I'm not sure you can safely interpret the phenomena without taking into account the local tables:
`11        localTablesVersion`
`8-9       subCentre`
`6-7       centre`

In addition, even if there is no local table, it would be nice to interpret the origin of the data (assuming that the centre and subcentre determine this if no local parameter table number is present).

0 indicates not used and 255 indicates missing (I'm assuming 255 would mean we could not interpret the phenomena, but this will need checking)
 the Local table (octet 11),


6-7       centre = 74 [U.K. Met Office - Exeter (grib1/0.table) ]

10        tablesVersion = 4 [Version implemented on 7 November 2007 (grib2/tables/1.0.table) ]