26. Daily precipitation forecast¶

Daily WeatherNext 2 ensemble rainfall statistics with a nominal 14-day horizon. The existing API identifier remains stable. The layer serves 24 weather fields, plus 6 diagnostic fields marked being removed below; those are scheduled for removal in kartoza/tomorrownow_gap#1718. Do not build new integrations on them.

26.1 precipitation_blend_forecast¶

Catalogue label: Precipitation Blend Forecast / Daily / 14-day.

Catalogue grid resolution: 27.8km. Check response coordinates for the actual grid.

API attribute	Name / meaning	Output unit	Ensemble field
blend_p_occurrence	Fraction (0-1) of ensemble members with daily precipitation >= 0.5 mm.	mm/mm	No
blend_p_heavy	Fraction (0-1) of ensemble members with daily precipitation >= 20 mm.	mm/mm	No
blend_mean	Ensemble mean of daily precipitation, in mm.	mm	No
blend_std	Ensemble standard deviation of daily precipitation, in mm.	mm	No
blend_q10	10th percentile of daily precipitation across ensemble members, in mm.	mm	No
blend_q25	25th percentile of daily precipitation across ensemble members, in mm.	mm	No
blend_median	50th percentile of daily precipitation across ensemble members, in mm.	mm	No
blend_q75	75th percentile of daily precipitation across ensemble members, in mm.	mm	No
blend_q90	90th percentile of daily precipitation across ensemble members, in mm.	mm	No
blend_iqr	Difference between the 75th and 25th percentiles of daily precipitation, in mm.	mm	No
blend_p_gt_1mm	Percentage (0-100) of ensemble members with daily precipitation >= 1 mm.	%	No
blend_p_gt_5mm	Percentage (0-100) of ensemble members with daily precipitation >= 5 mm.	%	No
blend_p_gt_10mm	Percentage (0-100) of ensemble members with daily precipitation >= 10 mm.	%	No
blend_p_gt_20mm	Percentage (0-100) of ensemble members with daily precipitation >= 20 mm.	%	No
blend_p_gt_50mm	Percentage (0-100) of ensemble members with daily precipitation >= 50 mm.	%	No
blend_w_probability	Fraction (0-1) of members with daily precipitation >= 0.5 mm; unavailable when fewer than 10 complete member-days are counted.	mm/mm	No
blend_w_p_heavy	Fraction (0-1) of members with daily precipitation >= 20 mm; unavailable when fewer than 10 complete member-days are counted.	mm/mm	No
blend_event	1 when rainfall event probability is >= 0.25, otherwise 0. Check primary for unavailable rainfall.	code	No
blend_heavy	1 when heavy rainfall event probability is >= 0.30, otherwise 0. Check primary for unavailable rainfall.	code	No
blend_consensus_mm	Alias of blend_q75: daily precipitation 75th percentile, in mm. The default precipitation mapping also uses Q75; primary is the separately gated amount.	mm	No
blend_scenario	0=no data, 1=dry, 2=marginal, 3=rain, 4=heavy, classified from ensemble occurrence and heavy rainfall probabilities.	code	No
blend_confidence	Occurrence-probability decisiveness: 0=low, 1=medium, 2=high. 0 also denotes unavailable data (blend_scenario=0). This is not a forecast skill score.	code	No
precipitation	Precipitation	mm	No
primary	Daily Q75 when the rainfall event flag is 1, zero for a valid non-event, and unavailable when fewer than 10 complete member-days are counted.	mm	No
blend_model_scenario	Active model scenario used in the blend (being removed)	code	No
blend_n_models	Number of models contributing to the blend (being removed)	code	No
blend_w_occ_gc	GenCast model weight for precipitation occurrence (being removed)	mm/mm	No
blend_w_amt_gc	GenCast model weight for precipitation amount (being removed)	mm/mm	No
blend_w_amt_heavy_gc	GenCast model weight for heavy precipitation amount (being removed)	mm/mm	No
blend_w_heavy_gc	GenCast model weight for heavy precipitation probability (being removed)	mm/mm	No

26.2 Choosing a rainfall field¶

• blend_q75 and blend_consensus_mm both return daily Q75. The default precipitation mapping also uses Q75, but that mapping is configurable.
• primary returns daily Q75 when occurrence probability reaches 0.25, zero for a valid non-event, and unavailable when the member-availability gate fails.
• blend_p_occurrence and blend_p_heavy are fractions from 0 to 1. blend_p_gt_* fields are percentages from 0 to 100 and use at or above the named threshold.
• blend_confidence describes ensemble decisiveness, not measured forecast skill. Zero can mean low decisiveness or unavailable data; check blend_scenario.

The probability metadata may retain mm/mm as the unit for fractions. Use the documented 0–1 scale. Missing or incomplete member/time coverage requires care: do not infer a dry day solely from a zero percentile or probability. Check availability and use the returned scenario and gated amount together.

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