Image caption
NOAA's Global Ensemble Forecasting System (GEFS for short) predicts that the Northern Hemisphere polar vortex will remain perturbed for the rest of December into January, with weaker west-to-east winds (top) and warmer temperatures (bottom). The spread of the individual forecasts (thin lines in each graph) remains wide, but the average (heavier line) predicts weaker-than-average winds and warmer-than-average temperatures. A few individual models predict a polar vortex reversal and major warming. Climatology of highest and lowest daily values is from Climate Forecast System Reanalysis. NOAA Climate.gov graph, adapted from original by Laura Ciasto.