Claim vs evidence
Polar vortex, early November 2026: what is forecast and what would count
As of 30 October 2026, forecasts show the polar vortex above the Arctic weakening in early November, but not clearly reversing. Most forecasts do not show its winds fully reversing, and the official outlooks for 4-12 November favor above-normal temperatures across most of the United States, not a freeze. A confirmed 'sudden stratospheric warming' needs the winds to reverse, and any effect at the surface would take weeks. The tests below were fixed on 30 October, before the outcome.
What is known, forecast and unknown
- Observed (analysis, approximate): 10 hPa 60N zonal-mean wind about +23 m/s on 27 Oct, about +15 to +17 m/s on 29-30 Oct (source: CPC chart).
- Model forecast (GFS/GEFS, issued 2026-10-30): ensemble members fall toward about 0 to +5 m/s around 10-13 Nov; a few slightly negative [f2].
- Human forecast (CPC, issued 2026-10-29 3 pm EDT, confidence 'about average, 3 out of 5' for 6-10 days): above-normal temperatures favored for most of the contiguous US 4-12 Nov [f3].
- Whether the wind reverses (no ECMWF forecast obtained; model counts quoted by news differ).
- Whether any cold outbreak follows, and when: effects usually take weeks and vary from event to event.
What is the polar vortex?
The stratospheric polar vortex is a ring of strong west-to-east winds around the Arctic, roughly 10 to 50 km up. It normally strengthens through autumn. Forecasters follow it with the zonal-mean wind at 10 hPa and 60 degrees North [c1].
What is forecast (as issued on 30 October 2026)
The analysed wind rose to about +23 m/s around 27 October and fell to roughly +15 to +17 m/s on 29-30 October (read from a chart, approximate) [f1]. Forecast ensemble members fall toward about 0 to +5 m/s around 10-13 November; a few members dip slightly below zero [f2]. NOAA's Climate Prediction Center (29 October) favors above-normal temperatures for most of the contiguous United States on 4-12 November, with probabilities above 70 percent from the Mid-Atlantic to the Great Lakes for 4-8 November, and lists West Coast rain, snow and wind risks but no cold hazard [f3].
What would count as a sudden stratospheric warming
By the usual convention a major event requires the wind at 10 hPa and 60 N to turn easterly (below 0 m/s) [c2]. Such events occur about six times per decade in midwinter [c3]. A November event is rare; published counts differ [c4]. A weakening is not a major event.
What it may mean for weather
After weak-vortex events the surface often shows an Arctic Oscillation-like pattern over the following weeks, but not every time [c5]. The 2021 Texas freeze followed a January warming event; researchers disagree about whether one caused the other [c6].
What a popular video said
A video explainer from 26 October was careful that a freeze was not confirmed [c7], said the first week of November was not forecast to be freezing [c8], and said the European model flips the winds while the American model stops short [c9]. The table below rates each statement.
Claims and ratings
Each statement is rated against the named source on the date it was read. The rating describes the statement, not the person who made it. “Forecast as issued (not rated)” means the source is shown, with no verdict.
- f1Verdict: observation (approximate reading)
Analysed 10 hPa 60N wind about +23 m/s (27 Oct), about +15 to +17 m/s (29-30 Oct)
- Said by
- NOAA CPC chart (GFS analysis)
- What the source says
- red analysis line on the chart, 'updated through DOY 303'; values read by eye, approximate
- Source
- CPC GFS 10 hPa 60N wind chart
Source date: 2026-10-30 · Retrieved: 2026-10-30 - How it was read
- chart opened
- f2Verdict: forecast as issued (not rated)
Forecast members fall toward about 0 to +5 m/s around 10-13 Nov, a few slightly negative
- Said by
- NOAA CPC charts (GFS and GEFS members)
- What the source says
- green member lines on the charts; no ensemble mean is plotted; approximate reading
- Source
- CPC GFS and GEFS 10 hPa 60N charts
Source date: 2026-10-30 · Retrieved: 2026-10-30 - How it was read
- charts opened
- f3Verdict: forecast as issued (not rated)
CPC outlook 4-12 Nov: above-normal temperatures favored for most of the contiguous US; no cold hazard listed
- Said by
- NOAA CPC (human forecasters)
- What the source says
- 6-10 day (4-8 Nov): above 70 percent from the Mid-Atlantic to the Great Lakes; 8-14 day (6-12 Nov): above normal across most of the CONUS; hazards outlook lists West Coast rain, snow and wind
- Source
- CPC 6-10 and 8-14 day prognostic discussion; US Hazards Outlook
Source date: 2026-10-29 · Retrieved: 2026-10-30 - How it was read
- discussion text and hazards synopsis opened
- c1Verdict: confirmed
The polar vortex is the stratospheric west-to-east wind ring, tracked at 10 hPa and 60N
- Said by
- general definition used in the video and by CPC
- What the source says
- CPC SSW monitoring page tracks zonal wind at 10 hPa, 60N
- Source
- CPC Stratosphere: SSW monitoring
Source date: page current 2026-10-30 · Retrieved: 2026-10-30 - How it was read
- page structure and chart titles opened
- c2Verdict: confirmed
A major SSW needs the 10 hPa, 60N zonal-mean wind to reverse to easterly
- Said by
- video explainer (26 Oct) and general convention
- What the source says
- WMO convention as used by Charlton and Polvani 2007 (J. Climate, DOI 10.1175/JCLI3996.1): easterly winds at 10 hPa and 60N, November-March window
- Source
- Charlton and Polvani 2007
Source date: 2007 · Retrieved: 2026-10-30 - How it was read
- abstract and excerpts only (via search); publisher page blocked by a bot check (HTTP 403) when opened on 2026-10-30, so not opened
- c3Verdict: confirmed
Major events occur about six times every 10 years
- Said by
- video explainer
- What the source says
- Charlton and Polvani: about six major midwinter events per decade (NDJFM)
- Source
- Charlton and Polvani 2007
Source date: 2007 · Retrieved: 2026-10-30 - How it was read
- abstract only; publisher page blocked (HTTP 403) on 2026-10-30, not opened
- c4Verdict: unable to verify
Only one major November event since 1958 (1968 and 2000 also mentioned)
- Said by
- video explainer
- What the source says
- news coverage of the November 2025 event gives conflicting counts (1968 and 1958; 1968 and 2000; three minor events in 70 years)
- Source
- news coverage, November 2025 (not a primary count)
Source date: 2025-11 · Retrieved: 2026-10-30 - How it was read
- search summary only; page blocked by a bot check (HTTP 403) on 2026-10-30, not opened
- c5Verdict: confirmed
After a weak-vortex event, cold can follow weeks later
- Said by
- video explainer
- What the source says
- Baldwin and Dunkerton 2001 (Science, DOI 10.1126/science.1063315): weak-vortex anomalies precede Arctic Oscillation-like surface patterns for about 60 days (a tendency, not every event)
- Source
- Baldwin and Dunkerton 2001
Source date: 2001 · Retrieved: 2026-10-30 - How it was read
- abstract only (via search); publisher page blocked (HTTP 403) on 2026-10-30, not opened
- c6Verdict: partly supported (contested)
Texas 2021: warming event and deep freeze may be linked
- Said by
- video explainer (cites an NCAR study that it was probably not the cause)
- What the source says
- Cohen et al. 2021 (Science, DOI 10.1126/science.abi9167) link the stretched vortex to the cold wave; Davis et al. 2022 (Nature Communications, DOI 10.1038/s41467-022-28836-1) find limited surface impact of the January 2021 warming; a 2023 response (DOI 10.1038/s41467-023-38772-3; a search result lists Cohen and colleagues as authors, not verified) disputes the methods
- Source
- Davis et al. 2022; Cohen et al. 2021
Source date: 2022 · Retrieved: 2026-10-30 - How it was read
- Davis et al. page opened on 2026-10-30 (title confirmed, HTTP 200), abstract via search; Cohen et al. page blocked (HTTP 403), abstract via search; the 2023 response page opened (title confirmed), authorship taken from a search result
- c7Verdict: confirmed
As of 26 October this is not a confirmed sudden stratospheric warming
- Said by
- video explainer
- What the source says
- CPC chart 30 Oct: analysed wind about +15 to +17 m/s, above 0; no reversal
- Source
- CPC GFS 10 hPa 60N wind chart
Source date: 2026-10-30 · Retrieved: 2026-10-30 - How it was read
- chart opened and read (approximate values)
- c8Verdict: confirmed (newer issue)
The government outlook shows no widespread freeze for the first week of November
- Said by
- video explainer, citing the 22 Oct outlook
- What the source says
- CPC 29 Oct discussion: above-normal temperatures favored for most of the contiguous US 4-12 Nov; no cold hazard in the hazards outlook text (the 22 Oct issue itself was not opened)
- Source
- CPC 6-10 and 8-14 day prognostic discussion; US Hazards Outlook
Source date: 2026-10-29 · Retrieved: 2026-10-30 - How it was read
- discussion text and hazards synopsis opened
- c9Verdict: partly supported (ECMWF side unable to verify)
European model flips the winds; American model stops short
- Said by
- video explainer
- What the source says
- GFS and GEFS ensembles on the CPC chart show members near 0 to +5 m/s about 10-13 Nov, a few slightly negative; no ECMWF forecast was obtained
- Source
- CPC GFS and GEFS 10 hPa 60N charts
Source date: 2026-10-30 · Retrieved: 2026-10-30 - How it was read
- both charts opened; ECMWF not opened
How to check
Tests fixed on: 2026-10-30 (before any outcome data)
- A (weakening): 10 hPa 60N zonal-mean zonal wind at or below +5 m/s on at least one day from 1 to 15 Nov 2026.
- B (major SSW, WMO type): the same wind below 0 m/s on at least one day from 1 to 30 Nov 2026.
- C (sustained reversal): below 0 m/s for at least 5 consecutive days, the first before 15 Nov 2026.
- D (surface response, evaluated only if B passes): daily or weekly mean Arctic Oscillation index negative on at least 7 of 14 days in a window starting 8 Nov to 8 Dec, and the NCEI CONUS monthly temperature anomaly for December 2026 below the 1991-2020 normal; each part reported separately.
| Series | Delay | Access tested |
|---|---|---|
| 10 hPa 60N zonal-mean wind (GFS analysis, daily chart) | same day | Yes |
| Arctic Oscillation index (CPC) | daily/monthly | page opened; daily file name not verified |
| NCEI CONUS monthly temperature anomaly (link: Not verified) | monthly + about 8 days | No |
Outcome
Checks on 5 and 15 November 2026. The tests below were fixed before the outcome. A cell that says “Not yet checked” means no check has been made yet; nothing has been filled in ahead of time.
| Test | Result 5 Nov 2026 | Result 15 Nov 2026 |
|---|---|---|
| A (weakening): 10 hPa 60N zonal-mean zonal wind at or below +5 m/s on at least one day from 1 to 15 Nov 2026. | Not yet checked | Not yet checked |
| B (major SSW, WMO type): the same wind below 0 m/s on at least one day from 1 to 30 Nov 2026. | Not yet checked | Not yet checked |
| C (sustained reversal): below 0 m/s for at least 5 consecutive days, the first before 15 Nov 2026. | Not yet checked | Not yet checked |
| D (surface response, evaluated only if B passes): daily or weekly mean Arctic Oscillation index negative on at least 7 of 14 days in a window starting 8 Nov to 8 Dec, and the NCEI CONUS monthly temperature anomaly for December 2026 below the 1991-2020 normal; each part reported separately. | Not yet checked | Not yet checked |
Data
| Date | Type | Value (m/s) |
|---|---|---|
| 2026-10-27 | analysis | 23 |
| 2026-10-29 | analysis | 16 |
| 2026-10-30 | analysis | 16 |
| 2026-11-10 to 2026-11-13 | forecast members (range) | about 0 to +5; a few about -3 |
Caveats
- The wind values are approximate; the underlying numbers were not available.
- No ECMWF forecast was obtained.
- Literature is cited from abstracts and excerpts, not full texts.
- Nothing here is a weather forecast for a place; see weather.gov.
- This card describes statements, not the people who made them.
References
- Charlton, A. J., and Polvani, L. M. (2007). A new look at stratospheric sudden warmings. Part I. J. Climate. DOI 10.1175/JCLI3996.1 (excerpts)
- Baldwin, M. P., and Dunkerton, T. J. (2001). Stratospheric harbingers of anomalous weather regimes. Science 294, 581-584. DOI 10.1126/science.1063315 (abstract)
- Cohen, J., et al. (2021). Linking Arctic variability and change with extreme winter weather in the United States. Science 373, 1116-1121. DOI 10.1126/science.abi9167 (abstract)
- Davis, N. A., et al. (2022). Limited surface impacts of the January 2021 sudden stratospheric warming. Nature Communications. DOI 10.1038/s41467-022-28836-1 (abstract)
- NOAA Climate Prediction Center, retrieved 2026-10-30 (WeatherWatch keeps saved copies of these pages and charts as they were that day; the public pages are updated daily): 6-10 and 8-14 day discussion https://www.cpc.ncep.noaa.gov/products/predictions/610day/fxus06.html ; US Hazards Outlook https://www.cpc.ncep.noaa.gov/products/predictions/threats/threats.php ; GFS 10 hPa 60N wind chart https://www.cpc.ncep.noaa.gov/products/stratosphere/SSW/gif_files/U_10mb_60N_2026-2027.png ; GEFS chart https://www.cpc.ncep.noaa.gov/products/stratosphere/SSW/gif_files/GEFS_U_10mb_60N_2026-2027.png