Cloud PointField Guide

High cloud

Ice-crystal cloud and the optics that come with it.

High — above 6,000 m10

22° Halo — The bright ring around sun or moon22° HaloIIIOften an early sign of an approaching warm front - rain possible within 12-24 hoursNoctilucent — Earth's highest, glowing-at-night cloudsNoctilucentIVNone - forms far above the weather, in the mesosphereCirrus — Delicate ice-crystal brushstrokesCirrusVIFair weather currently, but may signal approaching warm frontNacreous — 'Mother-of-pearl' clouds glowing in winter twilightNacreousXIIINone - forms in the polar winter stratosphere, far above the weatherSun dogs — Twin 'false suns' flanking the real oneSun dogsXVIIHigh cirrus moving in; can precede a warm front and rain within a day or twoCirrocumulus — Tiny rippled grains — rarest of the high cloudsCirrocumulusXXIGenerally fair weather, but may indicate approaching front within 24-48 hoursSun Pillar — A shaft of light standing above a low sunSun PillarXXVIIIIce crystals or diamond dust in the air; often bitterly coldCircumzenithal Arc — The 'upside-down rainbow' overheadCircumzenithal ArcXLIIHigh ice cloud with a low sun; can precede a warm frontHomomutatus — Aircraft contrails spread into man-made cirrusHomomutatusXLVIHumid air aloft preserving contrails; can precede a warm frontCirrostratus — The thin ice veil that haloes the sunCirrostratusXLVIIIRain or snow likely within 12-24 hours; often precedes warm fronts