Thanks to John Blair, Dayton Powered Paragliding.
It’s now super easy to get the local weather forecast using the web, 800-WX-BRIEF, TV, radio or even your VHF radio. Even so, at certain times of the year weather can change rapidly and you should continually keep a “weather eye” out, especially to the west, in order to foresee changes which might be impending.
Clouds are a tool you can use to predict or forecast weather. The type of cloud and direction of movement can warn you of weather changes that are imminent. Clouds are categorized by the altitude at which they appear and the shape that they take.
Cloud Group |
Cloud Height |
Cloud Types |
| High Clouds = Cirrus | Above 18,000 feet |
Cirrus |
| Middle Clouds = Alto | 6,500 feet to 18,000 feet | Altostratus Altocumulus |
| Low Clouds = Stratus | Up to 6,500 feet | Stratus Stratocumulus Nimbostratus |
| Clouds with vertical growth | Cumulus Cumulonimbus |
Note: This is not an in-depth study of clouds so much as highlights of the basics for ultralight pilots.
Definitions to categorize general cloud shapes:
-
- Cumulus means “heap, a pile, an accumulation”
-
- Stratus meaning “spread out, flatten, cover with a layer”
-
- Nimbus meaning “rainy cloud”
Variations of cloud types are created by combining the cloud’s shape/description with the altitudinal names as a prefix or suffix.
Cirros (high) or Cirro can be used with cumulus (heap) to indicate a cirrocumulus or high, lumpy cloud. Cirrocumulus clouds, sometime called “mackerel skies”, can indicate the approach of a hurricane in the tropics. It can also be used with stratus (flat, layered) as in cirrostratus to indicate a high, flat or layered cloud.
Alto can also be used with cumulus and stratus to indicate altocumulus and altostratus which are middle altitude lumpy clouds and middle altitude layered clouds respectively.
Nimbo or nimbus might be used with cumulus or stratus to indicate a cloud formation that is producing precipitation. These clouds could be either cumulonimbus which would be a lumpy, vertically-rising rain cloud or nimbostratus which would be a sheet or flat-looking rain cloud.
“High” clouds are above 18,000 feet
-
- Cirrocumulus are small, rounded puffs that usually appear in long rows. They are usually white, but sometimes appear gray. Cirrocumulus are usually seen in the winter and indicate fair, but cold, weather. In the tropics, they may indicate an approaching hurricane.
-
- Cirrostratus are sheetlike, thin clouds that usually cover the entire sky. The sun or moon can shine through Cirrostratus clouds. Cirrostratus clouds usually come 12-24 hours before a rain or snow storm.
-
- Cirrus, the most common high clouds, are composed of ice and consist of long, thin, wispy streamers, are usually white, and predict fair weather. Sometimes called mares tails, they stream with the wind. By watching the movement of cirrus clouds you can tell from which direction weather is approaching. They suggest a change in weather within 24 hours.
“Medium high” clouds are 6,500 feet to 18,000 feet.
These are called alto clouds. They’re used to predict weather changes in 6 to 12 hours.
-
- An Altostratus cloud usually covers the whole sky. The cloud looks gray or blue-gray. The sun or moon may shine through an Altostratus cloud, but will appear hazy. An altostratus cloud usually forms ahead of storms with continuous rain or snow.
-
- Altocumulus clouds are grayish-white with one part of the cloud darker than the other. Altocumulus clouds usually form in groups. If you see Altocumulus clouds on a warm, sticky morning, be prepared for thunderstorms by late afternoon.
“Low flat” clouds go up to 6,500 feet.
These Stratus clouds form a solid sheet or layer of cloud mass.
-
- Stratus clouds are uniform gray in color and almost cover the entire sky. Light mist or drizzle is sometimes associated with Stratus clouds.
-
- Stratocumulus clouds are low, lumpy and gray. Most form in rows with blue sky visible in between. Precipitation rarely occurs with Stratocumulus clouds, however, in frontal weather they may turn to Nimbostratus.
-
- Nimbostratus clouds are dark gray with a ragged base. Rain or snow is associated with Nimbostratus clouds.
Clouds with vertical growth
-
- Vertically developing clouds are the Cumulus type. These small, lumpy clouds are low “fair weather” clouds. However, as they develop vertically (by rising hot air) they may go from small, fair weather clouds to large, boiling, vertically-growing monsters called cumulonimbus.
-
- Cumulonimbus (thunderstorm clouds). High winds will flatten the top of the cloud into an anvil-like shape. Cumulonimbus are associated with heavy rain, snow, hail, lightning, and tornadoes. The anvil usually points in the direction the storm is moving.
If you still can’t remember all of the cloud names and formations, you can always watch the clouds for two specific weather situations that indicate a high probability of a storm:
1. A “lowering ceiling”: This means that the height of cloud formations continues to get lower and lower, usually caused by a warm front. As the ceiling lowers you will see clouds in the following order:
- Cirrus
- Cirrostratus
- Altostratus
- Stratus
- Nimbostratus – storm clouds!
2. On the other hand, watch for cumulus (puffy) clouds that start to rapidly develop vertically to become cumulonimbus thunderstorm clouds. On hot and humid days, these storms occur over water as the radiant heat from the land absorbs moisture from nearby water and rises to produce thunderheads. These storms can also indicate a cold front and may be preceded by squall lines, a row of black storm clouds. Wind shifts unpredictably and accelerates dramatically. Lightning can occur for miles in front of a storm and after the storm appears to have passed.
Other things to look for that indicate an approaching weather change:
- Weather changes generally come from the west so scan the sky with your weather eye, especially to the west.
- A sudden drop in temperature and change in the wind (increasing winds and/or seas) often means that a storm is near.
- If you have a barometer check it every two to three hours. A rapid drop in pressure means a storm is approaching.
About John: “I have been flying ultralights for some time, but I did not have a great understanding of weather. I was always in search of something related to weather that was easy to understand. I went on the Internet looking for weather related material. With lots of research and no luck I called a meteorologist that pointed me in the right direction. What I came up with is weather 101. Flying powered paragliders and knowing what type of weather you should fly in will not only insure a enjoyable flight but a safe flight as well.”