Chaseit · wiki

A field guide to UK storms

Every entry has an At a glance line pitched at a layman and a Deep divewritten for working forecasters. If you've never heard of CAPE before, start with CAPE and follow the related links. If you're a meteorologist, the Chaseit features section tells you what feeds what.

Parameters & indices

The numeric ingredients forecasters read off a sounding or a mesoanalysis — energy, shear, moisture, lapse rates.

Bulk shear (0–6 km)The vector difference between surface wind and the wind at 6 km — the single best predictor of whether a storm…
CAPE — Convective Available Potential EnergyCAPE is how much fuel a rising parcel of air has in the tank. More CAPE means stronger updrafts and, all else …
CIN — Convective InhibitionCIN is the lid on the pot. Before a storm can fire, the atmosphere has to spend energy breaking through a warm…
EHI — Energy Helicity IndexA simple product of CAPE × helicity that rolls 'enough energy' and 'enough spin' into one number. Higher is mo…
EL — Equilibrium LevelThe altitude where a rising storm parcel finally becomes neutral — roughly, where you see the anvil spread out…
LCL — Lifting Condensation LevelThe height where cloud base forms if you lift a parcel from the surface. Lower LCLs mean wetter, cooler air ne…
LFC — Level of Free ConvectionThe altitude at which a rising parcel becomes warmer than the air around it and can accelerate upward on its o…
Lifted Index (LI)A one-number instability check: the temperature difference between a lifted parcel and the environment at 500 …
PWAT — Precipitable WaterHow much rain would fall if you wrung every drop of water out of a vertical column of atmosphere. High PWAT = …
SRH — Storm Relative HelicityHow much spin the low-level wind profile hands to a storm. High SRH is what lets a mesocyclone exist.
STP — Significant Tornado ParameterA composite index that blends CAPE, low-level shear, helicity and LCL height into a single score calibrated to…

Storm types

From pulse cells through supercells to derechos — what's on the end of your radar.

Radar signatures

Hook echoes, BWERs, velocity couplets and dual-pol fingerprints — what to look for in a scan.

Chasing techniques

Target selection, staging, escape routes, reading storm structure from the ground.

UK context

Why UK convection doesn't look like the US Plains — Atlantic track, jet stream, maritime airmass.

Chaseit features

How the pages on this site fit together — what feeds what, and what the numbers mean.