Weatherwatch: Year’s worth of rain falls in Argentinian city in eight hours

Rainfall in Bahía Blanca led to 10 deaths, swept away vehicles, destroyed bridges and left areas underwater

The city of Bahía Blanca in Argentina had a new rainfall record on Friday, after a recent heatwave. More than 400mm (15.7in) of rain was recorded in just eight hours, more than twice the city’s previous record of 175mm set in 1930, and roughly equivalent to a year’s worth of rainfall.

The heatwave primed the atmosphere for heavy rainfall by creating high instability and raising humidity levels. Then on Friday, as a cold front swept across the region, this warm moist air was able to rise, cool and rapidly condense, leading to severe thunderstorms across the region. As the front then continued northwards towards Buenos Aires over the weekend, further severe storms were triggered, containing heavy rain, hail and strong gusts.

So far, 10 deaths have been recorded in Bahía Blanca as a result of the extreme weather, and more than 1,300 people were evacuated. Heavy rain caused flash flooding that swept vehicles away, destroyed bridges and left parts of the city under more than 2 metres of water.

There was also flash flooding on Indonesia’s main island of Java on Thursday. Heavy rain battered the island in the days before, prompting authorities to attempt to use cloud-seeding technology to move the downpours away from the capital, Jakarta.

Cloud seeding works by releasing cloud-condensing nuclei into the atmosphere, which allows water vapour to condense as droplets, forming clouds and consequentially manipulating the timing, intensity and location of rainfall. The Indonesian authorities released these cloud-condensing nuclei over the ocean, from the prevailing wind direction, in the hope that rain would fall over the water instead of the island. Although this method has previously been used in Indonesia, it remains an experimental technique, and its effectiveness and consequences are being closely monitored.

Further spells of heavy rain are expected throughout this week in Java, with the potential for further flooding across the Indonesian archipelago.

Eastern Europe is set to experience above-average temperatures this week under a more south-westerly flow. Temperatures will reach about 5-15C above the seasonal average, which will bring highs in the mid-to-high 20s Celsius for parts of Ukraine, Romania, Bulgaria and Greece. However, as this air mass originates from Africa, dust will also be transported across the Mediterranean, which could reduce visibility and enhance the potential for fog formation.

Cover photo:  The amount of rain that fell in Bahía Blanca more than doubled the city’s previous record of 175mm, which was set in 1930. Photograph: Juan Sebastian Lobos/Reuters