Ever blazing: Met Services expects more heatwaves

Mbongeni Mguni | Monday March 18, 2024 06:00

The very definition of heatwave demonstrates the gravity of the situation Batswana have faced every single month since summer started in October.

“For you to say an area is under a heatwave, you have to look at the average temperatures for at least the past 30 years, in that area.

“So, if the temperature goes five degrees or above that average, over three consecutive days, then you are experiencing a heatwave,” says Charles Molongwane, principal meteorologist at the Department of Meteorological Services.

That definition means most parts of the country have seen temperatures rise above the 30-year average, for more than three days at a time, on numerous occasions since October. For most, the entire summer season has felt like a single endless heatwave, broken very infrequently by scattered and inconsequential rains.

And while the announcements of heatwaves by the Met Services have become predictable, even commonplace, they remain dread-inducing. They mean yet another period of stifling hot temperatures, reduced productivity, discomfort to children and the elderly, higher electricity usage, and those sweaty nights spent twitching about for a cooler spot on the bed.

Molongwane, a veteran weatherman, explains the mechanism that leads to heatwaves. The heat is not just part of summer but has been worsened this year by the much-loathed El Niño phenomenon which in this part of the world is associated with dry seasons, drought and heat.

“In Botswana and Southern Africa, you will see a high-pressure system known as an anticyclone, at perhaps about 12 kilometres above the surface and if it stays stationary for three days, it suppresses the airflow because that air should escape into the atmosphere.

“It acts like a blanket.”

Being covered with a blanket is the perfect analogy for the situation most parts of the country have been in this summer. The mornings start slightly tolerable until about 10am, then the mercury starts shooting up before the inevitable scattered clouds come late afternoon to “blanket” the heat being emitted by the surface, resulting in sweltering nights.

Molongwane explains that the El Niño phenomenon means a drought year, which in turn is characterised by lower rainfall amounts, which contribute to higher temperatures.

El Niño, the climate phenomenon hated and feared in equal parts in Botswana and the region, has reared its ugly head this season, at an intensity last seen since the mayhem it caused in 2015–2016.

In the 2015–2016 summer, El Niño dried Gaborone Dam up for the first time in its history and triggered a water crisis in the capital, which forced residents to spend every waking moment scurrying about looking for the scarce running taps in neighbours’ homes. That season, the country was blighted by a series of heatwaves, each one longer and more ferocious than the other, while temperatures reached historic highs of up to 45º Celsius in some parts of the country.

“If you don’t have rain and it is dry all the time, it means it’s just the rays from the sun reaching down,” Molongwane says.

“The temperatures shoot up.

“At least if there was rain it would protect us from this heat.” The principal meteorologist also talks about a trend called climate variability where rainfall amounts and temperatures are deviating from the patterns and averages observed historically.

“It’s not all places in the country that are experiencing these heatwaves.

“We have seen that the northern parts of the country which people think have the highest temperatures like Maun and Kasane, are actually lower than the ones in the South.

“The weather patterns are changing.

“Ever since October, which was the start of summer, not a single month has passed without most parts of the country experiencing excessive temperatures and we are still expecting that in March some parts of the country will continue to experience that.” The principal meteorologist said studies were showing that El Niño was transiting to a neutral phase in the next few months, which could potentially ease the temperatures expected when summer returns towards the end of the year.

In the meantime, Batswana have to adjust to the “new normal,” he says.

“My advice is just for people to follow our weather reports.

“Every time you get up and wake your children, first check the weather report.

“Also, avoid planning your activities or work in the afternoon because the temperatures peak around 3pm.

“It’s the new normal due to climate variability and global warming.”