normal: +0.11° C
EC: 3.9° C
Alberniweather: 5.0° C
AES: 5.0° C
MAQ: 4.4° C
NEP: 5.0° C
Overall City Average: 4.85° C
1981-2000 Environment Canada Normal (A – Somass): 4.46° C
1981-2010 Environment Canada Normal (Robertson Creek): 3.79° C

Average Precipitation for December:
City Station Ave. Difference from Somass 1981-2010 normal: -238.45 mm
Official (Airport) Difference from Robertson Creek 1981-2010 normal: -304.97 mm
EC: 39.6 mm (ALL TIME RECORD)
Alberniweather: 39.4 mm
AES: 39.2 mm
MAQ: 34.0 mm
NEP: NA (not measured)
Overall City Average: 37.5 mm
1981-2000 Environment Canada Normal (A – Somass): 275.95 mm
1981-2010 Environment Canada Normal (Robertson Creek): 344.57 mm

Comparison to recent Decembers at Alberniweather (only).

2012:
Last December Wet. This December, DRY, but a little warmer.

2011:
It was cooler in December 2011 and dry… but not nearly as dry as this year.

2010:
410 mm of rain in December 2010. No, Really. That’s 12x more than this year. Not surprisingly, it was a little warmer too.

2009:
Quite cold in December 2009. Near normal precipitation.

2008:
December 2008 was quite cold and dry, but like 2011, not nearly as dry as this year.

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