Cloudy Start to a Nice Sunday
by Angela Schilling, Meteorologist
September 18, 2011 10:08 PM
Over the weekend the amount of cloud cover had a huge impact on highs, with temperatures in the 70’s west of the James and 50’s along and east of the I-29 corridor. By Sunday afternoon we saw quite a bit of sunshine, allowing temperatures to make it back up into the mid to upper 70’s…with 80’s along the Missouri River.
Oftentimes, the temperature goes hand in hand with the amount of cloud cover present. During the day clouds keep temperatures from rising, and during the nighttime clouds can act like a blanket, preventing temperatures from cooling off. Satellite images can be used to analyze the amount of cloud cover present, as well as the different types. Visible, infrared, and water vapor, are some of the satellite images meteorologists’ use on a daily basis. Similar to a camera, a visible satellite image captures reflected light, and can only be used during the daytime. Clouds appear white on a visible satellite image, and land features appear in shades of gray. The image below is from Sunday afternoon with thick clouds along and east of I-29.
Unlike visible satellite imagery, infra red is based on temperature, and can be used 24 seven. The brighter the image the higher the cloud is in the atmosphere. Low-level clouds are shown as a dark gray color and high level clouds are almost white or have a milky hue to them. Sometimes infra red images have their own color schemes, with different colors representing different temperatures in the atmosphere. Clouds are much colder aloft, and depending on the temperature and moisture content within the cloud, sometimes they can be composed of ice crystals…where as low level clouds are much warmer, and can be seen as a dark gray color on an infra red image. Saterday afternoon through Sunday morning we were socked in with both high and low level clouds. The first image is from Saturday night and the second image is from Sunday around 9:30pm. Notice the dark gray color on the first image, which is indicative of low level clouds...the thin wispy clouds in western Minnesota are probably cirrus. Also interesting to point out the bright white color around central South Dakota, where there are also a few showers and storms. Since infrared imagery is based on temperature and thunderstorms typically have higher tops than standard rain showers....they would appear much whiter or brighter in nature.
Captured from the upper levels of the atmosphere, water vapor imagery is a great way to analyze the jetstream…or what drives the weather. Water Vapor Imagery can have a variety of different color schemes. Oftentimes dry air corresponds with oranges and yellows…and a milky white color or blues and greens, represents a juicy air mass. The image below is from Sunday evening…with several bands of showers stretching from Wisconsin down through Texas. Behind the front is much drier air with dewpoints in the 40’s and 30’s. On the image below notice where all the moisture is…right along the bands of showers, where the imagery is also a milky white color. Indicating lots of dry air in the upper levels of the atmosphere, also notice the bright orange color just south of California.