Tomer Burg
Ph.D. Student | School of Meteorology
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  • Real-Time Stratosphere Forecasts

    This page displays the latest 31-member Global Ensemble Forecast System (GEFS) forecasts for the stratospheric polar vortex (SPV), using 10-hPa 60N zonal mean zonal wind.

    This page makes use of the extended 35-day GEFS forecasts, initialized once a day at 00 UTC. As the full extended cycle is delayed relative to the normal 15-day GEFS forecasts, the latest available cycle will be one day behind. Plots are generated for base climatologies from ERA5, as well as GEFSv12 Reforecast courtesy of Zachary D. Lawrence.

    Only a limited selection of GEFS products are available here. For more realtime stratosphere resources, check the following links:

    NOTE: Per Lawrence et al. (2022), the GEFS tend to exhibit a drift towards a strong vortex bias, so relative to the ERA5 climatology at longer lead times it may be biased towards higher percentile ranks than relative to its own climatology. Two climatologies are available using the 2000-2019 GEFSv12 Reforecast:

    Smoothed: This climatology applies smoothing to incorporate additional hindcasts, following methodology from Pegion et al. (2019).
    Raw: This climatology uses raw GEFSv12 hindcasts initialized on this day of year. As GEFSv12 hindcasts are only initialized once a week, only ~4-5 hindcasts are available for a given day of year.

    Extended GEFS Forecast

    This plot shows the 31-member extended GEFS zonal mean zonal wind from the latest available run.


    Extended GEFS Percentile Rank

    This plot shows the distribution of extended GEFS zonal mean zonal wind for each ensemble member with respect to ERA5 climatology.


    Extended GEFS Trend

    This plot shows the last 3 cycles of the extended GEFS, their interquartile range (IQR), and their extrema, alongside ERA5 climatology for a comparison.


    Cumulative SSW Probability

    This plot shows the cumulative percent of GEFS ensemble members that have at least one or more time step with an easterly zonal mean zonal wind.