Stratosphere · teleconnections · weeks 1 to 4 for Canada

Polar vortex and teleconnections

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How to use this page · tap any ? for a full explanation
  • The coloured label says how the polar vortex, the big ring of winter winds about 30 km above the Arctic, is doing right now and whether the models show it breaking down.
  • The map shows that vortex from above the North Pole. Drag the slider (or press ▶) to see the forecast up to 16 days ahead. The panel beside it shows what the same forecast means for temperatures across Canada that day.
  • Warming watch tracks the one number that defines a "sudden stratospheric warming": the west-to-east wind at 60°N. If it turns negative, the vortex has collapsed. The grey bands are what is normal for the date.
  • Teleconnections are the big see-saw patterns (AO, NAO, PNA, MJO) that steer the jet stream. Each one has a plain note on what it usually means for each part of Canada, measured at our own airports.
  • What it means for you sums it up by region for the next 1 to 4 weeks, with honest notes on how much to trust it.

New here? Start with what the polar vortex is, then what a sudden warming does. Words are explained in the glossary at the bottom.

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Maps and forecast numbers are computed by MeteoFrontier from NOAA GFS and GEFS open data; season-to-date values and their 1979–2026 percentiles are from NASA GMAO (MERRA-2 / GEOS FP); index values are from NOAA CPC and NOAA PSL. Details under Sources and methods. This page is not an official forecast.

The vortex from above, and what it means for Canada

Stratospheric polar vortex

Northern Hemisphere seen from above the pole. Shading: wind speed. Lines: height of the pressure level.

Polar-stereographic map of the stratospheric polar vortex

Temperature across Canada that day

Forecast daily temperature compared with the 1991–2020 normal for the date.

Map of Canada coloured by forecast temperature anomaly

Sudden stratospheric warming watch

Wind around the vortex: zonal-mean wind at 60°N, 10 hPa

Below the zero line the wind blows from the east: by the standard definition (Charlton and Polvani 2007) that is a major sudden stratospheric warming when it happens between November and March. The thin lines are the 31 GEFS ensemble members, the bold line is the GFS run; the analysed line up to today is NASA's MERRA-2 / GEOS FP.

Polar-cap temperature, 60–90°N, 10 hPa

Shape of the vortex: displaced or split?

Forecast vortex-centre latitude and aspect ratio (10 hPa moments, GFS) and the share of GEFS members that meet the displacement or split thresholds.

Waves pushing up from below: eddy heat flux at 100 hPa, 45–75°N

Large positive values mean strong planetary waves are travelling up into the stratosphere. A burst lasting a week or more often comes before a weakening of the vortex (Polvani and Waugh 2004).

Teleconnections: the jet-stream see-saws

Season used for the "what it means for Canada" tables.

Quasi-biennial oscillation (QBO)

When the tropical stratospheric wind at 30–50 hPa blows from the east, the winter polar vortex tends to be weaker and more disturbed (Holton and Tan 1980). The link is a tilt in the odds, not a rule.

ENSO link

Sudden warmings happen in both El Niño and La Niña winters, more often than in neutral winters in the observed record (Butler and Polvani 2011). ENSO also shapes the PNA, which is one reason El Niño winters are often mild in western Canada. Full details on the El Niño / La Niña tracker.

Madden–Julian Oscillation (MJO)

Phase diagram, last 40 days

What each phase has meant for Canada 10–20 days later (Nov–Mar)

Mean daily temperature anomaly at our airports, by region. Only days when the MJO was active (amplitude ≥ 1).

What it means for you: the next 1 to 4 weeks

How much to trust this. Weeks 1 and 2 come straight from the GFS forecast and are reasonably skilful for week 1, less so for week 2. Weeks 3 and 4 are a lean, not a forecast: they combine the signals that are active now with what those signals have meant at our airports in the past. Those patterns explain only a modest share of the day-to-day ups and downs, and about one sudden warming in three never reaches the ground (Karpechko et al. 2017; Domeisen et al. 2020). For official long-range outlooks see ECCC's monthly and seasonal forecasts.

History: major sudden warmings since 1979

Canada evidence: what each pattern has meant here

Composite temperature anomalies

Shading: 850 hPa temperature anomaly in NCEP/NCAR Reanalysis 1. Dots: daily mean temperature anomaly at our airports (NOAA ISD + METAR archive), each airport's own trend removed.

Maps of Canada showing composite temperature anomalies for the chosen pattern

By region (winter)

Sources and methods

  • Maps, forecast numbers, vortex shape: NOAA NCEP GFS 0.5° (0–384 h, every 12 h) from the NOAA Open Data Dissemination programme on AWS; geopotential height, wind and temperature at 10 and 50 hPa, temperature at 850 hPa and 2 m. Zonal-mean zonal wind = mean of the 720 grid points on 60°N; polar-cap temperature = cos(latitude)-weighted mean 60–90°N.
  • Ensemble plume: NOAA GEFS (31 members, 0.5°, every 24 h to 384 h), AWS. Same diagnostics per member.
  • Vortex shape: 2-D moments of the 10 hPa height field inside the vortex edge on a pole-centred equal-area plane (Mitchell et al. 2011), with a fixed height edge as in Seviour et al. (2013). Our edge is the 1991–2020 December–March mean 10 hPa height on 60°N in R1 (–). Thresholds: displaced if the centre is south of 66°N, split if the aspect ratio exceeds 2.4 (Seviour et al. 2013).
  • Season to date and percentiles: NASA GMAO Ozone Watch daily files (MERRA-2 reanalysis, GEOS FP for the latest months; climatology 1978/79–2025/26).
  • History and SSW catalogue: NCEP/NCAR Reanalysis 1 (Kalnay et al. 1996) from NOAA PSL, 1979 to March 2026 (PSL's copy ends there). Major SSW: first day of daily-mean easterly wind at 60°N, 10 hPa, 1 November–31 March; 20 westerly days between events; final warmings excluded (Charlton and Polvani 2007). Split/displacement from the moments within −5 to +10 days of the central date (a simplification of Seviour et al. 2013).
  • Teleconnection indices: NOAA CPC daily AO (1000 hPa), NAO and PNA (500 hPa) from the CDAS reanalysis, standardised by CPC, and CPC's GEFS forecasts of the same indices. QBO: CPC 30 and 50 hPa zonal-wind index. MJO: NOAA PSL real-time OLR MJO index (ROMI; Kiladis et al. 2014), drawn on the Wheeler–Hendon phase plane (x = PC2, y = −PC1). The Bureau of Meteorology RMM file is not used because the Bureau does not allow automated downloads.
  • Canada anomalies: forecast temperature minus our own 1991–2020 day-of-year climatology from R1 daily means (31-day smoothing), interpolated to the GFS grid. GFS and R1 differ systematically near the ground, especially over mountains and the Arctic, so the 2 m map has known biases of 1–3 °C in places; the 850 hPa map is cleaner.
  • Composites: airport daily mean temperature anomalies (each airport's month × hour climatology removed, then its linear trend), R1 850 hPa daily anomalies (trend removed). AO/NAO/PNA: days with index ≥ +1 or ≤ −1, same day. MJO: days with amplitude ≥ 1 in each phase, temperature averaged 10–20 days later (Lin and Brunet 2009 found the strongest Canadian response near this lag). SSW: mean over each event, then over events; dark-edged values in the table pass a t-test across events at p < 0.05. Airports with a trend beyond ±1.2 °C per decade are treated as inhomogeneous and left out.

References

  • Baldwin, M. P. and T. J. Dunkerton, 2001: Stratospheric harbingers of anomalous weather regimes. Science, 294, 581–584. doi
  • Butler, A. H. and L. M. Polvani, 2011: El Niño, La Niña, and stratospheric sudden warmings: a reevaluation in light of the observational record. Geophys. Res. Lett., 38, L13807. doi
  • Butler, A. H., J. P. Sjoberg, D. J. Seidel and K. H. Rosenlof, 2017: A sudden stratospheric warming compendium. Earth Syst. Sci. Data, 9, 63–76. doi
  • Charlton, A. J. and L. M. Polvani, 2007: A new look at stratospheric sudden warmings. Part I: Climatology and modeling benchmarks. J. Climate, 20, 449–469. doi
  • Domeisen, D. I. V. and co-authors, 2020: The role of the stratosphere in subseasonal to seasonal prediction: 2. Predictability arising from stratosphere–troposphere coupling. J. Geophys. Res. Atmos., 125, e2019JD030923. doi
  • Holton, J. R. and H.-C. Tan, 1980: The influence of the equatorial quasi-biennial oscillation on the global circulation at 50 mb. J. Atmos. Sci., 37, 2200–2208. doi
  • Hurrell, J. W., 1995: Decadal trends in the North Atlantic Oscillation: regional temperatures and precipitation. Science, 269, 676–679. doi
  • Kalnay, E. and co-authors, 1996: The NCEP/NCAR 40-year reanalysis project. Bull. Amer. Meteor. Soc., 77, 437–471. doi
  • Karpechko, A. Yu., P. Hitchcock, D. H. W. Peters and A. Schneidereit, 2017: Predictability of downward propagation of major sudden stratospheric warmings. Q. J. R. Meteorol. Soc., 143, 1459–1470. doi
  • Kidston, J., A. A. Scaife, S. C. Hardiman, D. M. Mitchell, N. Butchart, M. P. Baldwin and L. J. Gray, 2015: Stratospheric influence on tropospheric jet streams, storm tracks and surface weather. Nature Geosci., 8, 433–440. doi
  • Kiladis, G. N. and co-authors, 2014: A comparison of OLR and circulation-based indices for tracking the MJO. Mon. Wea. Rev., 142, 1697–1715. doi
  • Lin, H. and G. Brunet, 2009: The influence of the Madden–Julian Oscillation on Canadian wintertime surface air temperature. Mon. Wea. Rev., 137, 2250–2262. doi
  • Mitchell, D. M., A. J. Charlton-Perez and L. J. Gray, 2011: Characterizing the variability and extremes of the stratospheric polar vortices using 2D moment analysis. J. Atmos. Sci., 68, 1194–1213. doi
  • Polvani, L. M. and D. W. Waugh, 2004: Upward wave activity flux as a precursor to extreme stratospheric events and subsequent anomalous surface weather regimes. J. Climate, 17, 3548–3554. doi
  • Seviour, W. J. M., D. M. Mitchell and L. J. Gray, 2013: A practical method to identify displaced and split stratospheric polar vortex events. Geophys. Res. Lett., 40, 5268–5273. doi
  • Thompson, D. W. J. and J. M. Wallace, 1998: The Arctic Oscillation signature in the wintertime geopotential height and temperature fields. Geophys. Res. Lett., 25, 1297–1300. doi
  • Wallace, J. M. and D. S. Gutzler, 1981: Teleconnections in the geopotential height field during the Northern Hemisphere winter. Mon. Wea. Rev., 109, 784–812. doi
  • Wheeler, M. C. and H. H. Hendon, 2004: An all-season real-time multivariate MJO index. Mon. Wea. Rev., 132, 1917–1932. doi

NOAA (GFS, GEFS, CPC indices, PSL ROMI, NCEP/NCAR Reanalysis 1) and NASA (GMAO Ozone Watch, MERRA-2 / GEOS FP) data are US Government works, free to use; we credit them here and on every map. "NCEP/NCAR Reanalysis data provided by the NOAA PSL, Boulder, Colorado, USA, from their website at https://psl.noaa.gov". Station data: NOAA Integrated Surface Database and our METAR archive. All maps, diagnostics, composites and outlook text are computed by MeteoFrontier.

Glossary: words used on this page

See the site glossary.