What Does TCU Mean in a METAR?
TCU means towering cumulus: a building storm cloud, often a thunderstorm precursor. It stands for Towering CUmulus.
TCU in a real report
SCT035TCU
What it changes for you
TCU is a forecast tucked inside an observation. The cloud is not a thunderstorm
yet. The air that built it will keep building.
Treat it as a timing signal. A TCU at mid-morning on an unstable day often
becomes a CB by early afternoon. Check which side of that your arrival sits on.
What it feels like now
Strong updrafts and downdrafts, sharp turbulence, and icing up high if the
temperature is below zero. All of it arrives before the cloud earns the CB
label. So give it room now, not later.
Related codes
Decode a report containing this code
Paste a METAR, TAF, PIREP or SIGMET into the WxDecoder decoder. Every group comes back in plain English. The raw code sits beside it, so you can check the decode rather than trust it.
Frequently asked questions
What does TCU mean in a METAR?
Towering cumulus. A cumulus cloud with significant vertical development that has not yet become a thunderstorm. It signals unstable air and often precedes a cumulonimbus in the same air mass.
Should I avoid TCU the way I avoid CB?
Give it wide clearance. A towering cumulus already has strong updrafts and turbulence, and it can develop into a cumulonimbus quickly. It has no lightning yet, which makes it easier to underestimate than a CB.