Northwest Cloud formations Northwest Cloud formations Geology 252: The Earth and its Weather

Ron Kleinknecht

High Clouds (Cirrus) CH • Etymology: Latin , Tendril, flexible appendage

• Height: Above 10,000 ft. (3 km) to ~ 60,000 ft. (18 km). Tropopause

• Ice crystals

• Forms:

– mares tails, hooks, filaments & strands

– cirrofractus

– cirrostratus

– cirrocumulus (mackerel sky)

Mares’ tails over Whistler

Cirrus with strands, filaments and hooks

Cirrus with more strands and filaments

Cirrus (Stratus?)

Sun Dog (parahelia) Through Cirrostratus

Sundog in Perspective

Cirrocumulus (Mackerel Sky)

Cirrus and Stratus at Sunset

Alto, (high) mid- level clouds (Cm)

• Height: Between 6,500 ft. (2 km) and 25,000 ft. (8 km)• Forms:

– Altocumulus

– Altostratus

Altocumulus

Altostratus and Cumulus Congestus over Orcas Island

Winter Altostratus over South Bellingham

Layers of Cirrus, Altostratus and ?

Low Clouds (CL)• Height: ground to 6,500 ft. (2 km)

• Forms:– Fog– cumulus – stratus– Nimbostratus (rain)– cumulonimbus (rain/storm)

• Base starts low but can develop up to tropopause

October Cumulus with Moderate Vertical Development

Dissipating Cumulonimbus

Summer StratocumulusJuly 2001

Late Summer Stratus with Fog Lifting

Stratocumulus over the Bay at Summer SunsetJuly 2001

Altocumulus at night:Sailors’ delight or warning?

Where is the Virga?

Weather Dragons Come Out

Looking for the green flash