605 Chaser Tornado Target Finder automatically finds the best chase areas within 800 miles. Here's how to read and act on the results.
1
Open on chase morning
Open the app after 10Z (5am CT). The 06Z model run will be processed and the SPC Day 1 outlook will be up. This gives you the full picture for the day ahead.
2
Check the SPC banner first
The orange/red banner at the top shows the SPC tornado probability. The app only scores areas inside the SPC polygon — if there's no SPC risk, there's nothing to chase yet.
3
Read the target cards
Cards are ranked by composite score. The top card (red border) is the highest-confidence target. Each card shows the best time window — that's when parameters peak. Plan to be staged 30–60 minutes before the peak time.
4
Understand the score
Score is a weighted composite of all 6 parameters. Above 18 = high confidence, 12–18 = moderate, below 12 = marginal. A score of 15+ with SPC at 5%+ is a strong chase day.
5
Tap any card for a chase brief
Tapping a target opens a detailed brief with full parameter breakdown, suggested staging strategy, and a direct link to SPC mesoanalysis for that area.
6
Use Day 2 for pre-planning
Tap Day 2 to see tomorrow's setup. Use this for team coordination — share the top target county with Jeff, Brian, and Trace the night before so everyone can pre-position.
7
Refresh on chase day
Tap ↻ anytime to pull the latest model run and updated SPC outlook. Do this at 10Z, 16Z, and 22Z for the freshest data. Parameters shift significantly as the day develops.
Parameter Guide
The 6 key tornado parameters and what each tier means in the field.
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STP — Significant Tornado Parameter
The single best composite predictor of significant tornadoes (EF2+). Combines CAPE, SRH, shear, LCL height, and CIN. Values above 2 on a chase day warrant deployment.
4+ Significant2–4 Strong1–2 Marginal<1 Low
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0–1km SRH — Storm Relative Helicity
Measures the rotational energy in the lowest 1km. High SRH means low-level wind shear is favorable for tornado-producing mesocyclones. This is the layer that matters most for tornadoes near the surface.
300+ Very Strong200–300 Strong100–200 Marginal<100 Weak
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MLCAPE — Mixed Layer CAPE
Convective Available Potential Energy — the fuel for storms. Higher CAPE means stronger updrafts, taller storms, and more potential for violent tornadoes. Extreme CAPE alone doesn't guarantee tornadoes without shear.
The change in wind speed and direction from the surface to 6km. This is what organizes storms into supercells. Without sufficient deep-layer shear, even strong CAPE produces disorganized storms that can't tornado.
60+ Very Strong45–60 Strong30–45 Good<30 Weak
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EHI — Energy Helicity Index
Combines CAPE and SRH into a single number. EHI above 2 is strongly associated with significant tornadoes. It's the product of what a storm has to work with (CAPE) and the spin available (SRH).
4+ Significant2–4 Strong1–2 Marginal<1 Low
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UH — Updraft Helicity
A model diagnostic showing rotating updraft strength. High UH in the model forecast indicates the atmosphere is supportive of supercell mesocyclones. On chase day, confirm with live radar — real UH is shown as rotation tracks on NEXRAD.
125+ Very Strong75–125 Strong25–75 Moderate<25 Weak