Stable — Φ ≥ 0.78, Deff ≥ 3.9
Atmosphere is well-organized. Smooth temperature gradients, low wind shear, stable pressure patterns. Normal or fair weather.
Stressed — Φ 0.72–0.78, Deff 3.6–3.9
Organization is strained. Temperature inversions, increasing wind shear, frontal boundaries forming. Weather is transitioning.
Degrading — Φ 0.65–0.72, Deff 3.25–3.6
Coherence breaking down. Strong wind shear, chaotic temperature profiles, active storm dynamics. Severe weather likely.
Coherence Failure — Φ < 0.55, Deff < 2.75
Total atmospheric disorganization. The system has lost its structure — extreme turbulence, violent convection, or vortex collapse. Shown as pink/purple stripes.
Coherence Gradient — Smooth color overlay showing Φ(C) at each grid point. Green = stable, yellow = stressed, red = degrading, pink/purple stripes = failure.
Radar (NEXRAD) — Historical NOAA n0q composite radar synced to each timestamp. Shows precipitation intensity where land-based radar reaches (~200–300 mi offshore).
Satellite IR — GOES-19 infrared cloud imagery. Cold cloud tops (bright) = deep convection and thunderstorm cells. Covers the full storm system including the Atlantic side beyond radar range. Toggle on to see the complete storm extent.
Lightning — Real GOES-19 GLM (Geostationary Lightning Mapper) flash data from the actual storm, Feb 22–24 2026. Result: near-zero flashes across all frames (max 12/hour). This nor’easter was a stratiform system — organized large-scale energy transport, not convective discharge. The coherence failure zone produced almost no lightning. That distinction is scientifically significant.
Wind Arrows — Direction and strength of surface winds. Color indicates wind speed.
Cities — Major cities with surface temperature. Click for detailed coherence breakdown.
Danger Zones — Alert polygons drawn around low-coherence clusters, plus a pulsing marker at the exact point of lowest Deff.
COHERENCE WATCH — Φ 0.65–0.72
Conditions are developing. Coherence is strained and the atmosphere is losing organization. Like a tornado watch — conditions are favorable for severe weather but it hasn't fully materialized yet. Stay alert.
COHERENCE WARNING — Φ < 0.65
Active coherence degradation. The atmosphere has lost its structure at this location — severe weather is happening now. Like a tornado warning — take action. These are the zones of heaviest impact.
LOWEST Deff MARKER
Pulsing dot at the exact grid point with the lowest effective dimensionality — the single worst spot in the entire region. The label shows the Deff value. This is where the storm chasers would point and say “right there.”
As you step through the animation, watch how the alert zones shift and the lowest Deff marker moves:
- Storm approach: Watch zones (yellow dashes) appear first, then Warning zones (red solid) form inside them
- Storm peak: Warning polygons expand, the lowest Deff marker drops toward 2.0
- Recovery: Alert zones shrink from the west, Deff climbs back above 3.0, polygons disappear
The key insight: coherence predicts where the damage will be before single weather variables do. A point with high winds but organized temperature gradients stays coherent. A point with moderate winds but chaotic temperature profiles — that's where structures fail.
NOAA HRRR (High-Resolution Rapid Refresh) — 3km grid, 5 pressure levels (925, 850, 700, 500, 300 hPa)
NOAA NEXRAD — Historical radar composites via Iowa Environmental Mesonet
Event: Nor'easter, February 22–24, 2026