Once you are on the trail clouds are a tool that can be use to forecast changes in the weather. The cloud type and the direction of their movement are your first clue of potential weather change. Reading clouds can warn you of weather changes for tomorrow or of storms that are imminent.
The first step in identifying clouds is to understand their naming. Clouds are named for their altitude where they are and for their shape.
|High Clouds or Cirrus||Above 16,500 feet||Cirrus
|Mid Altitude Clouds or Alto||6,500 feet to 23,000 feet||Altostratus
|Low Clouds or Stratus||Up to 6,500 feet||Stratus
|Clouds with vertical development||Cumulus
What are the clouds trying to say?
Cirrus or Cirro can be used with cumulus Which makes cirrocumulus which looks like high fluffy clouds. Cirrocumulus clouds can indicate fair weather in winter. Cirro is also a prefix to stratus to form cirrostratus which is the name for high, flat or layered cloud. which may indicate the approach of a warm front.
Alto can also be used with cumulus and stratus to name mid-level clouds: altocumulus and altostratus.
Nimbus or Nimbo are the suffix or prefix used with cumulus or stratus to name the cloud type that is producing precipitation. These clouds could be either cumulonimbus which would be a fluffy, vertically-rising rain cloud like a thunderstorm or nimbostratus which would be a sheet like or flat-looking cloud that generally produce rain or drizzle over a long period of time.
High Altitude clouds (Cirrus)are above 16,000 feet
Med-Altitude clouds form between 6,500 feet to 23,000 feet. Alto clouds help predict weather changes in 6 to 12 hours.
Stratus clouds, from at altitudes up to 6,500 feet. These clouds form a solid sheet or layers of cloud.
When a cold front approaches, the cold air tries to displace the warmer air from beneath. Whereas a warm front overrides the colder air announcing its arrival well in advance.
As a warm front approaches you will notice that the ceiling of the clouds will lower. This is characterized by the approaching of high clouds that become lower over time. The clouds will appear in the following order:
As a cold front approaches and the colder air tries to push the warmer air up and cumulus clouds will form. Depending on the Stability of the warm air this will determine the amount of precipitation. If the warm air that the cold air displaces is stable and moist then the precipitation that follows will be continuous. Depending on the speed of the front, the rain or snow can last for a couple days. The clouds that form are usually stratiform.
If the warm air being displaced by colder air is moist and unstable then cumuliform clouds form. Rain from Thunderstorms will be present ahead and behind the front. Ahead of the front there may be some convective clouds that may also produce rain. After the front passes some fair weather cumulus clouds may develop as well. The following clouds are the signpost of a cold front.
Thunderstorms also form in the mountains due to heating. As the sun warms the mountain slope and in turn warms the air, the air rises. As the air rises into colder air above it expands and form cumulus clouds. With enough expansion and lifting these cumulus clouds can rapidly turn into cumulonimbus or thunderstorms.
Things to remember while hiking and watching the weather.
Things to Remember
- Changes in weather generally come from the west
- Watch mountain peaks for cumulus clouds to form in the morning. If they do not dissipate and start to build look for afternoon thunder showers.
- If your GPS has a barometer or Altimeter once at camp note the barometric altitude and if the altitude increases over time pressure is decreasing. Look for a change in the weather.
- If the temperature drops suddenly with an increase in wind speed often is an indicator of an approaching storm.