Cloud PointField Guide

Rare sights

The entries you may wait years for: brief, local, or dependent on a coincidence of light and ice.

High — above 6,000 m2

Noctilucent — Earth's highest, glowing-at-night cloudsNoctilucentIVNone - forms far above the weather, in the mesosphereNacreous — 'Mother-of-pearl' clouds glowing in winter twilightNacreousXIIINone - forms in the polar winter stratosphere, far above the weather

Middle — 2,000 to 6,000 m5

Asperitas — The newest, most ominous wavy undersideAsperitasXUnsettled, turbulent air, but usually disperses without a stormBanner cloud — The flag streaming off a sharp peakBanner cloudXVIIIStrong wind streaming over a sharp peak, otherwise clearKelvin-Helmholtz — Breaking ocean waves, frozen in the skyKelvin-HelmholtzXIXStrong wind shear aloft; little direct weather significanceHorseshoe Vortex — A horseshoe that vanishes in minutesHorseshoe VortexXXIXDaytime thermals with wind shear; fair but breezyLacunosus — A honeycomb of cloud holesLacunosusLIPockets of sinking air in thin cloud; no weather significance

Low — below 2,000 m5

Morning Glory — A 1,000 km tube of cloud glider pilots surfMorning GloryVMarks a passing atmospheric wave; often a sudden wind shift as it arrivesWall Cloud — The lowered base where tornadoes are bornWall CloudXXXIIA severe storm's updraught - a possible tornado if it begins to rotateCataractagenitusXXXIXLocalised to large waterfalls; no broader weather significanceMoonbow — A rainbow made by moonlightMoonbowXLVRain or spray opposite a bright moon at nightGreen Flash — The split-second green at the horizon at sunsetGreen FlashLIIClean air over a low, distant horizon at sunset or sunrise

Multi-level — spanning several layers3

Mammatus — The sky's hanging pouchesMammatusIISevere weather in the vicinity; often seen during or after thunderstormsPyrocumulonimbus — When a fire grows its own thunderstormPyrocumulonimbusXXXIVAn extreme fire-driven storm - lightning, fierce gusts, even fire tornadoesFunnel Cloud & Tornado — The spinning column reaching for the groundFunnel Cloud & TornadoXLA severe rotating storm - destructive winds if it reaches the ground