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Flashcards in Aviation Wx Forecasts Deck (9)
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What are Terminal Aerodrome Forecasts (TAF's)?

A terminal aerodrome forecast is a concise statement of the expected meteorological conditions significant to aviation for a specified time period within five statue miles of the center of the airport's runway complex. The TAF's use the same wx codes found in METAR wx reports, in the following format:

a) Type of reports - a routine forecast (TAF), an amended forecast (TAF AMD), or a corrected forecast (TAF COR).

b) ICAO station identifier - 4 letter station identifiers

c) Date and time or origin - the date and time of forecast follows the terminal's location identifier. It contains the day of the month in two digits and time in four digits in which the forecast is completed and ready for transmission, with a Z appended to denote UTC. Ex: 061737Z (TAF was issued on the 6th day of the month at 1737 UTC

d) Valid period date and time - The first two digits are the day of the month for the start of the TAF followed by two digits indicating the starting hour (UTC). The next two digits indicate the day of the month for the end of the TAF, and the last two digits are the ending hour (UTC) of the valid period. Scheduled 24HR and 30HR TAF's are issued four times a day at 0000, 0600, 1200, 1800z. Ex: A 00Z TAF issued on the 9th of the month and valid for 24 hours would have a valid period of 0900/0924.

e) Forecasts - wind, visibility, significant and vicinity wx, cloud and vertical obscuration, non-convective low level wind shear, forecast change indicators (FM, TEMPO, PROB).


Define aviation area forecast.

Abbreviated as "FA," this is a forecast of specified wx phenomena covering a flight information region or other area designated by the meteorological authority. Pilots should use the area forecast (in conjunction with AIRMET's, SIGMET's, convective SIGMET's, etc) to determine forecast en route wx and to interpolate conditions at airports that do not have TAF. FA's are issued three times a day.


What are the four types of In-Flight Aviation Wx Advisories?

SIGMET, convective SIGMET, AIRMET, CWA (center wx advisory. All heights are referenced MSL, except in the case of ceilings which indicate AGL.


What is a Convective SIGMET (WST)?

Convective SIGMET's (WST) implies severe or greater turbulence, severe icing and low-level wind shear. These are hazardous to ALL categories of aircraft. Bulletins are issued hourly at H+55. Special bulletins are issued anytime as required and updated at H+55. The text of the bulletin consists of either an observation and a forecast, or just a forecast which is valid for up to 2 hours. Convective SIGMET's may include:

a) severe thunderstorms 50 knots or greater, hail 3/4" in diameter, tornadoes
b) embedded thunderstorms
c) a line of thunderstorms
d) 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. SIGMET's are unscheduled products that are valid for 4 hours. Unscheduled updates and corrections are issued as necessary. SIGMET's are issued when the following is expected to occur:

a) Severe icing not associated with thunderstorms
b) Severe or extreme turbulence or clear air turbulence (CAT) not associated with thunderstorms.
c) Widespread dust storms or sandstorms lowering surface visibility below 3 miles.
d) volcanic ash


What is an AIRMET (WA)?

Advisories of significant weather phenomena that describe conditions at intensities lower than those which require the issuance of SIGMET's, intended for use by all pilots in the pre-flight and enroute phase of flight to enhance safety. AIRMET information is available in two formats: text bulletins (WA) and graphics (G-AIRMET). They are issued on a scheduled basis every 6 hours beginning at 0245 UTC. Unscheduled updates and corrections are issued as necessary.

Each AIRMET bulletin includes an outlook for conditions expected after the AIRMET valid period.


What are the different types of AIRMET's?

a) AIRMET Sierra - describes IFR conditions and/or extensive mountain obscurations
b) AIRMET Tango - describes moderate turbulence, sustained surface winds of 30 knots or greater, and/or non-convective low-level wind shear
c) AIRMET Zulu - describes moderate icing and provides freezing level heights.


Describe the winds and temperature aloft forecasts (FB)

Winds and temperature aloft forecasts are computer prepared forecasts of wind direction, wind speed, and temperature at specified times, altitudes, and locations. There are produced 4 times daily. some of the features include:

a) product header included date and time observations collected, forecast valid date and time and the time period during which the forecast is to be used.
b) Altitude up to 15,000ft reference to MSL
c) Temperature indicated in degrees C for the levels from 6,000 thru 24,000ft.
d) Winds direction indicated in tens of degrees (two digits) with reference to true north and wind speed is given in knots (two digits).

Light and variable winds are expressed by 9900. Forecast winds speeds of 100 through 199 knots are indicated by subtracting 100 from the speed and adding 50 to the coded direction. Ex: a forecast of 250 degrees, 145 knots, is encoded as 7545.


What valuable info can be determined from Winds and Temperature Aloft Forecasts?

a) Most favorable altitude - based on winds and direction of flight
b) Areas of possible icing - by noting air temperatures of +2 degrees C to -20 degrees C
c) Temperature inversions
d) Turbulence - by observing abrupt changes in wind direction and speed at different altitudes.