Aviation Weather Forecasts Flashcards
(12 cards)
What are Terminal Aerodrome Forecast (TAFs)
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/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. Example: 061737Z—the
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 24- and 30-hour TAFs are issued four (4) times per day, at
0000, 0600, 1200, and 1800Z. Example: 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 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 is a Graphical Forecast for Aviation (GFA)? (AWC)
The GFA is intended to provide the necessary aviation weather information
as a complete picture of the weather that may impact flight in the continental
U.S. The webpage includes observational data, forecasts, and warnings that
can be viewed from 14 hours in the past to 15 hours in the future, including
thunderstorms, clouds, flight category, precipitation, icing, turbulence and
wind.
What are the four types of Inflight Aviation Weather Advisories?
(AIM 7-1-5)
Inflight Aviation Weather Advisories are forecasts to advise enroute aircraft
of the development of potentially hazardous weather in four types: the
SIGMET (WS), the convective SIGMET (WST), the AIRMET (WA; text or
graphical product), and the center weather advisory (CWA). All heights are
referenced MSL, except in the case of ceilings (CIG) which indicate AGL.
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)? (AIM 7-1-5)
A SIGMET (WS) advises of weather that is potentially hazardous to all
aircraft. SIGMETs are unscheduled products that are valid for 4 hours;
SIGMETs associated with tropical cyclones and volcanic ash clouds are valid
for 6 hours. Unscheduled updates and corrections are issued as necessary. In
the conterminous U.S., SIGMETs are issued when the following phenomena
occur or are 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 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 7-1-5)
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.
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.
