Runway States
Coding Requirements
General format: DRDRCEttBB
Where
DRDR is the runway designator
C is the runway deposits designator
E is the extent of contamination
tt is the depth of the deposit
BB is the friction coefficient or braking action
When runways are affected by snow, slush or other contaminants, an encoded runway state report for each runway in use is required to be appended to METARs. Ideally, a new report should be prepared for each change. If a report is not received, the previous message may be repeated once, although it is important that repeated messages are kept to a minimum.
If a runway inspection is not possible, it is preferable to report changes by general assessment rather than let a clearly unrepresentative message be repeated, for example, when:
a) Snow is judged to be turning to slush.
Thunderstorm RETS
Freezing rain REFZRA
Freezing drizzle REFZDZ
Moderate or heavy rain RERA
Moderate or heavy snow RESN
Moderate or heavy drizzle REDZ
Moderate or heavy ice pellets REPL
Moderate or heavy snow grains RESG
Moderate or heavy showers of rain RESHRA
Moderate or heavy showers of snow RESHSN
Moderate or heavy shower of small hail RESHGS
Moderate or heavy showers of snow pellets RESHGS
Moderate or heavy showers of hail RESHGR
Moderate or heavy blowing snow REBLSN
Sandstorm RESS
Dust storm REDS
Funnel cloud REFC
Volcanic ash REVA
b) It is apparent that snow depth has increased/decreased.
c) It is considered that braking action is deteriorating.
Appropriate local arrangements should be in place to ensure that a runway state message is available to the observer in good time for insertion into the next METAR.
NOTE: Data used to compile the runway state group is commonly provided by the aerodrome authority.
The depth of the deposit reported should be the average of the readings for the usable length of the runway.
Examples of METAR runway state group coding
a) 99421594 A repetition of the last message because no new information received, dry snow is covering 11% to 25% of the runway to a depth of 15 millimetres. Braking action is medium or good.
b) SNOCLO The aerodrome is closed due to contamination of the runways.
c) 74692225 Runway 24 right has slush covering 51% to 100% of the runway to a depth of 22 millimetres. The friction coefficient has been measured and is 25%.
d) 88CLRD95 Contamination has been cleared from all runways and the braking action is good.
Table Runway state group coding for use in the METAR
DRDR Runway designator
27 = Runway 27 or 27L
77 = Runway 27R (50 added for ‘right’)
88 = All runways
99 = A repetition of the last message because no new information received
C Runway deposits
0 = Clear & dry
1 = Damp
2 = Wet
3 = Rime or frost covered
4 = Dry snow
5 = Wet snow
6 = Slush
7 = Ice
8 = Compacted or rolled snow
9 = Frozen ruts or ridges
/ = Not reported due to runway clearance in progress
E Extent of contamination
1 = 10% or less
2 = 11% to 25%
5 = 26% to 50%
9 = 51% to 100%
/ = Not reported due to runway clearance in progress
tt Depth of deposit
00 = <1mm
01 = 1mm etc
thru’ to
90 = 90mm
91 = not used
92 = 10cm
93 = 15cm
94 = 20cm
95 = 25cm
96 = 30cm
97 = 35cm
98 = 40cm or more
99 = Runways non operational due snow or clearance
// = Not measurable or not significant
BB Friction coefficient / Braking action
28 = Friction coefficient 28%
35 = Friction coefficient 35%
or
91 = Braking action poor
92 = Braking action med/poor
93 = Braking action medium
94 = Braking action med/good
95 = Braking action good
99 = Figures unreliable
// = not reported e.g. runway closed
If the aerodrome is closed due to contamination of runways, the abbreviation SNOCLO is used in place of a runway state group.
If contamination ceases to exist, the abbreviation CLRD is used between 88 and braking action.
