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In a TAF-message downloaded from NOAA I came across "11/2SM" as the reported visibillity. I have previously seen "1 1/2SM" which I've been told to read as 1.5 SM.

  • is "11/2SM" a typo (should it have been "1 1/2SM") ?
  • Should it be read as a fraction "11/2" = "5.5" ?
  • Should it be read as "11+1/2" = 11.5" ?

Edit: Entire TAF (look 4th last line):

CYYZ 090839Z 0909/1012 31015G25KT P6SM FEW020 BKN050
TEMPO 0909/0913 P6SM -SHSN BKN020 BKN050 
FM091300 29018G30KT P6SM -SHSN BKN025 OVC080 
TEMPO 0913/0920 4SM -SHSN BKN020 OVC080 
PROB30 0915/0920 11/2SM -SHSN 
FM092000 31020G30KT P6SM -SHSN BKN025 BKN080 
FM100100 33020G32KT 6SM -SN BKN020 
FM101000 33018G28KT P6SM BKN020 RMK NXT FCST BY 091200Z
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  • $\begingroup$ It's probably a typo, but it would help to read the entire TAF in context. $\endgroup$ – Ron Beyer Jan 9 at 12:24
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According to NOAA, there should be a space between the whole and fractional parts. But they would never use a fractional part greater than 1, so your example must be a typo and should have read "1 1/2SM".

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