November 5, 2024
Supercell approaches areas to the east of Boonah with strong outflow. Source: Weatherwatch Team.
Given the forecast issued yesterday, it was no surprise to see two supercells track across parts of northeastern NSW and southeastern Queensland today, once again delivering giant hail over 5cm in diameter across the region.
Giant hail near the NSW/QLD border. Credit: David Ellem.
3D radar scan at the time of giant hail, indicating 7cm hail within the storm. Note the BWER (Bounded Weak Echo Region) in the RHI scan. Source: MetCentre.
Seabreeze Played a Key Role in Storm Intensity
Thankfully, unlike last week, the largest hail fell in more rural areas, but the storm’s impact was certainly felt. The seabreeze once again played a critical role in intensifying the storm, as gusty northeast winds added the final element of wind shear required for supercell formation. Supercells thrive when winds come from opposing directions, and in this case, the seabreeze tilted the northwest winds to the northeast in the lower atmosphere. Combined with southwest winds in the upper atmosphere, this provided a full 180 degrees of turning, with bulk shear exceeding 50 knots.
Modified C3 sounding with observations showing excellent wind shear and strong instability. Source: MetCentre.
Storm Track and Hail Reports
The first supercell produced 5-6cm hail near the NSW/QLD border, but additional storm development on the western edge saw it redevelop westward, eventually passing through areas near Boonah and extending into southern Brisbane.
Hail was still reported in southern Brisbane, with reports of 1-2cm hail in Acacia Ridge. Fortunately, it was much smaller in size as the storm had weakened due to a strong “cap,” a layer in the atmosphere that limited instability, gradually “choking” the storm as it pushed further into the seabreeze.
3D radar scans can provide an excellent indication as to where the updraft is developing. In this case, the updraft was developing on the western flank, showing likely westward intensification. Source: MetCentre.
3D radar as the storm became mature, once again indicating giant hail with the presenced of a Bounded Weak Echo Region on the RHI scan. Source: MetCentre.
Photogenic storm emerges from the border near Boonah. Source: Weatherwatch Team
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