GaWx

1 hour ago, snowman19 said:

Day 14 on the operational 18z GFS 

 But the idea of a big Arctic plunge 12/12-17 deep down into the US (possibly from two highs per GFS) is becoming increasingly likely based on model guidance. This is very believable considering it would be during an EPS progged longest phase 8 in 50 years along with the highest % Dec 5th snowcover in the Midwest since at least 2002.

 This is also setting the table for a potential quite cold Dec/Jan considering the -PNA Dec -ENSO analogs suggesting a +PNA Jan, which would make it likely that DJF would end up colder than normal for much of the E US even if we get the favored mild Feb.

 The Euro Weeklies would have to bust badly to allow for a +PNA, but it’s been too strong with the SER since just before Thanksgiving.

18Z GFS:

2m anomalies for 0Z on 12/14:

Highest US snow-cover as of Dec 5th 2003-25 (%)(2003-24 avg 27%):

‘05 48 

‘25 45 

‘18 43

‘10 39

‘13 38

‘19 37

‘06 33

‘16 32

But more importantly for E US cold prospects is the Midwest snowcover: highest % as of Dec 5th (2003-24 avg 12%):

‘25 65

‘05 45

‘18 32

‘06 31

‘10 27

‘16 25

‘03 23

‘08 20

https://www.nohrsc.noaa.gov/nsa/index.html?region=Midwest&year=2025&month=12&day=5&units=e

4 hours ago, PhiEaglesfan712 said:

December 2016 and December 2022 seem like the best matches. We have a lot of the elements of those seasons this year: -ENSO, deep -IOD, la nina background, and strong Pacific jet. Plus, a cooler December. If we don't get the snowstorm, then I really like the 2016-17 and 2022-23 analogs even more (sorry Team Snow).

The only places I think that will do well in the East are places like upper New York (Buffalo to Albany), Vermont, and northern New Hampshire/Maine. Places near the coast are going to have a tough time getting snow.

US snowcover as of Dec 5th is way higher now than it was in ‘16 and even moreso vs ‘22.

10 hours ago, GaWx said:

 All 0Z ensembles are much colder in the E US 12/13-17 vs earlier runs.

Followup: this is only 8 days out

12Z GFS

 All 0Z ensembles are much colder in the E US 12/13-17 vs earlier runs.

New weeks 3-4 outlook makes sense since it’s similar to the Euro Weeklies. But hopefully they will end up too warm:

Chicago per model consensus is on track for a top tier cold Dec 1-20. Here are the 15 coldest Dec 1-20 at Chicago of the last 75 years (top 20 %) in reverse chronological order:

2016, 13, 10, 08, 05, 00, 89, 85, 83, 76, 72, 63, 58, 56, 50

 2025 appears at this time like it might compete with many of these.

At 1PM, there was a whopping 26F diff. between Valdosta’s 76 and Tifton’s 50. Tifton is a mere 45 miles N of Valdosta!

The yucky rainy pattern continues here. Luckily during a short break in the light rains yesterday evening, I squeezed in a walk.

Today so far has been different. The rains at times have been heavy, with my measurements suggesting ~0.75”. There’s been enough to be wary of hydroplaning if going too fast. This is the heaviest I’ve seen in several months. Thus, it’s the first minor test of my completed yard drainage projects as well as the city’s redug nearby street drainage ditch project. But it’s still not yet a complete tear as I need even heavier rains. Regardless, there will be more on and off rains through Sunday.

My temps have been mainly in the mid to upper 50s after dipping to the rain cooled upper 40s last night. Temps are 12 warmer in Brunswick 75 miles to the S.

4 hours ago, PhiEaglesfan712 said:

1984-85 and 2021-22 aren't good analogs because they had torch Decembers. In fact, both winters only had one really cold and snowy month (January). I'd go as far to say that 84-85 is the colder climate version of 21-22.

 9 of the last 11 of the Jans following -PNAs in Dec for -ENSO were either cold or pretty close to normal. You’ve been harping on the only two warm Jans of the 11. Feb will more than likely be mild. It’s not necessarily Jan and Feb being similar as you’ve been thinking. This indicator suggests that’s unlikely as of now.

15 minutes ago, donsutherland1 said:

Four of the first five days of December have seen the PNA come in with daily values < 0. The baseline idea of a predominantly negative PNA for December appears on course, especially if the latest guidance winds up being reasonably accurate.

Latest GEFS PNA forecast:

However, the WPO is forecast to be strongly negative. As a result, the WPO should overwhelm the PNA- and allow generally colder than normal conditions to persist in much of the eastern half of North America during the December 10-20 period. Some milder days are plausible, but the period will likely feature below normal temperatures overall. The Southeast has the highest probability of seeing a break in the cold due to the PNA- connection to SE ridging.

The most recent ECMWF weekly forecasts:

December 8-15:

December 15-22:

I’ll be rooting for a strong -PNA this month. Why?

For -ENSO: Strongest -PNA Decs since 1983-4: 

-2021-2: -2.56; Jan was +1.01/cold

-2010-11: -1.78; Jan was +1.29/cold

-1984-5: -1.60; Jan was +1.63/cold

-2008-9: -1.41; Jan was +0.61/cold

 ———

The Euro Weeklies continue with a pretty strong SER/-PNA in the first half of Jan. But it’s recently been correcting to a weaker one in late Nov/early Dec.

11 minutes ago, BlizzardWx said:

Really makes you wonder if the extended range guidance is going to be doing some hard corrections in the next week or two. Clearly at least somewhat at odds with what the MJO would say for that time of year. 

Agreed. But also keep in mind that the 15 days on that model (0Z EPS) preceding the map you showed are very cold in the NE 1/4 of the US and suggest one of the coldest 1st 19 days of Dec anomalies on record in the NE 1/4 of the US:

Days 1-10:

Days 11-15:

Today’s 2 week ensemble MJO forecasts:

-12/5 EPS steady as a rock with a 17+ day long phase 8, second (back to 1974-5) only to the 18 days of 1975-6: a cold E US weenie couldn’t place it any better though keep in mind that the MJO, itself, is only one index of many despite it having notable tendencies:

12/5 GEFS: though not steady like EPS with only a 5 day phase 8 followed by 3 days of weak phase 1 (which also is often cold in Dec) followed by 5 more days in phase 8 and then 4 days barely in phase 7, this is on the whole still favoring dominating cold in the E US:

 Related to the very cold Dec forecasts, natural gas is up a whopping 6% today, alone! Knowledgeable NG investors don’t normally go long NG in winter unless the forecast is for a cold E US.

1 hour ago, PhiEaglesfan712 said:

It's called regression to mean. Especially in a warming climate, it's hard to string together several below average temperature months in a row. Do not be surprised if there is a torch in January and February. That's been a staple of -ENSO/deep -IOD years in recent times (see 2016-17 and 2022-23).

 I still feel that Jan and Feb should be analyzed separately for the NE US. Since 1983-4 as regards -PNA Decs:

-3 times as many -ENSO -PNA Decembers were followed by cold Jans as mild Jans including the recent Jan of 2022. In addition, there were cold Jans in 2014, 2011, 2009, 1985, and 1984. Related to this, 9 of 11 of these Jans were either cold or pretty close to normal.

-But OTOH there were 6 times as many mild Febs vs the only cold Feb (2014) of these analogs in the NE.

3 minutes ago, EastonSN+ said:

1989/1990 season is a good example.

Record cold December followed be record warm January and February (snowy March).

Today some sites are breaking 1989 records.

 I don’t feel 1989-90 is an -ENSO analog to 2025-6. That’s because:

-Dec was slightly +ENSO per RONI (+0.09) and only a hair -ENSO per ONI (-0.01).

-Jan was already a solid +ENSO per RONI (+0.39) and slightly +ENSO per ONI (+0.11).

-Feb was +0.31 to +0.34.

4 hours ago, snowman19 said:

Yes, that SOI correlation only works during El Niños, not during La Niña’s. Unfortunately JB spread false info about it years ago and many people (apparently even some mets) believed him

Back to 1995-6, lowest SOI plunges -ENSO/lagged NYC wx

-52 on 2/17/17: MB 3/10-18 and 9.7”

-49 on 12/10/12: B 12/26-1/3 and 0.4”

-47 on 12/19/95: MB 1/2-12 and 25”

-47 on 2/2/13: B 2/7-10 and 11.4”

-44 on 12/4/25 (due to strong compact Tahitian low) ??? 


-39 on 12/14/01: 12/30-1/2 MB/0”

-34 on 1/19/17: 2/9-10 B/9.4”

-31 on 11/7/22: 11/14-21 MB/0”

 The above tells me that IF there’s possibly any partial correlation of a strong -SOI during -ENSO to cold and/or snow at NYC, it’s not until 1-4 weeks afterward. A period of very heavy snow and/or MB temps occurred 1-4 weeks after 6 of the 7 sub -30 cases. This could easily just be random considering the small sample size and that this is pretty spread out (1-4 weeks afterward).

 It’s been a semi-raw cloudy day here today with only low 50s most of afternoon and with occasional very light rain. Steadier not as light rain is about to start, which is just the beginning of Mon and off rainy period through Sunday. This should evap cool temps down into the high 40s soon. It’s going to be hard to get walks at the park in but I’ll try my best during any breaks.

 Just like yesterday, the GEFS and EPS disagree on how long the MJO will stay in phase 8:

GEFS: only 6 days though it returns for rd 2 on 12/18:

But the EPS, which recently has been much steadier and has been verifying better than GEFS since phase 7, once again is going with a very long phase 8 (16+ days, longest in 50 years): you can’t place an MJO better than this in Dec for E US cold lovers (and it looks to be cold the next 10 days per models though one must remember that there are always other factors to consider due to the complexity of the atmosphere):

2 hours ago, PhiEaglesfan712 said:

After that, do you think the winter returns, or are we going to torch in January and February, like in 2016-17 and 2022-23?

 Or will Jan be cold like in 1984, 1985, 2009, 2011, 2014, and 2022?

Or will Jan be within a few degrees of normal (in the NE at least) like 1997, 1999, and 2013?

 So, Jan has had 3 times as many cold vs warm for the analogs since 1983-4 that I’m looking at.

 OTOH, Feb has a better chance to torch in the NE imho as only 2014 of the analogs I’m looking at was solidly cold there vs 6 being cold in Jan. In Feb, these were mild: 1984, 1997, 1999, 2009, 2017, and 2023.

 So, in Feb, 6 times as many were mild vs cold. That compares to 3 times as many cold vs mild in Jan. Two very different months on average.

 I just took an invigorating walk at the park with middle to low 40s, dewpoints in the high 30s, and no more than a light breeze. This is close to ideal walking wx for me…well except for having the extremely rare snow on the ground to walk on. Nothing beats the soothing feeling of walking on snow!

2 hours ago, donsutherland1 said:

There's an ERA-5 dataset that goes back to 1940. 

https://www.psl.noaa.gov/mjo/mjoindex/omi.era5.1x.webpage.4023.txt

 Thanks, Don.
 

 Just to make sure there’s no confusion of the viewers, these ERA-5 values do not match the BoM RMM values. So, they aren’t substitutes for each other as they’re not the same way of tracking the MJO. Examples:

- The end of the ERA-5 is on 8/31/2023. Here are the values on 8/25-31/2023 from both the ERA-5 and the BoM RMM:

8/25: ERA-5 is in ph 7 at 1.1 amp

8/25: BoM is in ph 8 at 0.84 amp

8/26: ERA-5 is in ph 7 at 1.06 amp

8/26: BoM is in ph 8 at 0.85 amp

8/27: ERA-5 is in ph 7 at 0.97 amp

8/27: BoM is in ph 1 at 0.64 amp

8/28: ERA-5 is in ph 7 at 0.83 amp

8/28: BoM is in ph 2 at 0.46 amp

8/29: ERA-5 is in ph 7 at 0.66 amp

8/29: BoM is in ph 2 at 0.27 amp

8/30: ERA-5 is in ph 7 at 0.46 amp

8/30: BoM is in ph 3 at 0.28 amp

8/31: ERA-5 is in ph 7 at 0.24 amp

8/31: BoM is in ph 3 at 0.26 amp

ERA-5 MJO 1/2/1940-8/31/2023

https://www.psl.noaa.gov/mjo/mjoindex/omi.era5.1x.webpage.4023.txt
 

BoM RMM MJO 6/1/1974-present

https://www.bom.gov.au/clim_data/IDCKGEM000/rmm.74toRealtime.txt

 I’m assuming this Euro Weeklies H5 has a good chance to verify way off in the E US considering the projected MJO as well as PNA analogs that suggest a +PNA would be likely in Jan and also that the Euro has been correcting for a too strong SER recently:

IF these were to be close to reality, they’d open the door for frigid air to plunge into the US ~12/18-21: MJO phase 8 would be supportive in Dec

12Z EPS: frigid MT/W ND N into SW Canada

12Z EPS: cross polar flow

 

12Z GEFS: frigid N MT/N Plains/MN northwestward into SW Canada:

12Z GEFS: cross polar flow

The 12Z EPS is hinting at a 3rd NC snow threat on 12/12 with measurable snow from 7 of the 50 members, mainly from lows that move just offshore: