subroutine thick(ht_1000,ht_850,ht_700,wxts,wxtr,wxtz)
C
C THIS SUBROUTINE WILL EVALUATE VARIOUS THICKNESSES
C TO DETERMINE THE MOST LIKELY FORM OF PRECIPITATION,
C LIQUID, FROZEN, FREEZING
C
C     INPUT PARAMETERS:   ht_1000 = 1000 mb height in meters
C                         ht_850  =  850 mb height in meters
C                         ht_700  =  700 mb height in meters
C
C     OUTPUT PARAMETERS:  WXTS = 1, SNOW
C                         WXTR = 1, RAIN
C                         WXTZ = 1, FREEZING PRECIPITATION
C
C THICKNESS RULES ARE BASED ON RESEARCH PAPER BY UMPENHOUR (1968)
C CONTACT JOHN CORTINAS AT NSSL, 1313 HALLEY CIRCLE, NORMAN,
C OK, 73069 FOR A COPY OF THE PAPER.  THE PAPER SUGGESTS THAT
C LOW-LEVEL (1000-850) AND MIDLEVEL (850-700) THICKNESSES BE
C USED TO DISCRIMINATE BETWEEN PRECIPITATION TYPES.  THE THICKNESS
C VALUES ARE USED TO INFER THE THERMODYNAMIC STRUCTURE OF THE LOWER
C TROPOSPHERE.  THE THICKNESS OF THE MID- AND LOW-LEVEL THAT 
C CORRESPOND TO AN AVERAGE VIRTUAL TEMPERATURE OF 0C and -4C
C ARE USED TO IDENTIFY REGIONS WHERE A PARTICULAR TYPE OF PRECIPITATION
C IS EXPECTED TO OCCUR.
C     AVERAGE VIRTUAL TEMPERATURE OF OC BETWEEN 850 AND 1000 = 1300 M
C     AVERAGE VIRTUAL TEMPERATURE OF 0C BETWEEN 700 AND 850 = 1555 M
C     AVERAGE VIRTUAL TEMPERATURE OF -4C BETWEEN 700 AND 850 = 1540 M
C     Programmer:  John Cortinas, NSSL, 9/16/97
C     Modifications:    
      integer wxtz,wxtr,wxts



C
C COMPUTE THICKNESS VALUES
C

      t8501000=ht_850-ht_1000
      t700850=ht_700-ht_850
      print *,'850-1000',t8501000
      print *,'700-850',t700850


C
C SET PRECIPITATION TYPE VARIABLES TO ZERO.
C
      wxtz=0
      wxtr=0
      wxts=0

C
C USE IF-THEN STATEMENTS TO DETERMINE PRECIPITATION TYPE
C

      if (t8501000.gt.1300.) then
         wxtr=1
      else
         if (t700850.ge.1540.) wxtz=1
         if (t700850.lt.1540.) wxts=1
      end if

      return
      end