GaWx

What’s your Dec MJO prediction? What’s your Jan PNA prediction? I expect a +PNA due to all -ENSO PNA Decs since 83 transitioning to Jan +PNAs.

11/30 MJO 2 week runs 11/30 EPS: steady as can be (4th day in a row very similar) phase 8 12/3-14+, which would be the longest phase 8 in 50 years for any winter month! To show how consistent it has been, the EPS had this on 11/27 run, phase 8 12/3-11+: ————— GEFS 11/30 (not as consistent as EPS, which has been doing better with phase 7 than GEFS): also has phase 8 start Dec 3rd: JMA 11/30: phase 8 12/3-10+

Euro Weeklies 46 day 2m temp anomalies: 11/25 run: NYC and Chicago -3F 11/29 run: NYC -6F, Chicago -8F (would be coldest in many years for that period) Euro seasonal winter fcast issued Nov 1st: huge warm bust potential increasing, which could end up like last winter or even worse:

Although only barely, it’s now confirmed that we on 11/28/2025 just had the earliest major SSW (reversal) since 11/27/1968 with the zonal wind a whopping 30 m/s BN despite it only barely reversing: Kudos to the Euro Weeklies mean of 100 members predicting the weakest point of the SPV to the day a month before it occurred: This reminds me of the models being initially oblivious to the upcoming -NAO/-AO that appeared after the 2/16/2023 major SSW: EPS 11/25 12Z run: all +NAO EPS 11/30 0Z run: almost all -NAO including as early as Dec 4th, when 11/25 run had +NAO Similar comparisons for AO: EPS 11/25 12Z run: EPS 11/30 0Z run: like night and day

MJO from today’s 2 week runs: both now have 11+ day long phase 8s, longest since Feb 2010 and longest Dec since 1975. Lots of potential in 1st half of Dec and beyond! GEFS is all in 8 12/3-13 vs yesterday’s 7 for same period: EPS is same as yesterday:

Back down to neutral NAO/AO week 2 similar to 2 days ago:

1. EW 12/15-21: large change in just 3 days: will it hold? 11/25 run: 11/28 run: —————— 2. EW 12/8-14: huge change in just 3 days: will it hold? 11/25 run: 11/28 run: ————— 3. EW 12/1-7: huge change in just 3 days 11/25 run: 11/28 run: —————- -NYC has cooled from +1F to -4F for the 3 week period in just 3 days. -They now have NYC at -3F for Dec as a whole, which is ~36-37F. Similar cold ENSO Decs were in 1954, 1964, 1966, 1975, 1981, 1988, and 2007.

12Z EPS held into the cold partially because of this:

For Dec 1-10: 12Z EPS held onto its 0Z significantly colder temps vs 0Z GEFS. But also, 12Z GEFS came in significantly colder than 0Z GEFS: 0Z GEFS: 12Z GEFS: colder/in EPS direction: 12Z GEPS came in much colder than 0Z GEPS: 0Z GEPS: 12Z GEPS: colder than 0Z GEPS Edit: NG is up 7% on the colder model consensus.

12Z GEFS is coming in significantly colder than the 0Z for week 2:

Indeed, after doing poorly with phase 6, the EPS absolutely was doing much better than GEFS getting into phase 7 between the 11/15 and 11/18 runs: 11/15 EPS: poor for 6; much better for getting into 7 11/15 GEFS: great for 6 but bad for getting into 7 (way too slow as 7 actually started on 11/27): Similar comparisons for 11/17-8 runs: 11/17 EPS: almost spot on with 11/27 ph 7 timing: 11/17 GEFS: still not in 7 on 12/1 11/18 EPS: great with ph 7 11/18 GEFS: not into phase 7 til 12/2, 5 days too late Edit: 12Z GEFS coming in significantly colder than prior runs

Related to this, check out the differences in the means (green) between the +AO of the 0Z GEFS and the slight -AO of the EPS: GEFS: EPS:

With the unfavorable changes in the MJO and AO/NAO, today’s 0Z GEFS is not surprisingly significantly warmer than yesterday’s run for the 2nd week in Dec. However, today’s 0Z EPS, which maintained its very long phase 8, is much colder than yesterday as well as the GEFS: Yesterday’s 0Z EPS for 12/5-11 2m temps: Today’s 0Z EPS for 12/5-11: it’s pretty rare for a 7 day period of the EPS to have that much of a change within just 24 hours: As a result, the aggregate of today’s Euro Weeklies 12/1-7 and 12/8-14 2m temp anomaly maps will very likely be notably colder than yesterday’s.

MJO: Yesterday’s EPS: Edit: Adding yesterday’s ext-EPS: record shattering 26 day phase 8 Dec 3-28 (current record 18 days)! Today’s EPS excellent consistency with yesterday with a very long (10+ day) long phase 8: Yesterday’s GEFS: Today’s GEFS hopefully this is off as it went from yesterday’s similar to Euro very long phase 8 to no phase 8 through at least Dec 12th: In summary, mixed results today: fantastic EPS and not so good GEFS. Hoping with the aid of the current major SSW that the EPS will end up the winner for today’s runs!

It may be Twitter bait. But that’s not because they don’t go out far enough. Rather, it’s that that this Tweet’s runs are “bias corrected” versions, which have more often than not not been making the correct adjustments based on my following them. Here are the corresponding non-bc versions, which are very bullish for phase 8 within their runs: 11/26 ext GEFS: 8 day long phase 8 mid Dec (12/13-20) with a potential 2nd move into phase 8 a few days after this ends: 11/26 ext EPS: extremely bullish 15 day long phase 8 (12/13-27), which would be 2nd longest of all time on record for any month: