….A Tricky Business Lesson Objective: Know basic facts and general principles of the elements of weather. Samples of Behavior/Main Points: 1. Identify the types of clouds. 2. Identify the types of air masses and fronts. 3. Describe terrain factors that affect weather. 4. Describe the types of turbulence. 5. Identify normal weather patterns.

Overview 1. Terrain Factors 2. Turbulence 3. Normal Weather Patterns OVERVIEW: In this lesson we will discuss: 1. Clouds 2. Air Masses and Fronts 3. Terrain Factors 4. Turbulence 5. Normal Weather Patterns

Terrain Factors The presence of mountain ranges change the characteristics of a front. As air masses enter the United States the mountains cause them to rise. Along many seacoasts there is a breeze from the sea by day. This moist, relatively cool air rises and heats as it passes across land. Convectional clouds form and bring afternoon showers. (Gulf Coast) Terrain Factors The presence of mountain ranges in the path of a weather front can change the characteristics of the front greatly. Gentle rolling hills also contribute to the manufacturing of weather. As air masses enter the United States, the mountains cause them to rise. As the air rises, it cools and loses practically 100 percent of its moisture on the windward (facing the wind) slope. The leeward slopes remain dry. Along many seacoasts, there is a breeze from the sea by day. This moist, relatively cool air rises and heats as it passes across land. Convectional clouds form a short distance inland and may bring afternoon showers.

Mountain Wave Turbulence

Altimeter An altimeter is essentially a barometer measuring air pressure returning altitude influenced by: Temperature Pressure Fronts

Turbulence Thermal Turbulence Intense surface heating causes convection currents. More intense convection currents occur over dark-colored ground. Less convection currents will be over light-colored ground. Because velocity varies turbulent conditions are expected. Turbulence Thermal turbulence - caused by intense surface heating. Intense surface heating will create columns of rising air called convection currents or thermals. More intense convection currents will be present over dark-colored ground such as a black asphalt highway. Less intense convection currents will be present over light-colored ground such as wheat fields. Because the velocity of these currents varies according to the nature of the underlying surface, turbulent conditions should be expected.

Turbulence Thermal Turbulence Presents the biggest problem for aviators during landing. To eliminate during normal flight, climb above clouds. When cumulus clouds are present, convection currents and thermal turbulence exists. Thermal turbulence presents the biggest problem for aviators during the landing portion of the flight due to the increased tendency to either overshoot or undershoot the runway. To eliminate thermal turbulence during normal flights, climb above any cumulus clouds present. Thermal turbulence is not confined to only summer months. Anytime cumulus clouds are present, convection currents exists and thermal turbulence exists.

Turbulence Mechanical Turbulence - Low Level Results from strong wind gusts over rough terrain or manmade features. Produces turbulent eddies below 500 feet. Mechanical turbulence - caused by friction, the interaction of the air with another surface. Low level mechanical turbulence. Results from strong, gusty winds flowing over rough terrain or manmade features. This flow will produce turbulent eddies making flight conditions poor in the atmospheric layer below 500 feet.

Turbulence Mechanical Turbulence - Wake Turbulence Caused by aircraft flying through air. Presents a major hazard to another aircraft following too close. Most hazardous during landings and takeoffs. Wake turbulence Caused by aircraft flying through the air; disrupts the airflow. This strong, cone shaped, rotational flow trailing behind aircraft wings is referred to as wingtip vortices and presents a major hazard to another aircraft following too closely. This condition is most hazardous during landings and takeoffs.

Turbulence Wind Shear - Low Level Wind Shear (LLWS) Occurs below 10,000 feet. Primarily caused by frontal systems, low level jet streams and thunderstorms. Occurs rapidly. Wind Shear - caused by a sudden change in wind direction, wind speed or both for a short distance. Low level wind shear (LLWS). Occurs at altitude below 10,000 feet. Primarily caused by frontal systems, low level jetstreams, and thunderstorms. Low level wind shear occurs quite rapidly; therefore, a pilot should anticipate turbulence and be prepared to respond when conditions are present or forecasted.

Turbulence Wind shear - Clear Air Turbulence (CAT) Occurs above 15,000 feet. Not restricted to clear skies. Turbulence occurs in vicinity of upper level jetstream. Clear Air Turbulence (CAT) When turbulence occurs above 15,000 feet and is not associated with thunderstorms, it is CAT. Not restricted to clear skies, but may also occur in a solid cloud deck. As long as the clouds are not associated with thunderstorms, the turbulence frequently occurs in the vicinity of the upper level jetstream.

Climatic Provinces

Normal Weather Patterns Hawaii Two major factors determine weather. Dramatic heights and contours of land areas. Prevailing northeast trade winds. Pleasant temperatures. Little distinctions between summer and winter. Hawaii Two major factors determine the weather in the Hawaiian Islands. One is the dramatic heights and contours of the land areas. The other is the prevailing northeast trade winds that blow over cool ocean currents. These factors combine to provide typical Hawaiian weather, which is pleasant temperatures (usually in the 70's), plenty of sunshine, and very few tropical storms. Very little distinction is seen between summer and winter except for additional rainfall in the winter.

Normal Weather Patterns Alaska Has several different kinds of weather. No great extremes in southern part of state. Arctic slope lies in northern part of state. Broad valley and low mountain ranges. Continental weather. Temperatures from -70o F in winter to 90o F in summer. Alaska Unlike Hawaii, Alaska has several different kinds of weather, influenced by the varying terrain features. Mountains and warm ocean currents combine in the southern part of the state to make a climate with no great extremes of temperature. Rainfall is heavy, but varies from one section to the next depending on local geography. High mountains in the south intercept Pacific Ocean winds and wring out much of the moisture, which freezes and supports the glacier fields in the area. In the Aleutian Islands, the weather ranges from cool to cold and is always rainy. Fog is also present. Beyond the mountains in the northern section of Alaska lies the Arctic slope, an area exposed to winds from the Arctic Ocean. Temperatures are relatively mild in midsummer and early autumn. Ice stops shipping movements for up to 10 months of the year. Between the oceanic area of the south and the arctic area of the north lies a large area of broad valley and low mountain ranges. The interior section has continental weather comparable to the Great Plains of the western United States. Temperatures can drop to -70o F in the winter and can climb to 90o F during the long sunlight hours of the summer.

Summary 1. Terrain Factors 2. Turbulence 3. Normal Weather Patterns In this lesson we discussed: 1. Clouds 2. Air Masses and Fronts 3. Terrain Factors 4. Turbulence 5. Normal Weather Patterns