Contour lines of the (log)normal density function g(ln ${}_{\mathit{C}}{}^{}{\mathit{d}}_{\mathit{n}}^{\mathit{i}}$|ln Dⁱ, ln α, σ), equation (13): median (black solid line) and ±2σ intervals (dotted lines); intensities Dⁱ and ${}_{\mathit{C}}{}^{}{\mathit{d}}_{\mathit{n}}^{\mathit{i}}$ from Table 5 (1989–2015): Alibag (black, ABG) and the four standard Dst observatories (grey, open circles), Hermanus (HER), Kakioka (KAK), Honolulu (HON), San Juan (SJG). The model enables estimation of an exceedance probability G(ln ${}_{\mathit{C}}{}^{}{\mathit{d}}_{\mathit{n}}^{\mathit{i}}$|ln Dⁱ, ln α, σ), equation (14), for a local-noon sector (09:00 to 14:59) intensity ln ${}_{\mathit{C}}{}^{}{\mathit{d}}_{\mathit{n}}^{\mathit{i}}$, equation (12) from a single low-latitude observatory, where data have been sparsely sampled as done at Colaba during the Carrington storm, given an hourly average storm intensity Dⁱ, equation (5). G estimated with (blue) and without (orange) the extreme disturbance value at 06:20 UT.