Fronts, What to Expect Out There!
#1 FRONTS
WHAT TO EXPECT OUT THERE!
I begin this series on the basics of WEATHER. What causes different weather patterns, what should we expect to see on any flight based on what we see in the weather charts. This is a typical weather depiction map of fronts that we will see during our flying careers! All four types of fronts are displayed here.
What is a Front? A Transition Zone of separate air masses of differing characteristics. It is the leading edge (the Front) of a change in temperature, for example a “Cold Front” is the leading edge of an Air Mass with cooler temperatures compared to air mass in front that it’s replacing. What other indications do we see in a frontal movement or frontal passage, also known as a FROPA? We will see the direction of the wind change, often as much as 180 degrees; we will also see a rise or possibly a fall in air pressure. For example in a “Cold FROPA” we will see the winds change from a Southerly flow to a Northerly flow. A drop in air temperature and a fall followed by a rise in Atmospheric Pressure. Each type of front has its own characteristics of weather that we will expect to see while flying.
There are four types of Fronts you might run into and each front has predictable types of weather, and most importantly how to plan for, these fronts.
COLD FRONT:
Perhaps the easiest to forecast and see coming our way as pilots. This front is the fastest moving of all the fronts and has the most change in conditions over time. It is characterized as a wedge of cold air, that under-rides warmer air that it will replace. This is where warm air, coming from the South and contains moisture, is met by cold air, which is fast moving, associated with a LOW PRESSURE center, and is coming from the North or Northwest. Where they meet (at what altitude-depends on the rate of slope) will cause strong weather that is often not a good area for an aircraft.
WARM FRONT:
Is a Slow-moving area like a blob of warm air, usually associated with the backside of a HIGH Pressure area, starting to break down and give way to colder air. Characterized by still air often moist, hazy skies, light to no wind. The warm air overrides the cooler air, causing precipitation starting with light rain increasing in intensity as the front nears. In the summer months the air becomes stagnant and can be called Smog (poor air quality) and hang around for days. It is almost always replace by a COLD FROPA, and clearing air.
Pressure Systems:
There is either a High-Pressure System or a LOW-Pressure System. When looking at weather maps, we are always looking down at the weather system. HIGH Pressure systems are associated with good weather: clear skies, light winds, good visibility. They are said to flow; Clockwise with an Anti-Cyclonic rotation, the winds flow out of the center. Low Pressure systems are the opposite, Cyclonic flow and Counter Clockwise rotation, the winds flow into the center, usually means bad weather. More on pressure in the next of our series.
Fly Safely Check the Weather Know what to expect File Flight plan
Until next month…………Will Rondeau
References
Weather Elements, a text in elementary meteorology. Blair/Fite.
FAA Pilot’s Handbook of Aeronautical Knowledge, FAA-H-8083-25B. Chapters 12 and 13.