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Spring'ing' between the seasons in WA

Lachlan Maher, Saturday September 8, 2018 - 18:41 EST

An extreme diurnal temperature range is expected in southern parts of Western Australia on Sunday, with temperatures forecast to jump more than 25 degrees by midday.

In Southern Cross, early morning temperatures are likely to drop down to a near freezing 2 degrees, before warming as the sun rises to a maximum of 29 degrees. While warm days and cool nights are a staple of the Australian desert, it is fairly unusual for such a large range to be present.

In this case, a mix of synoptic conditions have set the stage for rapid warming in the early morning. Overnight, three separate factors look to help the air temperatures stay down; weak winds and cool skies enable the ground to cool, while a pool of cold and relatively dry air over the region helps temperatures drop further. Temperatures look to drop close to 2 degrees, likely reaching it just before the first rays of light.

As the sun comes up however, this cooling will be quickly reversed as the ground starts to heat up. While this normally would not be enough to make it to 29 degrees, strong northerly component winds look to pick up, funneling warmer air down into the region.

While these conditions look to create such a high diurnal range, it is a fairly infrequent occurrence. The highest range recorded so far this year at Southern Cross was 25.7 degrees back in April. This was also the only range higher than 23 degrees recorded by the site this year.

The desert is one of the best places to have a high diurnal range, as clear skies at night and during the day are effective at ensuring both low minimums and high maximums. Even with deserts making up a large proportion of Australia, diurnal temperature ranges reaching 27 degrees or more are very unusual, with about only two dozen occurrences recorded so far this year, making tomorrow's warming a spectacular occurrence.

Although it might be an interesting occurrence to know about, it will heat up quickly enough to make it feel like an above average day. By 8:00am, one could expect temperatures to be at least in the low teens and within the next two hours (by 10:00am) temperatures will likely have risen to the low twenties. Unfortunately for those who still enjoy the cooler winter maximums, the warm temperatures will likely linger into the evening.

This looks to be a one-off event, with the maximum temperatures dropping over the next few days back to its average of about 22 degrees. While minimums should stay frosty, a lowered peak means the diurnal range should stay under 20 degrees in the near future.

- Weatherzone

© Weatherzone 2018

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