Warning catalog (W1–W10)

nwp-compose validate, generate, and run collect a set of numbered warnings. Most are advisory (printed in yellow on stderr, the run proceeds). The WRF physics codes W-7 through W-10 are different: a configuration that trips them is blocked unless you explicitly acknowledge it, because it will produce a forecast that crashes or is physically meaningless.

Why some warnings block

The recurring scientific complaint this project takes seriously is “the tool warned but ran anyway, and I lost a six-hour job.” A CFL-violating time step is not a style nit — it is a guaranteed runtime failure. So the unphysical codes hard-block. To run one anyway (you know something the validator doesn’t), set acknowledge_unphysical: true at the workflow root; the acknowledgement is stamped into manifest.json for the record.

Cadence & resourcing (advisory)

Code	Triggers when	Fix
W1	cycling.lbc_interval_default is not one of {1, 3, 6} hours	Use a standard boundary cadence; non-standard intervals are rarely what you want.
W2	forecast_hours_default is not a whole multiple of lbc_interval_default	Adjust one so the last boundary update lands at or before the forecast end.
W3	lbc_interval_default == 1 and a data_ingest uses data_source: gfs	GFS is not published hourly for boundaries; use a 3- or 6-hour interval, or RAP.
W4	Peak post-processing rank occupancy exceeds the node estimate (mpassit_nprocs × max_active > tasks_per_node × nodes)	Lower mpassit concurrency (max active) or raise the node estimate (globals.estimated_node_count).

Physics & stability

Code	Path	Triggers when	Fix	Blocks?
W5	MPAS	mpas_run.dt > dx_km × 6.0 (CFL guideline)	Reduce the time step or coarsen the mesh.	advisory
W-7	WRF	cu_physics != 0 and dx_km < 4 (cumulus scheme at convection-permitting scale)	Turn off the cumulus parameterization (cu_physics: 0) below ~4 km.	blocks
W-8	WRF	time_step > 6 × dx_km (CFL analog)	Reduce time_step.	blocks
W-9	WRF	w_damping != 1 and dx_km < 4	Enable w_damping: 1 at CP scale to avoid vertical-velocity blowups.	blocks
W-10	WRF	(bl_pbl_physics, sf_sfclay_physics) is not a legal pairing	Choose a PBL/surface-layer pair from the compatible set.	blocks

W6 was retired

W6 (a housekeeping keep_upp check) was removed in Phase 2.6. The gap in numbering is intentional; codes are never reused.

Plugin prerequisites

Code	Triggers when	Fix
W-REQ-EXE	A component’s declared requires.executables / must_have entry is not on PATH	module load it, or install it into your environment. nwp-compose doctor checks these too.
W-REQ-ENV	A component’s declared requires.env_vars entry is unset	Export the variable before running.

Suppressing warnings

nwp-compose validate forecast.yaml --no-warnings   # hide advisory W-codes (does NOT bypass blocks)

--no-warnings only silences advisory output. It does not disable the W-7..W-10 hard block — that requires acknowledge_unphysical: true in the YAML, which is the auditable, deliberate escape hatch.

Want an explanation at the point of failure?

A future addition (nwp-compose explain W-8) will print this catalog entry inline. Until then, the warning text names the parameter and value that tripped it, and this page is the lookup.

Next

• Tutorial: your first forecast — W2 in context.
• The last mile — how validate/run apply the block.