Reflectivity is where every chase starts
Reflectivity is the radar product that measures how much energy is bouncing back to the radar from precipitation in the atmosphere. It's measured in dBZ (decibels relative to Z), and it's what people usually mean when they say "the radar."
Reflectivity is where every chase day begins on the screen. Before you look at velocity, before you look at CC, before you look at storm motion vectors — you look at reflectivity to see what's out there.
The dBZ color scale
Most radar apps use a similar color scheme:
| dBZ | Color | What it usually means |
|---|---|---|
| 5–15 | Light blue | Drizzle / virga |
| 20–35 | Green | Light to moderate rain |
| 40–50 | Yellow | Heavy rain |
| 50–60 | Orange / red | Very heavy rain or small hail |
| 60–70 | Magenta / pink | Large hail likely |
| 70+ | White / purple | Giant hail; rare |
A storm with a 60+ dBZ core is producing hail. A storm with a 70+ dBZ core is producing large hail, and you don't want to be under it.
The signatures you're looking for
Hook echo. A hook-shaped appendage on the southwest side of a supercell, where the rear-flank downdraft wraps moisture around the meso. The classic hook echo is one of the most recognizable radar signatures in meteorology. Not every supercell has a clean hook, but when one shows up — especially on a storm with a co-located velocity couplet — it's a major tornado red flag.
Bounded weak echo region (BWER). A "vault" of weaker reflectivity surrounded by stronger returns at higher elevations. The BWER means the updraft is so strong that precipitation can't fall into the heart of it — it's being lofted instead. BWERs are a hallmark of severe-hail-producing supercells.
Three-body scatter spike (TBSS). A spike of false reflectivity extending radially outward beyond the storm. It's caused by the radar beam bouncing off hail, down to the ground, back to the hail, and back to the radar — a signature unique to giant hail. If you see a TBSS, the storm is producing baseball-or-larger hail right now.
V-notch or flying eagle. An inverted-V shape on the leading edge of a supercell where strong upper-level winds split the precipitation flow around a powerful updraft. A clear V-notch is another strong signal of supercell organization.
Bow echo. A bowing line of storms — typically a QLCS — where strong rear-inflow jet pushes the leading edge forward into a bow. Often associated with damaging straight-line wind and embedded brief tornadoes (especially at the bow apex and northern "comma head").
The single-cell, multicell, supercell continuum
Reflectivity gives you a quick visual on storm mode:
- Single cell — round blob, lasts 30–60 min, no organization.
- Multicell cluster — multiple cells in a loose grouping, each in different lifecycle stages.
- Multicell line — squall line or QLCS; usually long and linear.
- Supercell — discrete, often with a hook, V-notch, BWER, or all three.
For tornado chasing, discrete supercells are the prize.
Storm motion and the inflow notch
On a classic supercell, you can often see the inflow notch — a concavity on the eastern side of the storm where warm, moist air is being pulled into the updraft. Combine that with the hook on the back and you can see, just from reflectivity, where the meso is and where the storm is heading.
A supercell that's moving right of the mean wind ("right-mover") is usually the dominant cell of a storm split — and right-movers are statistically the dominant tornado producers.
Common mistakes
- Confusing 60+ dBZ with tornadoes. A 65 dBZ core is hail, not a tornado.
- Only looking at the lowest tilt. A BWER is best seen by stepping through elevations.
- Ignoring storm splits. A storm that splits often produces a left-moving hail beast and a right-moving tornado machine.
- Trusting smoothed-out radar from non-NEXRAD sources. Always use Level III or higher resolution products for chase-day decisions.
How chasers use it in the field
- Get an overall view of the storm field on a wide zoom.
- Identify the dominant cell — usually the one with the most aggressive core, the cleanest reflectivity structure, and the highest tops on velocity / spectrum-width.
- Zoom in. Look for a hook, V-notch, BWER.
- Switch to velocity to check for a couplet.
- Switch to CC to check for a TDS.
- Watch the trend across multiple scans — is the structure tightening or falling apart?
How Meso fits
Reflectivity reading is a manual skill, and Meso doesn't replace it. But the app sits on top of the same radar feed and surfaces context you'd otherwise have to assemble manually: warning polygons, SPC outlook overlays, your distance and bail route to the storm, recent spotter reports. When a storm you're tracking suddenly takes on classic supercell signatures, Meso flags the development under "Did anything important just change?" — one of the eight core chaser questions — so you have time to reposition before the hook tightens.