Weather Information Flashcards
State the general characteristics in regard to the flow of air around high and low pressure systems in the N. hemisphere
Low Pressure - inward, upward, and counterclockwise
High Pressure - outward, downward, and clockwise
If your route of flight takes you toward a low-pressure system, in general what kind of weather can you expect? What if you were flying towards a high-pressure system
A low-pressure system is characterized by rising air, which is conductive to cloudiness, precipitation, and bad weather. A high-pressure system is an area of descending air which tends to favor dissipation of cloudiness and good weather
Describe the different types of fronts
Cold front - occurs when a mass of cold, dense, and stable air advances and replaced a body of warmer air
Occluded front - A frontal occlusion occurs when a fast-moving cold front catches up with a slow-moving warm front. Two types cold front occlusion and warm front occlusion
Warm front - The boundary are formed when a warm air mass contact and flow over a cold air mass
Stationery front - When the force of two air masses are relatively equal, the boundary or front that separate them remains stationary and influence the local weather for days. The weather is typically a mixture of both warm and cold fronts
What are the general characteristics of the weather a pilot would encounter when operating near a cold front and a warm front?
Cold Front - As the front passes, expected weather can included towering cumulus or cumulonimbus, heavy rain accompanied by lightning, thunder and/or hail; tornadoes possible; during passage, poor visibility, winds variable and gusting; temp/dew point and pressure drop rapidly
Warm Front - As the front passes expected weather can included stratiform clouds, drizzle, low ceilings, and poor visibility; variable winds; rise in temp
What is a trough
A trough, called a trough line, is an elongated area of relatively low atmospheric pressure. At the surface when air converges into a low, it cannot go outward against the pressure gradient, nor can it go downward into the ground; it must go upward. Therefore, a low or trough is an are of rising air. Rising air is conductive to cloudiness and precipitation; hence the general association of low pressure and bad weather
What is a ridge
A ridge, also called a ridge line, is an elongated area of relatively high atmospheric pressure. Air moving out of a high or ridge depletes the quantity of air; therefore, these are areas of descending air. Descending air favors dissipation of cloudiness; hence the association of high pressure and good weather
What are the standard temp. and pressure values
15 degrees C 29.99” Hg
What are isobars
An isobar is a line on a weather chart which connects areas of equal or constant barometric pressure
If the isobars are relatively close together on a surface weather chart or a constant pressure chart, what information will this provide
The spacing of isobars on these charts defines how steep or shallow a pressure gradient is. When isobars are spaced very close together, a steep pressure gradient exists which indicates. higher wind speeds. A shallow pressure gradient usually means win speed will be less
What causes the winds aloft to flow parallel to the isobars
The Coriolis force
Why do surface winds generally flow across the isobars at an angle
Surface friction
At what rate does atmospheric pressure decrease with an increase in altitude
1” Hq per 1,000 Feet
What does dew point mean
Dew point is the temperature to which a sample of air must be cooled to attain the state of saturation
When temperature and dew point are close together, within 5 degrees, what type of weather is likely
Visible moisture in the form of clouds, dew, or fog. Also, these are ideal conditions for carburetor icing
What factor primarily determines the type and vertical extent of clouds
The stability of the atmosphere
Explain the difference between a stable atmosphere and an unstable atmosphere. Why is the stability of the atmosphere important
The stability of the atmosphere depends on its ability to resist vertical motion. A stable atmosphere makes vertical movement difficult, and small vertical disturbance dampen out and disappear. In an unstable atmosphere, small vertical air movement tend to become larger, resulting in turbulent airflow and convective activity. Instability can lead to significant turbulence, extensive vertical clouds, and sever weather
List the effects of stable and unstable air on clouds, turbulence, precipitation and visibility
Stable: Clouds: Stratiform Turbulence: Smooth Precipitation: Steady Visibility: Fair to Poor
Unstable Clouds: Cumuliform Turbulence: Rough Precipitation: Showery Visibility: Good
When significant precipitation is occurring at the surface, how thick can you expect the clouds to be?
Significant precipitation usually requires clouds to be at least 4,000 feet thick. The heavier the precipitation, the thicker the clouds are likely to be
During your preflight planning, what type of meteorological information should you be aware of with respect to icing
Location of fronts - A front’s location, type, speed, and direction of movement
Cloud layers - The location of cloud bases and tops, which is valuable when determining if you will be able to climb above icing layers or descend beneath those layers into warmer air; reference PIREPs and area forecasts
Freezing levels - Important when determining how to avoid icing and how to exit icing conditions if accidentally encountered
Air temperature and pressure - Icing tends to be found in low-pressure areas and at temperatures at or around freezing
What is the definition of the term freezing level and how can you determine where that level is?
The freezing level is the lowest altitude in the atmosphere over a given location at which the air temperature reaches 0 degrees C. It is possible to have multiple freezing layers when a temperature inversion occurs above the defined freezing level. A pilot can use current icing products (CIP) and forecast icing products (FIP), as well as the freezing level graphics chart to determine the approximate freezing level. Other potential sources of icing information are: area forecasts, PIREPS, AIRMETs, SIGMEt, surface analysis charts, low-level significant weather charts, and wins and temps aloft
What conditions are necessary for structural icing to occur
Visible moisture and below freezing temp at the point moisture strikes the A/C
Name the main type of icing an aircraft may encounter in-flight
Structural, induction system, and instrument icing
Name the three types of structural icing that may occur in flight
Clear ice - forms after initial impact when the remaining liquid portion of the drop flow out over the A/C surface, gradually freezing as a smooth sheet of solid ice
Rime ice - forms when drops are small, such as those in stratified clouds or light drizzle. The liquid portion remains after initial impact freezes rapidly before the drop has time to spread out over the A/C surface
Mixed ice - forms when drops vary in size or when liquid drops are intermingled with snow or ice particles. The ice particles become imbedded in clear ice, building a very rough accumulation
What action is recommended if you inadvertently encounter icing conditions
The first course of action should be to leave the area of visible moisture. This might mean descending to an altitude below the cloud bases, climbing to an altitude above the cloud tops, or turning to a different course
Is frost considered to be hazardous to flight? Why?
Yes, because while frost does not change the basic aerodynamic shape of the wing, the roughness of its surface spoils the smooth flow of air, thus causing a slowing of airflow. This slowing of the air causes early airflow separation, resulting in a loss of lift. Even a small amount of frost on airfoils may prevent an aircraft from becoming airborne at normal takeoff speed. It is also possible that, once airborne, an A/C could have insufficient margin of airspeed above stall so that moderate gusts or turning flight could produce incipient or complete stalling
What factors must be present for a thunderstorm to form
Sufficient water vapor
An unstable lapse rate
AN initial upward boost (lifting) to start the storm process in motion
What are the three stages of a thunderstorm
Cumulus stage - Updrafts causing raindrops to increase in size
Mature stage - Rain at earth’s surface; it falls through or immediately besides the updrafts; lightning; perhaps roll clouds
Dissipating stage - Downdrafts and rain begin to dissipate
What is a temperature inversion
An inversion is an increase in temperature with height - a reversal of the normal decrease with height. An inversion aloft permits warm rain to fall through cold air below. Temp in the cold air can be critical to icing. A ground-based inversion favors poor visibility by trapping fog, smoke, and other restrictions into low levels of the atmosphere. The air is stable, with little or no turbulence
State two basic ways that fog may form
Cooling air to the dew point
Adding moisture to the air near the ground
Name several types of fog
Radiation fog Advection fog Upslope fog Frontal fog / precipitation-induced fog Steam fog
What causes radiation fog to form
The ground cools the adjacent air to the dew point on clam, clear nights
What is advection fog, and where is it most likely to form
Advection for results from the transport of warm humid air over a cold surface. A pilot can expect advection for to form primarily along coastal areas during the winter. Unlike radiation fog, it may occur with winds, cloudy skies, over a wide geographic area, and at any time of day or night
What is upslope fog
Upslope fog forms as a result of moist, stable air being cooled adiabatically as it move up sloping terrain. Once the upslope wind ceases, the fog dissipates. Upslope fog is often quite dense and extends to high altitudes
Define the term wind shear and state the areas in which it is likely to occur
Wind shear is defined as the rate of change of wind velocity (direction and/or speed) per unit distance; conventionally expressed as vertical or horizontal wind shear. It may occur at any level in the atmosphere but three areas are of special concern
Wind shear with a low-level temp. inversion
Wind shear in a frontal zone or thunderstorm
Clear Air Turbulence at high levels associate with a jet stream or strong circulation
Why is wind shear an operational concern to pilots
Wind shear is an operational concern because unexpected changes in wind speed and direction can be potentially very hazardous to A/C operations at low altitudes on approach to and departing from airports
What type of weather information will you examine to determine if wind shear conditions might affect your flight
Terminal forecasts - any mention of low level wind shear or the possibility of severe thunderstorms, heavy rain showers, hail, wind gusts suggest the potential for LLWS and microbursts
METARS - inspect for any indication of thunderstorms, rain showers, or blowing dust. Additional signs such as warming trends, gusty winds, cumulonimbus clouds, etc. should be noted
Severe weather watch reports - SIGMETS and convective SIGMETs severe convective weather is a prime source for wind shear and microbursts
LLWS reports - installed at 110 airports in the US; designed to detect wind shifts between outlying stations and a reference centerfield station
PIREPs - reports of sudden airspeed change on departure or approach and landing corridors provided a real-time indication of the presence of wind shear
What is the primary means of obtaining a weather briefing
Flight Service Station is the primary source for obtaining preflight briefings and inflight weather information. The FAA provides FSS via
1-800-WX-BRIEF
DUATS
Lockheed Martin SS DUATS 2
What are some examples of other sources of weather information
Telephone Information Briefing Services TIBS
Weather and aeronautical information available from numerous private sources
DUATS
In Alaska Transcribed Weather Broadcast TWEB
You’re planning a cross-country flight. Does your weather data provided by commercial and/or 3rd party vendors satisfy the preflight action required by 91.103
Pilots and operators should be aware that weather services provided by entities other than FAA, NWS, or their contractors such as the DUATS and DUATS2 might not meet FAA/NWS quality control standards. All operators and pilots contemplating using such services should request and/or review an appropriate description of services and provider disclosure. When in doubt, consult with an FAA FSS specialis
What type of weather briefings are available from an AFSS/FSS briefer
Standard briefing - Request when you are planning a flight and you have not received a previous briefing or have not received preliminary information through mass dissemination media
Abbreviated Briefing - Request when you need information to supplement mass disseminated data, update a previous briefing, or when you need only one or two items
Outlook Briefing - Request whenever your proposed time of departure is six or more hours from the time of the briefing; for planning purposes only
Inflight Briefing - Request when needed to update a preflight briefing
What pertinent information should a weather briefing include
Adverse Conditions VFR Flight not recommended synopsis current conditions Enroute forecast Destination forecast Winds aloft NOTAMs ATC delay
Pilots may obtain the following from FSS briefers upon request:
Info on Special use airspace and SUA related airspace including alert areas, MOA, MTR, IFR, VFR, VR, and SR training routes, warning areas, and ATCAA (assigned airspace); a review of the printed NOTAMs, approximate density altitude data; info on ATC services and rules; customs/immigration procedures; ADIZ rules; search and rescue; runway friction measurements values NOTAMs; GPS RAIM availability; and other assistance as required
What is HIWAS
Hazardous In-flight weather advisory service is a continuous broadcast of in-flight weather advisory including summarized aviation weather warnings, SIGMET, Convective SIGMET, Center Weather Advisory, AIRMET, and urgent PIREPs. HIWAS is an additional source of hazardous weather information which makes this data available on a continuous basis. Navaids with HIWAS capability are depicted on sectional charts with an H in the upper right corner of the identification box. Where implemented, HIWAS alerts are broadcast on all except emergency frequencies once upon receipt by ARTCC, terminal facilities, and FSS
What is a flight information service
FIS is a ground broadcast service provided through the Automatic Dependent Surveillance Broadcast (ADS-B) services network over the 978MHz UAT data link. The FAA FIS-B system provides pilots and flight crews of properly-equipped aircraft with a flight deck display of aviation weather and aeronautical information
Can onboard datalink weather FIS-B be useful in navigating an aircraft safely around an area of thunderstorms
Weather data linked from a ground weather surveillance radar system is not real-time information; it displays recent rather than current conditions. This data is typically updated every 5 minutes, but can be as much as 15 minutes old by the time it displays in the cockpit. Therefore, FIS aviation weather products are not appropriate for tactical avoidance of severe weather such as negotiation a path through a weather hazard area
While en route, how can a pilot obtain updated weather information
FSS on 122.2 and appropriate RCO ATIS broadcast along your route of flight HIWAS Datalink weather ATC workload permitting
What is a METAR and what are the two types
A METAR is an hourly surface observation of conditions observed at an airport. There are two types of METAR reports. Routine METAR report that is transmitted every hour and an aviation selected special weather report SPECI. This is a special report that can be given at any time to update the METAR for rapidly changing weather conditions, aircraft mishaps, or other critical information
Describe the basic elements of a METAR
Type of report METAR or SPECI
ICAO station identifier
Date and time of report - first two digits are the day of the month then two for the hour and two for the minutes in Zulu time
Modifier as required AUTO/AO1/AO2
Wind - 3 digit wind direction 2 digit with speed
Visibility - surface visibility in SM
Runway visual range as required
Weather phenomena qualifiers and phenomena
Sky conditions - heights are recorded in AGL
Temp/Dew point in C. M prefix means negative
Altimeter
Remarks as required
Describe several types of weather observing programs available
Manual Observations - with only a few exceptions these reports are from airport locations staffed by FAA personnel who manually observe, perform calculations, and enter their observations into the communication system
AWOS - Automated weather observing system; consists of various sensor, a processor, a computer-generated voice subsystem, and a transmitter to broadcast local, minute-by-minute weather data directly to the pilot.
ASOS/AWSS - Automated Surface Observing System / Automated Weather Sensor System; the primary US surface weather observing system. AWSS is a follow-on program that provides the identical data as ASOS. Both systems provide continuous minute-by-minute observations that generate METARs and other aviation weather information. Transmitted over a discrete VHF radio frequency or the voice portion of a local NAVAID, and are receivable to a maximum of 25 NM from the station and a maximum altitude of 10,000 AGL.
What are PIREPs (UA) and where are they usually found
A pilot report provides valuable information regarding the conditions as they actually exist in the air, which cannot be gathered from any other source. Pilots can confirm the height of bases and tops of clouds, locations of win shear and turbulence, and the location of inflight icing. There are two types of PIREPs; routine UA and urgent UUA. PIREPs should be given to the ground facility with which communications are established. PIREPS are available from an FSS and on the internet via the ADDS web page
What are Terminal Aerodrome Forecasts TAFs
A terminal aerodrome forecast is a concise statement of the expected meteorological conditions significant to aviation for a specific time period within five statute miles of the center of the airport’s runway complex. The TAF use the same weather codes found in METAR weather reports, in the following format
Type of report - TAF routine TAF AMD amended or TAF COR corrected
ICAO station ID
Date and time of origin
Valid period date and time
Forecasts
Define aviation area forecast
Abbreviated as FA, this is a forecast of specified weather phenomena covering a flight information region or other area designated by the meteorological authority. Pilots should use the area forecast in conjunction with AIRMAT, SIGMET, convective SIGMETS, CWAs etc) to determine forecast en route weather and to interpolate conditions at airports that do not have a terminal aerodrome forecast. FAs are issued 3 times daily for reach of the 6 areas in the contiguous 48 states. FAs are also issued for the Gulf of Mexico, Caribbean, Hawaii, and Alaska. More area forecast were canceled in 2017 replaced by GFA
What information is provided by FA
Area forecasts are issued for the conterminous US and cover the airspace between the surface and 45,000 feet AMSL. They include
Synopsis
Clouds and weather description of the clouds and weather for the first 12-h period for each state or group of states including
Cloud amount
Cloud bases and tops
Precipitation
Visibilities between 3 and 6 SM
Sustained surface winds 20 knots or greater
12 to 18 hour categorical outlook - IFR, MVFR, VFR
What is a Graphical Forecast for Aviation (GFA)
The GFA is intended to provide the necessary aviation weather information as a complete picture of the weather that may impact flight in the US. The webpage includes observational data, forecasts, and warnings that can be viewed from 14h in the past to 15h in the future, including thunderstorms, clouds, flight category, precipitation, icing, turbulence and wind
What are the four types of inflight aviation weather advisories
Inflight Aviation Weather Advisories are forecasts that advise enroute aircraft of the development of potentially hazardous weather in four types: SIGMET WS, convective SIGMET WST, AIRMET WA, and the center weather advisory CWA. All height are MSL except in the case of ceilings CIG which indicate AGL
What is a convective SIGMET
WST implies severe or greater turbulence, sever icing and low-level wind shear. They may be issued for any convective situation which the forecaster feels is hazardous to all categories of aircraft. Convective SIGMET bulletins are issued for the Easter, Central, and Western US US. They are not issued for Alaska or Hawaii. Bulletins are issued hourly at 55 minutes. The text of the bulletin consists of either an observation and a forecast, or just a forecast. The forecast is valid for up to 2 hours
Severe thunderstorms due to
surface winds greater than or equal to 50 knots
Hail at the surface greater than or equal to 3/4 inches in diameter
Tornadoes
Embedded thunderstorms
A line of thunderstorms
Thunderstorms producing greater than or equal to heavy precipitation that affects 40% or more of an area at least 3,000 square miles
What is a SIGMET WS
A SIGMET WS advises of weather that is potentially hazardous to all aircraft. SIGMETs are unscheduled products that are valid for 4h. SIGMET associated with tropical cyclones and volcanic ash clouds are valid for 6h. Unscheduled updates and correction are issued as necessary. In the US SIGMETs are issued when the following phenomena occur or are expected to occur
Sever icing not associated with thunderstorms
Sever or extreme turbulence or CAT not associated with a t-storm
Widespread dust storms or sandstorms lowering surface visibilities to below 3 miles
Volcanic ash
What is an AIRMET WA
Advisories of significant weather phenomena that describe conditions at intensities lower than those which required the issuance of SIGMETs, intended for use by all pilots in the preflight and enroute phase of flight to enhance safety. AIRMET information is available in two formats; text bulletins WA and graphics G-AIRMAT. They are issued on a scheduled basis every 6h beginning at 2:45 UTC. Unscheduled updates and corrections are issued as necessary
Each AIRMET bulletin included an outlook for conditions expected after the AIRMET valid period. AIRMET contain details about IFR, extensive mountain obscuration, turbulence, strong surface winds, icing, and freezing levels
What are the different types of AIRMETs
Sierra - describes IFR conditions and/or extensive mountain obscurations
Tango - Moderate turbulence, sustained surface winds of 30 knots or greater and/or non-convective low-level wind shear
Zulu - Moderate icing and provides freezing level heights
Describe the winds and temperature aloft forecasts
Wind and temp aloft forecasts are computer prepared forecasts of wind direction, speed, and temperature at specified times, altitudes, and locations. They are produced 4 times daily for specified locations in the US, Hawaii, and Alaska and costal waters, and the western Pacific Ocean. Amendments are not issued to the forecasts. Wind forecasts are not issued for altitudes within 1,500 feet of a location’s elevation
Some features are:
Date/time observation was collected, forecast valid period and the period during which the forecast is to be used
Altitudes up to 15,000’ in MSL, at or above 18,000 are in Flight Levels
Temp. indicated in degrees. 2 digits between 6,000-24,000’. Above FL240 minus sign is omitted since its always negative. Temp is not issued for altitudes within 2,500’ feet of locations elevation
Wind direction in tens of degrees, two digits, with reference to true north and wind speed is given in knots.
Light and variable winds or less than 5kt is 9900
100-199 kt subtract 100 from speed and add 50 to the coded direction
E.g 250 degrees at 145 kt is 7545
200kt or more is a forecast speed of 199 kt. E.g 7799 is decoded as 270 degrees at 199 kt or greater
What valuable information can be determined rom winds and temp aloft forecasts
Most favorable altitude based on wind and direction of flight
Areas of possible icing by noting air temp of 2 to -20 C
Temperature inversion
Turbulence by observing abrupt changes in wind direction and speed at different altitudes
What are Center Weather Advisories CWA
A CWA is an aviation warning for use by aircrews to anticipate and avoid adverse weather conditions in the en route and terminal environments. The CWA is not a flight planning product; instead it reflects current conditions expected at the time of issuance and/or is a short-range forecast for conditions expected to begin within 2h of issuance. CWA are valid for a maximum of 2h. If conditions are expected to continue beyond the 2h valid period a statement will be included in the CWA
Give some examples of NWS weather charts you will use during preflight planning
Surface analysis chart Weather depiction chart Short-range surface prognostic chart Significant weather prognostic chart Convective outlook chart Constant pressure analysis chart
What is a surface analysis chart
Surface analysis charts are analyzed charts of surface weather observations. The chart depicts the distribution of several items including sea level pressure, the position of highs and lows, ridges, troughs, the location and character of fronts, and the various boundaries such as dry lines, outflow boundaries, sea-breeze fronts, and convergence lines. The chart is produced eight times daily
What information does a weather depiction chart provide
The weather depiction chart contains a plot of weather conditions at selected METAR stations and an analysis of weather flying category. It is designed primarily as a briefing tool to alert aviation interests to the location of critical or near-critical operational minimums at terminals in the US and surrounding land areas. The chart is issued 8 times daily
Define LIFR, IFR, MVFR, VFR
LIFR - Low IFR ceiling less than 500’ and/or visibility less than 1 miles
IFR - Ceiling 500’ to less than 1,000’ and visibility 1 to less than 3 miles
MVFR - ceiling 1,000-3,000’ and/or visibility 3-5 miles inclusive
VFR - ceiling greater than 3,000’ and visibility greater than 5miles including clear sky
What are short-range surface prognostic charts
Short-range prog charts provide a forecast of surface pressure systems, fronts and precipitation for a 2.5 day period. they cover a forecast are of the 48 states and coastal waters, and are prepared by the NWS. Conditions are divided into 5 forecast periods: 12, 18, 24, 48, and 60h. Each chart depicts a snapshot of weather elements expected at the specified valid time. Issued 4 times daily and can be used to obtain the progression of surface weather during the included periods
Describe a US low-level sig. weather prog chart
The low-level SIGWX charts provided a forecast of aviation hazards primarily intended to be used as guidance products for pre-flight briefings. The forecast domain covers the US and the coastal waters for altitudes FL240 and lower. Depicts WX flying categories, turbulence, and freezing levels and are issued 4x daily in two types 12 and 24 h prog
Describe a mid-level SIGWX chart
Similar to low-level SIGWX the mid-level is issued 4x daily for 24h depicting weather at alt. between 10,000’ to FL450
What is a convective outlook chart
The convective outlook chart depicts ares of forecast to have the potential for sever tornado, wind gust 50 kt or more, or hail 3/4” or greater and non-sever general convection and specific sever weather threats during the following 3 days. The chart defines areas of slight risk SLGT, moderate risk MDT, or high risk HIGHT of severe thunderstorms for a 24-h period beginning at 1200 UTC. Day 1 and 2 also depict ares of general thunderstorms GEN TSTMS while the day 1, 2, and 3 Convective outlook may use SEE TEXT for areas where convection may approach or slightly exceed severe criteria
What are constant pressure analysis charts
Any surface of equal pressure in the atmosphere is a constant pressure surface. A constant pressure analysis chart is an upper air weather map where all information depicted is at the specified pressure of the chart. From these charts, a pilot can approximate the observed air temperature, wind, and temp/dew point spread along a proposed route. They also depict highs, lows, troughs, and ridges aloft by the height contour patterns resembling isobars on a surface map. Twice daily, five constant pressure charts are issued from observed data obtained at 00Z and 12Z
850 mb - 5K' 700 mb - 10K' 500 mb - 18K' 300 mb - 30K' 200 mb - 39K'
