1.5 x 10^6 line file. 35000 RAOB soundings. The number of lines per sounding varies, but there is always a 300 hPa line. Want the index of such for each sounding, this will be different for each sounding. Current code is:

tmp=where(plev EQ plevel, cntp)
if (cntp GE 1) then pind=tmp[0]

plev is the pressure at each line in a given sounding, one of which will be 300 hPa and plevel is 300 hPa.
BUT this gives cntp = 35000 and no 300 hPa level is given

Don’t know what to do now.