FA-71281 / Weather index computation / Open access

Pasquill-Gifford stability class: wind class boundary · case 01

A 5.0 m/s wind is assigned the lighter-wind class.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

The 3-5 m/s class includes 5.0.

THE FAILURE

The 3-5 m/s class includes 5.0.

Unsuccessful approach: Using 4 m/s moves 4.x winds into the next class.

Case contract

Wind class: <2, <3, <5, <6, >=6 (index 0..4). 8 octas returns "D" day or night. Day: tables by insolation strong [A,A-B,B,C,C], moderate [A-B,B,B-C,C-D,D], slight [B,C,C,D,D]; unknown insolation returns None. Night: >=4 octas [E,E,D,D,D], <=3 octas [F,F,E,D,D].

Why this case matters

Air-dispersion screening models choose plume spread from the stability class.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(wind_ms, is_day, insolation, octas):
    day = {"strong": ["A", "A-B", "B", "C", "C"],
           "moderate": ["A-B", "B", "B-C", "C-D", "D"],
           "slight": ["B", "C", "C", "D", "D"]}
    thin = ["E", "E", "D", "D", "D"]
    clear = ["F", "F", "E", "D", "D"]
    if octas == 8:
        return "D"
    i = 0 if wind_ms < 2 else 1 if wind_ms < 3 else 2 if wind_ms <= 5 else 3 if wind_ms < 6 else 4
    if is_day:
        if insolation not in day:
            return None
        return day[insolation][i]
    return (thin if octas >= 4 else clear)[i]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['wind 1.0 day strong 2 octas', [1.0, True, 'strong', 2], 'A'], ['wind 1.0 day moderate 5 octas', [1.0, True, 'moderate', 5], 'A-B'], ['wind 1.0 day slight 8 octas', [1.0, True, 'slight', 8], 'D'], ['wind 1.0 day slight 3 octas', [1.0, True, 'slight', 3], 'B'], ['wind 1.0 night None 3 octas', [1.0, False, None, 3], 'F'], ['wind 1.0 night None 4 octas', [1.0, False, None, 4], 'E'], ['wind 4.9 day moderate 5 octas', [4.9, True, 'moderate', 5], 'B-C'], ['wind 5.0 day strong 2 octas', [5.0, True, 'strong', 2], 'C']], [['wind 1.0 day overcast-ish 4 octas', [1.0, True, 'overcast-ish', 4], None], ['wind 1.0 night None 7 octas', [1.0, False, None, 7], 'E'], ['wind 1.0 day strong 7 octas', [1.0, True, 'strong', 7], 'A'], ['wind 1.9 day strong 2 octas', [1.9, True, 'strong', 2], 'A'], ['wind 1.9 day moderate 5 octas', [1.9, True, 'moderate', 5], 'A-B'], ['wind 1.9 day slight 8 octas', [1.9, True, 'slight', 8], 'D'], ['wind 4.9 day moderate 5 octas', [4.9, True, 'moderate', 5], 'B-C'], ['wind 5.0 night None 3 octas', [5.0, False, None, 3], 'D']], [['wind 1.9 night None 3 octas', [1.9, False, None, 3], 'F'], ['wind 1.9 night None 4 octas', [1.9, False, None, 4], 'E'], ['wind 1.9 night None 8 octas', [1.9, False, None, 8], 'D'], ['wind 1.9 day overcast-ish 4 octas', [1.9, True, 'overcast-ish', 4], None], ['wind 1.9 night None 7 octas', [1.9, False, None, 7], 'E'], ['wind 1.9 day strong 7 octas', [1.9, True, 'strong', 7], 'A'], ['wind 4.9 day moderate 5 octas', [4.9, True, 'moderate', 5], 'B-C'], ['wind 5.0 day moderate 5 octas', [5.0, True, 'moderate', 5], 'C-D']], [['wind 2.0 day moderate 5 octas', [2.0, True, 'moderate', 5], 'B'], ['wind 2.0 day slight 8 octas', [2.0, True, 'slight', 8], 'D'], ['wind 2.0 day slight 3 octas', [2.0, True, 'slight', 3], 'C'], ['wind 2.0 night None 3 octas', [2.0, False, None, 3], 'F'], ['wind 2.0 night None 4 octas', [2.0, False, None, 4], 'E'], ['wind 2.0 night None 8 octas', [2.0, False, None, 8], 'D'], ['wind 4.9 day moderate 5 octas', [4.9, True, 'moderate', 5], 'B-C'], ['wind 5.0 day strong 7 octas', [5.0, True, 'strong', 7], 'C']], [['wind 2.0 night None 7 octas', [2.0, False, None, 7], 'E'], ['wind 2.0 day strong 7 octas', [2.0, True, 'strong', 7], 'A-B'], ['wind 2.9 day strong 2 octas', [2.9, True, 'strong', 2], 'A-B'], ['wind 2.9 day moderate 5 octas', [2.9, True, 'moderate', 5], 'B'], ['wind 2.9 day slight 8 octas', [2.9, True, 'slight', 8], 'D'], ['wind 2.9 day slight 3 octas', [2.9, True, 'slight', 3], 'C'], ['wind 4.9 day moderate 5 octas', [4.9, True, 'moderate', 5], 'B-C'], ['wind 5.0 day slight 3 octas', [5.0, True, 'slight', 3], 'D']]]
for label, args, expected in fixtures[N - 1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
wind 1.0 day strong 2 octas	`A`	`A`	Passed
wind 1.0 day moderate 5 octas	`A-B`	`A-B`	Passed
wind 1.0 day slight 8 octas	`D`	`D`	Passed
wind 1.0 day slight 3 octas	`B`	`B`	Passed
wind 1.0 night None 3 octas	`F`	`F`	Passed
wind 1.0 night None 4 octas	`E`	`E`	Passed
wind 4.9 day moderate 5 octas	`B-C`	`B-C`	Passed
wind 5.0 day strong 2 octas	`B`	`C`	Failed

SHA-256 / 1219bc852b95d89f77acdb7a7b81bf5dbab75cd77f1d10bb9ad0c157f0562fc1

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(wind_ms, is_day, insolation, octas):
    day = {"strong": ["A", "A-B", "B", "C", "C"],
           "moderate": ["A-B", "B", "B-C", "C-D", "D"],
           "slight": ["B", "C", "C", "D", "D"]}
    thin = ["E", "E", "D", "D", "D"]
    clear = ["F", "F", "E", "D", "D"]
    if octas == 8:
        return "D"
    i = 0 if wind_ms < 2 else 1 if wind_ms < 3 else 2 if wind_ms < 4 else 3 if wind_ms < 6 else 4
    if is_day:
        if insolation not in day:
            return None
        return day[insolation][i]
    return (thin if octas >= 4 else clear)[i]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
fixtures = [[['wind 1.0 day strong 2 octas', [1.0, True, 'strong', 2], 'A'], ['wind 1.0 day moderate 5 octas', [1.0, True, 'moderate', 5], 'A-B'], ['wind 1.0 day slight 8 octas', [1.0, True, 'slight', 8], 'D'], ['wind 1.0 day slight 3 octas', [1.0, True, 'slight', 3], 'B'], ['wind 1.0 night None 3 octas', [1.0, False, None, 3], 'F'], ['wind 1.0 night None 4 octas', [1.0, False, None, 4], 'E'], ['wind 4.9 day moderate 5 octas', [4.9, True, 'moderate', 5], 'B-C'], ['wind 5.0 day strong 2 octas', [5.0, True, 'strong', 2], 'C']], [['wind 1.0 day overcast-ish 4 octas', [1.0, True, 'overcast-ish', 4], None], ['wind 1.0 night None 7 octas', [1.0, False, None, 7], 'E'], ['wind 1.0 day strong 7 octas', [1.0, True, 'strong', 7], 'A'], ['wind 1.9 day strong 2 octas', [1.9, True, 'strong', 2], 'A'], ['wind 1.9 day moderate 5 octas', [1.9, True, 'moderate', 5], 'A-B'], ['wind 1.9 day slight 8 octas', [1.9, True, 'slight', 8], 'D'], ['wind 4.9 day moderate 5 octas', [4.9, True, 'moderate', 5], 'B-C'], ['wind 5.0 night None 3 octas', [5.0, False, None, 3], 'D']], [['wind 1.9 night None 3 octas', [1.9, False, None, 3], 'F'], ['wind 1.9 night None 4 octas', [1.9, False, None, 4], 'E'], ['wind 1.9 night None 8 octas', [1.9, False, None, 8], 'D'], ['wind 1.9 day overcast-ish 4 octas', [1.9, True, 'overcast-ish', 4], None], ['wind 1.9 night None 7 octas', [1.9, False, None, 7], 'E'], ['wind 1.9 day strong 7 octas', [1.9, True, 'strong', 7], 'A'], ['wind 4.9 day moderate 5 octas', [4.9, True, 'moderate', 5], 'B-C'], ['wind 5.0 day moderate 5 octas', [5.0, True, 'moderate', 5], 'C-D']], [['wind 2.0 day moderate 5 octas', [2.0, True, 'moderate', 5], 'B'], ['wind 2.0 day slight 8 octas', [2.0, True, 'slight', 8], 'D'], ['wind 2.0 day slight 3 octas', [2.0, True, 'slight', 3], 'C'], ['wind 2.0 night None 3 octas', [2.0, False, None, 3], 'F'], ['wind 2.0 night None 4 octas', [2.0, False, None, 4], 'E'], ['wind 2.0 night None 8 octas', [2.0, False, None, 8], 'D'], ['wind 4.9 day moderate 5 octas', [4.9, True, 'moderate', 5], 'B-C'], ['wind 5.0 day strong 7 octas', [5.0, True, 'strong', 7], 'C']], [['wind 2.0 night None 7 octas', [2.0, False, None, 7], 'E'], ['wind 2.0 day strong 7 octas', [2.0, True, 'strong', 7], 'A-B'], ['wind 2.9 day strong 2 octas', [2.9, True, 'strong', 2], 'A-B'], ['wind 2.9 day moderate 5 octas', [2.9, True, 'moderate', 5], 'B'], ['wind 2.9 day slight 8 octas', [2.9, True, 'slight', 8], 'D'], ['wind 2.9 day slight 3 octas', [2.9, True, 'slight', 3], 'C'], ['wind 4.9 day moderate 5 octas', [4.9, True, 'moderate', 5], 'B-C'], ['wind 5.0 day slight 3 octas', [5.0, True, 'slight', 3], 'D']]]
for label, args, expected in fixtures[N - 1]:
    check(label, solve(*args), expected)
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
wind 1.0 day strong 2 octas	`A`	`A`	Passed
wind 1.0 day moderate 5 octas	`A-B`	`A-B`	Passed
wind 1.0 day slight 8 octas	`D`	`D`	Passed
wind 1.0 day slight 3 octas	`B`	`B`	Passed
wind 1.0 night None 3 octas	`F`	`F`	Passed
wind 1.0 night None 4 octas	`E`	`E`	Passed
wind 4.9 day moderate 5 octas	`C-D`	`B-C`	Failed
wind 5.0 day strong 2 octas	`C`	`C`	Passed

SHA-256 / aeef621693d4d5434a28edbe98de39794e7033a157be73da9f6f7a97a7622280

HELD IN THE MEMBER ARCHIVE

The verified repair and its recorded checks are member-only.

This mechanism has 8 recorded checks per implementation. The open-access tier publishes the failure and the unsuccessful fix; the repaired source that passes every check, and the observations that prove it, are available to members.

Every case sharing this mechanism uses the same contract and the same repair, so this one record is held back for all of them.

Member access is invitation-based. Sign in with your invited account to inspect the repair.

Verification & scope

Stipulated deterministic teaching model of an operational weather index; coefficients and thresholds are fixed by the contract and no claim of standards conformance is made. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:48:28.253894+00:00.

Case digest / ac3ecc1e5e4727c70fdaec8b7a6780974f19b082f0b9b76eb780d41e324bbfd1