MAIN WEATHER AND CLIMATE TRAITS IN THE NORTHERN HEMISPHERE AS OF SEPTEMBER 2024

Air Temperature

No such warm September as the one this year has been ever seen in the ETR before. New daily maxima of air temperature were recorded from the first to the last day of the month, especially in the North-West, Central and Volga federal districts. The air temperature anomalies were +2…6 or more degrees in the first decade, +2…8° or more in the second one, and +2…5° in the third. But at the beginning of the last decade, abnormally cold air broke through, resulting in frosts from -2 to -6° and setting new daily temperature minima in certain locations.

The monthly-averaged air temperature in the Urals and further eastwards was either close to or less than normal. In the third decade, negative temperatures became common, and new minima were set in Trans-Baikal. But at the same time, the weather in Yakutia was noticeably warmer than usual.

As a result, the monthly averages from the western border of Russia to the Urals or even to the Far East in the north were much higher than normal in September, by 2-5 or more degrees in the ETR.

In the European Territory of Russia, including the North-West and Central federal districts separately, September 2024 was the warmest in the meteorological chronicle recorded since 1891, and was among the top five warmest in the Southern, North-Caucasian, Volga and Ural federal districts. Cool or, in places, abnormally cold weather across the Asian Territory precluded from reaching a record-high monthly figure over the whole Russia, but still accounted for the third position in the ranking list, at about half a degree below the all-time warmest September 2020 when the average air temperature turned out to be above-normal almost everywhere in Russia.

In the East Asian countries, the month was extremely hot: the temperature averages were 2-4° higher than normal in China and two or more degrees higher on the Korean Peninsula and the Japanese Islands, and the instant values sometimes exceeded +35-39° in certain places. This September was the warmest in the history of regular meteorological observations in China where the same was true for five out of nine months of 2024, namely, for April, May, July, August and September.

South-East Asia received heat in near-normal amounts.

In India, September 2024 was among the top three warmest in the history of meteorological observations.

The temperatures were close to normal in the countries of the Near and Middle East, and noticeably greater than normal in Georgia and in some places in Turkey and Iran.

The September temperature averages in the Central Asian countries were about normal, albeit that against the background of positive anomalies in the north and of negative ones in the south. Record colds were observed in Kazakhstan.

September in North Africa was colder than usual in the west, and warmer than usual in the east; it was quite clearly seen in Libya and in parts of Egypt, Chad and Niger. As for the whole region, this September was the third warmest in the history of observations, and the last three years (2022-2024) were in the top five.

In the meteorological annals of Europe, September 2024 was the second warmest (alongside 2011 and 2016, and with 2023 still remaining the leader), and looked as if was an appendix of summer in Northern, Eastern and Central Europe. In various locations from the Scandinavian and Baltic states to Germany, Poland, the Czech Republic and Serbia, new temperature highs were observed, and the normal monthly averages were exceeded by 2-4 or more degrees. But the weather in the west of the continent was colder than usual, with new temperature minima in some locations of Spain, Italy and the Netherlands, and even with ground frosts in the latter country.

This September was exceptionally warm in North America. In Canada and the US, it was the warmest in the history of meteorological observations; there, the monthly-averaged temperature anomalies were 2-4° or higher.

In the Arctic, September 2024 was also very warm: the second warmest in history after the unprecedented September 2016.

As for the entire Northern Hemisphere, the monthly-averaged temperature reproduced, to an accuracy of 0.1°, the record-breaking value set last year.

In Moscow, this September was the warmest in the meteorological chronicle of the capital owing to the monthly-averaged temperature of +17.1° (corresponding to an anomaly of +5.2°) that surpassed the previous record high value measured in September 2023 (+15.0°).

Sea Surface Temperature

Despite that El Niño has long ended, the surface temperature of the Pacific Ocean remained very high, reaching the maximum value for the twelfth month in a row that started in October 2023. High positive SST anomalies in excess of 2-4° were observed at temperate latitudes, most notably in the western part of the Ocean and off the coast of Asia. Abnormally cold water was only observed in the north, namely, in the Bering Sea and the Sea of Okhotsk. Also, weak negative anomalies took place in the equatorial zone where the neutral phase of the Southern Oscillation persisted still.

The SST in the Atlantic Ocean was above-normal almost everywhere, 2-3 or more degrees above over a large water body. The average SST in the Northern Hemisphere reached the second maximum in the history of observations, with the record high of September 2023 still unbeaten. Water in all seas washing the European continent was abnormally warm, and the highest anomalies were measured in the Norwegian, Barents and Kara seas where the SST was 5-6° greater than normal in some locations.

Precipitation

This September was very dry in the ETR where the normal values were only reached along the Arctic coast and partially in the south of the Krasnodar Territory, while the monthly precipitation totals in the rest of the ETR were, as a rule, less than half the normal figures. For example, not a drop of rain fell in the Ryazan, Lipetsk, Tambov, Voronezh, Kursk, Belgorod, Penza, Saratov and Astrakhan Regions or in the Republic of Mordovia. Yet, occasional downpours did occur in the ETR, e.g., in the middle of the month when they brought new daily precipitation totals to Crimea, the south of the Krasnodar Territory and the Murmansk Region. At the end of the month, heavy rains fell in Central Russia and in the Russian North, bringing 20-30 mm of precipitation per day, or more.

The weather in the Urals was also dry, with the normal precipitation figures reached solely in the Yamal-Nenets Autonomous District in the north. In contrast, a lot of rain fell in Siberia where the normal precipitation amounts were either achieved or exceeded almost everywhere: e.g., exceeded by 1.5 times in the Novosibirsk Region and by 2 times in Taimyr. Heavy precipitation in the form of rain or sleet was observed in Evenkiya, in the central and southern regions of the Krasnoyarsk Territory, in the Kemerovo Region and in the Republic of Altai. At times, up to 25 mm of daily atmospheric precipitation accumulated in some places.

In the Far East, the precipitation amounts were two or more times above normal in the Magadan Region, normal in Yakutia, Amur Region, Khabarovsk Territory and Chukotka, and subnormal in Primorye and Sakhalin. Heavy and prolonged rains fell in the Magadan Region, in the north of the Khabarovsk Territory and in the south-east of Yakutia; in some places, up to 70 mm of precipitation fell there in two days. Pelting rains that set new daily maxima occurred in Trans-Baikal. In the last days of the month, up to 25 mm of rainwater fell on the Kuril Islands.

In East Asia, precipitation was abundant in Mongolia and in the northern provinces of China; there, the normal amounts in some places were exceeded by 1.5-2.5 or more times. Tropical cyclone Pulasan brought a lot of precipitation to China where new maxima of daily precipitation totals were set in the east of the country and 300 mm of atmospheric moisture fell in Shanghai in six hours. But the weather in the south of China was generally dry. The precipitation amounts on the Korean Peninsula and in Japan were close to normal. In the latter country, the unprecedented precipitation amounts with their totals up to 300 mm were also recorded, and heavy rains caused floods and landslides that killed people.

Numerous rains were allotted to the countries of South-East Asia where the normal figures were exceeded by 2-3 or more times. There, heavy downpours induced floods that destroyed roads, washed away bridges and disrupted phone communications. The fatalities were reported.

The Indian monsoon continued its disastrous activities, bringing up to 250 mm of rainwater per day to some regions of India. The authorities declared a red hazard level. Floods due to monsoon downpours in Bangladesh were recognised as the most severe in more than thirty years, and the number of their victims reached five million people. Several days of incessant rains in Nepal inundated roads and residential buildings, and demolished the infrastructure of the country, bringing 240 mm of rainwater to its capital, Kathmandu. These showers were deemed the heaviest in the last fifty years.

The weather in the Near and Middle East was basically dry. Rain fell in Turkey, Transcaucasia and Iran, leading to floods in some places.

The weather in most of Central Asia was dry.

A lot of rain fell in the west and north of the African continent in amounts 2-3 times greater than normal. Heavy rains pelted in the north of Morocco and Algeria where the precipitation quantities could exceed the normal annual figure in two days, causing floods and fatalities. Floods in Chad resulted in torrential rains that affected about a million of people, deluged agricultural lands, and killed more than sixty thousand heads of livestock.

In Europe, the second half of September was very rainy. Cyclone Boris passed through the entire continent, brought a huge amount of precipitation, and raised the level of rivers including Danube, thereby flooding many settlements in Austria, the Czech Republic, Poland, Romania, Slovakia and Hungary. Pelting rains in Germany and the UK could bring up to 50-60 mm of daily rainwater. The normal precipitation amounts were significantly exceeded in most of the continent.

The weather in Canada as well as in most of the United States was dry. As for the US, the normal precipitation figures were reached in the north-west and south-east of the country only, and in the latter case, were exceeded by 1.5-2.0 or more times in certain places.

In Moscow, only 11 mm of precipitation, i.e., 16% of the normal monthly value, fell in September. Accordingly, this September became the third driest in the meteorological chronicle of the capital. The precipitation amount in September 2023 was even less, namely, 8 mm, but the all-time driest September with 7 mm of precipitation was observed in 1949.