JJA Weather regimes

JJA  frequency of weather regime and daily classification. The first line recalls the weather regimes. The second line is the daily classification since the first day of the running season. The last line is the statistics of frequencies for the four regimes.

Upper panel: JJA weather regimes from NCEP SLP (1970-2000). The isolines are SLP anomalies for each centroid.

• Regime 1 is NAO-,
• Regime 2 is Atlantic RIDGE,
• Regime 3 is SCANDINAVIAN BLOCKING,
• Regime 4 is Atlantic Thalweg (or NAO+).

Beware that the classifiability of JJA months is rather low.

Middle panel:  daily classification since the first day of the running (or last) summer season. The diameter of circles indicate the spatial correlation with the four weather regimes (only positive correlations are shown).

Lower panel:  statistics of frequencies (percentage of occurrences during the season) for the four regimes since 1948. A png file can be obtained by clicking on the figure.