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We surface observers admire clouds for their beauty, but clouds are more than just pretty puffs. In fact, clouds can help you predict upcoming weather. Look out for these eight cloud types next time you're out backpacking or boating to avoid being caught off guard by a "sudden" rainfall or thunderstorm.
Cumulus Clouds: All Is FairTiffany Means
Cumulus clouds are most noticeable for their fluffy white appearance. These low-level clouds typically form on sunny days as the sun heats the ground and warms the air. As the warm air rises and meets cold air, water vapor cools and condenses forming these cotton-like clouds.
Cumulus clouds commonly have rounded tops and flat darker bottoms. Those with little vertical development indicate that the weather will be fair. Cumulus clouds can also grow vertically forming cumulonimbus clouds. These clouds indicate heavy rain and severe weather.
- Most Likely Weather: Fair
- Precipitation Cloud: No
Cirrus Clouds: All Is Fair (For Now)Wispy cirrus clouds. Westend61/Getty Images
Isolated cirrus occur in fair weather. Because they point in the direction of air movement, you can always tell what direction the wind is blowing at upper levels by simply observing the direction in which the cloud wisps are oriented.
However, if a large number of cirrus are overhead, this can be a sign of an approaching frontal system or upper air disturbance (such as a tropical cyclone). Therefore, if you see a cirrus-filled sky, it's a good indication that weather conditions may soon deteriorate.
- Most Likely Weather: Fair, but a change will occur in 24 hours.
- Precipitation Cloud: No
Altocumulus Clouds: Warm With a Risk of Storms
Altocumulus are popularly called "mackerel sky"-and for good reason. Besides resembling fish scales, the clouds (which are commonly seen on warm spring and summer mornings) can signal the development of thunderstorms later in the day.
Altocumulus are also commonly found between the warm and cold fronts of a low-pressure system, and sometimes signal the onset of cooler temperatures.
- Precipitation Cloud: No, but signals convection and instability at mid-levels of the troposphere.
Cirrostratus Clouds: Moisture Moving InCultura RM/Janeycakes Photos/Getty Images
Cirrostratus indicate a large amount of moisture in the upper atmosphere. They're also generally associated with approaching warm fronts. (Watch for cloud cover to thicken the closer the front nears.)
- Precipitation Cloud: No, but may signal impending precipitation in the next 12-24 hours, or sooner if the front is fast-moving.
Altostratus Clouds: Expect Light RainHiroshi Watanabe/Taxi Japan/Getty Images
Altostratus clouds are mid-level, flat clouds that appear as gray or blueish-gray clouds expanding across the sky. These clouds are thin enough to allow a distorted image of the sun or moon to peer through. Altostratus tend to form ahead of a warm or occluded front. They can also occur together with cumulus at a cold front.
- Precipitation Cloud: Yes, light rain and virga.
Stratus Clouds: FogMatthew Levine/Moment Open/Getty Images
Stratus clouds are very low forming, gray clouds. These uniform clouds typically develop as cold air passes over warm air, something that usually occurs in winter. If you see stratus hanging overhead, expect drizzle or snow flurries. You may also expect that colder air will soon be on its way. Other than that, stratus clouds don't indicate much meteorological activity.
- Precipitation Cloud: Yes, light rain.
Cumulonimbus Clouds: Severe StormsPeter Zelei/E+/Getty Images
Just like you see a cumulus cloud and know it means fair weather, cumulonimbus mean the weather is stormy. (Ironically, it is the very act of these harmless fair weather cumulus clouds overdeveloping that creates cumulonimbus.) Any time you see a cumulonimbus on the horizon, you can be sure that dangerous severe weather-such as short periods of heavy rain, lightning, hail, and possibly tornadoes-isn't far off.
- Precipitation Cloud: Yes, often with intense rain and severe weather.
Nimbostratus Clouds: Rain, Rain Go Away!James O'Neil/Stone/Getty Images
Nimbostratus are low-level, dark clouds that usually prevent you from seeing the sun. These shape-less clouds often blanket the entire sky making for a gloomy day. Nimbostratus are a sign of steady moderate to heavy rain or snow that can last for several days on end. When these clouds begin to break, it is an indication that a cold front is passing.
- Precipitation Cloud: Yes, steady rain or snow.
Article edited by Regina Bailey
- "Cloud Chart." National Weather Service, NOAA's National Weather Service, 22 Sept. 2016, www.weather.gov/key/cloudchart.
- "Cloud Types." UCAR Center for Science Education, University Corporation for Atmospheric Research, scied.ucar.edu/webweather/clouds/cloud-types.
- "Weather Facts: Cloud Types (Genera)." WeatherOnline, www.weatheronline.co.uk/reports/wxfacts/Cloud-types.htm.