Weather Information Flashcards
Most of Earth’s weather occurs in what region of the atmosphere?
Troposphere (SFC to 36,000 ft)
What are the standard temperature and pressure values for sea level?
15 C (59 F) and 29.92”Hg (1013.2 mb)
What are isobars?
Line on a weather chart that 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?
Steep pressure gradient exists, higher winds. Shallow gradient will indicate lower wind speeds
What does dew point mean?
Temperature to which air must be cooled to attain saturation
How does fog form?
When the temperature and dewpoint become identical or nearly so. Can be achieved by either cooling or adding moisture thereby elevating the dew point
What factor primarily determines the type and vertical extent of clouds?
Stability of the atmosphere
Explain the difference between a stable atmosphere and an unstable atmosphere. Why is the stability of the atmosphere important?
Stability depends on the atmosphere’s ability to resist vertical motion. Unstable atmosphere leads. to larger vertical air movement thereby producing turbulent airflow and convective activity
How can you determine the stability of the atmosphere?
Temperature decreases uniformly and rapidly as you climb (nearly 3 C per 1,000) indicates unstable air whereas little to no change would indicate stable air
List the effects of stable and unstable air on clouds, turbulence, precipitation, and visibility
Stable - stratiform, smooth, steady, fair to poor visibility
Unstable - cumuliform, rough, showery, good
State the general characteristics in regard to the flow air. around high-pressure and low-pressure system in the Northern Hemisphere
Low - inward, upward, and counterclock wise
High - 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 toward a high pressure system?
Low - cloudiness, precipitation, bad weather
High - clear and good weather
Describe the different types of fronts
Cold - cold, dense, stable air replaces a body of warmer air
Occluded - Fast moving cold front catches up with a slow moving warm front; cold front occlusion and warm front occlusion
Warm - Warm air mass flows over colder air mass
Stationary front - Forces of two air masses are relatively equal
What are the general characteristics of the weather a pilot would encounter when operating near a cold front? A warm front?
Cold - Towering cumulus or cumulonimbus; tornado possible; poor visibility, variable gusty winds, temp/dew point and barometric pressure drop rapidly
Warm - Stratiform clods, drizzle; low ceilings, and poor visibility; variable winds; rise in temp
Note: Weather associated depends on the moisture available, stability of the air, slope of front, speed of front, and upper wind flow
What is a trough?
An elongated area of relatively low atmospheric pressure; air unable to expand outward and cannot descend further due to the ground, therefore, is forced to move upward, therefore, is an area of rising air
What is a ridge?
Elongated area of high atmospheric pressure; descending air
What service does the FAA provide for pilots to obtain a weather briefing?
Flight Service by 1-800-WX-BRIEF or online
What are the two main categories of sources of weather data?
Federal government - FAA and National Weather Service (NWS) and is the only approved authority for sources of weather observations
Commercial weather information providers - repackage weather products based on NWS information and modify layout
Does the weather data provided by commercial and/or third-party vendors satisfy the preflight action required by 14 CFR 91.103?
May not qualify, consult with FSS if in doubt
What type of weather briefings are available from an FSS briefer?
Standard - Mass dissemination
Abbreviated - supplement mass disseminated data
Outlook - Departure time is 6 or more hours in advance; only for planning purposes only
Inflight - Update a preflight briefing
What pertinent information should a weather briefing include? 7-1-5
Adverse conditions
VFR not recommended
Synopsis
Current conditions
Enroute forecast
Destination forecast
Winds aloft
NOTAMs
ATC Delay
Any other route related information may be requested
What is a Flight Information Services - Broadcast (FIS-B)
Ground service provided thru the ADS-B (978 MHz UAT dat link) network to provide weather and aeronautical information
Can onboard datalink weather (FIS-B) be useful in navigating an aircraft safely around an area of thunderstorms?
No; weather data is not real-time information only recent conditions
What is ATIS?
Automatic Terminal Information Services - continuous broadcast of recorded non-control information in select high-activity terminal areas; updated hourly or special weather
What type of information is provided in an ATIS broadcast?
Latest weather, ceiling, visibility, temp, dew point, wind direction (magnetic) and velocity, altimeter, pertinent remarks, instrument approach and runway in use
While en route, how can a pilot obtain updated weather information?
FSS on 122.22 and appropriate RCO frequencies
ATIS, ASOS, or AWOS broadcasts along route of flight
ARTCC
Datalink weather
ATC (work permitting)
What is a METAR?
Aviation routine weather report - weather observer’s interpretation of weather conditions at a given site; two types - routine (METAR) and special (SPECI)
Describe several types of weather observing programs available 7-1-2
Manual - FAA personal who manually observe, calculate, and enter their observations
ASOS/AWOS - automated minute by minute broadcast of weather observation
What are PIREPs and where are they usually found?
Pilot report of actual conditions encountered in the air; two types - route (UA) and urgent (UUA). Available from ATC, FSS, and online
What are Terminal Aerodrome Forecasts (TAFs)?
A concise statement of expected meteorological conditions within 5 SM of the center of the airport’s runway complex; valid for 24 or 30 hours
From which primary source should the information be contained regarding expected weather at the ETA if your destination airport does not have a TAF?
Graphical Forecast Analysis (GFA)
Describe the GFA 7-1-4
Web based graphics that provide observation forecasts and warnings from 14 hours in the past to 15 hours into the future; covers CONUS from surface up to FL480
What are the four types of inflight aviation weather advisories? 7-1-6
SIGMET (WS)
Convective SIGMET (WST)
AIRMET (WA)
Center Weather Advisory (CWA)
What is a convective SIGMET?
Any convective related situation that is hazardous for all aircraft; issued hourly H+55 or special issued as needed; valid for 2 hours
Severe or greater turbulence, severe icing, low level wind sheer, severe thunderstorms (surface winds of 50 knots or greater, hail 3.4 inches in diameter, tornadoes), embedded thunderstorms, line of thunderstorms, thunderstorms that produce precipitation greater than or equal to heavy intensity affection 40% or more than an area of at least 3,000 sq miles
What is a SIGMET? 7-1-6
Weather that is potentially hazardous to all aircraft not related to convective activity; unscheduled and valid for 4 hours
Sever icing, severe or greater turbulence including clear air turbulence (CAT), dust storm or sandstorms lowering visibility to less than 3 miles, volcanic ash
What is an AIRMET?
Advisory of significant weather phenomena that are lower in intensity of which require the issuance of SIGMET; issued every 6 hours beginning at 0245 UTC
What are the different types of AIRMETs?
Sierra - mountain obcuration and/or IFR conditions
Tango - moderate turbulence, sustained surface winds of 30 knots or greater, and/or nonconvective low level wind shear
Zulu - Moderate icing and provides freezing level heights
What is a winds and temperature aloft forecast (FB)?
Forecast for specific locations of wind direction (True north) and speed along with the temp in C; issued 4 times daily; not issued for altitudes within 1,500 ft AGL
What valuable information can be determined from an FB?
Most favorable altitude
Areas of possible icing - temperatures near freezing
Temperature inversions - increase in temperature can mean stable layer aloft
Turbulence - abrupt changes in wind direction
What is a Center Weather Advisory (CWA)?
Aviation warning for use by aircrew to anticipate and avoid adverse weather conditions in the en route and terminal environments; issued as needed and valid for 2 hours
What is a Convective Outlook (AC)?
Narrative and graphical outlook of potential severe and non severe convective activity for the day, next day, and following day
What is a surface analysis chart?
Analyzed chart of surface weather observations; produced 8 times daily. Includes high and lows, ridges and troughs, sea level pressure, location and character of fronts, various other boundaries
Describe a Ceiling and Visibility Analysis (CVA)
Real time analysis (every 5 mins) of current ceiling and visibility conditions across the CONUS
Define the terms: LIFR, IFR, MVFR, and VFR
LIFR - ceiling <500 ft, visibility <1 miles
IFR - Ceiling 500 to <1000 ft, visibility <3 miles
MVFR - Ceiling 1,000 to 3,000, visibility 3 to 5 miles
VFR - Ceiling >3,000, visibility >5 miles
What information do short range surface prognostic charts provide?
Provide a forecast of surface pressure systems, fronts and precipitation for a 2.5 day period; divided into 5 forecast periods: 12, 18, 24, 48 and 60 hours
Note: Use the snapshots of each time slot to see the progression of weather
Describe a low level significant weather chart
Forecast of aviation weather hazards and intended to be used as guidance products for pre flight planning; covers FL240 and below with a 12 hour prog and 24 hour prog
How are freezing levels depicted on the freezing level graphics chart?
Color coded to represent the height in hundreds of feet MSL of the lowest freezing point. Initial and 3 hour period are updated hourly, 6, 9, 12 hour forecast are updated every 3 hours
What are NOTAMs?
Time critical aeronautical information which is of either temporary nature or not sufficiently known in advance to permit publication on aeronautical charts or in other operational publications
Describe the following categories of NOTAMs
Domestic NOTAM (D) - info disseminated for all nav facilities part of the NAS, all public use aerodromes listed in the Chart Supplement
Flight Data Center (FDC) NOTAM - flight information that is regulatory in nature including IAP amendments, TFRs, WAAS or GPS info
International NOTAM - distributed to more than one country and published in ICAO format, same info as (D) NOTAMs
Military NOTAM - Pertain to military related navaids or airports
All (D) NOTAMs will have keywords contained within the first part of the text. What are several examples of these keywords? 5-1-3
RWY, TWY, OBST, COM, STAR, ROUTE
Where can NOTAM information be obtained?
Call FSS
NOTAM Search on FAA website
Flight Service website
FIS-B via ADS-B
Note: FIS-B are limited to those issued or effective within the past 30 days, anything older is not provided
What are the three principal types of thunderstorms?
Single cell - Consists of one cell; easily circumnavigated; typically rare
Multicell (cluster and line) - Consists of a cluster of cells at different stages in their life cycles; may last several hours therefore makes it more difficult to circumnavigate; could have supercells embedded within
Supercell - Consists of a single, steady rotating updraft that persists for an extended period of time; updrafts may reach 9,000 fpm (100 knots); their size and persistence make it tougher to circumnavigate
When attempting to avoid turbulence around thunderstorms, explain several operational procedures a pilot should never attempt
Land or takeoff in the face of an approaching thunderstorm (sudden low level turbulence could cause loss of control)
Fly under a thunderstorm (turbulence and wind shear could be hazardous)
Fly under the anvil of a thunderstorm (potential for severe and extreme CAT)
Fly without airborne radar into a cloud mass containing scattered embedded thunderstorms (unable to circumnavigate visually)
Never trust the visual appearance to be reliable indicator of the turbulence inside a thunderstorm
Never assume ATC will offer radar navigation guidance or deviations around thunderstorms
Never use NEXRAD mosaic imagery as the sole means to navigate thru a thunderstorm
When flying an airplane without onboard thunderstorm detection equipment, describe procedures a pilot can take to avoid thunderstorms and/or turbulence associated with them
Tune in to ATC for PIREPs and greater situational awareness
Ask ATC for radar navigation guidance or approve deviations around thunderstorms
Use NEXRAD for route selection to avoid storms
Advise ATC when switching controllers of deviation before accepting rejoining the original route
Ensure route is clear of thunderstorms before accepting to rejoin original route
Avoid thunderstorms by at least 20 miles
Circumnavigate the entire area if the area has 6/10 thunderstorm coverage
Vivid and frequent lightning indicates probability of severe thunderstorms
Can ATC provide inflight assistance in avoiding thunderstorms and severe weather?
Yes if the workload permits; radar coverage may also be limited
Give some examples of charts and reports useful in determining the potential for and location of thunderstorms along your route
Convective Outlook (AC) - graphical outlook of risk of thunderstorm in a 24 hour period
Significant Weather Chart (SIGWX) - forecast of aviation weather hazards for the valid time
Weather Radar Observations - Graphical display of precipitation targets detected by weather radar
Convective SIGMETs (WST) - issued for any convective situations
Pilot Reports (PIREPs) - Actual conditions along route
Supplementary weather products - Help enhance situational awareness
What are microbursts?
Small intense downdrafts; presence of both vertical and horizontal wind shear hazardous to all aircraft, especially at low altitude; not easily detectable with convention radar or wind shear alert systems
Where are microbursts most likely to occur?
Almost anywhere there is convective activity
What are some basic characteristics of a microburst?
Size - less than 1 mile in diameter expanding up to 2.5 miles in diameter near ground level
Intensity - downdrafts as strong as 6,000 fpm; horizontal winds up to 45 knots from head to tail (90 knot total wind shear)
Duration - Rarely lasts longer than 15 mins from the time it strikes the ground until dissipation
What types of weather information will you examine to determine if microburst/windshear conditions might affect your flight?
TAFs - terminal forecast for convective activity
METARs - inspect for windshear clues (convective activity, rain, blowing dust)
Severe weather watch reports - convective activity would be active
LLWAS reports - Low Level Windshear Alert System, used to detect wind shift
TDWR - Terminal Doppler Weather Radar - Detects microbursts, gust fronts, wind shift and precipitation intensities and provide severe weather alerts and warnings to ATC and piltos
SIGMETs and convective SIGMETs - provide essential clues of convective activity
Visual clues from cockpit - Heavy rain with locacalized blowing of dust/debris, virga, rain core diverging away from core, or tornadic features, lightning
Define wind shear and state the areas in which it is likely to occur
Change of wind velocity either directional or speed and can occur anywhere in the atmosphere but most common in:
Low level temperature inversion
Wind shear in a frontal zone or thunderstorm
CAT at high levels associated with jet stream or strong circulation
While on a cross-country flight, you notice a lens-shaped cloud over a mountainous area along your route of flight. What does the presence of this type of cloud indicate?
Severe turbulence
Explain the difference between an increasing headwind shear and a decreasing headwind shear?
Increasing headwind indicates increase airspeed thus performance; aircraft will pitch up, can cause longer float on landing. Decreasing headwind (increasing tailwind) will decrease IAT and performance, aircraft will pitch down
Concerning wind shear and microburst direction systems, what do the abbreviations LLWAS, TDWR, WSP and ITWS indicate in the Chart Supplement U.S. information for an airport?
LLWAS - low level windshear alert system - provides wind shear alert and gust front info in and around an airport; does not provide microburst alerts and detect wind shear beyond the periphery of an airport
TDWR - terminal doppler weather radar - located 8 to 12 miles off the airport proper and designed to look for microburst, gust fronts, wind shifts, and precipitation intensities around and over airport
WSP - weather service processor - provides the same info as TDWR at a fraction of the cost
ITWS - integrated terminal weather system - provides alerts for microburst, wind shear, and significant thunderstorm activity and displays wind info oriented to the threshold or departure end of runway
What is clear air turbulence (CAT)?
Defined as sudden severe turbulence occurring in cloudless regions that causes violent buffeting of aircraft; typically associated with higher altitude turbulence associated with wind shear most commonly encounter outside of convective clouds including in cirrus clouds, within and in lenticular clouds, and vicinity of thunderstorms
