2B WX - Reports and Forecasts Flashcards
- Describe the various types of weather observing programs now in use. (AIM 7-1-12)
Manual observations—Reports made from airport locations staffed by FAA or NWS personnel.
AWOS—Automated Weather Observing System; consists of various sensors, a processor, a computer-generated voice subsystem, and a transmitter to broadcast local, minute-by-minute weather data directly to the pilot. Observations will include the prefix AUTO in data.
AWOS broadcasts—In addition to the AWOS computer-generated voice, some systems are configured to permit station personnel to append the automated report with an operator-generated message.
ASOS/AWSS—Automated Surface Observing System (ASOS)/Automated Weather Sensor System (AWSS), the primary surface weather observing system of the U.S. Provides the continuous minute-by-minute observations necessary to generate METARs and other aviation weather information. The information may be transmitted over a discrete VHF radio frequency or the voice portion of a local NAVAID.
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1. What is a METAR? (AC 00-45)
A METAR is an aviation routine weather report; a weather observer’s interpretation of the weather conditions at a given site and time. METARs contain the following elements in this order: Type of report, ICAO station identifier, date and time of report, modifier (as required), wind, visibility, runway visual range (RVR) (as required), weather phenomena, sky condition, temperature/dew point group, altimeter and remarks (RMK) (as required).
Example:
METAR KLAX 140651Z AUTO 00000KT 1SM R35L/4500V6000FT -RA BR BKN030 10/10 A2990 RMK AO2
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3. What are PIREPs and where are they usually found? (AC 00-45)
These reports contain information concerning weather as observed by pilots en route. Required elements for all PIREPs are message type, location, time (in UTC), flight level (altitudes are MSL), type of aircraft, and at least one weather element encountered (visibility in SM, distances in NM). A PIREP (abbreviation for “pilot reports”) is usually transmitted as an individual report but can be appended to a surface aviation weather report or placed into collectives. The two types of PIREPs are Urgent (UUA) and Routine (UA).
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4. What are Radar Weather Reports (SD)? (AC 00-45)
These include the type, intensity, and location of the echo top of general areas of precipitation observed by radar, reported each hour at H+35. All heights are reported above MSL. SDs should be used along with METARs, satellite photos, and forecasts when planning a flight to help in thunderstorm area avoidance; once airborne, pilots should depend on Flight Watch.
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5. What are Terminal Aerodrome Forecasts (TAFs)? (AC 00-45)
A 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 identifier.
c. Date and time of origin—the date and UTC 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, and forecast change indicators (FM, TEMPO and PROB).
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6. What is an Aviation Area Forecast (FA)? (AC 00-45)
An FA is a forecast of VMC, clouds, and general weather conditions over an area the size of several states. It is used to determine forecast enroute weather and to interpolate conditions at airports which do not issue TAFs. FAs are issued three times a day by the Aviation Weather Center (AWC) for each of the 6 areas in the contiguous 48 states. The weather forecast office in Honolulu issues FAs for Hawaii. The Alaska Aviation Weather Unit in Anchorage produces the FA for the entire state of Alaska.
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7. 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. All heights are referenced to MSL, except in the case of ceilings (CIG) which indicates above ground level. The advisories are of three types: Convective SIGMET (WST), SIGMET (WS), and AIRMET (WA).
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8. What is a convective SIGMET? (AC 00-45)
Convective SIGMETs (WST) imply 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. Bulletins are issued hourly at H+55, and 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 (valid for up to 2 hours):
a. 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.
b. Embedded thunderstorms.
c. A line of thunderstorms.
d. Thunderstorms that produce precipitation levels greater than or equal to heavy-intensity precipitation, affecting 40% or more of an area at least 3,000 square miles.
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9. What is a SIGMET (WS)? (AIM 7-1-6)
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.
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10. What is an AIRMET (WA)? (AIM 7-1-6)
An AIRMET is an advisory of significant weather phenomena that describes conditions at intensities lower than those which require the issuance of SIGMETs. They are issued every 6 hours beginning at 0245 UTC. Pilots should use AIRMETs 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). Each AIRMET bulletin includes an outlook for conditions expected after the valid period and contains details about IFR, extensive mountain obscuration, turbulence, strong surface winds, icing, and freezing levels.
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11. What are the different types of AIRMETs? (AIM 7-1-6)
There are three types of AIRMETs, 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.
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12. What is a winds and temperatures aloft forecast (FB)? (AC 00-45)
Winds and temperatures aloft are forecast for specific locations in the contiguous U.S. and also for a network of locations in Alaska and Hawaii. These forecasts, called FBs, are issued 4 times daily. In an FB, a 4-digit code group shows wind direction, in reference to true north, and wind speed in knots, with an additional 2-digit code group showing forecast temperatures in degrees Celsius.
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13. What valuable information can be determined from an FB? (AC 00-45)
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—a temperature increase with altitude can mean a stable layer aloft reducing the chance for convective activity.
Turbulence—by observing abrupt changes in wind direction and speed at different altitudes.
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14. What is a Center Weather Advisory (CWA)? (AC 00-45)
Issued by a CWSU (Center Weather Service Unit), this is an aviation warning for use by aircrews to anticipate and avoid adverse weather conditions in the enroute and terminal environments. The CWA is a short-term “nowcast,” pinpointing hazardous weather already causing an impact or expected to cause an impact within a 2-hour period; therefore it is an inflight advisory rather than a flight planning tool. 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.
- What is a Convective Outlook (AC)? (AC 00-45)
The AC is a narrative and graphical outlook of the potential for severe (tornados, wind gusts 50 knots or greater, or hail 1 inch diameter size or greater) and non-severe (general) convection and specific severe weather threats during the following three days. It defines areas of slight risk (SLGT), moderate risk (MDT) or high risk (HIGH) of severe thunderstorms for a 24-hour period beginning at 1200 UTC.
