Some meteorological and geo‐orographical factors related to cloud‐to‐ground flashes in Castilla‐Leon (Spain) are studied. The relationship between flash density and the number of days with thunderstorms (thunderdays) is analysed, and a clear dependence and geographical variability is found. It is also shown that flashes have an average delay of four hours with respect to the time of the beginning of convection. The effect on flashes of dry static instability and moisture content is analysed by classifying days into four types according to the average values of the 850–700 hPa temperature difference and the 850 hPa dew‐point temperature. A similar classification using the 700 hPa wind direction is used to analyse the effect of the mean‐level flow on flashes. The results suggest that the daily number of flashes is mainly affected by the moisture content. Finally, a relationship between the cloud‐to‐ground flash density and geo‐orographical factors (altitude, latitude and longitude) is deduced using multiple linear analysis. Copyright © 2001 Royal Meteorological Society

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Historic snowfall events in the northern Iberian Peninsula recorded between 1988 and 2018 are presented and analysed. This study makes use of data collected over a course of 31 years from 105 observation stations. These weather reports describe the temporal and spatial characteristics of five Spanish provinces facing the Cantabrian Sea. The average number of snow events observed per year (as recorded by all 105 stations) was 133, where a maximum of 421 snow events was recorded in 2010 and a minimum of 24 events were recorded in 2002. In addition, the monthly distribution of snow events per day had a maximum of 630 events, (February), with a mean monthly value of 170 snow events. Other features like the distribution of snow events depending on the altitude of each province studied and the corresponding spatial patterns are also shown. Furthermore, the circulation patterns responsible for heavy snowfall in the region were also examined. To carry out this study, we considered the daily patterns at 1,200 UTC of the geopotential height at 500 and 850 hPa pressure levels and sea-level pressure and temperature at 500 and 850 hPa, respectively. The synoptic situations were classified based on a principal component analysis coupled with a K-means clustering, and four groups associated with heavy snowfall events were subsequently identified. The analysis of the daily synoptic patterns showed that a trough was present over the Iberian Peninsula, or close by, and a low appeared over the Mediterranean Sea or Central Europe. The low-level flow was from the north (N) or northeast (NE) in 85% of the cases and the temperature at 850 hPa pressure level was lower than −3 C in 70% of the cases.

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