Rob Sharpe, 27 Nov 2014, 7:50 PM UTC
How the Brisbane super-cell thunderstorm was so powerful
Brisbane was trashed by a destructive thunderstorm yesterday afternoon in a near-perfect set-up for a super-cell.
The giant super-cell originally sparked up in warm and moist air on the Gold Coast Hinterland. The storm was triggered by the arrival of a southeasterly change, bringing just 8mm to Murwillumbah soon after 1pm.
The small storm cell then joined forces with another, when it first became severe before crashing through Beaudesert with 45mm. This included a 12 degree temperature drop in under half an hour and rain rates as high as 11mm in 10 minutes.
The reason why the thunderstorm was so severe was because it had such a good structure. The storm was helped to rotate and become a super-cell by the surface northeasterly seabreeze meeting the southeasterly change. Further rotation was provided by southerly winds in the mid-levels and the westerly winds in the powerful jetstream aloft. This rotation in the atmosphere meant that the storm could grow in strength by sucking moist air from in front of itself, whilst being pushed along by the midlevel southerly steering winds, right into Brisbane's CBD.
By the time the storm had reached Brisbane it had become a monster. Brisbane's CBD was engulfed by rainfall as heavy as eight millimetres in three minutes, large hail and wind gusts in excess of 80km/h. However, the strongest winds were reserved for the western side of the thunderstorm.
Archerfield Airport saw wild downbursts of 141km/h that played with airplanes like toys, flipping and tossing them around.
After smashing greater Brisbane, this storm continued to move north, slowly weakening before decaying in the Wide Bay and Burnett district in the evening.
Today there will just be a few showers in the Southeast Coast district before a high pressure ridge leads to mostly sunny weather over the weekend.
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