Lenticular Clouds over Plymouth, NH

Plymouth State University Meteorology Program Cloud Boutique

The Plymouth State Meteorology Program has developed this web page to provide explanations of and access to detailed pictures of some basic cloud forms. The cloud images show detailed structure and features. All of these pictures were taken in the local area around Plymouth, New Hampshire and most from the weather observation deck on the roof of the Boyd Science Center on the Plymouth State campus. Clouds can move and change shape quickly as indicated in this 30 minute time-lapse mpeg video loop. The purpose of this "boutique" is to provide a general cloud reference and is not intended to provide an all-inclusive list. Images will be added to or changed as opportunities permit.

Cloud Classification

Clouds are generally classified based on characteristics, such as, altitude, appearance, or origin. Altitude distinctions apply to those clouds that fit in various layers of the atmosphere as follows:
  In appearance, clouds may be thick or thin, have well defined edges or be very diffuse, appear hairlike, cellular, towering, or in sheets, and be associated with fair weather or precipitation. Most clouds owe their existence to upward vertical motion of air, hence they are often associated with weather producing phenomena, such as fronts, troughs, and low pressure systems. However, topography can also help move air upwards and produce clouds.

Cloud Descriptions and Pictures

This section provides verbal descriptions and pictures of clouds that have been observed in this area. Because of their size, these images have been stored in JPG format. To view a picture, click on the appropriate cloud name or other highlighted text.

High Clouds are primarily composed of ice crystals and include the following:

Middle clouds have many similarities to the cumuloform and stratiform high clouds. Since they are closer to a groundbased observer, the cumuloform elements in particular appear larger than their high cloud counterparts. They can contain ice crystals and/or water droplets and may occasionally be associated with some light precipitation.

Low clouds are most often composed of water droplets, but can have ice crystals in colder climates. Some of these clouds can develop into the multi-level clouds and can go through various phases, such as, a morning stratus deck turning into late morning stratocumulus, then early afternoon cumulus, and vertical development into cumulonimbus which can produce heavy rain and possible lightning and thunder.

Multi-layer clouds are the heavy precipitation producers. The depth of these clouds give precipitation hydrometeors a better environment to develop and grow.

Orographic clouds, as the name implies, are produced by the flow of air interacting with mountainous terrain.

Another "specialty" cloud is one that can develop due to Kelvin-Helmholtz (K-H) instability waves and subharmonic resonance with other waves in the atmosphere. This can result in an intertwined or spiral cloud pattern as shown in this picture, which was also taken by James D. Rufo. H-H instability is the result of strong wind shear. K-H clouds that form in early stages can resemble well-organized waves that appear to be breaking like ocean waves.

Another type of cloud can be formed from the vapor contained in the exhaust of a jet engine of an airplane when they are flying at high enough altitudes where cold temperatures cause the vapor to turn into ice crystals like cirrus clouds. These clouds are called "contrails" (short for "condensation trails") and look like lines in the sky. The photo shows two contrails. The one on the lower right was formed by a jet that flew a few minutes ahead of the jet which formed the contrail in the center. The newer contrail is narrower and hasn't had the chance to diffuse like the older one.

Another useful cloud information resource is the U of Illinois Cloud Catalog.