Freezing Level

[Port Strobe]

I'd like to ask how the temperatures are calculated for the Met form 214 and the freezing level for the 215? I find sometimes these don't exactly agree. Say if the freezing level is quoted as 5000' on the 215 and yet the temperature at 5000' on the 214 is +01. I know there's not much difference but I'm curious about the difference in the two. Has it something to do with the freezing level on the 215 being over a wide region perhaps? Something to do with the interpolation of figures on the 214 that's required if you reside between sampling points? Then sometimes would it be better to go by the 214 rather than the 215 for freezing level?

Thanks for any light you can shed, simply wondering why there is a difference between the two although I realise it may be a touch academic given the magnitude of the discrepancy. Cheers