Thunderstorms are occurring due to high temperatures | Video, Pictures

STRIKING TOO OFTEN: A severe thunderstorm brought heavy rainfall to the Central West on Monday. Photo: CHRIS SEABROOK 012819cstotm1a
STRIKING TOO OFTEN: A severe thunderstorm brought heavy rainfall to the Central West on Monday. Photo: CHRIS SEABROOK 012819cstotm1a

The recent thunderstorms that brought heavy rainfall have made residents wonder whether they are becoming frequent and more severe. 

Experts, however, are not convinced that the frequency of storms has increased despite anecdotal evidence.

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Data from Weatherzone showed the number of storm days at Sydney and Canberra airports has increased this year compared with the last year.

For instance, Weatherzone observed three storm days at Sydney airport between December 2017 and January 2018 compared with seven days between December 2018 and January 2019.

Similarly, the number of storm days went up from six days to 15 days at Canberra airport for the same period.

According to Weatherzone meteorologist Thomas Hough, it is not possible to say exactly how many thunderstorms occurred over the state in recent months. 

“There could have been more thunderstorms in areas [other than Sydney and Canberra airports] that are not witnessed,” Mr Hough said.

But he agreed that thunderstorms have generally been more severe due to warm season being near-neutral El Nino.

Experts say thunderstorms are more common during the summer months when solar energy is at its greatest.

Charles Sturt University Professor Kevin A Parton, who is studying temperature patterns in the Central West with his assistant Katherine Reed, says the number of high temperature days has increased on 20 years ago.

Professor Parton believes there could be a co-relation between the high temperature and thunderstorms.

“My data is for the Orange weather station, but I assume the trend will be similar for the other cities in the region,” he said.

“So far this summer we have had 26 days of above 30 degrees temperature. If you go back to the 1990s, the number averaged 13 days of above 30 degrees.”

The Bureau of Meteorology said NSW recorded its warmest January on record for mean, maximum and minimum temperatures.

“The north east of the state experienced one of the driest Januarys and Sydney had one of its warmest Januarys on record,” it said.

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BoM senior climatologist Dr Andrew Watkins said the heat through January was unprecedented.

"The main contributor to this heat was a persistent high pressure system in the Tasman Sea which was blocking any cold fronts and cooler air from impacting the south of the country,” Dr Watkins said.

"The warming trend which has seen Australian temperatures increase by more than one degree in the last 100 years also contributed to the unusually warm conditions."

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Dr Annika Dean, a senior researcher at the Climate Council, says analysis of the larger-scale environments conducive to severe thunderstorms in Australia indicates significant increases in the frequency of these environments in southern and eastern areas.

“Analysis suggests that the annual frequency of potential severe thunderstorm days is likely to rise by 14 per cent for Brisbane, 22 per cent for Melbourne, and 30 per cent for Sydney by the end of the century,” Dr Dean said.

Analysis suggests that the annual frequency of potential severe thunderstorm days is likely to rise by 14 per cent for Brisbane, 22 per cent for Melbourne, and 30 per cent for Sydney by the end of the century.

Dr Annika Dean

“Despite this, there is no consistent, long-term observational records in relation to trends in either the frequency or intensity of thunderstorms and hail.”

But Dr Dean said extreme weather events including tropical cyclones, extreme rainfall, thunderstorms and extra-tropical cyclones are now occurring in an atmosphere that is packing more energy and carrying more moisture than it did in the 1950s.