La Nina 2020/21
At the current time we are in a strong moderate La Nina. What that means is we are about half way between a moderate La Nina and a strong La Nina. Since 1950 there have been 4 moderate La Nina winters and 7 strong La Nina winter seasons. The moderate La Nina winters are 1955/56, 1970/71, 1995/96 and 2011-12. The strong La Nina winters are 1973/1974, 1974,75, 1988/89, 1999,2000, 2007-08 and 2010/11.I know that there has been some talk of a “back loaded” winter season this year. I took a look to see if that indeed is what happened in some past La Nina winter season. I will look only at moderate and strong La Nina’s at this time. First off the moderate La Nina winter season as that is what we are now in and there have only been 4 of them since 1950.
First up the winter of 1955/56. The winter of 1955/56 started off with a cold November with the mean of 35.3 and that was -4.8 below average there was 18.6” of snow fall that November. So that was a cold and snowy month. December was cold departure of -3.8 but not all that snowy with just 9.4” January seen temperatures near average -0.1 but very little snow fall with just 5.3”. February came in colder than average with a departure of -2.3 there was 22.9” of snow fall that February. March was much colder that average at -5.5 and snowier that average at 17.5” April was also cold with a departure of -4.1 and 5.5” more snow fall. The December thru March mean that winter was 26.1 and there was 79.3” of snow fall.
The winter season of 1970/71 November 1970 was a little colder than average at -1.9 and a near average snow fall with 6.1” December 1970 was cold with a departure of -3.5 and snowy with 33.3” January was very cold -6.1 and kind of snowy with 27.2” There was a solid snow pack all month. February remained cold -2.7 but very little snow 4.4” And while the month started with a good snow pack it melted down to a trace by the 28th March was very cold -6.6 and snowy 25.9” and there was snow on the ground until the 30th April was cold -4.2 and 4.1” of snow fall. The winter of 1970/71 was cold with a December thru March mean of 24.2 and 101.0” of snow fell that season. The winter of 1995/96 seen a very cold -8.1 and snowy 20.8” November. December was cold with below average snow fall of 17.4” January 1996 was colder than average at -2.7 but below average snow fall at 13.8” February it stayed cold -2.3 and once again little snow fall with just 6.9” March was very cold -7.2 and snowy with 19.3” April was cold -5.1. The Dec/March mean was 24.7 and that winter 79.2” of snow fell 20.8” of that fell in November. Then came 2011/12 November was warmer than average at +3.6 and just 0.7” of snow fall. December was the same with a departure of +5.8 and just 4.5” of snow fall. January was also well above average with departure of +5.3 but 27..0 of snow did fall. It stayed warm in February with a departure of 5.1 and that month 16.2” of snow fell. Then came March that March was the warmest of record with departure of +15.1 and just 2.8” of snow fell. While April was near average with a departure of +0.3 there was much crop damage with a hard freeze of 28 on the 29th For the season 51.2” of snow fell and the December thru March mean was a mild 36.9.
So how dose that play out for this winter? Well it looks like this year is falling more in line like the winter of 2011/12 than the other 3 La Nina winter season. Any way for Moderate La Nina winter season the average mean temperature for December. January, February and March is 28.0 the average snow fall is 77.8 of the 4 moderate La Nina seasons non were truly back loaded but 3 of the 4 did have winter hang on well into March