Tropical/Northern Hemisphere (RPCA daily)

CPC-method rotated-PCA Tropical/Northern Hemisphere pattern rebuilt from ERA5 500-hPa height, daily least-squares fit on patterns interpolated to the day. Positive: highs over the Gulf of Alaska and from the Gulf of Mexico into the western Atlantic, low over eastern Canada. Winter only (Dec–Feb). — Barnston & Livezey 1987; NOAA CPC