What is the Scandinavian Pattern Climate Index?

The Scandinavian Pattern (often referred to as the SCAND) has important impacts on European weather and can be useful in long-range subseasonal weather prediction.

What is the Scandinavian Pattern Climate Index – Introduction

The Scandinavian Pattern climate index is an atmospheric climate index (climate cycle or teleconnection) that describes flow patterns over Europe. The SCAND shapes the weather across Europe with characteristic patterns in evidence at different times of the year, making it a valuable input for long-range forecasters such as energy meteorologists.

In this discussion, we use the analog forecasting tools available in the World Climate Service to understand the impacts of different phases of the SCAND on European summer and winter weather.

Like most climate indices, the SCAND climate index has positive and negative phases with a particular time scale of variations. The progression of the last five years of the SCAND index is shown below. 

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Fig. 1: Five years of the Scandinavian climate index

Scandinavian Pattern – Positive Phase

The SCAND is largely driven by a pressure dipole between Southern Europe and Scandinavia. The World Climate Service 500 mb anomaly maps (Figures 2 and 3) show that a positive SCAND occurs when southern Europe experiences low pressure while northern Europe experiences higher pressures. 

Fig. 2: World Climate Service 500mb anomaly map for a strongly positive Scandinavian Pattern Climate Index in winter
Fig. 3: World Climate Service 500mb anomaly map for a strongly positive Scandinavian Pattern Climate Index in summer

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Scandinavian Pattern – European Winter Positive Phase Impacts

During the positive phase of the SCAND in the wintertime, much of Europe is likely to be cooler than normal, especially in the Northeast (Figure 4). 

At the same time, Northern Europe is likely to be drier than normal, while the South and parts of Eastern Europe, are more likely to be wetter than normal (Figure 5).

Fig. 4: World Climate Service temperature probability map for a positive Scandinavian Pattern Climate Index in winter
Fig. 5: World Climate Service rainfall probability map for a positive Scandinavian Pattern Climate Index in winter

Scandinavian Pattern – European Summer Positive Phase Impacts

During the positive phase of the SCAND in the summertime, Northern Europe is usually warmer than normal, while much of Southern Europe is likely to be cooler than normal (Figure 6).

At the same time, Northern Europe is likely to be drier than normal, while the southern and central parts of Europe, are more likely to be wetter than normal (Figure 7). 

Fig. 6: World Climate Service temperature probability map for a positive Scandinavian Pattern Climate Index in summer
Fig. 7: World Climate Service rainfall probability map for a positive Scandinavian Pattern Climate Index in summer

Scandinavian Pattern – European Negative Phase 

The negative phase of the SCAND is nearly an inverse image of the summer-time positive phase, with low pressure centered over Northern Europe and high pressure across much of Central and Southern Europe. In winter we also see troughing in the Southeast.

Fig. 8: World Climate Service 500mb anomaly map for a negative Scandinavian Pattern Climate Index in winter
Fig. 9: World Climate Service 500mb anomaly map for a negative Scandinavian Pattern Climate Index in summer

Scandinavian Pattern– European Winter Negative Phase Impacts

During the negative phase of the SCAND in wintertime, much of Central and Northern Europe is warmer than normal, but the south of Europe is usually cooler than normal (Figure 10).

At the same time, much of Northern Europe is wetter than normal, while the South is usually significantly drier than normal (Figure 11). 

Fig. 10: World Climate Service temperature probability map for a negative Scandinavian Pattern Climate Index in winter
Fig. 11: World Climate Service rainfall probability map for a negative SCAND Climate Index in winter

Scandinavian Pattern– European Summer Negative Phase Impacts 

In the summertime when the SCAND is negative we expect cooler than normal across Northern Europe, while the south of Europe is usually warmer than normal (Figure 12).

The summer rainfall pattern is similar to the winter pattern except that the dry weather extends further north into the North European Plain and wetter than normal weather is restricted to the northern tier (Figure 13).

Fig. 12: World Climate Service temperature probability map for a negative Scandinavian Pattern Climate Index in summer
Fig. 13: World Climate Service rainfall probability map for a negative SCAND Climate Index in summer

The World Climate Service provides a powerful data mining capability that enables users to quickly explore the SCAND Climate Index, and many other indices, by phase for each month of the year, showing impacts on all the major weather parameters right around the globe. 

What is the Scandinavian Pattern Climate Index – Long Range Forecasting

The Scandinavian Pattern Climate Index typically remains in a given phase from a few days to a few weeks. Thus the SCAND is very much a subseasonal climate index (as opposed to a longer-lasting seasonal climate index such as ENSO). Occasionally the subseasonal forecast models will latch on to a high probability of one phase or the other with a two- or three-week lead time. If this expectation appears in several models, then forecasters start to consider what typically happens in the predicted SCAND phase at that time of year. 

Scandinavian Pattern climate index
Fig. 14: SCAND chart from the World Climate Service showing how variable the SCAND can be

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What is the Scandinavian Pattern Climate Index – Conclusion

The Scandinavian Pattern climate index is a measure of the relative strength of the north-south pressure difference across Europe. The SCAND is a subseasonal phenomenon that changes phases inconsistently and rarely persists in one phase for more than a week or two. 

The SCAND Climate Index is an important consideration in subseasonal forecasting because it indicates characteristic weather patterns over Europe that vary with time of year. 

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