NOAA CPC monthly Arctic Oscillation index (historical source)
www.cpc.ncep.noaa.gov
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NWS La Crosse winter 2026–27 ENSO/QBO discussion
www.weather.gov
NWS Chicago official seasonal snowfall totals, July–June
www.weather.gov
NOAA CPC October 15 prognostic long-lead seasonal discussion
cpc.ncep.noaa.gov
NOAA CPC Relative Oceanic Niño Index (RONI), historical table
www.cpc.ncep.noaa.gov
ECMWF-based Arctic vortex diagnostics, Oct. 22, 2026 model cycle
www.polarvortex.earth
NASA GMAO MERRA-2 atmospheric reanalysis description
gmao.gsfc.nasa.gov