*2C Weather - Aviation WX Reports and Observations Flashcards
- What is a METAR and what are the two types?
AC 00-45
A METAR is an hourly surface observation of conditions observed at an airport. There are two types of METAR reports—a routine METAR report that is transmitted every hour and an aviation selected special weather report (SPECI). This is a special report that can be given at any time to update the METAR for rapidly changing weather conditions, aircraft mishaps, or other critical information.
- Describe the basic elements of a METAR.
AC 00-45
A METAR report contains the following elements in order as presented:
a. Type of reports—the METAR, and the SPECI (aviation special weather report).
b. ICAO station identifier—4-letter station identifiers; in the conterminous U.S., the 3-letter identifier is prefixed with K.
c. Date and time of report—a 6-digit date/time group appended with Z (UTC). First two digits are the date, then two for the hour, and two for minutes.
d. Modifier (as required)—if used, the modifier AUTO identifies the report as an automated weather report with no human intervention. If AUTO is shown in the body of the report, AO1 or AO2 will be encoded in the remarks section to indicate the type of precipitation sensor used at the station.
e. Wind—5-digit group (6 digits if speed is over 99 knots); first three digits = wind direction, in tens of degrees referenced to true north. Directions less than 100 degrees are preceded with a zero; next two digits are the average speed in knots, measured or estimated (or, if over 99 knots, the next three digits).
f. Visibility—surface visibility in statute miles, space, fractions of statute miles (as needed), and the letters SM.
g. Runway visual range (RVR), as required.
h. Weather phenomena—broken into two categories: qualifiers, and weather phenomena.
i. Sky condition—amount/height/type (as required) or indefinite ceiling/height (vertical visibility). Heights are recorded in feet AGL.
j. Temperature/dew point group—2-digit format in whole degrees Celsius, separated by a solidus (/). Temperatures below zero are prefixed with M.
k. Altimeter—4-digit format representing tens, units, tenths, and hundredths of inches of mercury prefixed with A. The decimal point is not reported or stated.
l. Remarks (RMK), as required—operational significant weather phenomena, location of phenomena, beginning and ending times, direction of movement.
Example: METAR KLAX 140651Z AUTO 00000KT 1SM R35L/4500V6000FT -RA BR BKN030 10/10 A2990 RMK AO2
- Describe several types of weather observing programs available.
(AIM 7-1-12)
a. Manual Observations—reports made from airport locations staffed by FAA or NWS personnel.
b. 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.
c. ASOS/AWSS—Automated Surface Observing System/Automated Weather Sensor System; the primary U.S. surface weather observing systems. AWSS is a follow-on program that provides the identical data as ASOS. Both systems provide continuous minute-by-minute observations that generate METARs and other aviation weather information. Transmitted over a discrete VHF radio frequency or the voice portion of a local NAVAID, and are receivable to a maximum of 25 NM from the station and a maximum altitude of 10,000 feet AGL. Observations made without human intervention will include the modifier “AUTO” in the report data.
- What are PIREPs (UA), and where are they usually found?
AC 00-45
The two types of PIREPs (routine, or “UA,” and urgent, or “UUA”) 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.
- What are Radar Weather Reports (SD)?
AC 00-45
A radar weather report (SD/ROB) contains information about precipitation observed by weather radar. It is a textual product derived from the WSR-88D NEXRAD radar without human intervention. Reports are transmitted hourly and contain the following: location ID, time, configuration (CELL, LN, and AREA), coverage, precipitation type and intensity, location, maximum tops, cell movement, and remarks. The resolution of an SD/ROB is very coarse, up to 80 minutes old, and should only be used if no other radar information is available.
