Aviation Weather Understand basic facts and general principles of aviation weather. 1. Explain the weather hazards associated with aviation. 2. List the types of severe weather that affect aviation. 3. Describe arctic and tropic weather characteristics.
Overview 1. Weather Hazards 2. Severe Weather 3. Arctic and Tropic Weather
Weather Hazards • Reduced Visibility • Three miles lateral visibility is acceptable for safe flight under visual flight rules (VFR). • Possibility for accidents is greatest when visibility is reduced and the pilot is not trained to fly according to instrument flight rules (IFR). • Clouds, rain, snow, fog, and obstructions. • Haze and smoke can reduce visibility when the wind is calm.
Weather Hazards • Reduced Visibility • Blowing dust, sand, and snow • Whiteouts
Weather Hazards • Icing • Ice is present in the atmosphere at all times-15,000 feet in summer and as low as 1,000 feet in winter. • Glaze and Rime ice form on an airplane’s windshield, its propeller, and other aerodynamic surfaces. • Glaze ice is formed and builds quickly as an airplane flies through super-cooled rain droplets.
Weather Hazards • Icing • Rime ice forms when an airplane is flying through super-cooled cloud condensation. • Frost disturbs airflow to reduce lift efficiency. • Larger, more sophisticated aircraft are equipped to break or melt ice as it is formed.
Severe Weather • The NWS severe weather classifications are based upon destructive effects with regard to surface cultural features.
Severe Weather • Thunderstorms • A storm accompanied by thunder and lightning. • A Thunderstorm is local in nature and is always produced by the growth of a cumulus cloud into a cumulonimbus cloud. • Three stages • Cumulus • Mature • Dissipating
Severe Weather • Thunderstorms - Cumulus Stage
Severe Weather • Thunderstorms - Mature Stage
Severe Weather • Thunderstorms - Dissipating Stage
Severe Weather • Tornadoes • Local storm that focuses destructive forces on a small area. • Occurs with severe thunderstorms. • When it touches the ground its path may be very erratic.
Severe Weather • Tornadoes • Destructiveness is caused by high winds. • Very low pressure gives tornadoes great suction.
Severe Weather • Tornadoes • Occur most often in the spring months and in the afternoon hours. • Very difficult to forecast.
Severe Weather • Hurricanes • A strong tropical cyclone with winds that surpass 100 mph. • A large revolving storm with a calm center (eye).
Severe Weather • Hurricanes • Born over the tropical water of the Atlantic and Pacific Oceans, the Gulf of Mexico and the Caribbean Sea. • Energy gained from heat given off by warm air.
Severe Weather • Hurricanes • Tropical depression • Tropical storm • Hurricane
Severe Weather • Hail • May be within a strong cumulus cloud before any type of precipitation falls to the surface. • The combined velocity of an aircraft and hail gives these small pellets a tremendous amount of energy. • If the pellets are “hard” because of exceptionally cold temperatures at their level, aircraft will experience damage.
Hail Orlando, Florida…1992
Severe Weather • Hail • Encounters with larger hail are even more damaging. Hail having the size, weight, (baseball size), and velocities produced by thunderstorms in the western and mountain areas could rip a small plane apart. • Hail and rain pulled into an aircraft engine can cause the engines to stall and flame out, as well as cause internal damage.
Arctic and Tropic Weather • Arctic Weather • Mountains around Arctic Circle holds in cold air • Precipitation is light • Strong winds occur in fall and winter • Visibility is a major problem
Arctic and Tropic Weather • Tropic Weather-fronts are rare and there is more moisture in the air, especially in the oceanic and coastal regions. • Oceanic Weather • Clouds cover about half the sky over the tropical oceans. • Northeast and southeast trade winds converge. • When the wind convergence gets strong, thunderstorms develop that may produce winds up to 70 mph.
Arctic and Tropic Weather • Tropic Weather • Continental Weather • Subject to extreme variations because of land features. • Weather ranges from hot and humid in the lower Congo River to arid Libyan Desert to snow-capped mountains of Kenya. • Day time temperatures may exceed 100o F. • Precipitation often evaporates before it reaches the ground. • Thick early morning steam fog often forms in the jungles.
Arctic and Tropic Weather • Tropic Weather • Island and Coastal Weather • Weather similar along coastal areas and mountainous islands. • During the day, large cumuliform clouds develop. • Clouds seen from long distances indicating presence of islands. • Trade winds result in onshore winds on one side of island and offshore winds on the other.
Arctic and Tropic Weather • Tropic Weather • Island and Coastal Weather • When approaching a coastal area or an island, the aviator should be prepared for instrument conditions. • Precipitation and cloudiness are heavier on windward side. • One of the major factors influencing tropical weather is the easterly wave. • As the wave line approaches, the pressure falls and the wind shifts to the east as the line passes.
Summary 1. Weather Hazards 2. Severe Weather 3. Arctic and Tropic Weather