Airline Transport Pilot
Flight Instructor: Airplane Single and Multiengine; Instrument Airplane
cell: 518.366.3957
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This document describes how to decode the periodic additional data on METARs and gives details of the Meteorological codes for use at observing stations.
Selected common additional data blocks
Note: for temperature reports, Sn indicates the Sign of the temperature: 0 for positive or zero degrees and 1 for negative degrees
Data | Descriptor | |
---|---|---|
Hourly Temperature and Dew point | TSnTTTSnTdTdTd
(in 0.1 degrees C) |
|
6-Hour Maximum Temperature
(in six-hour report*) |
1SnTxTxTx
(in 0.1 degrees C) |
|
6-Hour Minimum Temperature
(in six-hour report*) |
2SnTnTnTn
(in 0.1 degrees C |
|
24-Hour Maximum/Minimum Temperature
(in 0000 local standard time report) |
4SnTxTxTxSnTnTnTn
(in 0.1 degrees C) |
|
3-Hour Pressure Tendency
(in three- and six-hour reports*) |
5appp
(in hectopascals, starting at 10s) (see tendency code in table 12-7 below) |
|
3- and 6-Hour Precipitation Amount
(in three- and six-hour reports, respectively*) |
6RRRR
(in inches, starting at 10s) (see also precipitation units in table 12-6 below) |
|
24-Hour Precipitation Amount
(in 1200 UTC report) |
7R24R24R24R24
(in inches, starting at 10s) (see also precipitation units in table 12-6 below) |
|
Hourly Precipitation Amount
(if precipitation has occurred since last METAR) |
Prrrr
(in inches, starting at 10s) (see also precipitation units in table 12-6 below) |
|
Snow Depth on the Ground
(in six-hour reports*) |
4/sss
(in inches, starting at 100s) |
|
Cloud Types
(in three- and six-hour reports*) |
8/CLCMCH
(Low/Middle/High) (Cloud types as per WMO International Cloud Atlas) |
|
Water Equivalent of Snow on Ground
(in 1800 UTC report if snow greater than 2 inches) |
933RRR
(in inches, starting at 10s) |
|
Duration of Sunshine
(in 0800 UTC report) |
98mmm
(in minutes) |
|
* Three-hour report: 0300, 0900, 1500, 2100 UTC * Six-hour report: 0000, 0600, 1200, 1800 UTC |
RVRNO: | Runway Visual Range missing |
PWINO: | Precipitation Identifier Information not available |
PNO: | Precipitation Amount not available |
FZRANO: | Freezing Rain information not available |
TSNO: | thunderstorm information not available (may indicate augmenting weather observer not logged on) |
VISNO_LOC: | (Visibility) at second location not available |
CHINO_LOC: | (Cloud Height Indicator) sky condition at secondary location not available |
$ | Maintenance Check Indicator: |
Data | Data Block | Description |
---|---|---|
CLOUD HEIGHT/VISIBILITY | iRiXhVV | The iR is the precipitation data (group 6RRRtR) indicator (WMO code table 1819 -- see reference for WMO code tables below), while iX is the indicator for station type (manned or unmanned) and for present and past weather (group 7wwW1W2) (WMO code table 1860). The h is height (AGL) of lowest cloud (WMO code table 1600), and VV is horizontal surface visibility (WMO code table 4377). |
SKY COVERAGE/WIND | Nddff | The N is total sky cover in eighths or oktas (WMO code table 2700), while dd is the wind direction (hundreds and tens of degrees true) to the nearest 10 degrees, and ff is the sustained wind speed in the units indicated by iW. If winds exceed 99 (knots or meters per second), ff is encoded 99 and the 00fff group is included, with 00 as an indicator and fff as the wind speed in hundreds, tens, and units. |
AIR TEMPERATURE | SnTTT | The Snis the temperature sign, 0 for positive (or 0) and 1 for negative. This indicator is used throughout the Synoptic code to indicate the temperature sign. The TTT is the temperature in tens, units, and tenths of a degree Celsius. |
DEW-POINT TEMPERATURE | SnTdTdTd | The TdTdTd is the dew-point temperature in tens, units, and tenths of a degree Celsius. |
NOTE: | In the body of a METAR (as opposed to the additional data blocks)
|
|
STATION PRESSURE | 3POPOPOPO | The POPOPOPO is the station pressure in hundreds, tens, units, and tenths of hPa (thousands value omitted). [see note "P" below.] |
SEA-LEVEL PRESSURE | 4PPPP | Also indicated by SLP instead of a 4, the PPPP is the sea-level pressure in hundreds, tens, units, and tenths of hPa (thousands value omitted) [see note "P" below.]. |
STANDARD LEVEL HEIGHT | 4a3hhh | Reported by mountain stations in place of sea-level pressure, a3 is the standard isobaric surface reported (WMO code table 0264) and hhh is the geopotential height in meters, omitting thousands value. |
3-HOUR PRESSURE CHANGE | 5appp | The a is the pressure tendency (WMO code table 0200), and ppp is the 3-hour pressure change in tens, units, and tenths of hPa. [see note "P" below.] [See FMH No. 1, Table 12-7 following.] |
Type of Measurement | Unit of Measure |
---|---|
Liquid Precipitation | 0.01 inch |
Water Equivalent of Solid Precipitation | 0.01 inch |
Solid Precipitation | 0.1 inch |
Snow Depth | 1.0 inch |
Primary Requirement |
Description | Code Figure |
---|---|---|
Atmospheric pressure now higher than 3 hours ago. |
Increasing, then decreasing. | 0 |
Increasing, then steady, or increasing then increasing more slowly. |
1 | |
Increasing steadily or unsteadily. | 2 | |
Decreasing or steady, then increasing; or increasing then increasing more rapidly. |
3 | |
Atmospheric pressure now same as 3 hours ago. |
Increasing, then decreasing. | 0 |
Steady | 4 | |
Decreasing then increasing. | 5 | |
Atmospheric pressure now lower than 3 hours ago. |
Decreasing, then increasing. | 5 |
Decreasing, then steady, or decreasing then decreasing more slowly. |
6 | |
Decreasing steadily or unsteadily. | 7 | |
Steady or increasing, then decreasing; or decreasing then decreasing more rapidly. |
8 | |
NOTE:
|
Notes:
Note P: The terms "hectopascal" and "millibar" are synonomous. While the term millibar predates the term hectopascal in general aviation use, the Pascal is the SI (metric system) unit for pressure and is thus the now-accepted term for the measure of atmospheric pressure.
The standard conversions are
References:
The Federal Meteorological, Handbook No. 1, Office of the Federal Coordinator for Meteorology, retrieved 13 March 2014.
World Meteorological Organization (WMO)
rev. 5 February 2015
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Steve Sconfienza, Ph.D.
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