Kolibear,
It is the runway contamination.
The first two digits of the eight-digit group is the runway number. Add 50 for a right runway (so the group beginning 59 in the LHR METAR is for 09R). 88 means all runways. 99 means this is a repeat of the last message, no new information.
The third digit is the type of contamination:
- 0 - clear and dry
- 1 - damp
- 2 - wet, or water patches
- 3 - rime or frost covered
- 4 - dry snow
- 5 - wet snow
- 6 - slush
- 7 - ice
- 8 - compacted snow
- 9 - frozen ruts or ridges
- / - type of contamination not reported
The fourth digit is the extent of the contamination:
- 1 - 10% contaminated
- 2 - 11% to 25% contaminated
- 3 - 26% to 50% contaminated
- 9 - 51% to 100% contaminated
- / - extent of contamination not reported
The fifth and sixth digits are the depth of the deposit:
- 00 - less than 1mm
- 01 to 90 - whole mms depth
- 91 - not used
- 92 - 10cm
- 93 - 15cm
- 94 - 20cm
- 95 - 25cm
- 96 - 30cm
- 97 - 35cm
- 98 - 40cm or more
- 99 - runway(s) non-operational but depth not reported
- // - depth not significant, or not reported
The final two digits are the braking action:
- 91 - braking action poor
- 92 - medium to poor
- 93 - medium
- 94 - medium to good
- 95 - good
- 99 - figures unreliable, but braking action suspect
- // - not reported, or runway closed
No, I didn't know all this, I had to look it up!
FFF
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