Investigation 10: Mid-Latitude Cyclones
- Page ID
- 44871
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This investigation starts off with a story from Alicia Mullens, one of the authors of this lab manual:
"It was 12:30 am on a warm, humid Saturday night in central Texas. A major blizzard had been tearing through the Western part of Texas, and was forecast to arrive in our region by dawn the next morning. Being the weather enthuasist I am, I wanted to go outside and watch the thunderstorms that were on the leading edge of the blizzard. So after my wife went to bed, I went out into the back yard, and sat down with a couple of drinks, waiting for the storm to arrive. When I went outside, it was warm, windy, and humid… it felt more like a summer night than the late- December evening that it was. And it remained that way for a long time… 1 am… still warm… 2 am… still warm… 2:30 am… still warm… and then suddenly, an ICY wind blew in from the North… within minutes I was running for my jacket. The next weather observation showed a 25°F temperature drop in 20 minutes!!! It was snowing by the next morning!
I had just experienced something that I’ve taught about, and read in books, and heard others talk about… but had never experienced myself… I had experienced a frontal passage!"
Indeed, many weather systems, such as thunderstorms and mid-latitude cyclones can be responsible for such sudden, almost violent changes in weather conditions (Figure 10.1). We'll cover thunderstorms more in-depth in Investigation 11, but this investigation is focused on studying the presence, movement, and conditions of mid-latitude cyclones.
- Identify weather conditions before, during, and after a frontal passage.
- Determine, using a set of weather observations, when a cold front passed a region.
- Observe the movement of a well-defined mid-latitude cyclone.
- 10.1: Fronts
- The distinctions between warm and cold fronts is explored here, highlighting their effects on weather. Warm fronts involve gradual rises of warm, moist air over cold air, leading to mild precipitation, while cold fronts result in rapid warm air displacement, causing sudden weather changes and storms.
- 10.2: Air Pressure Changes in Frontal Passages
- The role of air pressure with warm and cold fronts is explored here, noting that air pressure typically decreases before a front and increases afterward. It uses a case study from July 28-29, 2019, focusing on a cold front in Bismarck, North Dakota, to illustrate key concepts. The discussion includes how air pressure changes, wind direction, and dew point signal cold fronts, highlighting the complexities of frontal passages.
- 10.3: Tracking Mid-Latitude Cyclones
- Mid-Latitude Cyclones, prevalent between 30° and 60° latitudes are covered here, highlighting their formation from warm tropical and cold polar air. It explains their structure, weather implications, and importance in forecasting, detailing cold and warm fronts. Additionally, it notes that a current cyclone will have minimal temperature effects on St. Louis during summer due to a small temperature gradient between air masses.
- 10.4: Alternative Text Descriptions for Investigation 10
- A set of detailed alternative text descriptions for Investigation 10.
Thumbnail: A mid-latitude cyclone in the Eastern United States. Extratropical Cyclone Auora by NASA is licensed in the Public Domain.