Radar DA case study — Macaé INEA, 16 December 2024 Nocturnal convective line · DA 14–17 Z · forecast 17 Z → 14 Z+1 · draft for WRF User Meeting 2026

CONVECT / Project Sharktopus · run 2026-06-11 · cross-case synthesis

The event. A strong nocturnal convective line on 16 December 2024, most active 18–20 Z near Arraial do Cabo (peak reflectivity 64 dBZ). The DA window ran 14–17 Z — 4 hourly 3D-Var cycles assimilating INEA Macaé radial velocity and reflectivity. The free forecast ran from 17 Z for 21 h (to 14 Z+1) on d01 → d02 → d03 via ndown.

Both branches share the same GFS lineage (fair same-lineage baseline). The picker placed d03 almost directly over the radar (centre −22.40°, −41.75°), climo <z> +0.64σ, with 16 gauge stations in the box.

d03 POD heatmap — DA recovers missed event — d03 POD heatmap: control = 0 hits; radar DA recovers the event (POD 0→0.385 at ≥1 mm/h).

case date

2024-12-16

nocturnal event, 18–20 Z; Arraial do Cabo, 64 dBZ

climo <z>

+0.64σ

favourable — DJF climatology

DA cycles

14, 15, 16, 17 Z — hourly 3D-Var, rv + rf

headline — d03

POD 0→0.385

control missed the event entirely; radar DA recovered it (≥1 mm/h)

The model was blind. The control forecast produced zero hits at every precipitation threshold on d03 (POD=0, CSI=0 at ≥1/2.5/5 mm/h). Radar DA recovered the event: POD ≥1 mm/h 0.00→0.385, ≥2.5 mm/h 0.00→0.10, ≥5 mm/h 0.00→0.20. BIAS ≈ 3 (DA over-forecasts the area but detects where the control had nothing). Spatial correlation d03 0.17→0.33 (accum). This is the clearest operational use-case in the three-case set.

Honest accounting — d02. At d02 the story is mixed: POD ≥2.5 mm/h drops (0.10→0.06), though BIAS improves (2.52→1.81). MODE centroid worsens at d02 (92.7→112.5 km, 5 matched hours). The d03 event recovery is the headline result; d02 scores are flat-to-negative.

Navigate the story

01 · placement

Where did the nest go?

Interactive picker — composite anomaly, per-variable convective index frames, placed d02/d03 boxes. Climo <z> +0.64σ.

Open the picker

02 · innovation

Did the DA move the state?

4 × 3D-Var cycles, cost function, OmB→OmA fit, and analysis increments of U, V, T, Q_vapor around the radar.

Open the innovation report

03 · verification

Did the free forecast benefit?

Control vs radar-cycled WRF at d01/d02/d03 — station POD/CSI/BIAS, 21-h accum, MODE, HiRA, and CREF viewer (obs × control × radar).

Open verification