The North Atlantic Oscillation Index (NAO Index) is based on the pressure differences between the Azures (outside Portugal) and Iceland. The index yields both positive and negative values (phase of NAO) with pressure anomalies.
According to NOAA, both phases of the NAO are associated with changes in the intensity of the North Atlantic jet stream and strom track, and patterns of heat and precipitation extending from eastern North America to western and central Europe.
I Norway positive phase of the NAO is associated with mild and wet winter conditions, while negative phase is associated with cold winter weather. In 2010 the NAO index showed a strong negative phase, which contributed to an especially cold winter. In 2020, a positive NAO phase contributed an especially mild winter.
Verstat updates NAO index values from NOAA on a daily basis (it seems that NOAA does not updates its dataset on a daily basis). Below you will find Daily, Monthly, and Yearly averaged NAO index, by winter months.
The last graph shows the last 1000 days NAO index values.
Daily winter average NAO index values
Monthly winter average NAO index values
Yearly winter average NAO index values
Daily average NAO index value (all)
Data is from NOAA, please follow link for information on calculation method and data documentation.
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