BSH

North Sea: Weather types and gales since 1948

Air pressure is a fundamental weather and climate element and the very basis of every weather map. Daily air pressure distributions provide information on airflow and the influence of high and low pressure systems, define the character of weather activity and thus yield insight into synoptic weather conditions.

Based on the air pressure distribution over the North Sea, we have compiled a catalogue of daily weather types, which covers more than 70 years by way of annual calendars from 1948 to the present day.

Weather patterns fall into six weather types, namely four directional (NE=Northeast, SE SW, NW) and two rotational types: low pressure (C=cyclonic) and high pressure (A=anticyclonic).
The strength of the atmospheric circulation is tabulated together with the weather type, if thresholds for gale (>), severe gale (>>) or very severe gale (>>>) are reached or exceeded.

Scientific Technique and References

Technique

Weather typing and gale analysis employ an objective technique used by Jenkinson and Collison (1977) in automated identification of so-called Lamb weather types. The original plethora of 27 weather types was reduced to six main classes. The Peak-Over-Threshold technique used in gale force estimation was recalibrated (Loewe et al., 2013) to the NCEP/NCAR Reanalysis I “Daily Sea Level Pressure” dataset (Kalnay et al., 1996), the single source of raw data for all products presented under “Weather types and Gales”.

References