Storm-based polygon matching for NWS warnings #71

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opened 2026-07-18 05:31:33 +00:00 by claude-bot · 1 comment

claude-bot commented

2026-07-18 05:31:33 +00:00

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NWS warnings carry polygon geometry; WeatherBot matches on zones (affectedZones), which over-alert relative to the actual warned polygon — a hilltop location gets the county's flash-flood warning. The point-in-polygon machinery already exists in spc.py. Use alert geometry when present (fall back to zones), per-location opt-in. Probably missed because zone matching was the natural MVP and SPC polygon code came later. Effort M, value High — directly reduces false alarms, the main quality lever for an alerting tool.

Filed from the 2026-07-17 codebase audit (docs/.internal/report-2026-07-17.md), finding I-01.

NWS warnings carry polygon geometry; WeatherBot matches on zones (`affectedZones`), which over-alert relative to the actual warned polygon — a hilltop location gets the county's flash-flood warning. The point-in-polygon machinery already exists in `spc.py`. Use alert geometry when present (fall back to zones), per-location opt-in. Probably missed because zone matching was the natural MVP and SPC polygon code came later. Effort M, value High — directly reduces false alarms, the main quality lever for an alerting tool. --- _Filed from the 2026-07-17 codebase audit (`docs/.internal/report-2026-07-17.md`), finding I-01._

claude-bot added this to the v1.5.0 - Feature enhancements milestone

2026-07-18 05:31:33 +00:00

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type:feature

area:notifications

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2026-07-18 05:31:33 +00:00

claude-bot commented

2026-07-19 14:29:33 +00:00

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Closing as already implemented. The polygon-matching this issue asks for already exists and is active in the alert path — the audit pointed at the SPC point_in_geometry helper and missed that the NWS-alert path has its own equivalent.

In app/services/alert_identity.py:

point_in_alert_geometry(location, alert) (lines 53-61) does point-in-polygon against the alert's Polygon/MultiPolygon geometry, returning True when the alert carries no polygon.
location_matches_alert(location, alert) (lines 64-69) requires a zone/county-zone intersection and point_in_alert_geometry — i.e. it already "uses the alert geometry when present, falls back to zones" when NWS supplies no polygon. NWSAlert.geometry is parsed in nws.py (~line 340), and the CAP ATOM fallback path sets empty geometry so it degrades to zone-only.

So a location inside a warned zone but outside the storm-based warning polygon is already not alerted — the exact over-alarm this issue describes is already avoided. The one thing not built is making it a per-location toggle, but since polygon precision is the correct default for storm-based warnings (the polygon is the threat area) and mandatory precision matches current behavior, we've decided (2026-07-19) not to add an opt-out toggle for now. If a "never-miss / alert me for my whole county" mode is wanted later, it can be filed fresh with that framing.

No milestone impact beyond removing this from v1.5.0 scope.

Closing as **already implemented**. The polygon-matching this issue asks for already exists and is active in the alert path — the audit pointed at the SPC `point_in_geometry` helper and missed that the NWS-alert path has its own equivalent. In `app/services/alert_identity.py`: - `point_in_alert_geometry(location, alert)` (lines 53-61) does point-in-polygon against the alert's `Polygon`/`MultiPolygon` geometry, returning `True` when the alert carries no polygon. - `location_matches_alert(location, alert)` (lines 64-69) requires a zone/county-zone intersection **and** `point_in_alert_geometry` — i.e. it already "uses the alert geometry when present, falls back to zones" when NWS supplies no polygon. `NWSAlert.geometry` is parsed in `nws.py` (~line 340), and the CAP ATOM fallback path sets empty geometry so it degrades to zone-only. So a location inside a warned zone but outside the storm-based warning polygon is already **not** alerted — the exact over-alarm this issue describes is already avoided. The one thing not built is making it a per-location toggle, but since polygon precision is the correct default for storm-based warnings (the polygon *is* the threat area) and mandatory precision matches current behavior, we've decided (2026-07-19) not to add an opt-out toggle for now. If a "never-miss / alert me for my whole county" mode is wanted later, it can be filed fresh with that framing. No milestone impact beyond removing this from v1.5.0 scope.

claude-bot closed this issue

2026-07-19 14:29:34 +00:00

claude-bot referenced this issue

2026-07-19 16:39:52 +00:00

Add v1.5.0 changelog #117