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December 2020 General Discussions & Observations Thread


bluewave
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53 minutes ago, rclab said:

I remember during a Mash holiday show Hawkeye Pierce talking about a white Christmas in his home town of Crabapple Cove Maine. He said we have a white Christmas from Halloween on...... As always ...

Caribou has a very long winter. To long for me. We were so over due for snow less seasons like the last 2. NYC Central Park actually averaged some 5-6 inches more snow the last 30 year climate period (1990-2020) as compared to the previous period of 1960-1990. The slightly milder temperatures seem to have given our area more precipitation and in the winter that can mean more snow.

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5 hours ago, Snowstorms said:

Same story up this way. Only 1981-82, 1984-85 and 1992-93 were above average and the rest were ratters. 80's winters were cold though. Maybe not as a whole winter but there was a lot of cold months. 

most of them were January and most of those were dry and cold lol..and the one December in 1989 which was historically cold but also hysterically dry....

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3 hours ago, bluewave said:

Yeah, it looks like more of a MJO 4 pattern as the AAM and PNA falls. So we get a Niño-like to Niña-like  progression this month. Something for all the different ENSO fans.

2C839F65-7C10-45B8-B8B6-D66E0CB2D3B0.png.48f2741b622063fc842b569fe6a1722a.png
D709028E-059E-4728-AE5A-C26375E8EC57.thumb.png.19d5f3077a380b0f4dca0fb9c21e6fbd.png

why cant we just not have ENSO anymore or at the very least not have it influence our weather anymore.

 

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3 hours ago, Allsnow said:

Weeklies have the cold shot and snow potential December 13-20th. It then goes full on Niña with cold west/warm East. Around January 15th (la la la land) it has -nao, -epo, and cold moving east. Looks like a niño pattern in the middle of January 

okay so an extended thaw between Dec 20 and Jan 15 lol

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48 minutes ago, lee59 said:

Caribou has a very long winter. To long for me. We were so over due for snow less seasons like the last 2. NYC Central Park actually averaged some 5-6 inches more snow the last 30 year climate period (1990-2020) as compared to the previous period of 1960-1990. The slightly milder temperatures seem to have given our area more precipitation and in the winter that can mean more snow.

I was browsing various Dec discussion threads looking for possible forecast maps for later in Dec lol, and came across this. its a great point. NYC climate always seems like a feast or famine place when it comes to snow. and lean times suck, but when you look at it, there was a lot of snow in recent years not long ago. The 2010s were actually the warmest (just barely), wettest, and snowiest decade on record for Detroit. Snowfall has increased across much of the Midwest and Northeast this century, so I just don't get the fear that snow is going away that some people have. Its not lol. The northeast will always be prone to noreasters. 

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A sustained period of cooler than normal to near normal temperatures is poised to develop. Initially readings will run somewhat above normal, but the colder regime could move into place near or during the coming weekend following a storm that could bring significant precipitation to the region. The storm could end as snow north and west of New York City and Newark. There remains some possibility that the precipitation could end as a period of wet snow or flurries even in the I-95 Corridor.

A fairly sharp cold shot is possible during the second week of December. There remains considerable uncertainty about the timing of the next change toward milder conditions. The development of a AO-/PNA+ pattern has shifted the outlook toward colder temperatures during the first half of December (consistent with statistical guidance) in parts of the Middle Atlantic region. Exceptional cold is unlikely through mid-December. A milder pattern could develop near mid-month. The duration of the AO-/PNA+ pattern will be key to how long the colder pattern persists.

Meanwhile, an extended duration much warmer than normal regime has now developed in western Canada. Record high temperatures included:

Calgary: 61° (old record: 55°, 1939)
Claresholm, AB: 65° (old record: 51°, 1993 and 2015)
Faro, YT: 45° (old record: 39°, 1992)
Fort Simpson, NT: 49° (old record: 31°, 2009)
Mayo, YT: 47° (old record: 39°, 1969)
Norman Wells, NT: 49° (old record: 23°, 2009) ***New December Record***
Paulatuk, NT: 35° (old record: 29°, 1987)
Watson Lake, YT: 42° (old record: 39°, 2004)
Wrigley, NT: 52° (old record: 27°, 2009) ***New December Record***

At Wrigley, the 52° (11.0°C) temperature exceeded both the December monthly record (46°/7.8°C, December 13, 1944) and the November monthly record (48°/8.9°C, November 23, 1954 and November 3, 1974). The previous latest 50° (10.0°C) temperature occurred on October 27, 1962 when the temperature reached 50° (10.0°C).

In recent years, there has been a disproportionately high frequency for high temperature records in western Canada. For example, in Calgary where the temperature record goes back to 1881, 61 record high temperatures have been set or broken from 2000 or later vs. 16 record lows (3.8:1 ratio). Those numbers are 25 and 3 since 2010 (8.3:1 ratio).

Tomorrow could see additional record high temperatures in that region.

Statistical guidance based on the ENSO state and teleconnections would typically favor a colder regime for the first half of December in the Middle Atlantic and southern New England regions. Both historic experience following exceptionally warm November cases suggest that a warmer than normal December remains the base case even if the first half of the month winds up colder than normal. Almost 90% of cases with a November mean temperature of 51.5° or above in Central Park (2020 saw the temperature average a record 52.9° in November) went on to record a warmer than normal December and just over three-quarters of such cases saw December register a monthly mean temperature of 40.0° or above.  

The ENSO Region 1+2 anomaly was -1.0°C and the Region 3.4 anomaly was -1.0°C for the week centered around November 18. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.87°C and the ENSO Region 3.4 anomaly has averaged -1.40°C. La Niña conditions will likely prevail at least through the winter.

The SOI was +11.31.

Today, the preliminary Arctic Oscillation (AO) figure was -0.711.

On December 2 the MJO was in Phase 4 at an amplitude of 0.982 (RMM). The December 1-adjusted amplitude was 0.953.

Based on the latest guidance, no significant stratospheric warming event is likely through the middle of the second week of December. Some warming above 3 mb is likely toward the latter part of the first week of December on account of strong Wave 1 activity. Recent guidance is a bit more impressed with the warming.

Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 10/11 (91%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. A predominant EPO+/AO+ pattern is very likely for winter 2020-21. It is likely that the Middle Atlantic and southern New England areas will see a warmer than normal winter with below normal snowfall.

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20 minutes ago, LibertyBell said:

why cant we just not have ENSO anymore or at the very least not have it influence our weather anymore.

 

We would probably need an ENSO time machine for that.

https://www.news.gatech.edu/2019/11/25/el-nino-swings-more-violently-industrial-age-hard-evidence-says

Blowing models away

The physical proof taken from three islands that dot the heart of the ENSO zone has also thrown down scientific gauntlets, starkly challenging computer models of ENSO patterns and causes. A prime example: Previously unknown to science, the study showed that in a period from 3,000 to 5,000 years ago, the El Nino-La Nina oscillations were extremely mild.

“Maybe there’s no good explanation for a cause. Maybe it just happened,” Cobb said. “Maybe El Nino can just enter a mode and get stuck in it for a millennium.”

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2 minutes ago, wizard021 said:

Strong - nao / 50/50 block.. but the pna is getting beaten up and thus allows this to miss.

Gut feeling mid atlantic gets a 6 to 12 type snow event, but cannot make it north of Phiiy. 

Lol. It’s definitely a possible outcome. Or the costal steals from the ULL and we get nothing. 

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The follow up Mon-Tue trof is a longshot for snow but it doesn't look completely impossible.  There are several interacting shortwaves that muddle the picture and there's probably not quite enough room behind the departing system.  But the airmass is a little colder and it's at least something to watch.  I could see SNJ getting grazed with precipitation.

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The next 8 days are averaging 41degs.(36/45).        Making it 36degs., or about -3.0, no change from yesterday.

Only EURO has even a Trace of snow(5th )&(10th.).       GEFS Control Member has a Trace there too-----then goes silent for 30 days!

btw:    Tampa's 32 month run of AN T's really is in some jeopardy, as I predicted.      The rest of December there must already beat +1.2, to keep the streak alive.

47*(66%RH) at 6am.         50* by 11:30am, back to 47* by 3pm with drizzle.

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Morning thoughts...

Today will be partly to mostly cloudy. Rain will likely develop. Temperatures will likely reach the upper 40s and lower 50s in most of the region. Likely high temperatures around the region include:

New York City (Central Park): 50°

Newark: 52°

Philadelphia: 51°

The storm will likely bring accumulating snow to parts of New England, but will be a “near miss” for most of the Middle Atlantic region into southern New England. Providence will likely see 1”-3” snow and Boston will pick up 3”-6”.  From Philadelphia to New York City, a general 0.50”-1.50” rainfall is likely with lower amounts north and west of that line.

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This was one of the highest daily December +PNA readings on record. It looks like it reached a +1.9. The only other years with a +1.9 that I could find were 2002 and 1989. December 2002 was a moderate El Niño and 1989 was a neutral ENSO. This would be the first for a moderate La Niña. November 2020 reached a -1.32 monthly Niño 3.4 anomaly.  Both those Decembers started much colder for NYC than this year with lows under 20 during the first week. So this year is an unusually warm +PNA. This is related to the record warm November lead up to this major amplification of the ridge over Canada. There was no cold to trap underneath for us and the ridge was flatter and extended further east to the Canadian Maritimes.
 

5B65DB69-A37E-47B6-8ABE-23B3483195F4.gif.9bdb4a81c78b6a86a8d14383da4f0ae2.gif

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32 minutes ago, bluewave said:

This was one of the highest daily December +PNA readings on record. It looks like it reached a +1.9. The only other years with a +1.9 that I could find were 2002 and 1989. December 2002 was a moderate El Niño and 1989 was a neutral ENSO. This would be the first for a moderate La Niña. November 2020 reached a -1.32 monthly Niño 3.4 anomaly.  Both those Decembers started much colder for NYC than this year with lows under 20 during the first week. So this year is an unusually warm +PNA. This is related to the record warm November lead up to this major amplification of the ridge over Canada. There was no cold to trap underneath for us and the ridge was flatter and extended further east to the Canadian Maritimes.
 

5B65DB69-A37E-47B6-8ABE-23B3483195F4.gif.9bdb4a81c78b6a86a8d14383da4f0ae2.gif

its odd the EPS initialized the PNA at +4 yesterday, maybe that is why it was way too far west with the storm tomorrow and for the past few days.

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6 minutes ago, qg_omega said:

its odd the EPS initialized the PNA at +4 yesterday, maybe that is why it was way too far west with the storm tomorrow and for the past few days.

Those vendors that show EPS teleconnections have their own custom indices. So they are not using the same methodology as the CPC. It’s an apples to oranges comparison. Plus they don’t have an archive of indices back to 1950 to compare against. 


https://ftp.cpc.ncep.noaa.gov/cwlinks/

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/teleconnections.shtml

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44 minutes ago, bluewave said:

This was one of the highest daily December +PNA readings on record. It looks like it reached a +1.9. The only other years with a +1.9 that I could find were 2002 and 1989. December 2002 was a moderate El Niño and 1989 was a neutral ENSO. This would be the first for a moderate La Niña. November 2020 reached a -1.32 monthly Niño 3.4 anomaly.  Both those Decembers started much colder for NYC than this year with lows under 20 during the first week. So this year is an unusually warm +PNA. This is related to the record warm November lead up to this major amplification of the ridge over Canada. There was no cold to trap underneath for us and the ridge was flatter and extended further east to the Canadian Maritimes.
 

5B65DB69-A37E-47B6-8ABE-23B3483195F4.gif.9bdb4a81c78b6a86a8d14383da4f0ae2.gif

The single most important piece to east coast storms is a good Pna. This is probably the best the pac has looked since March 2018. Just some bad luck that we are not snowing in this pattern. The storms tracks are there 

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7 minutes ago, Allsnow said:

The single most important piece to east coast storms is a good Pna. This is probably the best the pac has looked since March 2018. Just some bad luck that we are not snowing in this pattern. The storms tracks are there 

If its not one thing its another. Luckily its very early in the season. 

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10 minutes ago, Allsnow said:

The single most important piece to east coast storms is a good Pna. This is probably the best the pac has looked since March 2018. Just some bad luck that we are not snowing in this pattern. The storms tracks are there 

The +PNA ridge was too flat and merged with the ridge east of New England. Plus we are coming off a record warm November. Great storm track for a change, but very limited amounts of cold air this far south. Just goes to show how New England can get by with what are negative factors for us.

Forecast

B56829C9-AABF-4768-A5E0-E98BAC0F0A10.thumb.png.dba58736cc93e15996f8988ea32161ad.png

NYC biggest early December snowstorm composite since 2000.

 

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2 minutes ago, bluewave said:

The +PNA ridge was too flat and merged with the ridge east of New England. Plus we are coming off a record warm November. Great storm track for a change, but very limited amounts of cold air this far south. Just goes to show how New England can get by with what are negative factors for us.

Forecast

B56829C9-AABF-4768-A5E0-E98BAC0F0A10.thumb.png.dba58736cc93e15996f8988ea32161ad.png

NYC biggest early December snowstorm composite since 2000.

 

E6ACFBB0-CAD6-4BF2-B26F-E27FD0A3921D.gif.4ece2de84ca54257e550d77b8146495a.gif

Yep. That’s why New England avg so much more then us. Looks like another early season storm for BDL

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Seeing how difficult it is to get a snowstorm here makes you appreciate all the snowstorms in the 2000s & 2010s

Just think about what it takes to get it right. Perfect track, cold air supply, PNA, blocking, 50/50 low, etc. and you could have all those things and have the storm miss you by 50 miles. 

The difficulty will only increase with AGW making our climate more and more like Virginia.

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