Winter 20-21 Discussion

[Sam Kane]

There's a blizzard predicted around Christmas in the south similar to the one in 1993. The city of Montgomery is already planning on shipping in enough of snow plows for the city. This is crazy 2020!!!

[raindancewx]

I think you'll see the magnitude of warmth on the CFS shift a lot cooler in the next few days for December. Spatial arrangement may be about right.

[raindancewx]

Ignore this - image is from last year.

I don't pay for Weatherbell.  But looks like they changed their winter outlook again.

I'm colder in the West, similar in the middle of the US (I think Texas could legitimately be +5 in a lot of spots) and then warmer in the East.

[raindancewx]

Albuquerque missed each time, but pretty decent week for snow down here. Picture is Angel Fire Ski Resort. Snow pack at Taos Powderhorn (the mountain for Ski Taos) currently is third highest snowpack since 2010 for the date. Snow pack for New Mexico is not good overall, but should improve more in the next week. Northern areas are closest to normal as expected in my forecast. 

 

[Prospero]

On 11/26/2020 at 8:31 PM, Sam Kane said:

There's a blizzard predicted around Christmas in the south similar to the one in 1993. The city of Montgomery is already planning on shipping in enough of snow plows for the city. This is crazy 2020!!!

Wonder if 2020 will bring snow to Tampa Bay. I'm always eager, missing the ski areas out west.

 

[raindancewx]

Quick round up of emerging wildcards for the winter.

1) Solar Activity is rapidly increasing. My research is that some monthly precipitation and temperature patterns are far less or far more likely when solar activity sustains above 55 sunspots/month in a July-June year (i.e. the ENSO year). If we were to sustain at over 55 sunspots in 2020-21, I'd be a lot more optimistic about March precipitation/snow in the Southwest, particularly if the La Nina were to rapidly collapse toward an El Nino.

2) Fall doesn't look like any La Nina since 1950. There is no La Nina since 1950 with a cold middle, warm East/warm West look. The closest thing to a La Nina with that look is 1959, a near-La Nina with a warm NE Pacific. Other years with this look include 2018, 2019 with 2003 and 2014 also somewhat close.

3) After researching it, heavy snow is fairly likely to dump again in the Southwest at some point. This may be the part of the pattern when the NE cashes in again, as with October.

[raindancewx]

There is a pretty strong signal right now in Albuquerque precipitation data for a wet January.

I call this the "replication" method for analogs. We get so little precipitation here that if you match monthly totals July-December within 0.2 inches of observations, you can predict Jan-Jun totals pretty well. December is obviously not in yet, so the January signal will change if the month is very wet or very dry. Will update if necessary. Blue highlighted data is a wetter than average month. Top ten matches, and a simpler are blend are shown.

[raindancewx]

Canadian has a similar look to the CFS for December. Huge changes from the prior monthly outlook for December in the circled areas.

Winter overall trended warmer, but it did trend colder from the SE to NM and TX.

[raindancewx]

Ocean heat content for 100-180W at the equator came in at -1.04 - a bit lower than I had it.

Still like this blend.

Year	Sept	Oct	Nov
1999	-1.27	-1.07	-1.48
2000	-0.12	-0.37	-0.67
2007	-1.03	-1.19	-1.19
2007	-1.03	-1.19	-1.19
2011	-1.01	-1.26	-0.92
2011	-1.01	-1.26	-0.92
Blended	-0.91	-1.06	-1.06
2020	-0.87	-1.11	-1.04

 

[raindancewx]

Pretty snowy Fall overall. Generally pretty similar to my July-June snow outlook. Interior West, Midwest and New England were favored zones. I'd like to see IL/IN/MO fill in a bit more, but the dryness recently in the Dakotas is in par with the idea. Not sure when the NYC to Richmond zone will have their best shot.

[beavis1729]

^ Unfortunately, the above map is misleading...as it doesn't capture the current tenor of the season.  Most, if not all, of the snowfall in the US occurred prior to mid-Nov and has since melted...and there doesn't look to be significant snow anywhere in the next 10 days.  An awful spot to be in for winter lovers, as we head into the shortest days of the year and the holidays.  We need to build up the snowpack and cold up north, and it's not happening now.

Total snowfall is not very useful when considering whether a winter is good/bad.  Snow depth days (SDDs) are a better measure, i.e., the cumulative seasonal total of each day's snow cover (in inches), added together.

[griteater]

Snowfall Percent of Mean from 09/30 to 12/01

 

[raindancewx]

It actually snowed a lot out here in early September, so prefer July-June for snow maps. That's why I do it that way for my snow maps.

The short range models (3-km NAM and HRRR) have been trending up for mountain snow and maybe even a bit more for me tomorrow. That's the ten day lag after the last big SOI drop, so I've been watching this period for a while now. It's snowing fairly heavily at Angel Fire Resort at the moment as the snow expands. The depiction of snow has changed every six hours for like six days at this point. Not a well handled situation by the models.

I don't completely buy the model outlooks for December from the CFS and Canadian. I'd expect cold to retrograde West later in the month. Locally, we seem to be running about 15 days off 2007 - the warm week one Dec 2007 was here late November (11/16-11/22 or so). That said, some of the models do have MJO phase five now later in the month which is a cold Southwest warm East look in December. Late Dec 2007 was MJO phase five too.

 

[griteater]

Yeah I just chose 09/30 there because that was the date from the total snow map that you posted 

[raindancewx]

When I looked at all the years after a strongly +NAO November for December, I think there were only 2/23 from 1950-2019 with a warm West / cold East look. The most common outcomes were warm everywhere, warm East/cold West, and then cold South/warm North was next most common. Some weird mixed up patterns in there too.

If you look at the current CPC 6-10 and 8-14 analogs, a lot of the +NAO November years show up. Forgetting the model depictions, when I looked at Boston, Chicago, Minneapolis and Billings, temperatures looked generally +5 to +10 for 12/1-12/5. So the December 2000 and December 2010 looks for extensive and severe eastern cold are very unlikely.

Boston was mid-60s today for instance. Even in the South though, this first five day period has some warmth - Jacksonville has some 70s. So it's not super hard to see how the models came in warm for the month if this is the cold part of the month.

[raindancewx]

This is roughly how we're doing locally -

A lot more snow for the northern and western areas of town today. I had a dusting, the official site had nothing. I was at 7.5 inches with the October snow before the final inch or so came in and I couldn't measure it since I had to drive to work. But probably close to 9 inches at my place this season. Average for this part of town is around 11 inches.

[michsnowfreak]

I'm at 6.2" so far, but after a white start to December the ground is mostly bare today. The Nov 30-Dec 1 snowfall was beautiful. We now enter a quiet period in the Great Lakes but I can't imagine it stays that way for long in a la nina

[raindancewx]

CPC really isn't that optimistic on a cold look for the northern United States through mid-month, and it's already warm in those areas generally. 

They have warmth building even into the South too. My outlook didn't have the NE that warm, and even in the Southeast I wasn't super hot in December, generally +2 to +4 South, and +1 to +3 north. Will be curious to see how these do.

[DTWXRISK]

   JUST IN CASE    YOU DID NOT  NOTICE... since   the time I left ...  Oct  /Nov 2016   
we have NOT  have   BIG   widespread  northeast US snowstorms---

ya know like     RDU/ GSO     to   BOS     snowstorm   big  KU  event 

we have been  close  a few times    DEC   8-10  2017     Jan 3-5   2018   March 6-8  2018    DEC 12-13 2019  

 

[andyhb]

Curious if we see an uptick in severe weather potential later in winter given some of the parallels to years like 2007-08 (which saw significant tornado outbreaks in Jan-Feb including a historic one Feb 5-6) and 2011-12, which saw several significant events in Jan-March, including the back to back Leap Day and major 3/2 tornado events.

Seems like general consensus for a number of forecasts I’ve seen is for western troughing/eastern ridging to become more prevalent Jan-Feb, which would favor that.

We also have a significant drought across much of the SW, which is liable to yield enhanced capping due to EML advection, which is often a caveat in winter given the likelihood of strongly-forced synoptic scale waves.

[CheeselandSkies]

2 hours ago, andyhb said:

Curious if we see an uptick in severe weather potential later in winter given some of the parallels to years like 2007-08 (which saw significant tornado outbreaks in Jan-Feb including a historic one Feb 5-6) and 2011-12, which saw several significant events in Jan-March, including the back to back Leap Day and major 3/2 tornado events.

Seems like general consensus for a number of forecasts I’ve seen is for western troughing/eastern ridging to become more prevalent Jan-Feb, which would favor that.

We also have a significant drought across much of the SW, which is liable to yield enhanced capping due to EML advection, which is often a caveat in winter given the likelihood of strongly-forced synoptic scale waves.

Certainly interesting times ahead although it remains to be seen whether that translates into an active Plains/Midwest spring chase season which it did in 2008, not so much in 2012 where drought/capping dominated everything after a couple of early outbreaks.

[raindancewx]

We've now had multiple instances since October where Boston and north do well for snow despite a generally warm pattern. That was one of the ideas in my outlook for the northeast. The 'normal' line for snow should remains between NYC & Boston if I did it right. I know in 2007-08, snow totals were not that good for NYC and Philly and south, but pretty solid for New England. All that said, Boston itself hasn't had a flake of snow just yet at the official site (as of 3 pm) with the current system.

I'm sure parts of the Southwest will finish very dry for winter, but I'm still not convinced northern New Mexico, north TX, and southern Colorado will be that dry. The GFS has also been trending this feature north with subtropical origins. There were substantial SOI crashes around 12/1 which usually precedes a storm or subtropical impulse over the SW in 10 days. Some hint of a northern stream feature with some moisture in the 12/10 to 12/12 time frame too.

[raindancewx]

From 1931-32 to 2019-20 there is no year in Philadelphia over 30 inches of snow (Oct-May basis) if it doesn't snow by 12/20.

GFS currently has nothing through 12/20. The average for years with a first snow after 12/20 is 14.5 for Philadelphia.

My outlook back in October assumed La Nina would peak in November or December - that still looks right to me. Nino 4 should be the coldest zone in January, given the warming forecast in 1.2, 3, 3.4 while Nino 4 cools longer. The model has essentially a Modoki La Nina for a brief period.

A cold Nino 4 in January (say -1.0C) would be a strong wet signal for Ohio, Michigan, Kentucky and Indiana. Even though the south is strongly favored for warmth.

[DTWXRISK]

  IN MAJOR   DEVELOPMENT    the  ecmwf    enso model shwos   DRAMATIC  WEAKENING  of the Moderate  La Nina.

It is hard to understate   how  BIG  this is...or   COULD be... 

 a   rapidly  weakening   La Nina...   in essence a   WEAK  La nina combined with  SSW   EVENT

 t 

[40/70 Benchmark]

On 12/5/2020 at 9:01 PM, raindancewx said:

From 1931-32 to 2019-20 there is no year in Philadelphia over 30 inches of snow (Oct-May basis) if it doesn't snow by 12/20.

GFS currently has nothing through 12/20. The average for years with a first snow after 12/20 is 14.5 for Philadelphia.

My outlook back in October assumed La Nina would peak in November or December - that still looks right to me. Nino 4 should be the coldest zone in January, given the warming forecast in 1.2, 3, 3.4 while Nino 4 cools longer. The model has essentially a Modoki La Nina for a brief period.

A cold Nino 4 in January (say -1.0C) would be a strong wet signal for Ohio, Michigan, Kentucky and Indiana. Even though the south is strongly favored for warmth.

Makes sense to me. I had Philly in the 11-21" range this season.

[40/70 Benchmark]

20 hours ago, DTWXRISK said:

  IN MAJOR   DEVELOPMENT    the  ecmwf    enso model shwos   DRAMATIC  WEAKENING  of the Moderate  La Nina.

It is hard to understate   how  BIG  this is...or   COULD be... 

 a   rapidly  weakening   La Nina...   in essence a   WEAK  La nina combined with  SSW   EVENT

 t 

Hi Dave, glad to see you back.

The SSW still seems like mostly conjecture at a this point, and I think relying on a dramatic weakening of ENSO as the primary driver for a big second half is always risky...especially in a la nina, which usually do not have big endings in the east.

[raindancewx]

I'm a bit surprised there hasn't been more snow in the red circled area. That's my guess for the next area to fill in a lot.

[raindancewx]

The 12-km NAM, Euro, GFS and Canadian now have a pretty big precipitation event out here 12/10-12/12, in the correct time frame after the big SOI crash around 12/1.

3 Dec 2020	1013.45	1007.55	11.31	8.63	7.78
2 Dec 2020	1014.81	1008.05	15.78	8.74	7.73
1 Dec 2020	1014.91	1007.10	21.23	8.99	7.70
30 Nov 2020	1013.51	1006.20	28.18	9.24	7.69

This map from WPC looks pretty good to me. I'd go 0.20-0.60" for most of New Mexico, higher mountains and SW, lower SE (nothing to 0.20"). Arizona could easily get a winter of precipitation in the SE part of the state.

This is what the Euro has for days 2-4 (Thursday-Saturday). For a lot of places in the SE AZ / SW NM zone, these totals would be a winter of precipitation if they verified.

The 12-km NAM is a lot more optimistic, but I don't really buy these totals, yet.

[raindancewx]

https://www.weatherbell.com/final-winter-2020-21-forecast

Weatherbell updated their winter outlook. This image from above was right, they just labelled it wrong.

Weatherbell analog blend changed the from winters starting in 1973, 1988, 2010 (x2), to winters starting in 

1973
1974
1975
1995 (x2)
1998 (x2)
1999
2005
2007 (x2)
2010
2017

It's a warmer look. But would support a cold West / hot Southeast in Jan-Feb.

[DTWXRISK]

miller  b  event    seems  likely  DEC 16  for northern Mid Atlantic and  New England