FA-71038 / Weather index computation / Member archive

Keetch-Byram style drought index: wet spell reset · case 03

After the first storm of the season, later showers are never intercepted.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

State Q in hundredths of an inch (0..800). Each day [tmax_F, rain_in]: rain days extend the current wet spell; the first 0.20 in of each spell is intercepted and only newly exceeding rain reduces Q by 100*net (floor 0). A dry day ends the spell. If tmax > 50, Q increases by (800-Q)*(0.968exp(0.0486T)-8.30)*0.001/(1+10.88exp(-0.0441*annual_in)), capped at 800. Return daily Q rounded to integers.

Why this case matters

Wildfire danger ratings and burn bans use the daily drought index.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
station 1	`[161, 166, 151, 32, 33, 30, 1]`	`[161, 166, 151, 32, 33, 45, 1]`	Failed

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