November 2020 General Discussions & Observations Thread

[rclab]

2 hours ago, bluewave said:

It only took NYC 5 years to beat 2015 for warmest November. It took 14 years for 2015 to surpass 2001. And 2001 over 20 years to go ahead of 1979. 

Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Nov
Click column heading to sort ascending, click again to sort descending.

Rank	Year	Mean Avg Temperature	Missing Count
1	2020	53.0	0
2	2015	52.8	0
3	2001	52.7	0
4	1979	52.5	0
5	1948	52.4	0
6	1975	52.3	0
7	2011	51.9	0
-	2006	51.9	0
-	1994	51.9	0
-	1931	51.9	0
8	1902	51.4	0
9	2009	51.1	0
10	1999	50.8	0

Sad, BW. A century from now the Smithsonian will likely have a special section for sleds. As always ....

[SnoSki14]

2015 definitely felt like a turning point.

Ever since then cold air has been hard to come by and winters have mostly been very warm with a few notable exceptions due to extreme blocking.

And with warming continuing to accelerate I feel we're going to see a major drop in the annual snowfall averages this decade. 

[the_other_guy]

1 hour ago, SnoSki14 said:

2015 definitely felt like a turning point.

Ever since then cold air has been hard to come by and winters have mostly been very warm with a few notable exceptions due to extreme blocking.

And with warming continuing to accelerate I feel we're going to see a major drop in the annual snowfall averages this decade. 

Agreed. It is all lining up against prolonged cold.

New normal is close to 3 degrees above normal.

AN is 5 plus degrees...Not through a few days of extreme warmth, but a persistent above normal that wont dissipate.

Snowstorms require luck now. Prolonged snow on ground is non existent.

We will see if this is a few year trend or not, but I have a feeling you are right

[Roger Smith]

I dropped into the forum to check that in fact NOV 2020 was warmest on record at NYC. I have a research thread on another weather forum (net-weather in the UK) outlining my research into climate records for Toronto (1840-2020) and more recently with a lot of assistance from Don Sutherland, added in comparative data for New York City. That part is all on page 2 of this thread (all Toronto stuff on page 1) ... 

https://www.netweather.tv/forum/topic/93113-toronto-180-a-north-american-data-base-of-180-years/#comments

I have compared rankings of all months that overlap since 1869 and you'll find that in general there is close agreement. This past November didn't quite make it to top of the list for Toronto, 1975 held on and 2011, 2016 and 1931 were not passed either. 

As part of this research I have applied urban heat island filters to the temperature records of both sets of data. NYC is in an even larger city of course but urban heat islands don't grow much stronger after a city reaches a critical size, they grow in areal extent instead. So I've applied the same decade by decade changes to both data sets with the assumption that New York City had a small urban heat island at the start of its records, Toronto only began to acquire one after 1881. So although I've changed the temperature data sets by similar amounts per decade, I assume NYC has a larger urban heat island by 0.3 to 0.5 C (0.5 to 0.9 F) deg. That is an average of all weather conditions and of course the urban effect is much bigger than that in calm, clear weather. 

The total adjustment for the Toronto data was 1.1 C (2.0 F) deg applied in full to the years since 1980, with 0.1 reductions in the filter each decade before that, until one reaches "no urbanization" before 1881 (there may have been a small amount). Applied to NYC that means 1869 to 1880 would be a step down also but there could have been further steps down in any data before 1869 in stages so the NYC total urban heat island is presumed to be around 1.5 C (2.7 F) averaged over all data. This applies mostly to overnight temperatures and this is reflected in the count of new record high max and min temps since 1970 (have done the same study at both sites, the counts are similar, around 15% more than random expectation for record high maxima, and 120% more for record high minima.) At Toronto, 218 days have a new record high minimum since 1970, only 108 have a new record high maximum. About 10 have a new record low minimum and 25 a new record low maximum again showing the diurnal bias of the u.h.i. effect. 

You'll find in this link tables of rankings for raw temperature data and adjusted. It does give the more ancient data some chance to make an upward move in the rankings but seldom do the "way back" months push more than five to ten ranks ahead and usually not into the top ten. (Years in the middle decades get smaller boosts, and the boosts ended in 1980, assuming almost steady-state u.h.i. since then). 

There was a remarkably hot July in 1868 at Toronto, unfortunately that's the year before the NYC data begin, maybe some other source would show this, but one or two very hot summer months at Toronto were surprisingly cool at NYC, for example July 1916 and 1921 both top ten months at Toronto, rather average to cool at NYC. Many other cases though have more similar outcomes at both locations. There's a circulation type with a narrow ridge over the western Great Lakes and an offshore trough in the Atlantic that can result in that differential. Even so, just about all the record highs at each location are either the same dates, or within 1-2 days, or do no worse than fall into top five, so generally similar results. I think you have to get into the Midwest before you start seeing a whole different set of record highs and lows, certainly by the time you reach the central plains that would be true.

I regularly update these tables and will probably put the same thread into some part of American Weather (not sure where is best suited) when I finish the project of creating an excel file with all data available. That is very close to completion (I am entering or proofing existing entries for 2019 today and 2020 tomorrow) but it would make sense to wait for 2020 to end then have this year complete as well. 

Eventually I will publish similar precip tables for NYC as I have done for Toronto. Once again Don S has been very helpful and I have all the raw data available, going through it to establish daily extremes and other useful info such as dry spells. The Toronto climate is more similar to NYC in temperature than precip, a dry month in each region may be closer to average or even a bit wetter than average that far afield. Snowfall does not correlate very well either, east coast storms miss Toronto on many occasions and Toronto snowstorms are often Apps runners or low-trajectory Colorado lows that warm up NYC. But some storms overlap. 

I am expecting a bit of a wild ride this winter, as many are saying, generally on the milder side of normal, but not a constant blowtorch situation and a few much colder intervals likely, mid to late January would be the most likely time. 

[LibertyBell]

I think you guys would find this interesting.  TWC posted a color coded map showing where snowy Novembers led to snowy winters, or not-snowy winters or no correlation at all.  Around the Great Lakes it was a positive correlation, for the east coast it was a negative correlation and for the middle of the country there was no correlation.