Weather

DESCRIBE the effects of pressure changes on aircraft altimeters

*High to Low, Look Out Below - The aircraft is lower than indicated, thus the indicated altitude is higher than the aircraft. *Low to High, Plenty of Sky - The aircraft is higher than indicated, thus the indicated altitude is lower than the aircraft.

DESCRIBE the effects of temperature deviations from the standard lapse rate on aircraft altimeters

*High to Low, Look Out Below - The aircraft is lower than indicated, thus the indicated altitude is higher than the aircraft. *Low to High, Plenty of Sky - The aircraft is higher than indicated, thus the indicated altitude is lower than the aircraft.

DESCRIBE weather data on satellite imagery

*IR - The IR picture records heat radiation being emitted by the clouds and earth. The images show temperature differences between cloud tops and the ground, as well as temperature gradations of cloud tops over the surface of the Earth. *Visible - Thus, the visible picture is primarily used to determine the presence of clouds and the type of clouds from shape and texture based on cloud reflectivity.

Types of Altitudes

*Indicated altitude is the altitude read directly from the altimeter. *Calibrated altitude is indicated altitude corrected for instrument error. *Mean Sea Level (MSL) or True altitude is the actual height above mean sea level (MSL). It is found by correcting calibrated altitude for temperature deviations from the standard atmosphere. *AGL or absolute altitude is the aircraft's height above the terrain directly beneath the aircraft and is measured in feet above ground level (AGL). *Pressure altitude is the height above the standard datum plane. The standard datum plane is the actual elevation above or below the earth's surface at which the barometric pressure is 29.92 in-Hg. (FL350) *Density altitude (DA) is pressure altitude corrected for nonstandard temperature deviations. On a hot day, air molecules are farther apart, decreasing the air density and increasing the density altitude.

DESCRIBE the types of engine icing

*Induction - Similar to wing icing. However, the ducts may ice when skies are clear and temperatures are above freezing. The reduced pressure that exists at the intake lowers the temperature to the point that condensation and or deposition take place, resulting in the formation of ice. *Compressor - Ice forming on compressor inlet screens and compressor inlet guide vanes will restrict the flow of inlet air, eventually causing engine flameout. The reduction in airflow is noticeable through a loss of thrust and a rapid rise in exhaust gas temperature. As the airflow decreases, the fuel-air ratio increases, which in turn raises the temperature of the gases going to the turbine.

LIST the intensities of turbulence used in Pilot Reports (PIREPs)

*Light - Momentarily causes slight, erratic changes in altitude and/or attitude (pitch, roll and yaw). *Moderate - Similar to light but of greater intensity. Changes in altitude and/or attitude occur but the aircraft remains in positive control at all times. Causes variations in indicated airspeed. *Severe - Causes large, abrupt changes in altitude and/or attitude. It usually causes large variations in indicated airspeed. Aircraft may be momentarily out of control. *Extreme - The aircraft is violently toss about and is practically impossible to control. It may cause structural damage.

DESCRIBE the weather conditions associated with various clouds

*Low Clouds - Frequently present serious hazards to flying. The most serious hazard is the proximity of the cloud base to the surface of the Earth. Some of the low cloud types hide hills, making a collision with the terrain a very real danger, and visibility within low clouds is very poor. Low clouds may also hide thunderstorms. If the clouds are at or below freezing temperatures, icing may result. Icing accumulates faster in low clouds since they are generally denser than middle and high clouds. Turbulence varies from none at all to moderate turbulence. Expect turbulence in and below the clouds. Precipitation from low clouds is generally light rain or drizzle. Contain water droplets. Below 6500 ft *Middle Clouds (alto-) - Contains ice crystals and water droplets. Visibility in middle clouds varies depending on cloud density from ½ mile to a few feet. Turbulence may be encountered in middle clouds. Frequently these clouds are dark and turbulent enough to make formation flying difficult. Icing is common due to the presence of super -cooled water droplets. Rain, rain and snow mixed, or snow can be encountered in thick middle clouds. Virga, which is rain or snow that evaporates before reaching the ground, may be encountered below these clouds. 6500ft to 20,000 ft *High Clouds (cirro/cirrus) - High clouds have little effect on flying except for moderate turbulence and limited visibility associated with dense jet stream cirrus. Since high clouds are composed mostly of ice crystals, they have no precipitation and do not constitute an icing hazard. Severe or extreme turbulence is often found in the anvil cirrus of thunderstorms. 20,000 ft to 40,0000 ft. Mostly ice crystals. *Special Clouds with Extensive Vertical Development - This category consists of towering cumulus and cumulonimbus clouds. The bases of these clouds are found at the low to middle cloud heights and their tops extend through the high cloud category. Towering cumulus are clouds nearing the thunderstorm stage. They can produce heavy rain showers and moderate turbulence in and near the cloud. Icing is common above the freezing level. Cumulonimbus clouds are thunderstorm clouds. A cumulonimbus cloud is sometimes referred to as a "CB." Cumulonimbus is an exceedingly dangerous cloud, with numerous hazards to flight such as severe to extreme turbulence, hail, icing, lightning, and other hazards

DEFINE the terms used to report turbulence with respect to time

*Occasional - Less than 1/3 of the time *Intermittent - 1/3 - 2/3 of the time *Continuous - More than 2/3 of the time

DESCRIBE icing conditions associated with fronts

*Cold fronts and squall lines generally have a narrow band of both weather and icing. The associated clouds will be cumuliform. The icing zone will be about 10,000 feet thick, 100 mileswide, and the icing will be predominantly clear, accumulating rapidly. *Warm fronts and stationary fronts generally have a much wider band of weather and icing, reflecting the size of the warm frontal zone. The icing will be found mainly inside stratiform clouds, accumulating at a relatively low rate, due to the smaller size of the super-cooled water droplets. The vertical depth of the icing zone will generally be about 3000 to 4000 feet thick, possibly up to 10,000 feet. The type of icing will be predominantly rime, but may also contain mixed icing. *Occluded fronts often produce icing covering a very widespread area, containing both stratiform and cumuliform-type clouds. The depth of the icing zone will often be 20,000 feet-approximately double the de pth of icing zones with other type fronts. The types of icing will be clear, mixed, and rime, with a very rapid and heavy rate of accumulation.

DEFINE the types of visibility

*Flight Visibility - The average forward horizontal distance, measured in statute miles from the cockpit of an aircraft in flight, at which a pilot can see and identify prominent unlighted objects by day and prominent lighted objects at night. *Prevailing Visibility - The greatest horizontal visibility, measured in statute miles, equaled or exceeded throughout at least half the horizon circle, which need not be continuous. *Slant Range Visibility - The distance on final approach when the runway environment is in sight. *Runway Visual Range - The horizontal distance, expressed in hundreds of feet or meters, a pilot will see by looking down the runway from the approach end.

DESCRIBE the two main types of fog

*Radiation fog occurs due to nocturnal cooling, usually on clear nights, when the Earth releases relatively large amounts of radiation into the atmosphere, cooling the surface. Winds play an important factor in fog formation. Winds less than 5 knots usually results in shallow fog. Winds of 5 to 10 knots will usually cause dense fog. Winds of greater than 10 knots will usually dissipate the fog and cause low stratus or stratocumulus clouds to form. *Advection fog occurs when warm, moist air moves over a cold surface and the air is cooled to below its dew point. Common in coastal areas, it is often referred to as sea fog when observed to come from the sea. Fog of this type becomes thicker and denser as the wind speed increases, up to about 15 knots.

DESCRIBE the types of atmospheric stability

*Stable - f the ball is displaced, and tends to return to its original position, the ball is said to be stable. *Neutral stable - If a ball on a flat table is displaced, it will tend to remain in its new position and is said to be neutrally stable. It will not have a tendency to return to its original position, or move away from its final position. *Unstable - Once the ball is displaced, it will tend to move away from its original position, never to return, and the ball is said to be in an unstable condition.

DESCRIBE differences in U.S. civil, military, and international TAFs

1. U.S. civil stations will use statute miles instead of meters. 2. U.S. civil stations include date time group of transmission prior to the forecast period (e.g., 091720Z 081818). 3. When U.S. military stations amend, correct, or have a routine delayed forecast, a remark will be appended to the last line of the forecast with the appropriate time (e.g., AMD2218). 4. U.S. civil stations may include probability of precipitation occurrence. International differences: Valid period: variable vs 24 hrs. Winds reported in meters or kilometers per hour versus knots. And CAVOK used (Clear Air, Visibility OK)

DESCRIBE the four principal cloud groups

1.Low clouds, ranging from just above the surface to 6500 feet AGL. 2. Middle clouds with bases between 6500 and 20,000 feet AGL. 3. High clouds found above 20,000 feet AGL. 4. Special clouds with extensive vertical development.

STATE the average lapse rate in degrees Celsius

2° Celsius per 1000 ft

STATE the letter identifiers of each of the In-Flight Weather Advisories

???

Front (Weather)

A front is an area of discontinuity that forms between two contrasting air masses when they are adjacent to each other. A front can be thought of as a border, boundary, or line between the air masses.

DESCRIBE the characteristics of a squall line

A line of violent thunderstorms. They develop 50 to 300 miles ahead of the cold front and roughly parallel to it. They form when cold air downdrafts flowing ahead of a cold front lift additional warm, unstable air. The uplifted air develops its own updrafts and downdrafts and starts the thunderstorm development cycle.

DESCRIBE the signs and hazards associated with microbursts

A microburst is an intense, highly localized downward atmospheric flow with velocities of 2000 to over 6000 feet per minute. This downward flow diverges outward, producing a vortex ring of wind that can produce differential velocities ranging from 20 to 200 knots in an area only ¼ to 2½ miles in diameter. Low-level wind shear, gusty winds, heavy rain, or severe thunderstorm. Visual cues include virga, localized blowing dust (especially in circular or elliptical patterns), rain shafts with rain diverging away from the core of the cell, roll clouds, and, of course, experiencing vivid lightning or tornado-like activity.

DESCRIBE the aviation hazards of ash clouds

Aircraft flying through volcanic ash clouds have experienced a significant loss of engine thrust and/or multiple engine flameouts along with wing leading edges and windshields being sandblasted. Volcanic ash can cause rapid erosion and damage to the internal componentsnof engines with loss of thrust within 50 seconds.

Air Mass

An air mass is a large body of air that has essentially uniform temperature and moisture conditions in a horizontal plane, meaning that there are no abrupt temperature or dew point changes within the air mass at a given altitude. It may vary in size from several hundred to more than several thousand square miles.

DESCRIBE land breezes

At night, the circulation is reversed so that the air movement is from land to sea, producing an offshore wind called the land breeze.

Atmospheric Pressure

Atmospheric (barometric) pressure is the pressure exerted on asurface by the atmosphere due to the weight of the column of air directly above that surface.

DESCRIBE the sky coverage terms that define a ceiling

Broken (BKN) - 5/8 to 7/8 Overcast (OVC) - 8/8 Vertical Visibility (VV) - 8/8 (Given in three digit altitude)

DESCRIBE the cloud formations associated with mountain wave turbulence

Cap - Sit stationary over the top of the mountain, concealing the peak. Rotor - Occur on the leeward side of the mountain at the same height or higher than the mountain. Lenticular - Similar to rotor clouds but occur singularly or in layers usually above 20,000 ft.

STATE the temperature range most conducive to structural icing

Clear: 0C to -10C Rime: -10C to -20C Mixed: -8C to -15C Frost: Below freezing air into warmer more humid air

DESCRIBE the conditions associated with an inactive front

Clouds and precipitation due not accompany inaction (dry) fronts.

DESCRIBE the conditions associated with occluded fronts

Cold front overtakes a warm front (classified by which front remains on the ground). More toward the NE, wind shift is 180 degrees from SE to NW. Weather in front tends to be that of the warm front and weather behind tends to be that of a cold front. Weather in the middle is that of both types of fronts but is most severe in the area 100 NM south to 300 NM north of the frontal intersection.

DESCRIBE the four methods of lifting

Convergence - Convergence of two air masses, or parts of a single air mass, force the air upward because it has no where else to go. Frontal - Because of the shape of cold fronts, as they move through an area, they will lift the air ahead of the cold air mass. Orographic - Indicating that the force of the wind against a mountainside pushes the air upward. Thermal - Also known as convective lifting, is caused when cool air is over a warm surface, and it is heightened by intense solar heating.

DESCRIBE ground icing hazards

De-icing itself, however, can also be a hazard. De-icing fluids (discussed in the next section) are highly corrosive to internal aircraft and engine parts. Thus, it is imperative that de-icing crews understand the particular requirements for your type of aircraft. Additionally, taxiing through mud, water or slush on ramps and runways can create a covering of ice that can hamper the movement of flaps, control surfaces, and the landing gear mechanism.

INTERPRET Surface Analysis Charts

Do your own practice...

INTERPRET forecast weather conditions from a TAF

Do your own practice...

INTERPRET weather conditions from a METAR

Do your own practice...

DESCRIBE valley winds

During the day, warm air rises up the slopes of the valley and then cools causing it to descend back down to the valley floor pushing the warm air back up

DESCRIBE mountain winds

During the night, the slopes of the valley cool faster than the surrounding air causing it to descend to the valley floor pushing the warm air up (opposite valley winds)

DESCRIBE the structure of a front

First, fronts are named according to the temperature change they bring. For example, if the temperature will become warmer after the front passes, it is named a warm front. Second, fronts move across the country with their attached low-pressure system and isobars, as the corresponding air masses move. As they move, we are only concerned with any movement perpendicular to the line representing the front; thus, fronts are considered to move perpendicular to the way they are drawn. Also, cold fronts move faster than warm fronts, in general. Next, we usually see a 90° wind shift from one side of the front to the other, with two exceptions that will be explained below. Finally, every front is located in a trough of low pressure.

DESCRIBE the flight conditions associated with the stratosphere

Flying in the stratosphere is generally smooth with excellent visibility. The air is thin and offers very little resistance to the aircraft. The general lack of weather in this layer makes for outstanding flying.

DESCRIBE the parameters that define fog

Fog is a visible aggregate of minute water droplets that is based at or within 50 feet of the surface, is greater than 20 feet in depth, and reduces the prevailing visibility to less than ⅝ of a statute mile. Fog reduces horizontal and vertical visibility and may extend over a large area.

STATE the requirements for fog formation

For fog to form, three conditions must be satisfied: (1) condensation nuclei must be present in the air, (2) the air must have a high water content (a low dew point spread), (3) and light surface winds must be present.

DESCRIBE the use of Winds-Aloft Prognostic Charts

For general planning purposes, Winds-Aloft Prognostic Charts are the most useful, as they give a pictorial representation of the winds. They can quickly narrow the search for generally favorable winds, or provide a fast solution to finding an alternate route that avoids unfavorable winds.

DESCRIBE the use of Low Level Significant Weather Prognostic Charts

Forecast charts depict predicted positions of fronts and pressure centers, as well as forecast weather across the country.

DESCRIBE how frontal lifting creates turbulence

Frontal turbulence is caused by lifting of warm air by a frontal surface leading to instability, or by the abrupt wind shift between the warm and cold air masses.

EXPLAIN and identify gradient winds and Buys Ballot's Law ??? with respect to the isobars around pressure systems in the Northern Hemisphere

Gradient Winds flow perpendicular to the pressure gradient force parallel to the isobars resulting in circulation flows clockwise around highs, and counterclockwise around lows. Finally, gradient winds are found above 2000 feet AGL.

Dew Point Depression

If there is a difference between the air temperature and the dew point temperature, this is known as the dew point depression, or dew point spread, and the dew point will always be the lower of the two.

Standard Atmosphere

In aviation, everything is related to standard day conditions at sea level, which are 29.92 in-Hg (1013.2 mb) and 15° C (59° F). In the lower atmosphere, and thus for most aviation applications, a 1000 foot increase in altitude will result in a pressure decrease of approximately 1 in-Hg (34 mb) and a temperature decrease of 2° C (3.5° F).

STATE the standard units of pressure measurement

Inches of mercury (in-Hg) and millibars (mb)

Indicated Altitude

Indicated altitude is the altitude read directly from the altimeter.

DESCRIBE the use of Severe Weather Watch messages

Informs the pilot of severe weather in his or her intended flight path to include: funnel clouds or tornadoes and severe defined by frequent lightening and one or more of the following: 50 kt winds or greater, 3/4 in diameter hail or larger

DESCRIBE the use of METARs in flight planning

METARs are used to communicate the latest observed weather to meteorologists and aircrew so they can determine the existing weather at the destination or alternate, and whether a field is operating under conditions of instrument flight rules (IFR) or visual flight rules (VFR). These users can also use METARs to determine weather trends by checking the last several hours of reports to see if they indicate improving or deteriorating conditions. Additionally, METARs can provide a comparison between the observed and forecast weather, to determine if conditions are actually developing as originally forecast

DESCRIBE displayed data METARs

METARs, found on the METARs tab on the ADDS website, are scheduled observations taken between 55-59 minutes past the hour and used in flight planning to determine areas of IFR/VFR and to determine the minimum ceilings en route. METARs are available in both graphic and textual form. To view the graphic presentation, you would click on the desired region on the U.S. map. Reporting stations are depicted on the chart using station models.

DESCRIBE how mechanical turbulence develops

Mechanical turbulence results from wind flowing over or around irregular terrain or other obstructions. When the air near the surface of the Earth flows over obstructions, such as bluffs, hills, mountains, or buildings, the normal horizontal wind flow is disturbed and transformed into a complicated pattern of eddies and other irregular air movements.

DESCRIBE weather data on NEXRAD

NEXRAD presentations show precipitation levels in the area scanned by the radar system. The NEXRAD does not measure the rate of precipitation directly; rather, it measures the energy return from the precipitation particles. The image seen on the screen is actually a computer-generated compilation of returned energy shown in varying colors. Other unique features of the NEXRAD provide the capability to display areas of tornadoes, hail, wind shear, and microbursts.

Obscuring Phenomena

Obscuring phenomena are any collection of particles that reduce horizontal visibility to less than six miles. They may be either surface based or aloft. Examples include fog, haze, smoke, volcanic ash, and blowing spray, to name a few.

DESCRIBE the use of Pilot Weather Reports (PIREPs)

Provided updated information to previously foretasted WX.

EXPLAIN how radar can aid a pilot when flying in the vicinity of thunderstorms

Radar can be used to locate areas of strong thunderstorms (cells), and by doing allow the pilot to avoid the areas of strong intensity.

LIST the types of icing used in Pilot Reports (PIREPs)

Rime - Rough milky opaque ice formed by the instantaneous freezing of small supercooled water droplets. Clear - A glossy, clear or translucent ice formed be the relatively slow freezing of large super cooled water droplets. Mixed - A combination of rime and clear.

DESCRIBE the use of In-Flight Weather Advisories

SIGMETS: WX potentially hazardous to all aircraft. Are valid for up to 4 hours when any of the following weather phenomena occur or are forecast over an area of at least 3000 square miles: Severe or extreme non-convective turbulence, or CAT not associated with thunderstorms. Severe icing not associated with thunderstorms. Widespread dust storms or sand-storms lowering surface and/or flight visibilities to less than 3 miles. Volcanic eruption and ash clouds Convective SIGMETS: Issued as needed and include: Tornadoes. Lines of thunderstorms. Embedded thunderstorms. Thunderstorm areas greater than or equal to thunderstorm intensity (VIP level) of four or greater with an area of coverage of 40% or more. Hail greater than or equal to 3/4 inch in diameter or greater and/or wind gusts to 50 knots or greater AIRMETS: Indicate conditions at intensities lower than those that trigger SIGMETs. *Sierra-For widespread IFR conditions (ceilings less than 1000 feet and/or visibility less than 3 miles) affecting over 50% of the area or for extensive mountain obscuration. *Tango- For moderate turbulence or for sustained surface winds of 30 knots or more. *Zulu- For moderate icing or for freezing level data.

DESCRIBE the weather data entered on a DD Form 175-1

See pg. 464- 463 for the list.

DESCRIBE the flight conditions associated with a stable atmosphere

Stable Air: temperature inversions, low fog and stratus, and rising air temperature while climbing. Fronts: Warm Air mass: Warm Turbulence: Smooth Visibility: Poor Icing: Rime Precipitation: Steady Winds: Steady Cloud Types: Stratus

DIFFERENTIATE between sea level pressure and station pressure

Station pressure is the atmospheric pressure measured directly at an airfield or other weather station. Sea level pressure is the pressure that would be measured from the existing weather if the station were at mean sea level (MSL). This can be measured directly at sea level, or calculated if the station is not at sea level using the standard pressure lapse rate.

DESCRIBE structural icing

Structural icing is icing that forms on the external structure of an aircraft. Structural ice forms on the wings, fuselage, antennas, pitot tubes, rotor blades, and propellers. Significant structural icing on an aircraft can cause control problems and dangerous performance degradation. The types of structural icing are clear, rime, mixed, and frost.

EXPLAIN and identify the surface wind direction with respect to the gradient winds in a pressure system in the Northern Hemisphere

The PGF, Coriolis force, and friction all affect surface wind. When the new balance of these forces is reached, the air blows at an angle across the isobars from high pressure to low pressure. This angle varies as a result of the type of terrain, but for our purposes, we will assume a 45° angle.

DESCRIBE the use of Surface Analysis Charts

The Surface Analysis Chart depicts pressure centers, fronts, and barometric pressure lines. It is observed WX.

DESCRIBE the relationship between air temperature and dew point temperature with respect to saturation

The air can become saturated (RH = 100%) by one of two ways. If the air is cooled, the falling air temperature decreases the dew point spread closer to zero, while the RH rises closer to 100%. If evaporation occurs, this adds moisture to the atmosphere, increasing the dew point, which again lowers the dew point spread and increases the RH. Once the dew point spread reaches 4° F, the RH will be 90%, and the water vapor will begin to condense into fog or clouds. Any further cooling or evaporation will produce precipitation, as there will be more water present in the air than it can hold.

DEFINE saturation

The air reaches saturation when it contains the maximum amount of water vapor it can hold for that temperature.

DESCRIBE how jet streams are examples of wind shear turbulence

The rapid change of wind speed within a short distance of the jet core is particularly significant. The vertical shear is generally close to the same intensity both above and below the core, and it may be many times stronger than the horizontal shear. The horizontal shear on the cold air side of the core is stronger than on the warm air side. Thus, if it is desired to exit jet stream turbulence, a turn to the south should result in smoother air. Also, a climb or descent to a different flight level should also help, as jet stream turbulence often occurs in patches averaging 2000 feet deep, 20 miles wide, and 50 miles long.

EXPLAIN the term pressure gradient

The rate of pressure change in a direction perpendicular to the isobars (horizontal distance).

DESCRIBE the characteristics of the stratosphere

The stratosphere is characterized by increasing temperature with increasing altitude.

DESCRIBE the characteristics of the tropopause

The strongest winds, those of the jet stream, occur just below the tropopause. Moderate to severe turbulence is sometimes associated with the wind shear caused by the jet stream. Contrails frequently form and persist near the tropopause since it is normally the coldes area within the lower atmosphere. While clouds and weather are generally confined to the troposphere, severe thunderstorm tops may penetrate the tropopause into the stratosphere the average height of the tropopause over the US is 36,000 feet MSL, anvil tops of thunderstorms will spread out at the base of the tropopause, and a haze layer with a definite top frequently exists at the tropopause.

DESCRIBE the flight conditions associated with the tropopause

The strongest winds, those of the jet stream, occur just below the tropopause. Moderate to severe turbulence is sometimes associated with the wind shear caused by the jet stream. Contrails frequently form and persist near the tropopause since it is normally the coldest area within the lower atmosphere. While clouds and weather are generally confined to the troposphere, severe thunderstorm tops may penetrate the tropopause into the stratosphere.

DESCRIBE the use of Winds-Aloft Forecasts

The textual charts may also be consulted as additional information in selecting the best particular altitude for which to file the flight plan, or when the Winds-aloft Prognostic Charts are not available. Often, the wind information will not be forecast for the exact altitude for which a pilot may wish to file. In this case, one must interpolate to find the desired information.

DESCRIBE the use of TAFs in flight planning

This teletype information will also aid you in planning for the type of flight (IFR/VFR), type of approach you require, determining if an alternate is required, and selection of the best alternate. 1. Determine the arrival window, which would be 1520 -1720Z in this case. 2. Evaluate the whole TAF to determine the forecast time period to which each line applies. If any part of the 2-hour ETA window falls within the time period of that line,then the information in that line will be applicable. In this case, lines 2, 3, and 4 each cover part of the 1520 -1720Z window. 3. Finally, mix and match the weather from each line for use in flight planning, building a set of the worst-case scenario for each group: strongest winds, lowest visibility, worst weather, lowest ceiling, and lowest altimeter.

DESCRIBE the hazards associated with thunderstorms

Thunderstorms contain many of the most severe weather hazards. They are often accompanied by strong wind gusts, severe turbulence, lightning, heavy rain showers, severe icing, and possibly hail and tornadoes. See pgs 362-365 for more details)

DESCRIBE the characteristics of a warm front

To do so, the warmer, less dense air must ride up and over the top of the cold air mass. The warm air mass gradually moves up over the frontal surface creating a broad area of cloudiness. This cloud system extends from the front's surface position to about 500 to 700 miles in advance of it. A warm front typically moves at a slower speed than a cold front-15 knots on average-and produces a more gradual frontal slope, as well as sloping forward, ahead of the surface front. Because of this slower speed and gradual slope, warm fronts are not as well defined as cold fronts. The winds shift across a warm front from the SE to the SW.

DESCRIBE the flight conditions associated with an unstable atmosphere

Unstable Air: Thunderstorms, showers, towering clouds, dust devils, and rapidly decreasing air temperature while climbing Fronts: Cold Air mass: Cold Turbulence: Rough Visibility: Good, Outside of Clouds Icing: Clear Precipitation: Showery Winds: Gusty Cloud Types: Cumulus

DESCRIBE the discontinuities used to locate and classify fronts

*Temperature - In the lower layers of the atmosphere a greater temperature change will be noticed with frontal passage or when flying through a front. The amount and rate of change partially indicates the front's intensity. *Dew Points - The dew point temperature and the air temperature give an indication of the relative humidity of the air. Cold air masses will usually have lower dew point temperatures than warm air masses. Higher dew points indicate a greater amount of moisture available to produce clouds, fog, or precipitation. *Pressures - Therefore, when a front approaches a station, or a pilot flies toward a front, the pressure decreases. Pressure then rises immediately following frontal passage. It is extremely important to obtain a new altimeter setting when flying in the vicinity of a front. *Winds - Near the Earth's surface, the wind changes direction across a front. In the Northern Hemisphere, as the front approaches and passes a station the wind changes direction in a clockwise rotation. When flying across a front, because of this wind shift you must adjust heading to the right to maintain your original ground track

LIST the intensities of icing used in Pilot Reports (PIREPs)

*Trace - Ice becomes perceptible. Not hazardous even though deicing/anti-icing equipment is not used, unless encountered for extended period of time-over one hour. *Light - Rate of accumulation may create a problem if flight is prolonged in this environment - over one hour. Occasional use of deicing/anti-icing removes/prevents accumulation. Not a problem if de/anti-icing equipment used. *Moderate - Rate of accumulation is such that even short encounters become potentially hazardous and use of de/anti-icing equipment or diversion is necessary. *Severe - Rate of accumulation us such that de/anti-icing equipment fails to reduce or control the hazard. Immediate diversion necessary.

DESCRIBE techniques for flight in the vicinity of mountain waves

1. Avoid the turbulence if possible by flying around the areas where wave conditions exist. If this is not feasible, fly at a level that is at least 50% higher than the height of the highest mountain range along your flight path. This procedure will not keep the aircraft out of turbulence, but provides a margin of safety if a strong downdraft is encountered. 2. Avoid the rotor, lenticular, and the cap clouds since they contain intense turbulence and strong updrafts and downdrafts. 3. Approach the mountain range at a 45° angle, so that a quick turn can be made away from the ridge if a severe downdraft is encountered. 4. Avoid the leeward side of mountain ranges, where strong downdrafts may exist, until certain turbulence is not a factor. 5. Do not place too much confidence in pressure altimeter readings near mountain peaks. They may indicate altitudes more than 2500 feet higher than the true altitude. 6. Penetrate turbulent areas at air speeds recommended for your aircraft.

IDENTIFY the procedures to minimize or avoid the effects of icing

1. Don't fly into areas of known or forecast icing conditions. 2. Avoid flying in clouds with temperatures from 0° C to - 20° C. 3. Don't fly through rain showers or wet snow with temperatures near freezing. 4. Avoid low clouds above mountain ridges or crests. Expect the heaviest icing in clouds around 5000 feet above the mountaintops. 5. Do not make steep turns with ice on the airplane due to increased stall speeds. 6. Avoid high angles of attack when ice has formed on the aircraft since the aircraft is closer to stall speed in these maneuvers. 7. Under icing conditions, increased drag and additional power required increases fuel consumption. 8. Change altitude to temperatures above freezing or colder than -20° C. An altitude change also may take you out of clouds. 9. In freezing rain, climb to temperatures above freezing, since it will always be warmer at some higher altitude. Don't delay your climb since ice can accumulate quickly. If you are going to descend, you must know the temperature and terrain below. 10. Do not fly parallel to a front while encountering icing conditions. 11. Avoid icing conditions as much as possible in the terminal phase of flight due to reduced airspeeds. 12. Expect to use more power on final approach when experiencing structural icing. 13. Always remove ice or frost from airfoils before attempting takeoff.

DESCRIBE the types of precipitation

1. Drizzle -Very small droplets of water that appear to float in the atmosphere. 2. Freezing drizzle -Drizzle that freezes on impact with objects. 3. Rain -Precipitation in the form of water droplets that are larger than drizzle and fall to the ground. 4. Freezing rain -Rain that freezes on impact with objects. 5. Hail or graupel -A form of precipitation composed of irregular lumps of ice that develop in severe thunderstorms, consisting of alternate opaque and clear layers of ice in most cases. Water drops, which are carried upward by vertical currents, freeze into ice pellets, start falling, accumulate a coating of water, and are carried upward again, causing the water to freeze. A repetition of this process increases the size of the hailstone. It does not lead to the formation of structural ice, but it can cause structural damage to aircraft. 6. Ice pellets or sleet -Small translucent and irregularly shaped particles of ice. They form when rain falls through air with temperatures below freezing. They usually bounce when hitting hard ground and make a noise on impact. Ice pellets do not produce structural icing unless mixed with super-cooled water. 7. Snow -White or translucent ice crystals, usually of branched hexagonal or star-like form that connect to one another forming snowflakes. When condensation takes place at temperatures below freezing, water vapor changes directly into minute ice crystals. A number of these crystals unite to form a single snowflake. Partially melted, or "wet" snow, can lead to structural icing. 8. Snow grains -Very small white, opaque grains of ice. When the grains hit the ground, theydo not bounce or shatter. They usually fall in small quantities from stratus- type clouds, never as showers.

DESCRIBE the recommended procedures for flying through turbulence

1. Establish and maintain thrust settings consistent with turbulent air penetration airspeed and aircraft attitude. Severe turbulence may cause large and rapid variations in indicated airspeed. Don't chase airspeed. 2. Trim the aircraft for level flight at the recommended turbulent air penetration airspeed. Don't change trim after the proper attitude has been established. 3. The key to flying through turbulence is proper attitude control. Both pitch and bank should be controlled by reference to the attitude gyro indicator. Extreme gusts may cause large changes in pitch or bank. To avoid overstressing the aircraft, don't make abrupt control inputs. Use moderate control inputs to reestablish the desired attitude. 4. Severe vertical gusts may cause appreciable altitude deviations. Allow altitude to vary. Sacrifice altitude to maintain desired attitude. Don't chase the altimeter.

DESCRIBE the recommended techniques for avoiding thunderstorm hazards

1. Fly around (circumnavigate) the storm. 2. Fly over the top of the storm. 3. Fly under the storm. If it is not possible to avoid the storm(s) then, 4. Fly through the lower ⅓ of the storm.

DESCRIBE the three characteristics of precipitation

1. Showers-Characterized by a sudden beginning and ending, and abruptly changing intensity and/or sky conditions. Showers are associated with cumuliform clouds. 2. Continuous -Also known as steady (not showery). Intensity changes gradually, if at all. Continuous precipitation is associated with stratiform clouds. 3. Intermittent -Stops and restarts at least once during the hour. Intermittent precipitation maybe showery or steady, and therefore may be associated with cumuliform or stratiform clouds.

DESCRIBE the factors that influence frontal weather

1. The amount of moisture available (shown by the dew point) 2. The degree of stability of the lifted air 3. The slope of the front 4. The speed of the frontal movement 5. The contrast in the amounts of temperature and moisture between the two air masses.

DESCRIBE the characteristics of the troposphere

The average height of the troposphere over the United States is 36,000 feet MSL, but pressure systems and seasonal differences cause a variance in the height. Due to heating, the troposphere extends to a greater height in summer than in winter. The atmosphere becomes less dense with altitude, and roughly 50% of it, by weight, lies below 18,000 feet and 90% within 53,000 feet. Within the troposphere, the temperature normally decreases with increasing altitude. Large amounts of moisture and condensation nuclei are found in the troposphere because of its closeness to the Earth's surface, and nearly all weather occurs here. Winds are generally light near the Earth's surface and increase with altitude. Wind speeds over 200 knots may occur near the top of the troposphere. An abrupt change in the rate of temperature decrease with increasing altitude marks the boundary, called the tropopause.

DESCRIBE sea breezes

The cool air over the water moves toward the lower pressure, replacing the warm air over the land that moved upward. The resulting onshore wind, blowing from the sea is called a sea breeze (15 to 20 knots).

Lapse Rate

The decrease in atmospheric temperature with increasing altitude.

Dew Point Temperature

The dew point temperature (TD) is the temperature at which saturation occurs. The dew point is a direct indication of the amount of moisture present in the air. The higher the dew point, the greater chances for clouds, fog, or precipitation.

DESCRIBE the conditions associated with a stationary front

The front is stationary, winds run parallel to the front creating a 180 degree shift when crossing it. Weather conditions are similar to that of a warm front, just less severe.

DESCRIBE how temperature inversions are examples of wind shear turbulence

The inversion layer tends to move at a different speed than the normal layer above it therefore the area where the two collide tends to result in vertically oriented eddies turning a head wind into a tailwind which will decrease aircraft performance.

DESCRIBE the jet stream

The jet stream is a narrow band of strong winds of 50 knots or more that meanders vertically and horizontally around the hemisphere in wave-like patterns. These winds average about 100-150 knots but may reach speeds in excess of 250 knots. Since the jet stream is stronger in some places than in others, it rarely encircles the entire hemisphere as a continuous river of wind. More frequently, it is found in segments from 1000 to 3000 miles in length, 100 to 400 miles in width, and 3000 to 7000 feet in depth. The average height of jet stream winds is about 30,000 feet MSL, but they can be above or below this level depending on the latitude and the season. During the winter, the position of the jet stream is further south, the core descends to lower altitudes, and its speed is faster than in the summer.

Relative Humidity

The percent of saturation of the air.

STATE the requirements for the formation of structural icing

There are two requirements for the formation of aircraft icing. First, the atmosphere must have super-cooled visible water droplets. Second, the free air temperature (measured by the aircraft's outside air temperature gauge) and the aircraft's surface temperature must be below freezing.

LIST the classifications of turbulence used in Pilot Reports (PIREPs)

Thermal Mechanical Frontal Large-Scale Wind Shear

DESCRIBE how thermal turbulence develops

Thermal (or convective) turbulence is caused by localized vertical convective currents resulting from surface heating or cold air moving over warmer ground.

DESCRIBE the conditions associated with a cold front

Usually, though, as the cold front approaches, the southwesterly winds in the warm air mass ahead of the front begin to increase in speed. Meanwhile, the barometric pressure decreases, and altocumulus clouds appear on the horizon. Next, the cloud bases lower, and rain or snow showers begin as the cumulonimbus clouds move into the area. The precipitation increases in intensity and may persist as the front nears the station. As the front passes, the pressure rises sharply and the wind shifts approximately 90° from SW to NW. The post frontal weather includes rapidly clearing skies, fair weather cumulus clouds, and decreasing temperature and dew point. Weather with fast-moving cold fronts occurs in a narrow band, is usually severe, and clears rapidly behind the front. Cumuliform clouds, showers, or thunderstorms may form near the front position. Lines of fast-moving thunderstorms, or squall lines, can form well ahead of the front.Weather with slow-moving cold fronts (usually from late fall through early spring) occurs over a large area, is less severe, but may persist for hours, even after the front is past

DESCRIBE the flight conditions associated with the troposphere

Winds are generally light near the Earth's surface and increase with altitude. Wind speeds over 200 knots may occur near the top of the troposphere.

IDENTIFY the hazards of aircraft icing

he presence of ice on an aircraft decreases lift, thrust, and range, and increases drag, weight, fuel consumption, and stall speed. The added weight with reduced lift and thrust can be a dangerous combination. Ice can alter the shape of an airfoil, changing the angle of attack at which the aircraft stalls therefore increasing the stall speed. Ice reduces lift and increases drag on an airfoil. Ice thickness is not the only factor determining the effect of icing. Location, roughness, and shape are important, too. The buildup of ice on various structural parts of the aircraft can result in vibration, causing added stress to those parts. This is especially true in the case of propellers and rotors, which are delicately balanced. Structural icing can block the pitot tube and static ports. This can cause a pilot to either lose or receive erroneous indications from various instruments such as the airspeed indicator, VSI, and altimeter.