Robert Twardosz

Episodes of pronounced cooling during transitional months can have substantial environmental and economic impacts, particularly after the onset of the growing season, when frost events lead to losses in field agriculture and orchards. The weather in Poland in May 2025 exhibited widespread negative temperature anomalies with the occurrence of late frosts. It provides a salient example of such an event under conditions of ongoing climate warming. This study quantifies the magnitude and spatial structure of temperature anomalies in Poland in May 2025 and examines the circulation conditions associated with them in the context of long-term temperature change. The analysis is based on observations from 60 synoptic stations over 1951–2025. Spatial autocorrelation diagnostics (Moran’s I, LISA), linear regression, and structural change tests were applied. May 2025 featured a mean nationwide anomaly of −2.3 °C, with local departures exceeding 2 SD. The anomaly field exhibited statistically significant positive spatial autocorrelation and distinct regional clustering of cold anomalies, particularly in eastern Poland. The cooling was associated with a predominance of cyclonic circulation and an Omega-type blocking pattern, conducive to sustained advection of cold air masses from the north. The long-term analysis confirms a statistically significant warming trend in May temperatures over 1951–2025, with no evidence of a significant structural shift in recent decades. Therefore, negative anomalies observed during the last decade, including 2025, do not represent a reversal of this trend but do not provide evidence of a reversal of the long-term warming trend. The results indicate that, in transitional months, variability in circulation regimes can intermittently mask the warming signal, and cold episodes—though less frequent—remain statistically plausible in a warming climate.

Poland’s location in the mid-latitudes determines a moderate influx of solar radiation and characteristic circulation conditions that strongly control weather variability. Of particular importance is the dominance of westerly circulation, enhanced by the zonal configuration of relief. The frequent passage of cyclones and atmospheric fronts, together with the advection of air masses with highly contrasting thermal properties, results in pronounced weather variability. Depending on the direction of air-mass advection, both extremely warm and extremely cold conditions may occur.Since the late 20th century, the climate has been characterized by the predominance of anomalously warm months, seasons, and years. Notable examples include the exceptionally hot summer of 2003 in Western Europe and the summer of 2010 in Eastern Europe, both of which caused thousands of excess deaths among populations unaccustomed to prolonged heat stress. At the same time, extreme cold events still occur. Although they have become less frequent and less intense than during the 20th century, they continue to generate severe economic and biometeorological impacts. An example is January 2017 in the Balkan Peninsula, which was among the coldest and snowiest months on record in that region.In the current year, a pronounced negative temperature anomaly was also observed: in May, snowfall and widespread frost occurred over large parts of Poland, as widely reported by the media. The aim of this study was therefore to assess how strongly thermal conditions in May 2025 deviated from the long-term climatological mean in Poland. Specifically, the study seeks to quantify the magnitude of the air-temperature anomaly and to identify the synoptic conditions responsible for the persistence of anomalously low temperatures.The primary dataset consists of mean monthly air temperatures for May for the period 1951–2025 from 60 synoptic stations in Poland. These publicly available data were obtained from the database of the Polish national meteorological service (IMGW-PIB, https://danepubliczne.imgw.pl/). This dataset was used to calculate the magnitude of the temperature anomaly in May 2025. Anomalies were expressed both in absolute terms (°C) and in standardized units (multiples of the standard deviation, SD). A second dataset, also obtained from IMGW-PIB, comprises daily mean, maximum, and minimum air temperatures for May for the 75-year period 1951–2025 from selected stations. Synoptic conditions were analysed using surface and upper-air weather charts from the Polish (meteo.imgw.pl) and German (www.wetter3.de) meteorological services.Preliminary results indicate that the cold conditions over Poland were primarily controlled by low-pressure systems that induced advection of cold air from the northern sector. Their persistence was favoured by a characteristic omega-blocking pattern over Western Europe and the presence of a deep upper-level trough over Central Europe. This configuration effectively inhibited the eastward progression of baric systems, allowing the prevailing weather regime to persist over the region for an extended period.

This study presents an analysis of patterns in mean monthly air temperature increases in Poland using the deep learning model Neural Basis Expansion Analysis for Time Series (N-BEATS) algorithm. The dataset comprises mean monthly temperatures recorded between 1951 and 2024 at eight meteorological stations across Poland. The research was conducted in two phases. In the first phase, the 74-year period was divided into two distinct intervals: one characterized by relative temperature stability, and the other by a marked upward trend. In the second phase, the N-BEATS neural network was employed to extract temporal patterns directly from the data and to forecast future temperature values. The results confirm the capacity of machine learning methods to identify persistent climate trends and demonstrate their utility for long-term monitoring and prediction.

Catastrophic precipitation is an inherent feature of temperate climates. Its occurrence is a manifestation of climate change, but also of the variability of atmospheric circulation. Mountainous areas may be particularly vulnerable as they receive more precipitation and are also areas where relief plays an important role in modifying the distribution of precipitation. One such area is the Polish Western Carpathian Mountains, especially the area around the city of Bielsko-Biała, located at their foot and directly exposed to rain-bearing winds. In 2024, two episodes of unusually heavy precipitation in quick succession occurred in this area, resulting in severe damage to infrastructure. This painful experience inspired a study focusing on the frequency of such catastrophic precipitation events and their synoptic circumstances spanning the period from the mid-20th century to the present day. Daily precipitation totals covering the study period of 74 years were used to identify a category of catastrophic precipitation (here set at above 100 mm). The six events identified to match the criteria appeared from May to September, always accompanied by cyclonic circulation types with advection from the northern sector and with a cyclonic trough situation over southern Poland. The study showed that the leading role in their formation was played by deep convection, especially a Genoa low moving along the Vb Van Bebber track. The damage and destruction suffered as a result were a consequence of the cumulative impact of high-intensity rainfall, itself caused by a combination of specific synoptic thermodynamic and orographic conditions.

This study provides a climatological analysis of annual and long-term variability of dry days and sequences of dry days in the Polish Carpathians between 1986 and 2020. The input data for the research was compiled from the daily precipitation totals from 17 meteorological stations and the T. Niedźwiedź catalogue of circulation types over southern Poland. The frequency of sequences of dry days of different duration has been presented. The incidence of long-term periods has been related to the atmospheric circulation. The number of dry days and the averages of both the number and of the duration of sequences of dry days were analysed for the study period. This yielded an average annual number of dry days ranging from 142 to 195 (39–53% of days in a year), depending on the altitude above sea level and longitude. A general pattern emerged in which the number of dry days increased from west to east. At most stations, there were no statistically significant trends with respect to the dry day characteristics analysed. This is an obvious result of high year-to-year variability, which means that only large changes can achieve statistical significance. Dry days have been evidenced to relate to circulation types. The vast majority of dry days are related to anticyclonic systems, particularly the anticyclonic wedge (Ka) and western anticyclonic (Wa) situations. On the other hand, no clear-cut relationship was established between an increase in air temperature and the occurrence of dry days.

This study aims at providing a climatological analysis of annual and long-term variability of dry periods in the Polish Carpathians in the period of 35 years between 1986 and 2020. Aside days with precipitation, dry periods, namely sequences of days with no precipitation, constitute an inherent characteristic of the climate. The input data for the research was formed by daily precipitation totals from 17 meteorological stations acquired from the Institute of Meteorology and Water Management - National Research Institute, and T. Niedźwiedź catalogue of circulation types over southern Poland. Frequency of dry periods of different duration has been presented. The incidence of long-term periods has been related to the atmospheric circulation. An analysis was performed regarding the change of the average quantity and average length of dry sequences in the 35-year period covered. At most stations, there were no statistically significant trends with respect to the analysed dry day characteristics. This is an obvious result of high variability year-to-year, which means that exclusively large changes may achieve statistical significance. Dry days have been evidenced to related to circulation types. A vast majority of dry days is related to anti-cyclonal systems, particularly the anti-cyclonal wedge (Ka) and western anti-cyclonal (Wa) situations.

This article studies the intra-annual and long-term variability in the maximum daily precipitation totals and their association with atmospheric circulation in Kraków. It investigates daily precipitation maxima by year and by month. The research is based on daily precipitation totals in the years 1863–2021 and draws on the calendar of atmospheric circulation types by Niedźwiedź. It examines the frequency of precipitation maxima in individual months and their variation from one year to another. No statistically significant trend of change in precipitation over the study period has been found. All annual maximum daily precipitation totals in Kraków fall into the category of heavy precipitation (>10 mm), and almost 99% qualify as very heavy (>20 mm). In the summer months, these are about 3–4 times higher than in winter. The share of the daily precipitation maximum in the monthly total exceeds 30% in all months. The maximum daily precipitation occurring on 5 August 2021 was the highest in the period that extends from the start of instrumental measurements. The study period saw 12 cases of maximum precipitation that belong to ‘flood-inducing’ categories (over 70 mm/day). Such cases of the very heaviest precipitation occurred in cyclonic situations: Cc, Bc, Nc, NEc, Ec and SEc. Most spring and summer maxima were seen on days with a cyclonic circulation. The instances of high daily precipitation in the Kraków area led to the flooding of residential and historic buildings, as well as of municipal infrastructure.