5       raw variables and mean/spread/prob info
U10M   33   105  D1  10  
V10M   34   105  D1  10
RH     52   105  D1  2
T2M    11   105  D1  2  
PRCP   61    1   D1  0 
  3      special derived variables, each  of which, needs code to process specially
APCP   61   1   M0     P1  3 > T1 0.25
FIRW   147  2   M0     P1  0  = T1 1.0 
CPTP   301 200  M0     P1  0  = T3 1.0 2.0 3.0