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This page displays a live archive of stratospheric monitoring products for the Northern Hemisphere, updated four times per day from the ERA5 reanalysis dataset and the GFS forecast model. The products (GPH Anomaly, U60 Zonal Wind, Polar Cap Temperature, Wave1/2 Amplitude Anomalies, and Eddy Heat Flux Anomaly) together describe the full chain of stratospheric variability, from the initial thermal signal through to the dynamical response most relevant for extended-range surface weather forecasting.
Shows the daily polar-cap mean geopotential height (65-90°N, all longitudes), expressed as a normalised anomaly in standard deviations (σ) relative to the 1991-2020 ERA5 climatology. Blue shading indicates heights below climatology (stronger, colder polar vortex); red/orange shading indicates heights above climatology (weaker or displaced vortex). This is the primary indicator of overall polar vortex strength and is most active during the November-March stratospheric monitoring season.
Shows the daily zonal mean zonal wind at 60°N latitude across all pressure levels. The last 60 days view additionally overlays anomaly contours in purple; the full period view shows the absolute wind speed in m/s (westerly = positive, easterly = negative). A reversal of the 10 hPa wind from westerly to easterly at 60°N is the WMO definition of a Sudden Stratospheric Warming (SSW). This product is the most direct link between stratospheric conditions and tropospheric weather impacts over Europe and North America.
Shows the daily cos(lat)-weighted area mean temperature over the polar cap (65-90°N), expressed as a normalised anomaly (σ) relative to the 1991-2020 ERA5 Climatology. Blue = colder than climatology (strong, cold vortex); red = warmer than climatology (vortex weakening or SSW). Temperature anomalies in the upper stratosphere (1-10 hPa) typically lead the wind reversal by several days, making this the earliest available signal of an impending SSW event.
Shows the daily planetary Wave 1 geopotential height amplitude anomaly at 65°N, expressed as a normalized anomaly (σ) relative to the 1991-2020 ERA5 climatology. Purple shading indicates below-normal wave activity (suppressed wave forcing); orange/brown shading indicates above-normal wave activity (enhanced wave forcing, potential SSW precursor). Wave 1 dominance is associated with vortex displacement events.
As above but for planetary Wave 2. Wave 2 dominance is associated with vortex split events, the more dramatic class of Sudden Stratospheric Warming consequences. A simultaneous increase in Wave 2 and decrease in Wave 1 can be a precursor to a split SSW.
Shows the daily meridional eddy heat flux (v'T'), averaged over 40-80°N at each pressure level, expressed as a normalised anomaly (σ) relative to the 1991-2020 ERA5 climatology. Teal shading indicates below-normal (equatorward, cold-air) flux; orange/brown shading indicates above-normal (poleward, warm-air) flux, the direct signature of planetary waves transporting heat into the polar stratosphere. Unlike the Wave 1/2 amplitude charts, which describe the size of the wave disturbance itself, eddy heat flux measures the actual heat transport the wave is doing, and is often the earliest signal in the whole chain, typically leading the polar cap temperature and GPH response by one to two weeks.
Plots produced by Giuseppe Petricca (hebweather.net). Data: ECMWF ERA5 Reanalysis, NOAA/NCEP GFS. If you use these plots in publications, posts, or presentations, please cite the source and include a link to this page.