Winter 20-21 Discussion

[raindancewx]

Next shot at something down here is likely around 12/19.

Date	Tahiti (hPa)	Darwin (hPa)	Daily Contribution	30 day Av. SOI	90 day Av. SOI
9 Dec 2020	1013.79	1009.05	5.29	9.93	8.11
8 Dec 2020	1015.26	1010.05	7.73	9.84	8.05
7 Dec 2020	1015.79	1009.15	15.15	10.02	7.90

CPC is pretty confident in a warm period starting 12/17.

Texas had near to record warmth in a lot of spots today. Going forward, you'll see some days like that in other parts of the south to help burn off the cold.

 

[raindancewx]

At this point - and I don't expect this to happen - the winter of 1959-60 may be a best case scenario for what 2020-21 can do. You can see a similar look to early December, with a warm NE Pacific, similar north Atlantic, and cold Nino zones - although not a La Nina.

The 1959-60 winter gets very cold in 1960. That said, the Indian Ocean, waters by Australia, La Nina, and Western Pacific, not to mention solar activity (very high in 1959-60) and the cold November 1959 - are all very different even if December finishes similarly.

The rest of December 1959 does look like what CPC is showing generally for later in the month. I think a warmer version of the January map is possible, but I wouldn't bet on it either.

[raindancewx]

The fetch of subtropical moisture with the current system over the Southwest ended a 110 day rainless period in Phoenix, and a 242 day rainless period in Yuma. There were periods of long dry weather over the Southwest in the 2017-18 La Nina, but it was centered more over Texas & New Mexico, rather than Arizona and Southern California.

Amarillo went close to five months without measurable precipitation in 2017-18, and Albuquerque went 96 days without precipitation in that event. A lot of Arizona and New Mexico are now running near average for December precipitation totals, and I'd expect more systems by the end of the month.

[raindancewx]

Very close to 1959 so far, although colder in TX, NM and the interior NW.

These are the totals from the SW storm - a lot of the SW is now running well above average for precipitation totals winter to date.

[raindancewx]

[raindancewx]

[raindancewx]

Meanwhile...in the 'warm dry' Southwest...

[raindancewx]

Snow totals for Philadelphia, New York City and Boston are not final yet, but for reference:

In Boston, from 1931-32 to 2019-20, from October-May, 84/89 years see four or fewer days with at least six inches of snow. It's not official yet, but I'd expect Boston to top 6 inches on 12/17. The median from 12/18 to 5/31 is one day with six inches of snow. I would go above the median though for Boston, with 3-5 days over six inches, since my analogs had four for Boston.

In New York City, from 1931-32 to 2019-20, from October-May, 82/89 years see two or fewer days with at least six inches of snow. It's not official yet, but I can't see NYC not topping 6 inches today. The median from 12/17 to 5/31 is one day with six inches of snow. So I would expect two days overall with 6"+ this winter, instead of the median of one.

In Philadelphia, from 1931-32 to 2019-20, from October-May, 85/89 years see two or fewer days with at least six inches of snow. It's not official yet, but I think Philly will (just) top 6 inches today. The median from 12/17 to 5/31 is zero days with six inches of snow. So I would expect just this one day overall with 6"+ this winter, especially with the snowstorm today and in October following my winter outlook idea, with rapid deterioration in totals from Boston to NYC and NYC to Philly, i.e. more extreme cut off than the normal 41"/25"/22" seasonal totals.

[raindancewx]

As of Midnight eastern: 

Central Park had 6.5"

Philadelphia had 6.3".

The difference is, Philadelphia has had rain/freezing rain in recent hours, while NYC (Central Park) is still reporting snow at this hour. From 1931-2019, Philadelphia has only had at least six inches of snow on a December calendar day 12 times - so this was pretty solid. The bigger snows that can happen are almost always later in the season.  Philadelphia went over to plain cold rain for about an hour around Midnight, so I'd imagine some to most of the snow is gone already.

[raindancewx]

Looks like 6.6" total for Philadelphia, 10.0" total for Central Park, and 12.9" for Boston (Logan). Those figures are all within range of my five winter analogs.

[raindancewx]

The Weather Channel says winter is over. Don't really buy it personally. I wouldn't expect the South or Southwest to be cold overall, but I think January won't be super warm out here, and I doubt March will be real warm in the Southeast or Northeast. Southwest should roast in March, but I don't buy it getting into Wyoming or Nebraska either. It may be more of a +3 look than the +5 or +8 they seem to be implying.

[raindancewx]

Let's say the -NAO holds on for December. The transition from a +NAO November to a -NAO December is extremely rare: only seven years do it from 1950 to 2019. Those years are 1953, 1958, 1967, 1976, 1978, 1989, 2001.

None of these years are La Ninas. But, 1967 is close, and 1978 and 1989 and 2001 are cold-Neutral. The closest match to US temperatures in Nov-Dec is actually 1953 though and it isn't close. But: 1989, 2001 are next, and then 1958. I would weight the years like this for January:

1954 (x3) - closest temperature match Nov-Dec, and low solar

1959 (x1) - follows an El Nino

1968 (x1) - closest to a La Nina

1979 (x1) - cold-Neutral following two El Ninos

1990 (x2) - OK temp match, neutral

2002 (x2) - OK temp match, neutral

 

[Great Snow 1717]

On 12/16/2020 at 11:24 PM, raindancewx said:

Snow totals for Philadelphia, New York City and Boston are not final yet, but for reference:

In Boston, from 1931-32 to 2019-20, from October-May, 84/89 years see four or fewer days with at least six inches of snow. It's not official yet, but I'd expect Boston to top 6 inches on 12/17. The median from 12/18 to 5/31 is one day with six inches of snow. I would go above the median though for Boston, with 3-5 days over six inches, since my analogs had four for Boston.

In New York City, from 1931-32 to 2019-20, from October-May, 82/89 years see two or fewer days with at least six inches of snow. It's not official yet, but I can't see NYC not topping 6 inches today. The median from 12/17 to 5/31 is one day with six inches of snow. So I would expect two days overall with 6"+ this winter, instead of the median of one.

In Philadelphia, from 1931-32 to 2019-20, from October-May, 85/89 years see two or fewer days with at least six inches of snow. It's not official yet, but I think Philly will (just) top 6 inches today. The median from 12/17 to 5/31 is zero days with six inches of snow. So I would expect just this one day overall with 6"+ this winter, especially with the snowstorm today and in October following my winter outlook idea, with rapid deterioration in totals from Boston to NYC and NYC to Philly, i.e. more extreme cut off than the normal 41"/25"/22" seasonal totals.

What site do you use for the snowfall data?

 Thanks!

 

 

[raindancewx]

I use this for snowfall data. Locally it is imperfect and has some small data issues, but it's 99% right.

https://xmacis.rcc-acis.org/

 

[raindancewx]

Nino 4 in the prior winter is fairly predictive of what the NAO does in February. Bodes better for February 2022 in the East with Nino 4 likely to finish in the low 27s. But Nino 4 was 29.19C last winter. Not a good sign for this year. Above 28.7C in Nino 4 the prior winter, only 1 in 20 winters is below -0.2 for the Feb NAO. February NAO averages +0.6 for years following Nino 4 over 28.7C in winter, but averages -0.1 in the remaining colder years.

This is your +NAO La Nina composite - although I'd expect a somewhat different result.

[raindancewx]

Date	Tahiti (hPa)	Darwin (hPa)	Daily Contribution	30 day Av. SOI	90 day Av. SOI
20 Dec 2020	1011.45	1005.80	10.02	12.80	9.49
19 Dec 2020	1012.11	1002.50	30.57	13.03	9.54
18 Dec 2020	1012.34	1002.05	34.10	12.68	9.35
17 Dec 2020	1013.64	1003.35	34.10	12.22	9.08

Those 20 point crashes are rare...but fun usually.

No idea if this will work, but if you run objective "closest high" matches for 22 US cities and then pull out the most common top-10 close matches as analogs, you get a pretty good map for December, followed by an extremely warm US winter. I would say, very generally, either 2011 or 2012 or both were common western matches, while 1999, 2011, 2017 were more likely in the East. Overall, 2001 was the year that most commonly appeared as a top 10 match, which surprised me a bit.

[raindancewx]

Will be interesting to see how the winter transitions after December. Currently looks like Dec 2017 and Dec 2018 as a blend.

[raindancewx]

I realized yesterday that there is monthly data for the WPO, the West Pacific Oscillation, which is actually super powerful as a predictor in some months. Check out October (-2.44 was actually the WPO September reading, should say -1.18 on the graphic for Oct):

Since October, the index has been positive. Check out December, v. the rolled forward +WPO, +PNA, +AO, +NAO blend for November:

I don't think the +WPO, +PNA, -AO, -NAO December look is right for January. It looks pretty off to me. But we can see. The look is essentially January 2000, which didn't have the +WPO or +PNA, and I'd bet on both continuing at least a bit in January. Arctic is probably wrong too. But just thought I'd show the composite.

The WPO is actually very powerful at out here for Feb-Apr, so I am hoping it stays positive.

[StormchaserChuck!]

WPO is usually a 10-15 day cycle, it trends into -NAO at like -0.1 correlation, and switches in 30 days at +0.05 correlation. I did all indexes +60 days one time. 

[raindancewx]

When I did my forecast for winter, I knew 2007-08 had a +WPO just from looking at temperature patterns in Asia and the US, but I didn't realize there was a formalized index for it. It's a weird time frame to do a forecast, but the WPO is super useful for trying to figure out if Feb-Apr will be cold or warm out here. In the meantime, CPC still has the Western US cold for a while, especially the interior.

I was doing an analysis of my analogs earlier today for 12/1-12/21 v. US observations. I'm pretty close in a lot of the eastern Midwest, Northeast (outside Maine), interior West, and the edges of the South (VA, Arkansas, Oklahoma). I'm not close at all Northern Plains and Deep South, but the deeper we get into the month, the more the month has looked like my blend. One of the ideas in my forecast was at least some cold periods in the interior West this winter, based on low sea ice in the Summer + cold ENSO. That's at least partially right. If you use Albuquerque as a proxy, we haven't hit 60 this month. Even on a 'warm' day like today when we'll be mid-50s, it was 22 in the morning, which prevents the highs from getting out out control. I'm curious to see if the areas outside the Northern Plains and Deep South can trend toward what I had more by the end of the month. 

[StormchaserChuck!]

It sometimes takes a +climate event to get a +WPO- or vortex over the Bering straight. The default, especially in this time of melting arctic ice is ridging there. 

Descending PDO from June on, through November looks like this:

 

 

 

[raindancewx]

Those four years above as a blend are very warm for January.

I've been looking at the January cold-ENSO years following two El Nino winters. Those are pretty cold in the West pretty reliably.

1929-30/1930-31 El Ninos ---> Jan 1932

1957-58/1958-59 El Ninos --> Jan 1960

1968-69/1969-70 El Ninos --> Jan 1971 (may look warm in the West, but featured a record cold shot and record warmth)

1976-77/1977-78 El Ninos --> Jan 1979

1986-87/1987-88 El Ninos --> Jan 1989

2014-15/2015-16 El Ninos --> Jan 2017

I think I'd add 3.0F to this in the Plains for lack of snow cover and +1.5 everywhere else since the analogs are centered on the 1970s.

 

 

[raindancewx]

Here is a weird question for everybody. When I look at the EPO index, it is clear the positive phase is the one that is correlated to cold in the Central/East. But then I see sites where the EPO in the negative phase is supposed to do that. I know what the EPO is and what it does, but did CPC change the definition of which phase was positive? There seems to be a common split, where some people refer to the -EPO as "good" for cold in the East and others refer to +EPO as "good" for cold in the East, even though they are clearly talking about the same thing, where one is named incorrectly.

This is Nov 2014, 2018, 2019 which all have major +EPO phases on the CPC index. But according to a site like the one below (not picking on them it just popped up), should be a -EPO. When people talk about a positive or negative EPO...are people even talking about the same thing? Phases seem to be defined oppositely in some places. On the same index from CPC, Nov 2016 is negative and very warm in the places that are cold below.

https://psl.noaa.gov/data/correlation/epo.data

 2014   1.11   0.31   1.24   0.05   0.77  -0.69   0.33  -1.03   0.20  -0.66   3.21 -99.90
 2015   1.27   1.18   1.13  -0.35   0.49   1.72   0.23  -0.28  -1.38   0.33  -0.94 -99.90
 2016  -0.35   0.23   0.24   1.47   0.14   1.26  -0.36  -0.42  -1.41  -0.84  -1.43 -99.90
 2017   0.39   0.21  -1.04   1.04  -0.72   0.50   0.00  -1.65  -0.46  -0.58   0.41 -99.90
 2018   0.66   0.23   0.30  -0.18  -0.98   0.05  -0.16  -0.78  -0.83   1.17   1.42 -99.90
 2019   1.07   1.20   2.11   0.67   0.32   1.74   0.10  -1.18  -1.50  -0.47   1.93 -99.90
 2020  -0.60  -1.79   0.44   1.54   0.04  -0.69  -1.97  -2.39   0.06   0.57  -0.66 -99.90

https://www.wisconsinwx.com/teleconnections

[Orangeburgwx]

Here is a weird question for everybody. When I look at the EPO index, it is clear the positive phase is the one that is correlated to cold in the Central/East. But then I see sites where the EPO in the negative phase is supposed to that. I know what the EPO is and what it does, but did CPC change the definition of which phase was positive? There seems to be a common split, where some people refer to the -EPO as "good" for cold in the East and others refer to +EPO as "good" for cold in the East, even they are clearly talking about the same thing, where one is named incorrectly.
This is Nov 2014, 2018, 2019 which all have major +EPO phases on the CPC index. But according to a site like the one below (not picking on them it just popped up), should be a -EPO. When people talk about a positive or negative EPO...are people even talking about the same thing? Phases seem to be defined oppositely in some places.

https://psl.noaa.gov/data/correlation/epo.data

2014   1.11   0.31   1.24   0.05   0.77  -0.69   0.33  -1.03   0.20  -0.66   3.21 -99.902015   1.27   1.18   1.13  -0.35   0.49   1.72   0.23  -0.28  -1.38   0.33  -0.94 -99.902016  -0.35   0.23   0.24   1.47   0.14   1.26  -0.36  -0.42  -1.41  -0.84  -1.43 -99.902017   0.39   0.21  -1.04   1.04  -0.72   0.50   0.00  -1.65  -0.46  -0.58   0.41 -99.902018   0.66   0.23   0.30  -0.18  -0.98   0.05  -0.16  -0.78  -0.83   1.17   1.42 -99.902019   1.07   1.20   2.11   0.67   0.32   1.74   0.10  -1.18  -1.50  -0.47   1.93 -99.902020  -0.60  -1.79   0.44   1.54   0.04  -0.69  -1.97  -2.39   0.06   0.57  -0.66 -99.90

https://www.wisconsinwx.com/teleconnections

The fact we need a ridge over Alaska means it needs to be the orange and reds on the 500mb maps

Sent from my LGL322DL using Tapatalk

[raindancewx]

I know what it takes to make it cold in the East. I'm saying that the orange and reds up there are sometimes called a -EPO and sometimes called a +EPO.

To give another example, this is from Weatherbell. They seem to be in the '-EPO' = heights by Alaska. But the index seems to be opposite on the CPC site. November 2014 has a +EPO on the index, but seems to fit the -EPO definition some people use. I don't get why people use different phases of the index to describe the same thing. I get what it does. That's not the issue.

Does this clarify my point about the definition being variable? I get what it does, but it's just weird seeing it defined differently.

EPO: Eastern Pacific Oscillation (https://www.weatherbell.com/glossary)

A dipole pattern similar to the NAO in the Atlantic, but located in the eastern Pacific. There is a tendency for heights/pressures/temperatures to be higher to the north and lower to the south in the negative phase and lower to the north and higher to the south in the positive phase. The negative phase corresponds to widespread cooling over central and eastern North America and the positive phase to warming.

CPC Definition: https://www.cpc.ncep.noaa.gov/data/teledoc/ep.shtml

The East Pacific - North Pacific (EP- NP) pattern is a Spring-Summer-Fall pattern with three main anomaly centers. The positive phase of this pattern features positive height anomalies located over Alaska/ Western Canada, and negative anomalies over the central North Pacific and eastern North America.

 

 

[griteater]

raindance - I've never picked up on that, but you are correct on the sign difference there.  

This page indicates that the "EP/NP index replaces the old EP index which is no longer maintained by CPC" - https://psl.noaa.gov/data/climateindices/list/

-EPO means ridging over Alaska.  Here is a site for the EPO.  It gives a definition for the EPO, but it looks like the data links are broken - https://psl.noaa.gov/data/timeseries/daily/EPO/

Here is an EPO site that was constructed by Alan Marinaro, but the data hasn't been updated since 2016 - http://www.wxmidwest.com/epo/

Back to the EP/NP Index, here is a composite of all January's in which the EP/NP Index was +1.00 or higher.  Basically, it looks just like the EPO, but with reversed sign.  In this case, +EP/NP Index means ridging over Alaska

[raindancewx]

7 minutes ago, griteater said:

raindance - I've never picked up on that, but you are correct on the sign difference there.  

This page indicates that the "EP/NP index replaces the old EP index which is no longer maintained by CPC" - https://psl.noaa.gov/data/climateindices/list/

-EPO means ridging over Alaska.  Here is a site for the EPO.  It gives a definition for the EPO, but it looks like the data links are broken - https://psl.noaa.gov/data/timeseries/daily/EPO/

Here is an EPO site that was constructed by Alan Marinaro, but the data hasn't been updated since 2016 - http://www.wxmidwest.com/epo/

Back to the EP/NP Index, here is a composite of all January's in which the EP/NP Index was +1.00 or higher.  Basically, it looks just like the EPO, but with reversed sign.  In this case, +EP/NP Index means ridging over Alaska

I appreciate that. 

I don't really use the indexes much, but if I do I use the +EPO that matches the index on the CPC site. I was just trying to point this out because when Weatherbell puts out their teleconnection stuff, I'm wondering if people are looking for the wrong sign of the EPO when they look for Eastern cold if they use a -EPO as ridging while CPC is using a +EPO as ridging. It's also possible Weatherbell is using a different calculation than CPC. This is one of the things I can't stand about Twitter, I see people reference the indexes but it's clear there is a 50/50 split on whether a -EPO or a +EPO is ridging by Alaska from different forecasters, I was trying to show that with the Wisconsin site earlier.

[Great Snow 1717]

On 12/18/2020 at 3:24 PM, raindancewx said:

I use this for snowfall data. Locally it is imperfect and has some small data issues, but it's 99% right.

https://xmacis.rcc-acis.org/

 

Thank you

[raindancewx]

This is what I have for correlations for all the major indexes for January. You can see for New Mexico, it's at least possible all five will be favorable at the same time for cold in January. I don't expect all five to be favorable the whole month though, but it seems like they'll align at times. Blues and purples are negative correlations, greens and yellows are positive. The SOI is probably going to warm the south pretty quickly by February - which mechanism that is by is anyone's guess.

[raindancewx]

Highs and lows are remarkably different this month: