FA-71213 / Weather index computation / Member archive

K-index and Total Totals: severe threshold · case 03

TT = 50 does not raise the severe flag.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

K = (T850 - T500) + Td850 - (T700 - Td700); VT = T850 - T500; CT = Td850 - T500; TT = VT + CT. Thunderstorm potential from K: <20 none, <=25 isolated, <=30 widely scattered, <=35 scattered, else numerous. Severe flag "severe possible" when TT >= 50 else "weak". Return [K, TT, potential, flag].

Why this case matters

Convective outlooks use K and TT as quick stability screens.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
sounding 850 20/8 700 7/0 500 -11	`[32, 50, "scattered", "weak"]`	`[32, 50, "scattered", "severe possible"]`	Failed

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