Radar Interpretation

This page is a short field reference for a few common radar signatures and for the Bolt overlays that can add context while you are watching them.

Hook Echo & Mesocyclones

The hook echo is one of the most recognizable radar signatures—a curving appendage on the southwest flank of a supercell where precipitation wraps around the updraft. When you spot one, the storm likely has a well-organized mesocyclone.

What to look for

• Reflectivity gradient: A tight gradient on the inflow side of the hook can indicate stronger low-level organization.
• Deepening hook: Compare 2–3 volume scans instead of relying on one frame.
• Occlusion: When the hook wraps completely around the updraft, the mesocyclone may be occluding.
• Inflow notch: A "bite" out of the reflectivity on the storm's southeast flank. A pronounced notch means the storm is ingesting a lot of unstable air—watch for rapid intensification.

Velocity Couplets

A velocity couplet is a tight pairing of inbound and outbound velocities on storm-relative velocity data.

Reading couplets effectively

• Gate-to-gate shear: The tighter the transition from inbound to outbound over a short distance, the stronger the rotation tends to be.
• Use SRV, not base velocity: Storm-relative velocity removes the storm's forward motion, giving you a cleaner picture of the rotation itself.
• Check multiple tilts: A couplet visible on the lowest tilt (0.5°) and extending upward indicates a deep, vertically coherent mesocyclone. Shallow couplets may be transient.
• Track the translation: Know where the couplet is moving so you don't end up downstream. Use Bolt's live map to compare your position against the storm's motion vector.

Confirm with dual-pol

• ZDR arc: An elongated area of high differential reflectivity on the storm's right flank confirms size-sorting in the updraft—further evidence of a well-organized supercell.
• CC drops: Correlation coefficient values below 0.80 co-located with strong rotation may indicate a tornado lofting debris (see below).

Debris Signatures

A tornado debris signature (TDS) is the clearest radar confirmation of a tornado on the ground. It appears as a localized drop in correlation coefficient (CC) co-located with a strong velocity couplet, often accompanied by low ZDR values.

Identifying a TDS

• CC below 0.80: Non-meteorological targets (debris, dirt, building material) produce chaotic return signals that reduce CC.
• Co-located with rotation: The CC drop must align with a velocity couplet—otherwise it could be ground clutter, birds, or smoke.
• Low ZDR: Debris tends to tumble randomly, producing near-zero differential reflectivity compared to the oriented raindrops around it.
• Increasing reflectivity: Large debris can produce reflectivity values higher than rain alone.

Placefiles & Overlays

Bolt placefiles can put shared location data on top of other radar overlays:

• Device tracks and intent markers
• Lightning overlays
• MRMS hail estimates
• Road or DOT overlays
• NWS warning polygons

Exclusion Zones & Privacy

Sometimes you need to operate near sensitive locations without broadcasting your exact position. Bolt's exclusion zones let you define areas where your tracker automatically suppresses precise coordinates.

• Set up exclusion zones before the chase so you don't forget under pressure.
• Use Bolt's privacy modes to control who sees your live location (Public, Organization, or Private).
• Review your account and sharing settings if the outing involved sensitive locations.