November 2, 2024
Large hail impacted inner parts of eastern Brisbane and produced amazing supercell structure. Credit: Phillip Basil-Jones
Yesterday, a powerful supercell hailstorm swept through Brisbane, covering many suburbs in golf-ball-sized hail. This was yet another MSEC (Modified Southeast Change) setup—a storm pattern notorious for producing significant hail and, at times, destructive winds. In fact, the setup was quite similar to Brisbane November 27, 2014 hailstorm (with a near analogous path taken), but thankfully the winds in this storm were far lighter.
Storm Intensity Map showing the path of the severe storm that swept through Brisbane bringing large to giant hail. Source: Weatherwatch HailTracker
Why This Storm Was Different
Unlike the previous day, which saw multiple hailstorms, only one main storm moved through Brisbane. This was due to a strong atmospheric “cap,” which limited convection, making it hard for storms to develop off the ranges.
Explosive updrafts as the storm tracks towards Brisbane indicating the presence of a very significant thunderstorm.
By 1pm, a cluster of storms formed along the Border Ranges, with a few cells on the northwest edge intensifying. At the same time, the boundary of the modified southeast change pushed through, rapidly intensifying the storm.
A cluster of storms develops on the Border Ranges. It then interacts with the approaching SE change (evidenced by the discolouration in the light and dark blues) and adopts a more NNE path to track into Brisbane and produce significant hail. Source: MetCentre
For a slower version of this loop, click here.
What Is a Modified Southeast Change?
Modified Southeast Change days occur when a southeast change moves into a hot, dry airmass. This creates a brief period where the airmass takes on properties from both cooler, humid southeast winds and hot, dry northwest winds. The result is locally increased instability, with CAPE (Convective Available Potential Energy) values exceeding 2000-3000 j/kg. This instability is ideal for producing severe storms.
ACCESS C surface wind & Dew Point loop. This shows the moisture rushing into Southeast Queensland helping to fuel the strong instability and thunderstorm activity. Source: MetCentre
Modified Southeast Change & Seabreeze Interaction
The real "kicker" was the enhanced wind shear generated by the southeast change. When it mixed with the seabreeze, it created an east to northeast surface flow, adding significant “turning” in the atmosphere. Combined with 30-knot westerly winds in the mid-levels, this produced a bulk shear of 50 knots—more than ample for supercells.
ACCESS C sounding. Note that the atmosphere has been artificially warmed due to the model forecasting convection. This means instability was likely close to ~2500-3000J/kg. Further, we note the strong low level easterly winds in the bottom 1km of the atmosphere (20-25 knots), and then the W/SW winds at 30 knots between 700mb and 500mb making conditions ideal for supercells. Source: MetCentre
Supercell approaching Archerfield.
At one point, a hook echo (a radar signature often seen in only high-end severe storms and sometimes the precursor to a tornado) appeared southwest of Brisbane, and the storm maintained a classic "inflow notch" signature for much of its lifespan, including as it moved over Brisbane.
3D radar view of the hook echo south of Brisbane at 2:45pm. Source: MetCentre
Note the "hole" in the middle of the 3D radar scan. This occurs due to the updraft wrapping precipitation around itself from the rotation in the storm. Source: MetCentre
Why Did it Hail When The Radar Showed No Precipitation?
The storm briefly weakened as the cooler outflow from the Rear Flank Downdraft (RFD) pushed ahead of it, temporarily cutting off the warm inflow. However, the storm’s inflow quickly fought back (thanks to the deep, gusty, easterly winds in the lower atmosphere), “bringing the storm back to life” and intensifying it across central to eastern Brisbane, where it delivered extensive large to golf-ball-sized hail.
For many, the hail came as a surprise, falling even before rain appeared on radar. This phenomenon, known as “clear-air hail,” can occur in strong storms when hail wraps around or falls ahead of the updraft due to intense winds. Because this hail occurs in the storm’s overhang, it can sometimes be missed by radar, especially if hailstones are sporadic.
In some cases, the updraft ahead of the storm can stop rain from falling to the ground as the rain is too light to fall through the updraft. This is known as a "Weak Echo Region." However, as hail is heavier than rain, the hail can fall down through the updraft and reach the ground. So even when there is no precipitation showing on the ground, sporadic hailstorms can occur giving the impression that it's "hailing out of thin air." Source: MetCentre
How Can I Access Hail Alerts?
Currently, Weatherwatch, (in partnership with the Early Warning Network), collaborates with many insurers across Australia to deliver geo-targeted, timely hail alerts, helping you avoid large hail. If you have insurance, there’s a good chance your insurer already provides Weatherwatch Hail Alerts—but you may need to opt-in. Check with your insurer to confirm. If they don’t provide this service, feel free to contact us, and we’ll work with your insurer to explore bringing Hail Alerts to you.
For those without access to Hail Alerts through their insurer, Weatherwatch also provides hail information to the public via the MetCentre® radar. Although this platform isn’t as detailed as our commercial HailTracker® service—which gives highly specific hail size information down to street level—it still provides a valuable overview of which storms to avoid, especially for large hail and severe weather impacts.
Whether you access our hail services directly or through one of our authorised partners and resellers, Weatherwatch is committed to being Australia’s leading source for hail and severe weather information, alerts, and forecasts—keeping you safe and your assets protected.
Weatherwatch's HailTracker® services provides live and historical hail information, forecasts and alerts across Australia.
Did a Tornado Occur in Brisbane?
The answer is an unequivocal yes! A tornado did occur in Brisbane, as evidenced by extensive video footage. However, the key question is—what type of tornado was this? Was it connected to the mesocyclone (rotating updraft), a gustnado, or a landspout tornado? These distinctions are common debates in the meteorological world, and even top experts can disagree.
While a mesocyclone was present within the storm, the mesocyclone rotated clockwise - but this tornado rotated anti-clockwise (which also matches up to some of the anti-cyclonic rotation observed within the base of the storm). This suggests a disconnect between the mesocyclone and the tornado which leans towards possibly a landspout type tornado or gustnado. The lack of a condensation funnel also is surprising as most tornadoes associated directly with the mesocyclone have a visible condensation funnel. As such, the most likely classification would be a gustnado or type of landspout (rather than mesocyclonic).
3D radar view the storm tracking across Brisbane. An inflow notch is still present over the inner parts of east Brisbane. Source: MetCentre
Regardless of the definition, this doesn't take away how impressive and frightening it looked coming across the Brisbane River. But a key point is that if this was, in fact, a classic tornado (connected to the mesocyclone), it was exceptionally weak. It’s crucial to keep in mind that most tornadoes are far stronger and shouldn’t be represented by this event. Many tornadoes are extremely dangerous and deadly, capable of significant destruction.
The rounded updraft shows the rotation of the storm as it approaches Logan. Source: MetCentre
A Few Quieter Days - But Storms Could Return Next Week
GFS Lifted Indices suggest more instability likely on Tuesday and Wednesday of next week but currently storms are less likely around the Brisbane region and more likely further west and south. Source: MetCentre
Thankfully, today will be much quieter for storms in Brisbane with just some weaker storms possible as the severe storm potential contracts northwest. However, another trough is expected to approach next week, potentially bringing more storm activity which we'll monitor for further severe potential.
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