Distinctive characteristics of weather conditions were: drastic changes, considerable anomalies of the temperature regime, early frosts in September, rather early settling of the winter regime with a lasting snow cover in practically the entire territory of Ukraine, frequent floods of rivers in the western regions, and disastrous flooding in the Transcarpathian area on 4-8 November.
As to the temperature regime, the year of 1998 was warmer than usual. The average annual air temperature was higher than normal by 0.2-0.8°C; in the Crimea, the eastern regions and in some sites of the central regions it was 0.9-1.2°C higher. The quantity of precipitation was characterized by the following values: in the eastern, south-eastern, Poltava and Dniepropetrovsk regions and in the Crimea precipitation was 65-95% of the annual level, in the of rest territory it was 100-150%; in certain sites in the Transcarpathian and Forecarpathian areas it was 180-215% of the annual level.
January was characterized by considerable variations in the air temperature.
In the right tributaries of the Prypyat River, warm weather and snow thawing caused a rise of water levels with flooding of land and buildings and national economic objects located in low-lying areas near the Stokhid and Goryn rivers.
On 21-23 January the wind intensified to 25-30 m/s in the Crimea and Genichesk (Kherson Region). A wind-induced surge in Saki Region (the Autonomous Republic of the Crimea) led to the destruction of dikes, flooding of a settlement (250 persons were evacuated), and the disconnection of electric power lines. Flooding of buildings took place in the town of Vylkovo (Odesa Region). Dangerous levels of water were also observed on the Azov Sea beach.
In the third decade the winter regime of the weather became settled for a short period under the influence of the Siberian anticyclone. In the eastern areas minimum air temperatures fell to -17-20°C.
February also appeared to be anomalously warm, with an inconsiderable quantity of precipitation in most parts of the Ukraine territory.
On certain days maximum temperatures were higher than the absolute indices.
In the first decade of February in south-western Ukraine, and in the second decade in north-eastern Ukraine, the average daily air temperature rose above 0°C 20-35 days earlier than normal. The snow cover was unstable and at the end of the month it had almost disappeared throughout the country.
On 13-14 February spring flooding began in the Azov Sea rivers, which was 6-13 days earlier than the average.
At the end of the second decade of February spring flooding began in the rivers of the Siversky Donets Basin, 10-24 days earlier than normal. A general rise of water levels was 0.5-2.5 m higher than the preflooding marks, and flooding of low-lying sites and bridges was observed in Novopskiv and Starobil districts in Lugansk Region.
The extremely warm weather of January-February led to a reduced use of fuel and energy resources.
Weather conditions in March were marked by the influence of cyclones. As a result there was broken weather with considerable precipitation.
In the second decade and up to the end of the month a series of northern cyclones created intricate weather conditions in the territory of Ukraine: moderate, sometimes heavy precipitation, blizzards, icing, sticking of wet snow, increase of wind up to 15-20 m/s, and fogs in the south. The 20-30 cm thick snow cover lasted until the end of the month.
On the whole, the average daily air temperature in March appeared to be higher than the normal level by 1-2°C, precipitation being 2-4 times the monthly average.
A danger of snow avalanches was observed in the Alpine Carpathians.
Spring flooding took place in the course of the month on the Dnieper above the Kyiv reservoir and the rivers of the Left Bank Area; from 6-11 March thaw and rain floods were observed in the Carpathian rivers with a general rise of levels by 0.3-2.2 m. On the diked sites of the Tysa and Latorytsa rivers near Chop the rise was 3.0-4.4 m.
In the entire territory of Ukraine the transition to spring (temperatures exceeding +5°C) occurred 3-5 days earlier than usual (from 1 to 7 April, and in the far south and the Crimea at the end of March).
In April broken weather with precipitation prevailed. In most parts of Ukraine the precipitation quantity was normal; in the southern regions it was 2-3 times the monthly average; whereas in the steppe regions of the Crimea and in certain sites in the east, precipitation was only 20-45% of the normal level.
During this month there were ground frosts, and air frosts at various sites throughout the entire territory.
Flooding continued in the Dnieper above the Kyiv reservoir and in the Desna within the boundary of Ukraine. Heavy prolonged rainfalls on 19-21 April caused flash floods in the Carpathian rivers. The rise of water levels above the preflooding marks was from 1 to 3.6 m on the rivers of Lviv Region and from 0.5 to 1.7 m on rivers of Ivano-Frankivsk and Zakarpattya regions. Flooding of low territories and certain settlements was observed in certain districts of Lviv and Zakarpattya regions.
May was characterized by considerable air temperature variations and by a shortage of precipitation in most regions of Ukraine.
The end of April and the first half of May were very warm. The day air temperatures rose to 25-28°C, in the west to 29-31°C.
In the second half of May light ground frosts were observed in the western regions and in the Transcarpathian area.
The average monthly temperature was close to the normal level; in the Forecarpathian area it was lower than the normal level by 1°C.
The quantity of precipitation was less than the norm; however, in the Forecarpathian area and in the southern regions it was 1.5 times the monthly average, and in the Crimea and the Azov Sea area up to three times the monthly average.
On 18-20 May very heavy rainfalls (31-100 mm per 12-30 hours) in Ivano-Frankivsk and Chernivtsi regions led to a rise of water levels in the mountain rivers, destruction of agricultural lands, electric power lines, motor-roads and bridges, and 922 dwellings were flooded.
In the first half of June the weather was hot. Showers, thunderstorms, hail and squalls were observed in the western, southern and northern regions, while the eastern regions had dry winds.
The average daily air temperatures exceeded the normal average by 2-8°C and reached 18-23°C, with 20-26°C recorded in certain sites.
In the third decade of June and in the first half of July the weather was cool. The average daily temperatures were lower than the average values of many years by 1-4°C. Showers (in certain sites very heavy), thunderstorms, hail and squall intensification of winds were observed in most regions of Ukraine, with the exception of the eastern parts and the Crimea.
From the end of the second decade of July, under the influence of the Azor anticyclone, the weather in most regions of Ukraine was dry and very hot.
In the daytime the maximum air temperature in the steppe regions rose to 32-38°C. In Odesa, Poltava and Mykolaiv regions temperatures reached 40°C.
The quantity of precipitation in July was distributed unevenly: in the largest part of
the territory the quantity was within one to three times the monthly average, and only in
the eastern, certain central and southern regions was the quantity less, constituting only
20-40% of the normal level in certain sites.
Heavy showers accompanied by thunderstorms, hail and squalls resulted in a significant rise of water levels in western regions, and in destruction of hundreds of dwellings and farming structures. Thousands hectares of farm crops were washed off, miles of motor-roads were flooded, bridges and electric power lines were destroyed, and many people lost their lives.
The beginning of August was characterized by very dry and hot weather.
From 6 August, under the influence of active south-western cyclones, the weather conditions changed: the air temperature decreased, and there were heavy and very heavy showers with thunderstorms and squalls.
On the whole, the temperature regime in August was close to the normal level. The
quantity of precipitation in most parts of the territory was normal; in Sumy Region and in
the south of the Crimea it was 1.5-2.5 times the monthly average; while in the steppe
regions of the Crimea, the Azov Sea area and in Kherson Region it comprised less than 30%
of the monthly average.
In September, apart from the first decade, the weather was warm. The average daily temperature was 2-6°C higher than the average. The daytime air temperatures rose to 20-28°C, and in the south and east they reached 30-32°C on certain days.
A sharp cooling at the beginning of the month was connected with the Arctic
anticyclone. Frosts (0-3°C) were observed on the ground and in the air.
During September winter fronts caused showers of short duration with thunderstorms, and on 12-14 September there was an increase of wind in the entire territory of Ukraine up to 15-20 m/s, in certain regions up to 23-26 m/s, in Khorly (Kherson Region) and Ovruch (Zytomyr Region) up to 25-29 m/s, which led to the destruction of roofs of buildings and communication and electric power lines.
In Dniepropetrovsk, Lugansk, Donetsk, Zaporizhzhya regions and in the Crimea the danger of fire danger increased significantly and was extremely high.
The high-temperature regime and shortage of precipitation, especially in the steppe and forest-steppe regions of the country, caused a further intensive decrease in productive humidity resources in the ground. Consequently, by the end of the month nearly 35% of areas intended for winter crops had unsatisfactory humidity of the arable ground layer.
In October the weather was characterized by significant variations in the temperature regime. On the whole, the average monthly temperature proved to be close to the norm.
In the first decade, due to cold Arctic winds, a sharp cooling took place in the entire territory of Ukraine, excluding the Transcarpathian area. The minimum air temperature dropped to -3-5°C, in Lugansk Region it fell to -10°C. The cooling was foreseen in good time.
Warm wind masses from the west caused a rise of air temperatures from the beginning of the second decade and until the end of the month. On certain days maximum temperatures rose to +16-23°C, while in the Crimea, the Azov Sea area and in Lugansk Region temperatures rose to +26-31°C.
The quantity of precipitation was mainly within 1.3-2 times the monthly average, in some parts of Khmelnytsk, Vinnytsa, Cherkasy, Kyiv and Odesa regions it was 2.5-3 times the monthly average. Only in Crimea, Kherson, Dniepropetrovsk, Donetsk and Lugansk regions was the quantity close to the normal level.
On 2-9 October frosts in the air and on the ground were observed in the entire territory of Ukraine.
The cool weather of the first decade of October was harmful to the winter crops in northern regions, and at certain locations they were totally destroyed.
The warm and rainy weather in the second and third decades was beneficial for the winter crops in most regions of the country. Rains made field work in certain regions, especially in the west, more difficult.
At the end of the month, rains caused flooding, with a rise of water levels of 1-2 m and in certain sites of the Transcarpathian area rivers 3-5 m above preflooding marks, in rivers of the Transcarpathian area and of the Dniester, Prut and Syret basins. Buildings, roads, and agricultural lands in low-lying areas were flooded.
Weather conditions in November were extreme and characterized by anomalously low temperatures, large quantities of precipitation and also by early (1.5-2 weeks earlier than ordinary) settling of the snow cover.
At the beginning of the month the weather was mild and rainy. The maximum air temperature rose to +15-20°C, and average daily temperatures exceeded values recorded over a number of years by 2-5°C.
A considerable fall in air temperatures with departures of the average daily temperature from normal by 8-14°C was observed from the end of the first decade until the end of the month in most regions of Ukraine. The minimum air temperature dropped to -15-20°C. Except for the Crimea, snow covered the entire territory of Ukraine.
The average monthly air temperature was 2-5°C lower than the norm, in southern and south-eastern regions 1-2°C lower.
The quantity of precipitation was 1-2 times the monthly average, in Odesa Region and in
certain sites in Mykolaiv Region it was 2.5-3 times the average.
In most regions of Ukraine on 12-13 and 16-17 November, and in Odesa Region on 20-22 November, intricate weather conditions caused damage to electric power lines, motor transport traffic was stopped, energy supply of settlements was switched off, and the operation of public services became difficult. A wind-effected phenomena on the Danube River near Vylkovo caused a rise of the water level, and 15% of the town territory was flooded.
On 4-7 November heavy and very heavy rains and high humidity caused rivers of the mountain part of the Dniester Basin to flood, with water levels rising above the preflooding marks by 0.4-2.6 m, in certain sites up to 3.1 m, and in the Dniester River (Galych-Zalishchyky) 3.2-3.7 m.
The combination of heavy rains, town discharges, and a rise of ground and river water levels led to the flooding of agricultural lands, buildings and to damage of agricultural objects in Turkiv, Skoliv, Stryy and Zhydachiv districts of Lviv Region.
On 4-8 November rains caused the Transcarpathian rivers to flood. The flooding was disastrous due to a dramatically increased rise of water levels. The maximum levels on 13 hydrological posts were the highest ever recorded. General rises of water levels above preflooding marks were 1.1-3.6 m, in the Tysa River near Tyachev and Vylok and the Latorytsa River near Mukachevo levels rose by 4.1-6.1 m. About 200 settlements were flooded, and more than 2,000 buildings as well as bridges, motor-roads and railways were destroyed. Mud flows and landslides were observed. People were evacuated from the zones of natural disaster, and about 20 lives were lost.
December was cold, the average monthly air temperature was 1-4°C lower than the norm, and only in Donetsk and Lugansk regions was it close to normal. The weather was particularly cold at the beginning of the month.
The air temperature minimum in most parts of the Ukraine territory was -22-28°C, in Vinnytsa and Kyiv regions it was -29-30°C.
The quantity of precipitation in the western and northern regions was within the normal level, in the eastern and south-eastern regions it was from 1 to 2 times the monthly average, and in most central and southern regions it was 20-50% of the normal level.
December was characterized by a snow cover of 1-28 cm and by freezing drizzle on roads in the entire territory of Ukraine, excluding the southern regions and the Crimea.
At times fogs, precipitation, icing, and freezing drizzle made motor transport, energy supply, communication and public services very difficult.
On 5-6 December a considerable change of weather conditions occurred in the entire territory of Ukraine, excluding the south: warming, precipitation, in certain sites in the west and north very heavy, sticking of wet snow, and in the south an increase of wind up to 15-20 m/s.
The extraordinary cold weather on 1-3 December complicated the wintering conditions of winter crops and perennial grasses in the eastern part of the country. The minimum ground temperature at the depth of tillering node bedding of winter crops (3 cm) decreased in Lugansk and Kharkiv regions, in certain sites down to -15-17°C, approaching critical freezing temperatures for the weak winter wheat and winter barley plants.
The hydrological regime of rivers was determined by a high content of water and by changes in water levels which were caused both by snow thawing and by the weakening of ice formations.