Fibratus

Definition

A cloud species applied to cirrus and cirrostratus, describing straight or slightly curved filaments that do not end in hooks or tufts. The cloud looks like a set of fine hairs stretched across the sky.

Field note

Cirrus fibratus is usually the very first sign of an approaching warm front, typically 24 to 36 hours ahead of rain. If it never thickens into cirrostratus, the system is passing to your north or south.

Related terms

• Cirrus · Cirrus
• Uncinus · uncinus
• Cirrostratus · Cirrostratus