*2D Weather - Aviation WX Forecasts Flashcards
- What are Terminal Aerodrome Forecasts (TAFs)?
AC 00-45
A terminal aerodrome forecast (TAF) is a concise statement of the expected meteorological conditions significant to aviation for a specified time period within five statute miles (SM) of the center of the airport’s runway complex (terminal). The TAFs use the same weather codes found in METAR weather 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 of origin—the date and UTC for when the forecast was actually prepared, displayed in ICAO format. Valid time, TEMPOs and PROBS are presented ddhh/ddhh, FROM groups are presented ddhhmm. Note: This TAF date and time format recently changed to conform to international (ICAO) standards. This change provides 30-hour TAFs for 32 high-impact U.S. airports. The remainder of TAF reporting stations will continue with 24-hour forecasts.
d. Valid period date and time—valid forecast period is a 2-digit date followed by the 2-digit beginning and 2-digit ending hours in UTC. Routine TAFs are valid for 24 hours and are issued four times daily at 0000Z, 0600Z, 1200Z, and 1800Z.
e. Forecasts—wind, visibility, significant and vicinity weather, cloud and vertical obscuration, non-convective low level wind shear, forecast change indicators (FM, TEMPO and PROB).
- Define “aviation area forecast.”
AC 00-45
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 AIRMETs, SIGMETs, convective SIGMETs, CWAs, etc.), to determine forecast en route weather and to interpolate conditions at airports that do not have a terminal aerodrome forecast (TAF). FAs are issued 3 times daily for each of the 6 areas in the contiguous 48 states. FAs are also issued for the Gulf of Mexico, the Caribbean, Hawaii, and Alaska.
- What information is provided by an FA?
AC 00-45
Area forecasts are issued for the conterminous U.S. and cover the airspace between the surface and 45,000 feet AMSL.
They include:
a. Synopsis—brief discussion of the synoptic weather affecting the FA area during the 18-hour valid period.
b. Clouds and weather—description of the clouds and weather for the first 12-hour period for each state or group of states, including:
• Cloud amount (SCT, BKN or OVC) for clouds with bases higher than or equal to 1,000 feet AGL and below FL180,
• Cloud bases and tops (AMSL) associated with the above,
• Precipitation,
• Visibilities between 3 and 6 SM and obstruction(s) to visibility,
• Sustained surface winds 20 knots or greater.
c. 12 to 18-hour categorical outlook—IFR, marginal VFR (MVFR), or VFR, including expected precipitation and/or obstruction(s) to visibility.
- What are Inflight Aviation Weather Advisories (WST, WS, WA)?
(AIM 7-1-6)
Inflight aviation weather advisories are forecasts to advise en route aircraft of development of potentially hazardous weather in 3 types: the SIGMET, the convective SIGMET, and the AIRMET (text or graphical product). All heights are referenced MSL, except in the case of ceilings (CIG), which indicate AGL.”
Excerpt From: Michael D. Hayes. “Private Oral Exam Guide.” Aviation Supplies and Academics, Inc., 2012-05-25. iBooks.
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- What is a Convective SIGMET?
AC 00-45
Convective SIGMETs (WST) implies severe or greater turbulence, severe 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 Eastern (E), Central (C) and Western (W) United States (Convective SIGMETs are not issued for Alaska or Hawaii). Bulletins are issued hourly at H+55. Special bulletins are issued at any time as required and updated at H+55. 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.
a. Severe thunderstorm 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
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)?
AC 00-45
A SIGMET (WS) advises of non-convective weather that is potentially hazardous to all aircraft. SIGMETs are issued for the six areas corresponding to the FA areas. The maximum forecast period is four hours. In the conterminous U.S., SIGMETs are issued when the following phenomena occur or are expected to occur:
a. Severe icing not associated with a thunderstorm;
b. Severe or extreme turbulence or clear air turbulence (CAT) not associated with thunderstorms;
c. Duststorms or sandstorms lowering surface or inflight visibilities to below 3 miles;
d. Volcanic ash.
- What is an AIRMET (WA)?
AC 00-45
Advisories of significant weather phenomena that describe conditions at intensities lower than those which require 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-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. AIRMETs contain details about IFR, extensive mountain obscuration, turbulence, strong surface winds, icing, and freezing levels.
- What are the different types of AIRMETs?
AIM 7-1-6
There are three AIRMET types: Sierra, Tango, and Zulu:
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 nonconvective low-level wind shear.
c. AIRMET Zulu describes moderate icing and provides freezing level heights.
- Describe the winds and temperature aloft forecasts (FB).
AC 00-45
Winds and temperature aloft forecasts are computer prepared forecasts of wind direction, wind speed, and temperature at specified times, altitudes, and locations. They are produced 4 times daily for specified locations in the continental United States, Hawaii, Alaska and coastal 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 of the features of FBs are:
a. Product header includes date and time observations collected, forecast valid date and time, and the time period during which the forecast is to be used.
b. Altitudes up to 15,000 feet referenced to MSL; altitudes at or above 18,000 feet are references to flight levels (FL).
c. Temperature indicated in degrees Celsius (two digits) for the levels from 6,000 through 24,000 feet. Above 24,000 feet, minus sign is omitted since temperatures are always negative at those altitudes. Temperature forecasts are not issued for altitudes within 2,500 feet of a location’s elevation. Forecasts for intermediate levels are determined by interpolation.
d. Wind 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 wind or wind speeds of less than 5 knots are expressed by 9900. Forecast wind speeds of 100 through 199 knots are indicated by subtracting 100 from the speed and adding 50 to the coded direction. For example, a forecast of 250 degrees, 145 knots, is encoded as 7545. Forecast wind speeds of 200 knots or greater are indicated as a forecast speed of 199 knots. For example, 7799 is decoded as 270 degrees at 199 knots or greater.
- What valuable information can be determined from Winds and Temperatures Aloft Forecasts (FB)?
Most favorable altitude—based on winds and direction of flight.
Areas of possible icing—by noting air temperatures of +2°C to -20°C.
Temperature inversions.
Turbulence—by observing abrupt changes in wind direction and speed at different altitudes.
- What are Center Weather Advisories (CWA)?
AC 00-45
A Center Weather Advisory (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 2 hours of issuance. CWAs are valid for a maximum of 2 hours. If conditions are expected to continue beyond the 2-hour valid period, a statement will be included in the CWA.
