So I thought I would post my observations for Saturday. I started to break down the forecast soundings on Monday. I was looking at the possibility on Sunday after the storm hit. Saturday was standing out like a sore thumb on the GFS and really grabbed my attention.
Technical Breakdown
Locations
Brisbane (Lat -27.4, Lon 153.1)
CAPE: 2495 J/kg — strong instability.
CIN: 18 J/kg — quite weak, so not much suppression.
Lifted Index (LI): -8.8 °C — very unstable.
TT Index: 56.5 — firmly in the severe range.
LCL: 890 mb (≈ 1 km) — relatively low, supportive of surface-based storms.
Shear: 5 km HEL = -24; 3 km HEL = -6 → modest directional shear, not explosive but enough for organised updrafts.
PW: 43 mm — deep moisture, suggesting potential for heavy rainfall cores.
➜ This is a primed environment for strong updrafts and large hail, though upper support will dictate coverage.
Dalby (Lat -27.2, Lon 151.2)
CAPE: 1685 J/kg — decent inland energy.
CIN: 21 J/kg — slightly stronger cap than Brisbane, but not overly restrictive.
LCL: 762 mb — quite low, good surface moisture recovery.
LI: -7.5 °C — solid instability.
TT: 60 — extremely high (very rare to see that value without severe outcomes).
Shear: 5 km HEL = -44; 3 km HEL = -11 → better veering with height than Brisbane.
PW: 36 mm — a bit drier than coastal areas, but enough for big convection.
➜ This sounding looks like classic “explosive inland storms moving east” territory — especially if capping erodes late afternoon.
Moree (Lat -29.3, Lon 150)
CAPE: 933 J/kg — lower, but still supportive.
CIN: 22 J/kg — moderate cap.
LCL: 720 mb — slightly higher base, drier boundary layer.
TT: 53.8 — moderate instability.
Shear: 5 km HEL = -27 — modest shear, supportive of multicells rather than strong supercells.
PW: 31 mm — moisture notably lower.
➜ This profile suggests initiation may start here but peak intensity lies eastward (toward Dalby/Brisbane corridor).
Key Takeaways
Trend:
Each run continues to slightly improve parameters — CAPE and low-level moisture have both nudged up.
Capping remains manageable, not overly suppressive.
Shear is moderate but sufficient for structured storms and possibly severe multicells or marginal supercells.
Concern:
The combination of high CAPE + improving dewpoints + TT > 56 is a volatile mix.
If surface heating reaches forecast levels and low-level moisture continues to deepen Friday, Saturday’s environment could support very large hail, damaging winds, and intense rainfall.
(Monday’s simplified breakdown.
The GFS is showing a setup for possible severe thunderstorms on Saturday. The model puts a lot of energy into the atmosphere (so storms could be strong), and the profile is favourable for large hail and damaging winds — however, low-level moisture is a little weak in some inland spots. In short: the ingredients are there, but timing and how much humidity arrives will decide whether it becomes widespread or only a few isolated severe storms.
