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
  • $\begingroup$ It's probably a typo, but it would help to read the entire TAF in context. $\endgroup$
    – Ron Beyer
    Jan 9 '19 at 12:24

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".


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.