How to read a hodograph
A hodograph plots the wind vector at different heights all in one graph. Once you learn to read it, you can spot a supercell environment in five seconds.
The setup
A hodograph is a polar plot. The center is calm wind. The tip of each vector represents the wind at a specific altitude — 0, 1, 3, 6, 8 km AGL, typically. Connect the dots and you get a curve.
The direction from center to the tip tells you where the wind is going. The distance tells you speed.
Two curves that matter
The critical low-level curve
Zoom in on just the first kilometer of the hodograph. That is where tornado potential lives.
- Straight low-level: shear present but no rotation available for the mesocyclone to stretch.
- Slightly curved low-level: tornadic supercells possible.
- Sharply curved low-level ("scorpion tail"): significant tornado potential. This is what meteorologists call streamwise vorticity — spin oriented along the storm-relative flow that goes straight into the updraft.
Storm-relative motion
The storm's motion vector is overlaid on the hodograph as a filled dot. Draw a line from the storm-motion dot to each altitude's wind vector — those are storm-relative winds. If the storm-relative wind at the surface is at least 30 kt, you have good tornado potential.
Hodograph size matters
A tiny hodograph means low bulk shear — probably pulse thunderstorms or multicells. A big hodograph — 60+ kt long — means strong deep-layer shear and supercell potential.
Where to see hodographs live
- SPC Mesoanalysis — has a hodograph tab
- Pivotal Weather — plots forecast hodographs
- RAP soundings — real-time hodographs
- Radiosonde launches — real observations twice daily