Weather Flashcards
(163 cards)
1
Q
What causes weather?
A
The uneven heating of the earths surface
2
Q
Why is 1800WX-Brief and fore-flight legal?
A
Because they receive their information through Leidos which is an FAA approved
3
Q
Is winds aloft msl or agl?
A
MSL
4
Q
Why are some Winds Aloft have info at 3000 while others do not?
A
The data is at those altitudes are not reliable due to possible too close to the ground where surface effects the wind and temp, or elevation is too close
5
Q
Are Winds true or magnetic North?
A
Winds are true North
6
Q
What is the composition of the atmosphere?
A
Nitrogen 78%
Oxygen 20%
Argon .92%
Carbon Monoxide/Methane .04%
7
Q
What are the layers of the atmosphere, and what are their characteristics
A
Troposphere: Up to 36,000’, weather occurs here; temperature decreases with height.
Stratosphere: Up to 31 miles, temperature increases due to UV absorption; low turbulence.
Mesosphere: Up to 53 miles, temperature decreases with height.
Thermosphere: Up to 430 miles, temperature increases significantly but feels cold.
Exosphere: Outermost layer, extends to 6,200 miles, where atoms escape into space.
8
Q
What are the standard temperature and pressure values in the atmosphere?
A
Temperature: 59°F (15°C)
Pressure: 29.92” Hg (1013.25 hPa)
9
Q
How do high-pressure systems behave, and what weather do they bring?
A
Characteristics: Outward, downward, clockwise flow.
Associated with clear skies, stable air, fog, and possible temperature inversions.
10
Q
How do high-pressure systems affect wind?
A
Winds flow outward, downward, and clockwise. They are generally weaker near the center and stronger along the periphery.
11
Q
How do low-pressure systems behave, and what weather do they bring?
A
Characteristics: Inward, upward, counterclockwise flow.
Associated with turbulent, unstable air, good visibility, clouds, and precipitation.
12
Q
How do low-pressure systems affect wind?
A
Winds flow inward, upward, and counterclockwise. These winds are typically stronger and associated with turbulent conditions.
13
Q
What is wind?
A
Air in motion relative to the surface
14
Q
What does wind cause?
A
Wind cause the formation, dissipation, and redistribution of weather
15
Q
What forces affect wind formation and movement?
A
Pressure Gradient Force (PGF): Wind flows from high to low pressure.
Coriolis Force: Deflects wind due to Earth’s rotation.
Friction: Slows wind near the surface; decreases with altitude.
16
Q
What is the pressure gradient force, and how does it influence wind?
A
The pressure gradient force drives air from areas of high pressure to low pressure. The greater the pressure difference, the stronger the wind.
Whenever a pressure difference developed over an area, the PFG makes the wind blow in an attempt to equalize the difference
17
Q
The pressure gradient force can be seen in what charts?
A
Identified by height contour gradient on constant pressure chart and by isobar gradient on surface charts
18
Q
How does the Pressure gradient force move in the contour and surface charts?
A
Parallel to the contours/isobars
19
Q
What can you expect of the winds if the Contour/Isobars are widely spaced vs. closely spaced?
A
Widely spaced will signify light winds
Closely spaced will signify strong winds
20
Q
Why are the contour/Isobars not a straight path when moving from high pressure to low pressure?
A
Due to the Earths rotation the Coriolis force effects the direction of the wind flow as well
21
Q
What is the Coriolis Force?
A
A moving mass travels in a straight line until acted by an external force. If the mass is viewed from a rotating platform, the path of the moving object appears curved
On the earth, the effect tends to deflect moving objects to the right in the northern hemisphere and to the left in the southern and is important in the formation of cyclonic weather systems.
22
Q
How does the Coriolis force effect the winds?
A
Since the earth is rotating the air at the equator is traveling faster in comparison to the air in the poles
If the air traveling from the equator moves upward the inertia will cause the air to remain the same speed traveling at a faster speed in comparison to the air in the poles
air traveling towards the equator falls behind
air traveling from the equator pushes ahead
23
Q
How does the Coriolis Force effect a low pressure cell?
A
Since high pressure seeks low pressure
the air coming from the equator is traveling faster defecting to the right
the air coming from the poles falls behind deflecting to the left
resulting in a circular air current spinning counterclockwise
24
Q
How does the Coriolis Force effect influence wind direction and speed?
A
The Coriolis force deflects wind to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. It does not affect wind speed but changes its direction based on latitude.
25
What factors influence the strength of the Coriolis Force?
The strength increases with wind speed and latitude. It is zero at the equator and strongest at the poles.
26
What does wind friction mean?
the force that opposes the movement of wind
Friction between the wind and terrain surface slows the wind
27
How does a rougher terrain effect the winds?
The greater the frictional effect, the stronger the winds
28
What can cause a decrease of wind friction?
Frictional drag of the ground decreases with height and becomes insignificant above the lowest few thousand feet
29
What effects the winds above the wind friction layer?
only the pressure force gradient and the Coriolis force effect the horizontal motion of the air
30
What is temperature?
The measure of the average kinetic energy of the particles of a substance
Higher temp = higher kinetic energy
Temp is an internal energy of air
31
What is Heat Transfer or a Heat Exchange?
When an object/fluid is at a different temperature than its surroundings heat transfer occurs such that the object/fluid and the surrounding reach equilibrium.
Ex: Warm and cold water mixed is lukewarm
32
What ways are heat transferred into and through the atmosphere?
Radiation: This is the transfer of heat energy through electromagnetic waves, like sunlight reaching the Earth's surface
Conduction: Heat transfer through direct contact between molecules, primarily occurring near the Earth's surface where air touches the ground
Convection: Heat transfer through the movement of air masses, where warm air rises and cooler air sinks, creating circulation patterns.
33
What is Radiation?
The majority of heat reaching the Earth's atmosphere comes from the sun via radiation. Once the Earth's surface absorbs this solar radiation, it then radiates heat back into the atmosphere.
Ex: being near a fire - the side of your body nearest the fire warms up.
34
What is Conduction?
Transfer of energy by molecular activity from one substance to another in contact, or through a substance
35
How does heat travel between objects?
heat always flows from the warmer substance to the colder substance
warmer substance cools/loses heat while the cooler substance warms/gains energy
36
What is Convection?
The transport of hear within a fluid (air or water)
This is the most significant way heat is distributed throughout the atmosphere. As air near the Earth's surface is heated, it rises, carrying heat upward. Cooler air then moves in to replace it, creating a continuous circulation pattern
37
What resist temperature changes more water or land?
Water warms and cools more slowly
Helps moderate nearby temperatures (coastal cities less seasonal variations)
38
What is the standard laps rate?
Temperature generally decreases at an average rate of 2°C per 1,000'
* in the troposphere, temp can remain constant or increase with altitude changes
39
What is a Isothermal Layer?
An atmospheric layer where temperature remains constant with height
40
What is a Temperature Inversion?
A layer in which the temperature increases with altitude (instead of following the standard laps rate)
41
What are the types of inversions?
Based inversion (at the surface):Occurs over the land on clear nights with light winds, air in contact with ground cools
Inversion aloft (not at the surface): current or warm air aloft overrunning cold air near the surface *stable and very little turbulence inside
42
What are the necessary ingredients for moisture and precipitation?
Water vapor
Sufficient Lifting - condenses the water vapor into clouds
Growth process - allows cold droplets to grow large and heavy enough to fall and precipitate
43
How does rain happen?
All clouds contain water but only some produce precipitation (not heavy enough).
44
What is the significance of growth process in cloud?
The growth process allows cloud droplets to grow large enough to fall as precipitation
45
What is the Collision-Coalescence?
Collision occurs between cloud droplets of varying size, sticking together to form larger droplets
46
Where is the primary growth of collision - coalescence?
Primary growth process in warm, tropical air masses with a very high freezing level
47
What is Ice Crystal Process?
Occurs in colder clouds when both ice crystals and water droplets are present, water vapor deposits onto the ice crystals
*crystals become heavy enough to fall
48
What are the types of Precipitation?
Snow
Ice Pellets
Freezing Rain
Rain
49
What is snow?
Occurs when the temperature is below freezing throughout the entire depth of the atmosphere
50
What is Ice Pellets?
Requires a shallow, above freezing layer aloft, and a deep, below freezing layer at the surface
*as snow falls into the shallow, warm layer, the snowflakes partially melt. As the precipitation enters the below freezing surface air it freezes into ice pellets.
51
What is Freezing Rain?
Occurs with a deep, above freezing layer aloft and a shallow, below freezing layer at the surface
52
What is Rain?
Occurs when there is a deep layer of above freezing air based at the surface
53
What is a Air Mass?
A large body of air with generally uniform temperature and humidity.
54
What is a Source Region?
The area from which an airmass originates
Air Masses are classified according to temperature and moisture properties of the source region
55
What are Air mass classifications for Temperature properties of a air mass?
Arctic - extremely deep cold air mass; develops mostly in winter over arctic ice/snow
Polar - A relatively shallow cold to air mass which develops over high latitudes
Tropical - A warm to hot air mass which develops over low latitudes
56
What are the Air Mass classifications for Moisture properties of a air mass?
Continental - a dry air mass which develops over land
Maritime - A moist air mass which develops over water
57
What are the types of Air Masses (Temperature + Moisture Properties)?
Continental Arctic - Cold, Dry
Continental Polar - Cold, Dry
Continental Tropical -
Hot, Dry
Maritime Polar - Cool, Moist
Maritime Tropical - Warm, Moist
58
What is a Front?
A front is a boundary or transition zone between two air masses and classified by which type of air mass (cold or warm) is replacing the other
59
How can you detect a Front at the surface?
Significant temperature gradients
Winds usually converge
pressure typically decreases as a front approaches and increases after it passes
60
Explain a Cold Front
Cold fronts have a steep slope, and the warm air is forced up abruptly. (shoveled)
61
Cold Front
A cold front occurs when a mass of cold, dense air pushes under a mass of warmer, lighter air, forcing the warm air to rise rapidly. This interaction creates distinctive weather patterns depending on the air’s stability:
Weather Characteristics
Cloud Development:
Warm air rising rapidly leads to cloud formation.
If air is unstable: Cumulonimbus clouds with strong vertical development.
If air is stable: Nimbostratus clouds with more gradual vertical movement.
Precipitation:
Unstable Air: Heavy rain showers, thunderstorms, hail, and possibly tornadoes.
Stable Air: Light to moderate, steady rain or drizzle.
Winds:
Strong, gusty winds are common near the front due to pressure differences.
Wind direction shifts quickly, typically from south or southwest to northwest as the front passes.
Temperature:
A sudden drop in temperature occurs after the front moves through.
Visibility:
Poor during heavy precipitation but often clears quickly after the front passes.
Movement and Speed
Cold fronts move faster than warm fronts, leading to more abrupt weather changes that are intense but short-lived.
Cold fronts are associated with unstable and turbulent air, making them a significant factor for pilots to plan around.
62
What would the weather look in a cold front with stable warm air rising?
In a cold front with stable warm air rising, the weather would typically include:
Clouds: Stratiform clouds such as nimbostratus or altostratus, with limited vertical development.
Precipitation: Steady, light to moderate rain or drizzle that can last for an extended period.
Winds: Gradual shifts in wind direction as the front passes, without significant gusts.
Visibility: Reduced due to rain and low cloud cover.
Temperatures: A noticeable drop in temperature after the front passes.
63
What would the weather look in a cold front with unstable warm air rising?
In a cold front with unstable warm air rising, the weather would be intense and rapidly changing, characterized by:
Clouds: Towering cumulonimbus clouds with significant vertical development.
Precipitation: Heavy rain showers, often accompanied by thunderstorms, lightning, and possibly hail.
Winds: Strong, gusty winds with potential wind shear and turbulence near the front.
Visibility: Poor during heavy precipitation but rapidly improving after the front passes.
Temperatures: A sharp drop in temperature following the passage of the front.
Other Phenomena: Potential for severe weather like tornadoes in highly unstable conditions.
64
Explain a Warm Front
Warm fronts have a gentle slope (blanket) so the warm air rising along the frontal surface is gradual
65
What would the weather of a Warm Front look like?
Favors development of widespread layered or stratiform cloudiness and precipitation along, and ahead of the front if the warm rising air is stable
66
Warm Front
A warm front occurs when a mass of warm air advances over a retreating mass of cooler air. Because the warm air is less dense, it rises gently over the cooler, denser air, creating a gradual slope. This leads to distinct weather patterns
67
Stationary front
Stationary fronts occur when the forces of two air masses are relatively equal, causing the front not to move.
A stationary front can sit over an area for a prolonged amount of time.
Weather conditions associated with a stationary front vary widely, but they’re generally a mix of cold and warm front conditions.
68
What are the characteristics of a Warm Front?
Weather Characteristics
Cloud Development:
Clouds form in layers due to the gentle ascent of warm air.
Progression: Cirrus → Cirrostratus → Altostratus → Nimbostratus.
Precipitation:
Steady, light to moderate precipitation develops ahead of the front, often over a wide area.
May include drizzle, rain, or snow, depending on the temperature.
Winds:
Winds shift direction as the front passes, often moving from easterly to southerly.
Temperature and Humidity:
Gradual increase in temperature and humidity as the front approaches and passes.
Visibility:
Visibility deteriorates due to rain and low clouds but improves after the front moves through.
Movement and Speed
Warm fronts typically move slower than cold fronts, allowing the weather changes to occur more gradually and last longer.
Warm fronts are generally associated with stable air, creating widespread, less intense weather compared to cold fronts.
69
What is a Stationary Front?
A stationary front occurs when a boundary between two air masses (one warm, one cold) remains relatively still, as neither air mass is strong enough to displace the other. The result is a prolonged interaction between the two, leading to persistent weather patterns.
70
What are the characteristics of a stationary front?
Air Movement:
The warm air rises gently over the cooler air at the boundary, but the air masses do not move significantly.
Winds on either side of the front blow parallel to the boundary, preventing forward movement.
Clouds:
Stratiform clouds, such as nimbostratus or altostratus, often dominate.
In unstable conditions, cumulonimbus clouds may develop, leading to thunderstorms.
Precipitation:
Continuous or intermittent light to moderate rain, drizzle, or snow.
Precipitation can persist for several days, particularly in areas of high moisture.
Temperature:
Sharp contrasts exist on either side of the front, with warmer temperatures on the warm air side and cooler temperatures on the other.
Visibility:
Reduced due to precipitation, fog, or mist near the front.
Key Hazards
Persistent precipitation can lead to flooding.
Reduced visibility and low ceilings create challenges for aviation.
71
What makes a Stationary Front stationary?
The lack of significant movement is due to a balance between the forces of the opposing air masses or a lack of sufficient upper-level wind to push the front forward. This stationary behavior distinguishes it from faster-moving warm or cold fronts.
72
How long can a Stationary front last?
A stationary front can remain in a single area for several days to weeks. This prolonged presence occurs when neither the warm nor the cold air mass has enough force to dominate and displace the other.
The reasons include:
Balanced Forces:
The opposing air masses are of similar strength, preventing significant movement.
Weak Upper-Level Winds:
Jet stream or upper-level winds, which typically drive frontal movement, may be weak or misaligned, failing to push the front.
Geographical Influences:
Features like mountains or valleys can trap air masses, anchoring the front in place.
Low Pressure Along the
Front:
A weak or slow-moving low-pressure system may stall, keeping the boundary stationary.
73
What are the impacts of a long lasting Stationary Front?
Persistent cloud cover and precipitation, which can lead to flooding in affected areas.
Gradual mixing of air masses, causing subtle but prolonged changes in temperature and humidity.
Aviation challenges due to reduced visibility, low ceilings, and extended adverse weather conditions.
74
Occluded front
An occluded front occurs when a cold front overtakes a warm front, lifting the warm air mass completely off the ground. The weather associated with an occluded front depends on whether it is a cold occlusion or a warm occlusion:
Types of Occlusions
Cold Occlusion:
The air behind the cold front is colder than the air ahead of the warm front.
The cold air undercuts both the warm air and the cooler air ahead of the warm front.
Warm Occlusion:
The air behind the cold front is warmer than the air ahead of the warm front.
The cooler air ahead of the warm front remains near the ground, forcing the milder cold air aloft.
75
What are the weather characteristics of an occluded front?
Cloud Development:
Combination of cumulonimbus and nimbostratus clouds, depending on moisture and air stability.
Precipitation:
Prolonged and widespread.
Includes steady rain, drizzle, and sometimes thunderstorms, especially near the surface boundaries.
Winds:
Winds shift as the front passes, often becoming more complex due to the merging air masses.
Temperature:
Gradual cooling follows the occluded front as the warm air is displaced aloft.
Visibility:
Poor during precipitation but improves after the front clears.
Movement and Speed
Occluded fronts typically move slower than cold fronts but faster than warm fronts, with weather changes lasting for extended periods.
Occluded fronts represent the later stages of a low-pressure system's lifecycle, often leading to widespread cloud cover and mixed precipitation patterns.
76
What is an Occluded Front?
A Cold Front typically moves faster than a Warm Front, they catch up to a Warm Front causing an occluded front.
77
What is happening during a Occluded Front?
The cold air undercuts the retreating cooler air mass, further lifting the already rising warm air.
Clouds and precipitation can occur in areas of frontal lift along, ahead of, and behind an occluded front
78
What is the difference between a Cold Front and an Occluded Front?
The primary difference between an occluded front and a cold front lies in how the air masses interact and the resulting weather patterns:
Cold Front: Interaction: A cold air mass directly pushes under a warm air mass, forcing the warm air to rise rapidly. The boundary is between the cold air and warm air at the surface.
Occluded Front: Interaction: A cold front overtakes a warm front, lifting the warm air mass completely off the ground. The cold air meets cooler air (not warm) ahead of the warm front. The boundary is between the cold air behind the cold front and the cooler air ahead of the warm front, with warm air aloft.
In a cold front, the boundary between cold and warm air remains at the surface, producing a sharper, more intense weather transition. In an occluded front, the warm air is lifted entirely off the surface, creating broader, more stratified weather with mixed precipitation and cloud layers.
79
What is a Cold Front Occlusion?
Fast moving cold front is cooler than the air ahead of the slow moving warm front
Cold air replaces the cool air and forces warm air aloft the atmpsphere
80
Cold Front Occlusion
A cold front occlusion occurs when the cold front’s air mass is colder than the air mass in front of the slow-moving warm front.
The cold air replaces the cool air and forces the warm front aloft into the atmosphere.
Typically, the cold front occlusion creates a mixture of weather found in both warm and cold fronts, provided the air is relatively stable.
81
What is a Warm Front Occlusion?
Air ahead of the warm front is colder than the air of the cold front.
if air being forced aloft by the warm front is unstable: severe weather
Embedded Thunderstorms
Rain
Fog
82
Warm Front Occlusion
A warm front occlusion occurs when the air ahead of the warm front is colder than the air of the faster-moving cold front.
When this occurs, the cold front “rides up” and travels over the warm front’s cold air mass.
If the air forced upwards by the warm front occlusion is unstable, the weather is more severe than the weather found in a cold front occlusion. Embedded thunderstorms, rain, and fog are likely to occur.
83
What are the different atmosphere layers that divide clouds?
High (Cirro)
Middle (Alto)
Low
84
Explain high clouds
Cirrus: Ice Crystals, no significant icing or turbulence
Cirrocumulus: supercooled water droplets, ice crystals, turbulence and icing
Cirrostratus: Ice crystals, no turbulence, little icing
85
Explain middle clouds
Altocumulus: some turbulence, some icing, small liquid water droplets, possible ice crystals
Altocumulus Lenticularis: shape of almonds or waves, mountainous areas
Altostratus: Often overcast, little to no turbulence, light to moderate icing in the supercooled water
Nimbostratus: Nimbo = precipitation, little turbulence, can pose a significant icing threat near or below freezing
86
Explain Low Clouds
Cumulus: some turbulence and no significant icing
Towering Cumulus: strong turbulence, clear icing above freezing levels
stratocumulus: water droplets, possible soft hail, snowflakes, virga under the clouds, rare precipitation, turbulence and possible icing.
Stratus: Does not create precipitation often, little to no turbulence, temperatures near or below freezing can create hazardous icing conditions
87
What is a cloud?
A cloud is a mass of floating water droplets or ice crystals
88
What is Turbulence?
Turbulence is an irregular motion of the air resulting from eddies and vertical currents.
89
What causes Turbulence?
Turbulence is cause by
Convective Currents
Obstructions in the wind flow
Wind shear
Frontal Movement
90
What are the types of Turbulence?
Convective
mechanical (mountain wave)
Wind shear
Temperature inversion
Clear air
91
What is Convective Turbulence?
Turbulence caused by convective currents and subsequent rising and sinking of air. For every rising current there is a compensating downward current.
*because of uneven heating the strength of convective currents can vary considerably within short distances.
Cumuliform clouds
Expected turbulence below or in the clouds
When air is too dry for cumuliform clouds, convective currents can still be actvice
92
Explain Mechanical Turbulence
Turbulence caused by obstructions to the wind flow
mechanical turbulence is caused by trees, building, mountains and so on
93
What are Mountain Waves?
*its a form of Mechanical
Are a form of mechanical turbulence which develops waves above and downwind of mountains
Stable air flow passes over a mountain or ridge,
*violent downdrafts
94
What is Wind Shear Turbulence?
the rate of change in wind direction or speed, either a wind shift or a wind speed gradient at any level in the atmosphere
95
Temperature Inversion
Layer of atmosphere in which temperature increases with altitude
inversion commonly occurs within the lowest few thousand feet above ground due to nighttime radiation
Strong wind shears often occur across temperature inversions layers. Generates turbulence.
96
Clear Air Turbulence
erratic air currents that occur in cloudless air at high altitudes, usually above 15,000 feet.
It's caused by air masses moving at different speeds, and is often associated with jet streams
97
What is Turbulence Factors?
How an aircraft will respond to turbulence varies with: intensity of the turbulence, aircraft size, wing loading, airspeed, and aircraft altitude
98
What ingredients are needed to cause a thunderstorm?
Sufficient Water vapor
Unstable atmosphere
Lifting mechanisms (Fronts, low pressure system, trout , convective, Orographic lifting, Dry-lines, Outflow Boundaries)
99
What is an unstable atmosphere as one of the ingredients when it comes to creating a thunderstorm?
warm air near the surface rises because it is less dense than the cooler air above it.
As the warm air rises, it continues to ascend until it reaches an altitude where the surrounding air is cooler than the rising air, allowing it to keep rising and condensing into clouds. This process can lead to the development of thunderstorms if other conditions are also present.
Key points about an unstable atmosphere for thunderstorms:
Rising warm air: The warm air near the surface heats up, becomes lighter, and rises through the cooler air above it. As it rises, it cools at a slower rate than its surroundings, which creates instability.
Continuous vertical development: The more unstable the atmosphere, the stronger the upward motion of air, which can lead to the formation of cumulonimbus clouds (thunderstorm clouds). These clouds can grow vertically to great heights, sometimes reaching the stratosphere.
Thunderstorm formation: The rising warm, moist air cools and condenses, forming clouds and releasing latent heat, which further fuels the rising air. As this cycle continues, it can lead to the development of intense thunderstorms with updrafts, downdrafts, and other severe weather phenomena like lightning and hail.
100
What is Unstable atmosphere?
An unstable atmosphere occurs when the air in the atmosphere is warmer than the surrounding air, causing it to rise. This happens when the lapse rate (rate at which temperature decreases with altitude) is steeper than the adiabatic lapse rate, meaning that the air parcel is cooler than its surroundings as it rises.
101
What is stable air?
A stable atmosphere is one where air resists vertical movement. This happens when the temperature of the air decreases at a rate slower than the adiabatic lapse rate (the rate at which an air parcel cools as it rises). In a stable atmosphere, if an air parcel is displaced upward, it will be cooler and denser than the surrounding air, causing it to sink back down. This stability inhibits the development of strong vertical air currents and cloud formation.
102
What is a lifting mechanism?
Lifting mechanisms are processes that cause air to rise, which is a key ingredient for thunderstorm development. When air is lifted, it cools and condenses, forming clouds and potentially leading to thunderstorms if other conditions are met.
103
What are some common lifting mechanisms for a thunderstorm?
Connective lifting, low pressure systems, fronts , trot, dry lines,
Convective Lifting: Occurs when the surface air is heated by the sun, making it rise due to being warmer (and thus less dense) than the surrounding air. This is often the primary mechanism for afternoon thunderstorms.
Orographic Lifting: Happens when air is forced to rise over a mountain range or other elevated terrain. As the air rises, it cools and may form clouds or precipitation.
Frontal Lifting: Occurs when a warm air mass is forced to rise over a colder, denser air mass at a weather front (e.g., cold front, warm front). The warmer air is lifted, cooling and condensing to form clouds and possibly thunderstorms.
Mechanical Lifting: Occurs when air is physically forced upward by obstacles like buildings, hills, or other terrain features, causing turbulent air that can lead to cloud formation.
104
What are the stages of a Thunderstorm?
Towering Cumulus stage: (strong updrafts)
Maturing stage: Updrafts and strong downdrafts. When precipitation reaches the surface
Dissipating stage: Strong downdrafts, subsiding air replaces the updrafts throughout the cloud cutting off the supply of moisture
105
What are the different types of Thunderstorms
Single Cells
Multi Cells
Super Cells
106
Why are Thunderstorms are described as "convective"?
because they are primarily formed and sustained by the process of convection, which is the vertical movement of air where warm, moist air rises and cooler air sinks, creating the rising updrafts and falling downdrafts that are essential for thunderstorm development and structure; essentially, the rising air within a thunderstorm acts like a convection current, fueling the storm's intensity and precipitation formation
107
What does the term cell means in relation to a thunderstorm?
When discussing thunderstorms, the term cells refers to the individual convective systems within the storm. Each cell is a self-contained unit of rising air, precipitation, and associated weather phenomena.
Thunderstorm cells go through distinct life stages and can occur as isolated entities or as part of larger storm systems.
108
What is a Single Cell?
one cell, easily circumnavigated except at night or when embedded in other clouds.
Single cell thunderstorms are rare; almost all are multi-cells
these are isolated, short-lived storms (30–60 minutes) formed by a single updraft.
Typically small and non-severe.
Often form on warm afternoons due to surface heating. Moderate rain, brief lightning, and occasional hail.
109
What is a Multi-cell?
Clusters of cells at various stages of their life cycle
as first cell matures, it is carried downwind, and a new cell forms upwind to take its place
line of storms can extend for hundreds of miles
Can last for several hours.
Hazards: Strong winds, heavy rain, lightning, and occasional severe hail or tornadoes.
Squall lines, mesoscale convective systems
110
What is a supercell?
A highly organized storm with a single, powerful, and persistent rotating updraft (mesocyclone).
dangerous convective storm that consists of primary a single; steady rotating updraft that last for a extended period of time
Severe weather, including large hail, strong tornadoes, and damaging winds.
updrafts up to 9,000 fpm
111
What are some hazards of Thunderstorms?
Lighting
Adverse Winds
Downburst (Microbust)
Turbulence
Icing
Hail
Rapid Altimeter Changes
Static Electricity
Tornados
112
What is a microbust
A microburst is a localized, intense downdraft that spreads outward rapidly upon reaching the ground. It is a highly dangerous weather phenomenon, especially for aviation, because of the sudden and severe wind shear it creates near the surface.
Typically lasts 5–15 minutes.
Diameter: Up to 2.5 miles.
Downdraft speeds: Can exceed 6,000 feet per minute.
Horizontal winds: Up to 100 knots as air spreads outward.
113
Outflow Boundaries
Cool air from downdrafts spreading out in some or all directions to create a boundary
Acts similar to a cold front (lifting mechanism)
Depicted on some Prog charts and radar
Can create new convective storms lasting several hours
114
Describe Tornadoes
Forms under cumulonimbus clouds typically supercells
warm, moist air near the ground and cooler, dry air above (dry line)
wind shear with height
115
What is a dry line?
A dry line is a boundary that separates moist air from dry air
a significant factor in severe weather frequency. It's also known as a dew point line or Marfa front.
116
Explain frost
on cool, clear, calm nights, the temperature of the ground and objects on the surface can cause temperatures of the surrounding air to drop below the dew point
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What are the different types of Icing
Structural Icing:
-Rime
-Clear
-Mixed
Induction Icing
(engine icing)
Icing in the induction system blocking air into the engine
Instrument Icing:
Icing in the pitot static system
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Describe Rime Icing
rough, milky, opaque ice formed by instant freezing of small, supercooled water droplets after they strike the aircraft
colder temperatures, more common in stratiform clouds
opaque because air is trapped inside
usually forms between -10°C and -20°C
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Clear Icing
A glossy, clear, or translucent ice formed by relatively slow freezing of lare, supercooled water droplets
exist more in warmer environment, higher liquid water contents
small portion of the drop freezes while remaining unfrozen portion flows or smears over the aircraft surface and gradually freezes
More common in cumuliform clouds, between 0°C and -10°C
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What is Mixed Icing
A mixture of clear and rime Ice
Poses similar hazard to aircraft as clear ice
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What type of structural icing is the most dangerous?
Clear Ice is more Hazardous than Rime ice
It tends to disrupt airflow considerably more than rime icing
It is clear and more difficult to see
More difficult to remove
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What are some hazards of Icing
Degrades engine performance
Destroys smooth airflow over the wing and increases drag
Reduce lift approx 30% and increases drag 40%
Aircraft may stall at much higher airspeed
Increases weight on aircraft
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Freezing level
Pilot should be on alert for icing everytime the temperature approaches 0°C and visible moisture is present
when carried above the freezing level, water becomes supercooled freezes on impact with an aircraft
air and dew point meet to become visible moisture
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What is Fog
Miniture water droplets that are based at the surface and reduce visibility to less than 5/8 statue miles
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What is the difference between fog and clouds?
Fog differs from cloud only in that its base must be at the surface while clouds are above the surface
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What are the different types of fog?
Radiation
advection
upslope
steam
precipitation
Ice
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What is Radiation Fog?
Produces over land on a calm, cool, and clear night
generally at night time occurrence
Terrestrial radiation cools the ground, the ground cools the air, air reaches dew point, fog forms
ground fog generally burns off rapidly after sunrise
Not common over water due to it holding heat longer than the ground can
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What is Advection Fog?
Forms when moist air moves over a colder surface, air cools to its dew point
mostly common around coastal areas, especially U.S west coast.
Winds less than 15 knots lifts fog into a layer of low status or stratocumulus clouds
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What is Upslope Fog?
Moist, stable air being adiabatically cooled to its dew point as it moves up sloping terrain
wind speeds of 5 - 15 knots are most favorable; stronger winds tend to lift the fog into a low layer of status clouds
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What is Steam Fog?
Very cold and dry air moves over warm water, enough moisture may evaporate from the water surface to produce saturation
Steam fog is often very shallow; as the steam rises; it evaporates in the unsaturated air above.
expect convective turbulence flying through it
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What is precipitation Fog?
Warm rain falls through cool air, the precipitation saturates the cool air.
This fog is dense and long lasting
when mixed in with rain, it can be tough to determine exactly where precipitation fog is and isn't
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What is Ice Fog?
Similar to radiation fog, however, temperature and dew point are below freezing
everything the fog touches tends to have a layer of ice over it
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What are the altitutes
Pressure Altitude
The altitude indicated when the altimeter is set to the standard pressure of 29.92" Hg.
Used for performance calculations and above 18,000 feet MSL (Class A airspace).
Density Altitude
Pressure altitude corrected for temperature deviations from standard.
Represents the altitude your aircraft performs as if it were at; higher temperatures or humidity increase density altitude.
Indicated Altitude
The altitude shown on the altimeter when set to the local altimeter setting.
True Altitude
The actual altitude above mean sea level (MSL). Used for obstacle clearance and chart elevations.
Absolute Altitude
The altitude above ground level (AGL).
Critical during landings and low-level navigation.
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Headings
Headings
True Heading (TH)
The direction your aircraft points relative to true north (geographic north).
Calculated from your true course (correcting for wind drift using wind correction angle).
Magnetic Heading (MH)
The direction your aircraft points relative to magnetic north, which differs from true north due to magnetic variation.
MH = TH \pm \text{Magnetic Variation} ]
Compass Heading (CH)
The direction you fly as shown on the magnetic compass, adjusted for compass deviation (errors caused by the aircraft’s magnetic fields).
CH = MH \pm \text{Deviation} ]
Course
The intended path over the ground (relative to true or magnetic north). Adjust headings to maintain the course in the presence of wind.
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If you are pre-flying and are concerned about the possibility of icing, where would you look for the information?
Current Icing Product (CIP)
Forecast Icing Product (FIP)
-determine probability and severity of icing aloft
-forecasts available out to 18 hrs of various altitudes
-available at aviationweather.gov and in mobile apps
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If your IFR flight requires you to fly over mountains terrains, what are some concerns with weather?
If flying over mountains terrains you should look at the forecast winds at the ridge level
if the velocity is over 20-30 kts you can expect up and down drafts and turbulence at lower levels downwind of the mountains
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what is the degree in temp that will allow the atmosphere to double in moisture?
for each 11°C rise in temp the ability of the atmosphere to hold moisture is doubled
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What is the most hazardous aspect of structural icing?
the Aerodynamic effects
Ice alters the shape of an airfoil, reducing its capacity to produce lift and decreases the angle of attack contributing to the wind stalling.
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What is a supercooled waterdroplet?
a water droplet that has been lifted from an above freezing temperature to a below freezing temperature
the water droplet will remain liquid until it is disturbed
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What are some contributing factors that can create an environment for the most severe icing?
An area where there is moisture and where there is lifting
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When should you expect icing?
Airfract icing is most likely in visible moisture when the temperature is below 2°C and -10°C
expect icing when flying in visible precipitation, such as rain or cloud droplets, and the temperature is between 2°C and -10°C
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Besides clear, rime, and mixed Ice there is one more. which one is that and what are the conditions?
the 4th type is Light Rime Ice
accumulates slowly in status clouds between 5 and -10°C below freezing
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Whats the difference between snow and ice
snow is already frozen water droplets while ice is supercooled droplets that freeze when disturbed
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What is freezing rain?
Freezing rain is when the warm air above starts to rain, as the water droplets fall they enter a colder atmosphere cooling the waterdroplets
Anti and de-icing systems are not certified for flight in freezing rain
If an approach is made in freezing rain the lower you go the worse the icing will become
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How is freezing rain created?
it occurs north of a warm front, when warm rain falls into freezing rain at the surface
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As the plane increases in speed, does the surface temperature of the plane change?
yes, a plane traveling at a faster speed will have a warmer surface area (this can play a factor when it comes to icing conditions)
an increase of 170 IAS would increase the surface of the plane by 12°C
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How much icing is needed to reduce lift by 30% and increase drag by 40%
ice as thick and rough and medium sandpaper
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What must an aircraft have to be able to fly in known icing conditions
It must have a flight into known icing (FIKI) ceertification
conplete system - tested in a prescribed variety of icing conditions
non modifications - valid only as approved by the manufacturer
*single engine aircraft requires dual electrical and vacuum systems, in addition to the ice-protection systems
This certification is only allowed for a limited amount of type
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Usually, the greatest turbulence is found on the front side of the storm, as well as the side from which it is being fed moisture. A storm that is moving east in a moist, southerly flow could be meanest on the east and the south side; mean being only a relative term here
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Where could we find Embbeded thunderstorms?
They can usually be found in warm or stationary frontal zones
The general conditions might be rain showery with heavier rain surrounding by the less severe conditions
in tropical storm weather there has been indications of tornado activities
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What is the recommended thunderstorm avoidance?
stay at least 5 miles away from thunderstorms, and 20 miles away when severe thunderstorms are forecasted
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What is the main difference between the Extended Convective Forecast Product (ECFP) and the Traffic Flow Management Convective Forecast (TCF)?
ECFP: A computer-generated model showing thunderstorm probability. It provides long-range planning guidance but does not include echo tops.
TCF: A meteorologist-created forecast with high confidence, specifying coverage and expected echo tops. It’s used for tactical decision-making in the short term.
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How does the ECFP indicate thunderstorm probabilities, and why is this important for pilots?
Hashed areas: 40-59% probability
Solid lined areas: 60-79% probability
Solid blue filled areas: >80% probability
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What are the most important environmental factors that indicate possible thunderstorm development?
Thunderstorm-favorable conditions:
A front or low-pressure system nearby.
Warm, humid air near the surface and cold, dry air aloft.
Wind shear (significant changes in wind speed or direction with altitude).
Seasonal patterns where storms are common.
❌ Stable conditions that suppress storms:
Sinking air (high pressure).
Cold, dry air at the surface.
Warm, humid air aloft with little temperature change.
Lack of wind shear.
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What is a microburst, and why is it dangerous for aircraft?
Definition: A localized, intense downdraft within a thunderstorm, producing strong horizontal outflow winds when it reaches the surface.
Characteristics:
Downdrafts can exceed 6,000 ft/min.
Horizontal winds 45+ knots, rapidly changing direction.
Diameter 2-3 miles, lasting less than 15 minutes.
Effects on Aircraft:
Initial headwind → airspeed increase (false sense of performance gain).
Downdraft → rapid loss of altitude.
Tailwind → airspeed drop, reduced lift, and potential crash.
Recognition & Warning Signs:
Thunderstorms, virga, or heavy rain in the area.
ATC warnings or pilot reports of significant airspeed changes (15+ knots).
Surface temperature-dew point spread of 15-30°C.
Avoidance & Response:
✅ Avoid known or suspected microburst activity.
✅ Use maximum power on takeoff and be prepared for sudden airspeed changes.
✅ On approach, increase airspeed margin and be ready for a go-around.
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Wind Shear Basics & Recognition
Wind Shear: A sudden change in wind speed or direction over a short distance, occurring at any altitude.
First Indication in Cockpit: A sudden, unexpected change in indicated airspeed.
Low-Level Wind Shear: Especially dangerous near the surface, affecting aircraft performance during takeoff and landing.
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How does wind shear affect an aircraft during approach?
✅ Headwind to Tailwind Shear (Performance decrease):
Airspeed drops, nose pitches down, descent rate increases.
Pilot must add power to maintain glide slope or risk landing short.
✅ Tailwind to Headwind Shear (Performance increase):
Airspeed rises, nose pitches up, descent rate decreases.
Pilot must reduce power initially, then add power as needed to prevent overshooting.
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Microbursts: Identification & Impact
Definition: A localized, intense downdraft within a thunderstorm, creating strong outflow winds at the surface.
Characteristics:
Downdrafts exceed 6,000 ft/min.
Horizontal winds 45+ knots.
Small diameter (2-3 miles) and short duration (less than 15 minutes).
Effects on Aircraft:
Initial headwind → performance increase (false sense of security).
Downdraft & tailwind → rapid performance loss → possible crash.
📌 Takeaway: Microbursts are extremely hazardous and often exceed aircraft performance capabilities. Avoidance is the best strategy.
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How can pilots minimize the risks of wind shear and microbursts?
✅ Before Flight:
Check weather reports (SIGMETs, ATIS, pilot reports).
Be aware of convective activity, large temperature-dew point spreads, and strong winds aloft.
✅ During Takeoff:
Use longest suitable runway.
Apply maximum rated power.
Consider a higher liftoff airspeed.
✅ During Landing:
Stabilize approach early (by 1,000 ft AGL).
Avoid large power reductions.
Use increased approach speed for safety.
Be ready for a go-around if conditions deteriorate.
📌 Takeaway: Preparation and awareness are key—pilots should respect wind shear warnings, adjust flight plans accordingly, and prioritize avoidance.
Would you like any refinements or more focus on specific areas?
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What is datalink weather, and why is it useful for IFR pilots?
Datalink weather provides in-flight weather updates through ADS-B or SiriusXM, displaying radar, METARs, TAFs, PIREPs, and more on avionics or tablets. It helps pilots make informed decisions but does not replace real-time weather observation.
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What are the differences between ADS-B and SiriusXM weather?
ADS-B: Free, ground-station-based, limited coverage at low altitudes or in mountainous terrain.
SiriusXM: Subscription-based, satellite-delivered, nationwide coverage even on the ground.
Radar Resolution: ADS-B has lower resolution beyond 250 miles, while SiriusXM maintains higher resolution nationwide.
Additional Products: SiriusXM includes storm cell tops, satellite imagery, and surface forecasts.
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What are the key limitations of datalink weather?
Delayed Data: Radar images can be 5-20 minutes old; METARs update hourly.
Not for Tactical Use: Use it for big-picture route changes, not for picking through storms.
Terrain & Altitude Impact (ADS-B Only): Limited reception at low altitudes or in valleys.
Incomplete Data: Pilot reports may not include all ATC-received updates.
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