NMC Office Note 84

                           Packing and Identification
                                       of
                              NMC Grid-Point Data



       INTRODUCTION

            The purpose of this Office Note is to provide information
       related to NMC grid point data fields.  It describes the data
       structure used and presents the rationale and details involved in
       identifying and packing the fields.  Because of the availability
       and efficiency of existing software as well as the convenience of
       augmenting existing data sets, a large number of requirements have
       been accommodated since the procedures were first introduced years
       ago.  As might be expected, some exceptions to these procedures
       have crept into usage.  These involve a minor amount of non-
       conformity to the ON84 standard units and to the usual packing
       procedures.  These exceptions, where known, are indicated.


       NMC PACKED BINARY DATA FORMAT

             Most NMC grid point data fields are packed by transforming
       32-bit IBM floating point numbers into 16-bit IBM halfword
       integers using a scaling algorithm which will be described later.
       A 12-word label which prefaces each data array serves two
       purposes:  1) it uniquely identifies the data field for retrieval
       of the data set from where it is stored, and 2) it contains count
       and scaling information so that the data, which follows the label,
       may be unpacked and converted back into an array of floating point
       numbers.   Spectral coefficients are stored without packing.  In
       this case, each complex coefficient is composed of two 32-bit IBM
       floating point real numbers.


       DATA PACKING AND UNPACKING

             The most common method for scaling and packing the data is
       as follows.

             First, compute a reference value  A  by finding the maximum
       and minimum data values,  QMAX  and  QMIN, respectively.  Use
       these two values to determine the mid-range of the data array:

                               A = (QMAX + QMIN) / 2.0

             Next, find the binary scaling value  n, the least integer
       such that:

                                 (QMAX - A) <  2**n


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        The reference value  A  is stored as a 32-bit IBM floating
  point number in word 10 of the 12-word label.  The binary scaling
  value  n  is stored as an IBM halfword integer in the right half
  of word 11.  (See Figure 1.)

        Then the data array is scaled according to:

                  H(j) = (Q(j) - A) * 2**(15 - n),  j=1,J

  where  Q(j)  is a 32-bit IBM floating point number to be packed,
  and  J  is the number of data points to be packed.  The scaled
  values  H(j)  are rounded, converted to halfword integers, and
  stored in sequence following word 12 of the label.  If the field
  is of two dimensions or more, the points are taken in the order
  they occur in storage.  J  will be the product of the dimensions.
  Negative values of  n  as well as negative values of  H(j)  are
  stored in standard IBM two's complement form.

        NMC data fields can be packed and unpacked following the
  method just described with library subroutines W3AI00 and W3AI01.
  The casual users of NMC packed fields need not concern themselves
  further with the packing details except to note that signed values
  with 15-bit precision are maintained. The precision of the data
  that is retained by the scaling algorithm depends inversely on the
  range of values in the original array; i.e., the smaller the
  range, the greater the precision retained.  The procedure of using
  a reference value which is the mid-range of the data array and
  forming anomalies for packing yields the same precision as using a
  reference level which is the minimum value of the data array and
  forming positive anomalies packed into 16-bit halfwords.  The
  functions IW3GET and IW3PUT have the unpacking and packing
  subroutines built in for the convenience of the user.

        In packing a data field, the reference value  A  and the
  scaling factor  n  can, of course be preset by the creator of the
  field rather than using the packing subroutine (W3AI00). This
  procedure affects only the precision of the data generated and
  does not prohibit the use of the unpacking subroutine (W3AI01), as
  long as all 12 label words are properly set.


  IDENTIFYING THE DATA FIELDS

        Each packed data field is uniquely identified in the first 5
  words of its 12-word label.  These 5 words specify the data type,
  the type and value of the (constant) surface on which the data are
  given, the forecast (projection) time (including the value zero),
  the grid type, and any other parameters needed.

        Most NMC data fields can be thought of as some quantity  Q
  on a horizontal or quasi-horizontal surface  S  at some level
  value  L. For example, a 500-mb height field would be identified
  by specifying  Q = height,  S = pressure, and  L = 500.  Another
  example is  Q = pressure,  S = mean sea level, and  L = 0 (not

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       applicable).  If the quantity  Q  is for a layer, the domain of
       the layer is given by  S1  at  L1  and  S2  at  L2.  In this case,
       the surface of  S1  is the one physically above the surface of S2.
       For example, the thickness of the (500/1000)-mb layer is specified
       by Q = height,  S1 and S2 = pressure,  L1 = 500, and  L2 = 1000.
       Another possibility is that the quantity  Q  is formed by
       differencing two fields of the same data type, e.g., constant
       pressure height for different levels (thickness) or constant
       pressure height for the same level for different times (tendency).
       The identifications for these examples, as well as for many other
       possibilities, can be constructed by carefully considered
       combinations of the markers T,  M,  X,  and  N, as described in
       Tables 2 through 5, below.

             The numerical value of the level  L  for the corresponding
       surface  S  is coded in words 2 and 4 of the label as follows.

             Represent  L  as:

                                    L = C * 10**E

            where  C  is a 5-digit signed decimal integer whose high-
       order digit is non-zero unless  L  itself is zero, and  E  is a
       signed integer, zero if  L  is zero.  For example, if  L = 500:

                                      C = 50000

                                       E = -2

       so that:

                                L = 50000 * 10**(-2)

             Again, if L = 0.83333

                                      C = 83333

                                       E = -5

       so that:

                                L = 83333 * 10**(-5)


       LABEL ELEMENT VALUES

             Table 1 gives the code figures for  Q  and  S, the data type
       and surface.

             Table 2 gives the values for the marker  T  which is used to
       specify time intervals.  It also explains how the values of  F1
       and  F2  are to be specified.



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        Table 3 gives values for the marker  M  which is used to
  specify data fields involving layers, and to indicate whether
  fields have been initialized.

        Table 4 gives values to be used for the exception marker  X,
  which is used to specify a data field whose date/time (YYMMDDII)
  precedes that of the date/time found in the data set identifier
  table.  (This option is used, for example, to store first guess
  fields from an earlier cycle in a current cycle data set).

        Table 5 gives values for the miscellaneous marker  N, which
  is used to specify types of spectral coefficient data and also to
  indicate that forecast times are in units of half days rather than
  hours.

        Table 6 gives values for the markers  CM  and  CD  which
  specify climatological data fields.

        Table 7 gives values for the marker  K  which identifies the
  grid for which the data are given.  Table 7 lists a combination of
  grids currently in operational use at NMC as well as others which
  have been used in the past.  The grids thought to be active as of
  the date of this Office Note are so indicated in the table.

        The vertical grid lines of an NMC grid can be considered
  columns (i) and the horizontal grid lines can be considered rows
  (j). The coordinate system is the normal right-hand cartesian
  system in which  i  increases from left to right and  j  increases
  from bottom to top.  Grid point values for the columns are stored
  in consecutive array locations starting with the bottom row.
  Succeeding rows are stored in a like manner progressing from the
  bottom to the top of the grid.  This follows the usual FORTRAN
  indexing procedure for a two-dimensional array.

        For polar stereographic projection grids, the orientation is
  defined as the longitude value 1) which parallels the vertical
  grid lines and 2) for which latitude increases as  j increases.
  This longitude may lie within or without the domain of the grid
  and may or may not coincide with a grid line.

        Table 8 gives the values for the marker  KS  which
  identifies how the field was derived; e.g., by spectral methods,
  by departures from climatological normals, etc.

       Values from the tables described above, used in combination
  with values for surfaces (C1,E1  and  C2,E2) and values for
  forecast hours  F1  and F2, are sufficient to identify a data
  field.

        Word 6 is for internal (computer) use and can be ignored.

        Word 7 gives the date and time of either the nominal
  observation time of the data used in the analysis, or the initial
  time of the forecast.  The time  II  is specified in Universal

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       Coordinated Time (UTC) in hours:  00-23.  For example, for
       midnight UTC  II = 00, for noon UTC  II = 12.  YY is the year of
       the century, 00-99,  MM  is the month of the year, 1-12, and  DD
       is the day of the month, 1-31.  The date and time are entered as
       8-bit integers in the format YYMMDDII.

             The remainder of the label should be filled out as shown in
       Figure 1.  Note that most users rely upon standard NMC library
       subroutines to accomplish packing the data.  These subroutines
       will also initialize words 9 and 10 and the scaling value in word
       11.  The user must supply  J, the number of data points, in word 8
       for the packing subroutine (W3AI01).

             Table 9 gives the values of the marker  R  which specifies
       the run within the cycle.

             Table 10 gives the values for the marker  G  which specifies
       the program which generated the field.  Programs which are
       currently in operational use as of the date of this Office Note
       are so indicated.

             Tables 9 and 10 are intended primarily for internal NMC use.
       The markers  R  and  G  in some data fields may have these
       parameters specified in a manner other than that given in this
       Office Note.

             Table 11 contains the hexadecimal representations of some
       commonly used values of  C.  Negative values of  C  and  E  are
       indicated by turning on the high-order bit of these parameters,
       thus using sign-and-magnitude representation.

             Table 12 shows some examples of identifying some commonly
       generated data fields.

             Table 13 gives the values for the marker  P  which specifies
       the number of bits which have been used to pack each grid point
       value. While the most common number of bits used is 16 (for which
       P = 0), there are some fields which have been packed using fewer
       bits.  In these cases, the data array is scaled according to:

                     H(j) = (Q(j) - A) * 2**((P-1) - n),  j=1,J














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                          Table 1 - Q and S

                       PARAMETERS AND SURFACES


    Number   Abbreviation        Item                   Units
  Hex   Dec      (*)
  -----------------------------------------------------------------

                       Height wrt mean sea level
    1     1    -HGT--    Geopotential                   gpm
    2     2    -P-ALT    Pressure altitude              gpm


                       Distance wrt Earth's surface
    6     6    -DIST-    Geometric distance above       m
    7     7    -DEPTH    Geometric distance below       m

    8     8    -PRES-    Atmospheric pressure           mb
    9     9    -PTEND    Pressure tendency              mb/sec


                       Temperature
   10    16    -TMP--    Atmospheric temperature        degree K
   11    17    -DPT--    Dewpoint temperature           degree K
   12    18    -DEPR-    Dewpoint depression            degree K
   13    19    -POT--    Potential temperature          degree K
   14    20    -T-MAX    Maximum temperature            degree K
   15    21    -T-MIN    Minimum temperature            degree K
   16    22    -TSOIL    Soil temperature               degree K


                       Vertical motion
   28    40    -V-VEL    Vertical velocity dp/dt        mb/sec
   29    41    -NETVD    Net vertical displacement      mb
   2A    42    -DZDT-    Vertical velocity dz/dt        m/sec
   2B    43    -OROW-    Orographic component dz/dt     m/sec
   2C    44    -FRCVV    Frictional component dz/dt     m/sec


                       Wind
   30    48    -U-GRD    U comp. of wind wrt grid       m/sec
   31    49    -V-GRD    V comp. of wind wrt grid       m/sec
   32    50    -WIND-    Wind speed                     m/sec
   33    51    -T-WND    Thermal wind speed             m/sec
   34    52    -VW-SH    Vertical speed shear           1/sec
   35    53    -U-DIV    Divergent u comp wrt grid      m/sec
   36    54    -V-DIV    Divergent v comp wrt grid      m/sec







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         Number   Abbreviation        Item                   Units
       Hex   Dec      (*)       Table 1 - Q and S (cont)
       -----------------------------------------------------------------

        37    55    -WDIR-    Direction from which wind is   degree
                                blowing (wrt North)
        38    56    -WWND-    Westerly comp. of wind         m/sec
        39    57    -SWND-    Southerly comp. of wind        m/sec
        3A    58    -RATS-    Ratio of speeds                non-dim.
        3B    59    -VECW-    Vector wind (spectral)         m/sec
        3C    60    -SFAC-    Steadiness factor              percent
        3D    61    -GUST-    Wind gustiness                 m/sec
        3E    62    D-DUDT    Diffusive u-comp. accel.       m/sec**2
        3F    63    D-DVDT    Diffusive v-comp. accel.       m/sec**2


                            Fluid flow functions
        48    72    -ABS-V    Absolute vorticity             1/sec
        49    73    -REL-V    Relative vorticity             1/sec
        4A    74    -DIV--    Divergence                     1/sec

        50    80    -STRM-    Stream function                m**2/sec
        51    81    -V-POT    Velocity potential             m**2/sec

        52    82    -U-STR    Westerly comp. of wind stress  N/m**2
        53    83    -V-STR    Southerly comp. of wind stress N/m**2
        54    84    -TUVRD    Westerly wind comp. accelera-  N/m**2
                                tion by vertical diffusion
        55    85    -TVVRD    Southerly wind comp. accelera- N/m**2
                                tion by vertical diffusion
        56    86    XGWSTR    x-component of gravity wave    N/m**2
                                drag
        57    87    YGWSTR    y-component of gravity wave    N/m**2
                                drag

                            Moisture
        58    88    -R-H--    Relative humidity              percent
        59    89    -P-WAT    Precipitable water             kg/m**2
        5A    90    -A-PCP    Accumulated total precip       meter
        5B    91    -P-O-P    Probability of precipitation   percent
        5C    92    -P-O-Z    Prob. of frozen precipitation  percent
        5D    93    -SNO-D    Snow depth                     m
        5E    94    -ACPCP    Accumulated convective precip  m
        5F    95    -SPF-H    Specific humidity              kg/kg
        60    96    -L-H2O    Liquid water                   kg/kg
        61    97    -RRATE    Rainfall rate                  kg/m**2/sec
        62    98    -TSTM-    Probability of thunderstorm    percent
        63    99    -CSVR-    Conditional probability of     percent
                                severe local storm
        64   100    -CTDR-    Conditional probability of     percent
                                major tornado outbreak
        65   101    -MIXR-    Mixing ratio                   kg/kg
        66   102    -PSVR-    Unconditional probability      percent
                                of severe local storm

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   67   103    -MCONV    Moisture convergence           kg/kg/sec






















































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         Number   Abbreviation        Item                   Units
       Hex   Dec      (*)       Table 1 - Q and S (cont)
       -----------------------------------------------------------------

        68   104    -VAPP-    Vapor pressure                 mb
        69   105    -NCPCP    Accumulated non-convective     m
                                precipitation
        6A   106    -ICEAC    Ice accretion rate             m/s
        6B   107    -NPRAT    Non-convective precip rate     kg/m**2/sec
        6C   108    -CPRAT    Convective precipitation rate  kg/m**2/sec
        6D   109    -TQDEP    Deep conv. moisture tndcy.     kg/kg/sec
        6E   110    -TQSHL    Shallow conv. moisture tndcy.  kg/kg/sec
        6F   111    -TQVDF    Vertical diffusion moisture    kg/kg/sec
                                tendency

                            Stability
        70   112    -LFT-X   @Lifted index                   degree K
        71   113    -TOTOS   @Total totals                   degree K
        72   114    -K-X--   @K-index                        degree K
        73   115    -C-INS   @Convective instability         degree K
        74   116    -4LFTX    4-layer lifted index           degree K
        75   117    -A-EVP    Accumulated evaporation        meters


                            Wave components
        78   120    -L-WAV    Long wave component of         gpm
                                geopotential
        79   121    -S-WAV    Short wave component of        gpm
                                geopotential


                            Miscellaneous surfaces/levels
        80   128    -MSL--    Mean sea level                 -----
        81   129    -SFC--    Earth's surface (base of       -----
                                atmosphere)
        82   130    -TRO--    Tropopause                     -----
        83   131    -MWSL-    Maximum wind speed level       -----
        84   132    -PLYR-    Oceanographic primary layer    -----
        85   133    -A-LEV    Anemometer Level               -----
        86   134    -T-AIL    Top of Aircraft Icing Layer
        87   135    -B-AIL    Bottom of Aircraft Icing Layer


                            Sigma domain
        90   144    -BDY--    Boundary                       -----
        91   145    -TRS--    Troposphere                    -----
        92   146    -STS--    Stratosphere                   -----
        93   147    -QCP--    Quiet cap                      -----
        94   148    -SIG--    Entire atmosphere              -----






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    Number   Abbreviation        Item                   Units
  Hex   Dec      (*)       Table 1 - Q and S (cont)
  -----------------------------------------------------------------

                       Miscellaneous parameters
   A0   160    -DRAG-    Drag coefficient               non-dim.
                           approx. range:
                            100-1200  (on maps 5&27)
                           .001-.009 (on maps 29&30)
   A1   161    -LAND-    Land/sea flag                  non-dim.
                             values: land=-1; sea=0
   A2   162    -KFACT    K factors (700 mb to 500 mb    non-dim.
                           normal ratio)
   A3   163    -10TSL    Conversion consts (1000 mb to  mb/m
                           sea level pressure)
   A4   164    -7TSL-    Sea level pressure specifi-    mb/m
                           cation from 700 mb heights
   A5   165    -RCPOP    Regression coefficients for    percent/m
                           probability of precip.
   A6   166    -RCMT-    Regression coefficients for    deg K/m
                           mean temperature
   A7   167    -RCMP-    Regression coefficients for    m(precip)/m
                           mean precipitation
   A8   168    -ORTHP    Orthogonal pressure function   mb
   A9   169    -ALBDO    Albedo                         non-dim.
                           approx. range: 0.06 - 0.80
   AA   170    -ENFLX    Energy flux                    watt/m**2
   AB   171    -TTHTG    Temperature tendency from      deg K/sec
                           heating
   AC   172    -ENRGY    Energy statistics              (various)
   AD   173    -TOTHF    Total heat flux downward       watt/m**2
   AE   174    -SPEHF    Sensible + evaporative heat    watt/m**2
                           flux upward
   AF   175    -SORAD    Solar heat flux downward       watt/m**2
   B0   176    -LAT--    Latitude                       degree N
   B1   177    -LON--    Longitude                      degree W
   B2   178    -RADIC    Radar intensity                non-dim.

   B3   179    ------  @@Ceiling Height (TDL)           m
   B4   180    ------  ##Visibility (TDL)               m
   B5   181    ------    Liquid Precip. (Y/N) (TDL)     binary
   B6   182    ------    Freezing Precip. (Y/N) (TDL)   binary
   B7   183    ------    Frozen Precip. (Y/N) (TDL)     binary

   B8   184    -PROB-    Probability                    percent
   B9   185    -CPROB    Conditional probability        percent
   BA   186    -USTAR    Surface friction velocity      m/sec
   BB   187    -TSTAR    Surface friction temperature   degree K
   BC   188    -MIXHT    Mixing height                  m






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         Number   Abbreviation        Item                   Units
       Hex   Dec      (*)       Table 1 - Q and S (cont)
       -----------------------------------------------------------------

        BD   189    -MIXLY    Number of mixed layers next    (integer)
                                to the surface
        BE   190    -DLRFL    Downward flux of long-wave     watt/m**2
                                radiation
        BF   191    -ULRFL    Upward flux of long-wave       watt/m**2
                                radiation
        C0   192    -DSRFL    Downward flux of short-wave    watt/m**2
                                radiation
        C1   193    -USRFL    Upward flux of short-wave      watt/m**2
                                radiation
        C2   194    -UTHFL    Upward turbulent flux of       watt/m**2
                                sensible heat
        C3   195    -UTWFL    Upward turbulent flux of water kg/m**2/sec
        C4   196    -TTLWR    Temperature tendency from      deg K/sec
                                long-wave radiation
        C5   197    -TTSWR    Temperature tendency from      deg K/sec
                                short-wave radiation
        C6   198    -TTRAD    Temperature tendency from      deg K/sec
                                all radiation
        C7   199    -MSTAV    Moisture availabililty         non-dim.
        C8   200    -RDNCE  **Radiance                    watt/m**2/sr/m
        C9   201    -BRTMP  **Brightness temperature         degree K
        CA   202    -TCOZ-  **Total column ozone             kg/m**2
        CB   203    -OZMR-  **Ozone mixing ratio             kg/kg
        CC   204    -SWABS    Rate of absorption of short-   watt/m**2
                                wave radiation
        CD   205    -TTLRG    Temperature tendency from      deg K/sec
                                large scale precipitation
        CE   206    -TTSHL    Temperature tendency from      deg K/sec
                                shallow convection
        CF   207    -TTDEP    Temperature tendency from      deg K/sec
                                deep convection
        D0   208    -TTVDF    Temperature tendency from      deg K/sec
                                vertical diffusion
        D1   209    -STCOF    Soil thermal coefficient   joules/m**2/deg
















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    Number   Abbreviation        Item                   Units
  Hex   Dec      (*)       Table 1 - Q and S (cont)
  -----------------------------------------------------------------

                       Cloud-cover variables
   D2   210    -CDLYR    Amount of non-convective cloud non-dim.
   D3   211    -CDCON    Amount of convective cloud     non-dim.
   D4   212    -PBCLY    Pressure at the base of a      mb
                           non-convective cloud
   D5   213    -PTCLY    Pressure at the top of a       mb
                           non-convective cloud
   D6   214    -PBCON    Pressure at the base of a      mb
                           convective cloud
   D7   215    -PTCON    Pressure at the top of a       mb
                           convective cloud
   D8   216    -SFEXC    Exchange coefficient at     (kg/m**3)*m/sec
                           surface
   D9   217    -ZSTAR    Surface roughness length       m
   DA   218    -STDZG    Standard deviation of ground   m
                           height

                       Oceanographic variables
  130   304    -UOGRD    U comp. of current wrt grid    m/sec
  131   305    -VOGRD    V comp. of current wrt grid    m/sec
  180   384    -WTMP-    Water temperature              degree K
  181   385    -WVHGT    Height of wind-driven waves    m
  182   386    -SWELL    Height of sea swells           m
  183   387    -WVSWL    Combined height of waves and   m
                           swell
  184   388    -WVPER    Period of wind-driven waves    sec
  185   389    -WVDIR    Direction from which waves     degree
                           are moving (wrt North)
  186   390    -SWPER    Period of sea swells           sec
  187   391    -SWDIR    Direction from which swells    degree
                           are moving (wrt North)
  188   392    -ICWAT    Ice-free water surface         percent
  190   400    -HTSGW    Significant wave height        m
  191   401    -PERPW    Primary wave period            sec

















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         Number   Abbreviation        Item                   Units
       Hex   Dec      (*)       Table 1 - Q and S (cont)
       -----------------------------------------------------------------

       192   402    -DIRPW    Direction from which primary   degree
                                waves are moving (wrt North)
       193   403    -PERSW    Secondary wave period          sec
       194   404    -DIRSW    Direction from which secondary degree
                                waves are moving (wrt North)
       195   405    -WCAPS    White cap coverage             percent



       -----------------------------------------------------------------

       *   Abbreviations are 6 characters.  A dash (-) is used to
           indicate a blank when printed.

       **  These data types do not use the standardized ON84
           identification scheme and may have been stored in non-
           standard units.  Contact NMC/CAC/AIB for further infor-
           mation.

       @   273.15 degrees has been added to the original data values.

       @@  Has been stored in units of 100s of feet.

       ##  Has been stored in the units of miles.

           wrt means "with respect to"

       --------------------------------------------------------------






















       88-01-01                   13                   NMC Office Note 84










                             Table 2 - T
                             TIME MARKER

                               (4 bits)

   T (Dec)     Meaning                      F1 (*)      F2 (*)
  ----------------------------------------------------------------

    0   Instantaneous field. E.g., 500-mb   Fcst time  0
        height forecast: Q                  of Q
        F1 = 0 denotes an analysis unless
        M set equal to 8, 9, or 10.  See Table 3.

    1   Field formed from 2 fields whose    Fcst time  Fcst time
        valid times are equal but whose     of Q2      of Q2 minus
        forecast times may or may not be               fcst time
        equal. E.g., difference between 2              of Q1
        analyses (times equal), or diff-
        erence between a forecast and the
        verifying analysis (times unequal):
             Q2 - Q1

    2   Field formed from 2 fields whose    Fcst time  Valid time
        forecast times are equal but whose  of Q1 and  of Q2 minus
        valid times are unequal. E.g., a    Q2         valid time
        tendency field formed by differ-               of Q1
        encing 2 analyses which are 12
        hours apart:  Q2 - Q1

    3   Field formed from 2 fields whose    Fcst time  Fcst time
        initial times are equal but whose   of Q2      of Q2 minus
        forecast times are unequal. E.g.,              fcst time
        a forecast tendency field: Q2 - Q1             of Q1

    4   Field of normal values averaged     Days used  0
        over a number of days, where F1     in average
        = number of days and F2 = 0, or
        averaged over a number of years,       -or-       -or-
        where F1 = 0 and F2 = number of
        years.                              0          Years used
                                                       in average

    5   Non-instantaneous field. E.g., a    Fcst time  Fcst time
        field of forecast probability of    at end of  at end of
        precipitation during some time      period     period minus
        period.                                        fcst time
                                                       at bgng.








  88-01-01                   14                   NMC Office Note 84










        T (Dec)     Meaning                      F1 (*)      F2 (*)
       ----------------------------------------------------------------

         6   Field of time-averaged values.      Fcst time   Length of
             E.g., a 5-day height mean:          of bgng of  period in
               (Q1+Q2+Q3+Q4+Q5)/5                period in   half days
             with F1 the fcst time of Q1 in      half days,
             half days and F2 = 8 half days.     high-order
                                                 bit on if
                                                 negative

         7   Field of differences between 2      Fcst time   Fcst time
             fields of time-averaged values of   of Q2 in    of Q2 minus
             type T=6. E.g., the difference of   half days   fcst time
             two 5-day height means Q2 - Q1,                 of Q1 in
             Q2 centered at D+8, Q1 centered at              half days
             D+3.





        10   Same meaning as case T=2 except F1
             and F2 are in days.


       (*) F1 and F2 are in hours unless N=15 (Table 5) or unless half
           days, days or years are specified.

       ----------------------------------------------------------------

























       88-01-01                   15                   NMC Office Note 84










                             Table 3 - M

              LEVEL DIFFERENCE AND INITIALIZATION MARKER

                               (4 bits)



   M                Value
  -----------------------------------------------

   0       Indicates  S2  and  L2  are not applicable.
           (In this case S2 = L2 = 0)

   1       Indicates a field formed by taking the
           value of  Q  at  S1  minus the value of  Q
           at  S2.

   2       Indicates a field of  Q  for a layer
           bounded by  S1  and  S2.

   3 - 7   Available


   8 - 10  Same meanings as 0-2 above except the
           field has been initialized by a model
           identified by the Generating Code in Table 10.
           Such initialized fields are often referred to
           as "00-hour forecasts".

  11 - 15  Available







  -----------------------------------------------
















  88-01-01                   16                   NMC Office Note 84










                                  Table 4 - X

                                EXCEPTION MARKER

                                    (8 bits)

         X               Value
       -------------------------------------------------------------

         0     Indicates the date/time of the field is the
               same as the date/time of the file in which
               the field is stored.

         1     Indicates the date/time of the field is 6
               hours prior to the date/time of the file
               in which the field is stored.

         2     Indicates the date/time of the field is 12
               hours prior to the date/time of the file
               in which the field is stored.

        ...     ...

         n     Indicates the date/time of the field is 6*n
               hours prior to the date/time of the file
               which the field is stored.

        ...     ...

        80     Special use marker to indicate a field produced with
               spectral wave truncation.

       100     Field formed from NMC field and ECMWF field

       101     Field formed from NMC field and UKMET field

       255     Not applicable.  The exception marker does not apply
               to this field.

       -------------------------------------------------------------















       88-01-01                   17                   NMC Office Note 84










                             Table 5 - N

                         MISCELLANEOUS MARKER

                               (4 bits)
      N                   Value
   --------------------------------------------

      0          None of the following

      1          Spectral specification

      2          Zonal coefficient

      3          Spectral amplitude

      4          Spectral phase angle

      5          Summation over wave numbers 0 - 5



     15          F1  and/or  F2  are in half days
   --------------------------------------------































  88-01-01                   18                   NMC Office Note 84










                              Table 6 - CM and CD

                              CLIMATOLOGY MARKERS

                                 (8 bits each)

                             CM       Month-Hour
                           -------------------------

                             00    Not applicable

                             01    JAN - 0000 UTC
                             02    FEB - 0000 UTC
                            ...    ...
                             12    DEC - 0000 UTC

                             13    JAN - 1200 UTC
                             14    FEB - 1200 UTC
                            ...    ...
                             24    DEC - 1200 UTC

                           -------------------------



                             CD    Day of Month
                           -------------------------

                             00    Not applicable
                             01    1st day of month
                             02    2nd day of month
                            ...    ...
                             31    31st day of month

                           -------------------------




















       88-01-01                   19                   NMC Office Note 84










                             Table 7 - K

                              GRID TYPE

       K                        Grid                      Grid
  Hex   Dec                                             Increment
  -----------------------------------------------------------------

    0     0 A  1977-point N. Hemisphere polar stereo-   381 km
               graphic grid (octagon) oriented 80W;     at 60N
               Pole at (24,26).

    1     1 A  1679-point (73x23) Mercator grid with    5 degs of
               (1,1) at (0W,48.09S), (73,23) at (0W,    longitude
               48.09N); I increasing eastward, Equator
               at J=12.

    2     2    1752-point (73x24) Mercator grid for     5 degs of
               latitudes 49.73S to 49.73N.              longitude

    3     3    3021-point (53x57) N. Hemisphere polar   381 km
               stereographic grid oriented 80W; Pole    at 60N
               (27,29).

    4     4    reserved

    5     5 A  3021-point (53x57) N. Hemisphere polar   190.5 km
               stereographic grid oriented 105W; Pole   at 60N
               at (27,49).

    6     6    1977-point octagonal subset of grid      190.5 km
               type 5; Pole at (24,46).                 at 60N

    7     7    2329-point N. Hemisphere polar stereo-   381 km
               graphic grid (octagon) oriented 80W.     at 60N

    8     8    5104-point (116x44) Mercator grid with   3.1035
               (1,1) at (0W,48.67S) and (116,44) at     degs of
               (3.1035W,61.05N); I increasing eastward, longitude
               Equator at J=19.

    9     9 A  Station grid (US and Canada) for TDL
               wind, cloud, flight weather, sunshine,
               dewpoint, temperature, and max/min
               products.  Number of stations varies
               from product to product, but usually
               ranges from 143 to over 200.








  88-01-01                   20                   NMC Office Note 84










           K                  Table 7 - K (cont)               Grid
       Hex   Dec                  GRID TYPE                  Increment
       -----------------------------------------------------------------

         A    10 A  Station grid (US cities) for TDL prob-
                    ability of precipitation type (POPT).

         B    11    286 US cities for TDL precipitation
                    amount.

         C    12    1702-point (74x23) Mercator grid for     5 degs of
                    latitudes 48.09S to 48.09N.              longitude

         D    13    576-point (36x16) N. Hemisphere
                    longitude/latitude LRPG diamond array--
                    pole stored at top of every 10 degs of
                    longitude--for latitudes 15S to 90N.

         E    14    108 U.S. stations for TDL max/min
                    temperatures.

         F    15    40 U.S. stations for TDL max/min
                    temperatures.

        10    16    1560-point (39x40) N. Hemisphere polar   95.25 km
                    stereographic grid (Eastern U.S.)        at 60N
                    oriented 80W.

        11    17 A  221-point (17x13) N. Hemisphere polar    381 km
                    stereographic grid oriented 105W; Pole   at 60N
                    at (7,21).  US grid used for TDL
                    trajectory model.

        12    18    Reserved.

        13    19    1977-point S. Hemisphere polar stereo-   381 km
                    graphic grid (octagon) oriented 100E;    at 60S
                    Pole at (24,26).

        14    20    2655-point (45x59) Mercator grid for     1.5 degs of
                    latitudes 30S to 30N.                    longitude

        15    21 A  1387-point (73x19) N. Hemisphere lon-    5 degs
                    gitude/latitude grid for latitudes 0N
                    to 90N.










       88-01-01                   21                   NMC Office Note 84










      K                  Table 7 - K (cont)               Grid
  Hex   Dec                  GRID TYPE                  Increment
  -----------------------------------------------------------------

   16    22 A  1387-point (73x19) S. Hemisphere lon-    5 degs
               gitude/latitude grid for latitudes 90S
               to 0S.

   17    23    783-point (29x27) N. Hemisphere polar     190.5 km
               stereographic grid oriented 105W.        at 60N
               US grid is used for NMC/TDL boundary
               layer model.

   18    24 A  651-point (31x21) N. Hemisphere polar    190.5 km
               stereographic grid oriented 98W; Pole    at 60N
               at (15,41).  US grid is used for TDL
               probability of precipitation, max/min
               temperature, dewpoint, surface temp-
               erature, and sunshine.

   19    25    3021-point (53x57) S. Hemisphere polar   381 km
               stereographic grid oriented 100E; Pole   at 60S
               at (27,29).

   1A    26 A  2385-point (53x45) N. Hemisphere polar   190.5 km
               stereographic grid oriented 105W; Pole   at 60N
               at (27,49).

   1B    27 A  4225-point (65x65) N. Hemisphere polar   381 km
               stereographic grid oriented 80W; Pole    at 60N
               at (33,33).

   1C    28 A  4225-point (65x65) S. Hemisphere polar   381 km
               stereographic grid oriented 100E; Pole   at 60S
               at (33,33).

   1D    29 A  5365-point (145x37) N. Hemisphere lon-   2.5 degs
               gitude/latitude grid for latitudes 0N
               to 90N; (1,1) at (0E,0N).

   1E    30 A  5365-point (145x37) S. Hemisphere lon-   2.5 degs
               gitude/latitude grid for latitudes 90S
               to 0S; (1,1) at (0E,90S).












  88-01-01                   22                   NMC Office Note 84











           K                  Table 7 - K (cont)               Grid
       Hex   Dec                  GRID TYPE                  Increment
       -----------------------------------------------------------------

        1F    31 A  327-point TDL field composed of 4 grids: 381 km
                    US, Alaska, Hawaii, and Puerto Rico.     at 60N
                    The US grid is a 255-point (17x15)
                    N. Hemisphere polar stereographic grid
                    oriented 80W; Pole at (13,22).  Alaska
                    grid is a 56-point (7x8) N. Hemisphere
                    polar stereographic grid oriented 80W;
                    pole at (11,8).  The Hawaii grid is a
                    12-point (3x4) N. Hemisphere polar
                    stereographic grid oriented 80W; Pole
                    at (23,7).  The Puerto Rico grid is a
                    4-point (2x2) N. Hemisphere polar stereo-
                    graphic grid oriented 80W; Pole at (-4,23).
                    (These grids are used to archive MRF
                    Model data).

        20    32 A  744-point (31x24) N. Hemisphere polar    190.5 km
                    stereographic grid oriented 105W;        at 60N
                    Pole at (13,42).  The TDL grid (US)
                    is used to archive LFM data.

        21    33 A  8326-point (181x46) N. Hemisphere lon-   2 degs
                    gitude/latitude grid for latitudes 0N
                    to 90N; (1,1) at (0E,0N).

        22    34 A  8326-point (181x46) S. Hemisphere lon-   2 degs
                    gitude/latitude grid for latitudes 90S
                    to 0S; (1,1) at (0E,90S).

        23    35    228 U.S. cities for TDL MOS max/min
                    temperatures.

        24    36 A  1558-point (41x38) N. Hemisphere polar   190.5 km
                    stereographic grid oriented 105W; Pole   at 60N
                    at (19,42).  The TDL grid (N. America)
                    is used to archive LFM and NGM data.

        25    37    5365-point (145x37) N. Hemisphere lon-   2.5 degs
                    gitude/latitude grid for latitudes
                    1.25 to 88.75N; (1,1) at (1.25E,1.25N);
                    row 37 is fictitious.









       88-01-01                   23                   NMC Office Note 84











      K                  Table 7 - K (cont)               Grid
  Hex   Dec                  GRID TYPE                  Increment
  -----------------------------------------------------------------
   26    38    5365-point (145x37) S. Hemisphere lon-   2.5 degs
               gitude/latitude grid for latitudes
               88.75S to 1.25S;  (1,2) at
               (1.25E,88.75S); row 1 is fictitious.

   27    39    8326-point (181x46) N. Hemisphere lon-   2 degs
               gitude/latitude grid for latitudes 1N
               to 89N, (1,1) at (1E,1N); row 46 is
               fictitious.

   28    40    8326-point (181x46) S. Hemisphere lon-   2 degs
               gitude/latitude grid for latitudes 89S
               to 1S, (1,2) at (1E,89S); row 1 is
               fictitious.

   29    41    850-point (34x25) N. Hemisphere lon-     1 deg
               gitude/latitude grid for latitudes 22N
               to 46N; (1,1) at (87W,22N).

   2A    42    Reserved.

   2B    43    4225-point (65x65) N. Hemisphere polar   381 km
               stereographic grid oriented 105W; Pole   at 60N
               at (33,33).

   2C    44    4225-point (65x65) S. Hemisphere polar   381 km
               stereographic grid oriented 75E; Pole    at 60S
               (33,33).

   2D    45    2425-point (97x25) N. Hemisphere lon-    3.75 degs
               gitude/latitude grid for latitudes
               0N to 90N; (1,1) at (0E,0N).

   2E    46    2425-point (97x25) S. Hemisphere lon-    3.75 degs
               gitude/latitude grid for latitudes
               90S to 0N; (1,1) at (0E,90S).

   2F    47 A  10057-point (113x89) N. Hemisphere       47.625 km
               polar stereographic grid oriented 105W;  at 60N
               Pole at (41,161).











  88-01-01                   24                   NMC Office Note 84










           K                  Table 7 - K (cont)               Grid
       Hex   Dec                  GRID TYPE                  Increment
       -----------------------------------------------------------------

        30    48    3477-point (61x57) N. Hemisphere         190.5 km
                    polar stereographic grid oriented 105W;  at 60N
                    Pole at (27,49).

        31    49    16641-point (129x129) N. Hemisphere      190.5 km
                    polar stereographic grid oriented 80W;   at 60N
                    Pole at (65,65).

        32    50    16641-point (129x129) S. Hemisphere      190.5 km
                    polar stereographic grid oriented 100E;  at 60S
                    Pole at (65,65).

        33    51 A  16641-point (129x129) N. Hemisphere      190.5 km
                    polar stereographic grid oriented 105W;  at 60N
                    Pole at (65,65).

        34    52    Reserved.

        35    53    5967-point (117x51) Mercator grid with   3.1035
                    (1,1) at (0W,61.05S) and (117,51) at     degs of
                    (0W,61.05N); I increasing eastward,      longitude
                    Equator at J=26.

        36    54 A  1050-point (35x30) N. Hemisphere polar   95.25 km
                    stereographic grid oriented 80W; Pole    at 60N
                    at (1,75).  The TDL grid (eastern US)
                    is used for a boundary layer model.

        37    55 A  6177-point (87x71) N. Hemisphere polar   254 km
                    stereographic grid oriented 105W; Pole   at 60N
                    at (44,38).

        38    56 A  6177-point (87x71) N. Hemisphere polar   127 km
                    stereographic grid oriented 105W; Pole   at 60N
                    at (40,73).

        39    57    Reserved

        3A    58    100 U.S. cities for 24-hour accumulated
                    precipitation.











       88-01-01                   25                   NMC Office Note 84










      K                  Table 7 - K (cont)               Grid
  Hex   Dec                  GRID TYPE                  Increment
  -----------------------------------------------------------------

   3B    59    5293-point (79x67) subset of grid type   127 km
               56 (used for LFM-II mountains); Pole     at 60N
               at (40,73).

   3C    60 A  3249-point (57x57) N. Hemisphere polar   190.5 km
               stereographic grid oriented 105W; Pole   at 60N
               at (29,49).

   3D    61 A  Spectral coefficients, scalar fields.    30 modes
               (961 COMPLEX*8 words).

   3E    62 A  Spectral coefficients, U- or V-          30 modes
               component fields.
               (992 COMPLEX*8 words).

   3F    63 A  1095-point (73x15) longitude/latitude    5 degs
               grid for latitudes 35S to 35N; (1,1)
               at (0,35S) and I increasing eastward.

   40    64    Available

   41    65    Available

   42    66    2701-point (73x37) longitude/latitude    5 degs
               grid for latitudes 90S to 90N; (1,1)
               at (0,90S); I increasing eastward.

   43    67 A  13689-point (117x117) N.W. Atlantic      23.8125 km
               polar stereographic grid oriented 80W;   at 60N
               Pole at (9,317).

   44    68 A  13689-point (117x117) Gulf of Mexico     23.8125 km
               polar stereographic grid oriented 105W;  at 60N
               Pole at (-35,361).

   45    69 A  13689-point (117x117) Gulf of Alaska     23.8125 km
               polar stereographic grid oriented 105W;  at 60N
               Pole at (177,209).













  88-01-01                   26                   NMC Office Note 84











           K                  Table 7 - K (cont)               Grid
       Hex   Dec                  GRID TYPE                  Increment
       -----------------------------------------------------------------

        46    70 A  13689-point (117x117) Calif. Pacific     23.8125 km
                    polar stereographic grid oriented 105W;  at 60N
                    Pole at (169,285).

        47    71 A  13689-point (117x117) Mexican Pacific    23.8125 km
                    polar stereographic grid oriented 105W;  at 60N
                    Pole at (137,377).

        48    72    406-point (29x14) Mercator grid with     2.5 degs of
                    (1,1) at (170.00E,46.40N) and (29,14)    longitude
                    at (120.00W,64.40N).

        49    73    13056-point (128x102) global gaussian    R40 trans
                    longitude/latitude grid.

        4A    74 A  10800-point (180x60) N. Hemisphere       2.0 deg lon
                    longitude/latitude grid for latitudes    1.5 deg lat
                    0N to 90N; (1,1) at (0E,0N).

        4B    75 A  12321-point (111x111) N. Hemisphere      40 km at
                    Lambert Conformal grid.  No fixed        30&60 deg N
                    location; used by QLM Hurricane model.

        4C    76 A  12321-point (111x111) S. Hemisphere      40 km at
                    Lambert Conformal grid.  No fixed        30&60 deg S
                    location; used by QLM Hurricane model.

        4D    77 A  12321-point (111x111) N. Hemisphere      40 km at
                    Mercator grid.  No fixed location;       equator
                    used by QLM Hurricane model.

        51    81 A  7921-point (89x89) N. Hemisphere polar   190.5 km
                    stereographic grid oriented 105W; pole   at 60N
                    at (44.5,44.5)

        52    82 A  15066-point (243x62) N. Hemisphere       variable
                    T80 gaussian transform lat/lon grid

        53    83 A  15066-point (243x62) S. Hemisphere       variable
                    T80 gaussian transform lat/lon grid

        64   100 A  6889-point (83x83) N. Hemisphere polar   91.452 km
                    stereographic grid oriented 105W; Pole   at 60N
                    at (40.5,88.5). (NGM Original Grid C)

        65   101 A  10283-point (113x91) N. Hemisphere       91.452 km
                    stereographic grid oriented 105W; Pole   at 60N
                    at (58.5,92.5). (NGM Expanded Grid C)


       88-01-01                   27                   NMC Office Note 84










   99   153 A  240-point (16x15) N. Hemisphere polar    190.5 km
               stereographic grid oriented 105W; Pole   at 60N
               at (-2,47).  TDL grid (Gulf of Mexico)
               used for wind wave forecasts.



   FF   255    Not applicable.

  -----------------------------------------------------------------

  Footnote:  "A" indicates a currently active Grid Type











































  88-01-01                   28                   NMC Office Note 84










                                  Table 8 - KS

                               DERIVATION MARKER

                                    (8 bits)


         KS            Derivation method
       ----------------------------------------------------

          0     None of the following

          1     Hough spectral method

          2     Field formed by subtracting a climatological
                normal from each data value; e.g., a field
                of departure from normal heights.

       ----------------------------------------------------


                                  Table 9 - R

                                   RUN MARKER

                                    (8 bits)


         R             Run
       ----------------------------------------------------

         0      Early run (ERL)

         1      Initializing run (NMC)

         2      Regional run (RGL)

         3      Aviation run (AVN)

         4      Medium Range Forecast run (MRF)

         5      Final operational run in a given
                  observational cycle (FNL)

         6      Hurricane Run (HCN)


        15      Runs from non-NMC networks

       255      Not applicable

       ----------------------------------------------------



       88-01-01                   29                   NMC Office Note 84










                             Table 10 - G

                          GENERATING PROGRAM

                               (8 bits)


       G            Name of program generating data          Map
   Hex  Dec                                                 Label
  -----------------------------------------------------------------

    0     0    Objective analysis (Cressman octagon)
    1     1 A  Barotropic fcst model                        BATROP
    2     2    Mesh model 1958
    3     3    Mesh model 1964 (imprv. terr.)
    4     4    Reed 1000-mb fcst model
    5     5    3-level baroclinic fcst model
    6     6    4-level baroclinic fcst model
    7     7    4-layer Primitive Equation model (PE)

    8     8    6-layer PE model
    9     9 A  Maximum and minimum temperature fcst
    A    10    Sea height and swell fcst
    B    11    Tropical analysis
    C    12    Tropical fcst
    D    13    Bat analysis
    E    14    Tropical fcst
    F    15    Tropical fcst with satellite modification

   10    16    Sub-synoptic advection model
   11    17    Compute long wave components
   12    18 A  Trajectory forecast
   13    19 A  Successive Correction Method analysis         SCM
   14    20    Limited-area successive correction method    LFM1
   15    21    Perfect prog precipitation fcst
   16    22 A  Hough analysis                               HOUGH
   17    23    Eddy analysis and SANBAR fcst (NHC Miami)

   18    24    NWRC/NCAR climatology data
   19    25 A  Snow cover
   1A    26    Planetary boundary layer analysis and fcst
   1B    27    Extended fcst data processor
   1C    28    PE and trajectory model output statistics
   1D    29    9-layer global PE model (5-deg mesh)
   1E    30    9-layer N.H. PE model (2.5-deg mesh)
   1F    31    6-layer PE model (360/195 version)           6LPE









  88-01-01                   30                   NMC Office Note 84










            G               Table 10 - G (cont)                   Map
        Hex  Dec            GENERATING PROGRAM                   Label
       -----------------------------------------------------------------
        20    32    Sea surface temp., satellite derived
        21    33    Land shelter temperature analysis
        22    34    Energy statistics code
        23    35    9-layer global PE model (2.5-deg mesh)
        24    36    As above except used for 6-hour cycle
        25    37    3-layer global PE model
        26    38    7-layer PE Hemis. fine mesh model, 190.5 km  7LPE
        27    39 A  Nested Grid Model                            NGM

        28    40    9-layer N. H. PE model (2-deg mesh)
        29    41    LFM with 127-km grid increment               LFM2
        2A    42    7-layer PE model (381 km grid)               7LCM
        2B    43 A  Global Optimum Interpolation analysis        GOI
        2C    44 A  Sea surface temperature analysis
        2D    45 A  Spectral Model Global 24-mode 12-layer       SMG2C
        2E    46 A  Spectral Model Global 30-mode 12-layer       SMG3C
        2F    47    Spectral Model Hemis. 24-mode-12 layer       SMH2C

        30    48    Spectral model Hemis. 30-mode-12 layer       SMH3C
        31    49    Ozone Analysis Tiros Operational             TOVS
        32    50    Spectral model Global 24-mode 6-layer        SMG26
        33    51    Spectral model Global 30-mode 6-layer        SMG36
        34    52    Ozone Analysis Nimbus 7                      SBUV
        35    53 A  LFM with Fourth-Order differencing           LFM
        36    54    Spectral model Hemis. 24-mode 6-layer        SMH26
        37    55 A  N. American sea level pressure analysis

        38    56 A  N. H. sea level pressure analysis
        39    57 A  European Center for Medium-range Wea. Fcst.  ECMWF
        3A    58    Fleet Numerical Oceanography Center          FNOC
        3B    59    Air Force Global Weather Central             AFGWC
        3C    60    NWS Central Region                           CRGN
        3D    61    NWS Western Region                           WRGN
        3E    62    NWS Eastern Region                           ERGN
        3F    63 A  Spectral model Global 40-mode 12-layer       SMG4C

        40    64 A  Regional Optimum Interpolation Analysis      ROI
        41    65 A  Spectral model Global 40-mode 18-layer       SMG4I
        42    66 A  U.K. Meteorological Office                   UKMET
        43    67 A  Statistical correction by linear regression  SCLR
        44    68 A  10-layer hurricane model                     HCN
        45    69 A  Medium Range Forecast Model w/ GFDL Physics  MRF
        46    70 A  Quasi-Lagrangiam Hurricane Model             QLM
        47    71 A  Stastical Blending (MRFG)

        48    72 A  Isentropic Analysis
       -----------------------------------------------------------------

       Footnote:  "A" indicates a currently active Generating Program



       88-01-01                   31                   NMC Office Note 84











                               Table 11

                HEXADECIMAL EQUIVALENTS FOR FREQUENTLY
                           USED VALUES OF C

                            (Coding of L)

                        Decimal      Hexadecimal
                       -----------------------
                         10000         02710
                         16667         04116
                         15000         03A98
                         15240         03B88
                         18290         04772
                         20000         04E20
                         21340         0535C
                         25000         061A8
                         27315         06AB3
                         27430         06B26
                         30000         07530
                         30480         07710
                         33333         08235
                         35000         088B8
                         36580         08EE4
                         40000         09C40
                         41667         0A2C3
                         42670         0A6AE
                         45000         0AFC8
                         50000         0C350
                         55000         0D6D8
                         58333         0E3DD
                         60000         0EA60
                         65000         0FDE8
                         66667         1046B
                         70000         11170
                         75000         124F8
                         80000         13880
                         83333         14585
                         85000         14C08
                         90000         15F90
                         91400         16508
                         91667         16613
                         95000         17318
                         99000         182B8
                       -----------------------









  88-01-01                   32                   NMC Office Note 84










                                    Table 12

                 EXAMPLES OF IDENTIFIER WORDS FOR COMMON FIELDS



       (1)  1000-mb height analysis for N.H. (grid type 27):

                 00100800 00271081 00000000 00000000 0000001B

       (2)  500-mb height analysis for N.H. (grid type 27):

                 00100800 00C35082 00000000 00000000 0000001B

       (3)  500-mb temperature analysis for N.H. (grid type 27):

                 01000800 00C35082 00000000 00000000 0000001B

       (4)  500-mb 12-hour height forecast for LFM (grid type 26):

                 0010080C 00C35082 00000000 00000000 0000001A

       (5)  12-hour forecast of potential temperature for the
            boundary layer, expressed in sigma coordinates,
            for the N.H. 2.5 long/lat (grid type 29):

                 0130900C 00000000 20009000 00271084 0000001D

       (6)  100-mb forecast height tendency, for 6 to 18 hours
            after an initial time, which is 12 hours prior
            to the date/time of the file (grid type 27):

                 00100812 30271082 0020000C 00000000 0000001B

       (7)  Precipitation at the surface which is forecast to be
            accumulated between 24 and 30 hours after the initial
            time (grid type 27):

                 05A0811E 30000000 00000006 00000000 0000001B
















       88-01-01                   33                   NMC Office Note 84










                             Table 13 - P

                            PACKING MARKER

                               (4 bits)

                    P                 Value
             --------------------------------------------

                    0        16 bits used for packing

                    2         2 bits used for packing

                    4         4 bits used for packing

                    8         8 bits used for packing

                   12        12 bits used for packing
             --------------------------------------------
  DJDE FORMS=JOY,END;



































  88-01-01                   34                   NMC Office Note 84










                  Figure 1 - NMC Format for Packed Data Fields
       W                Upper left: Table reference, if any
       o                Upper right: Field size in bits
       r       Bit . . . .
       d  0     3 4     7 8    11 12   15 16           23 24           31
         _________________________________________________________________
         |1                    12|1                    12|              8|
       1 | Q  Data type          | S1  Type of surface 1 | F1  Time 1    |
         |_______________________|_______________________|_______________|
         |2  T  4|      Numerical value of             20|              8|
       2 |Marker | C1   Surface 1 = C1 * 10**E1          | E1            |
         |_______|_______________________________________|_______________|
         |3  M  4|4  Exception  8|1                    12|              8|
       3 |Marker | X Marker      | S2  Type of surface 2 | F2  Time 2    |
         |_______|_______________|_______________________|_______________|
         |5  N  4|      Numerical value of             20|              8|
       4 |Marker | C2   Surface 2 = C2 * 10**E2          | E2            |
         |_______|_______________________________________|_______________|
         |6  Climat day 8|6   Climat    8|8  Derivation 8|7             8|
       5 | CD of month   | CM Month Hour | KS  Method    | K  Grid type  |
         |_______________|_______________|_______________|_______________|
         | =0,1 4      For internal    12|     For internal use        16|
       6 |1st GES  RN  use by I/O only   | NW  by I/O routines only      |
         |_______________________________|_______________________________|
         |              8|              8|              8|    Initial   8|
       7 | YY  Year      | MM  Month     | DD  Day       | II Hour       |
         |_______________|_______________|_______________|_______________|
         |9   Run       8|10 Generating 8|                             16|
       8 | R  Marker     | G  Program    | J  Number of data points      |
         |_______________|_______________|_______________________________|
         |    Number of bytes          16|    Exclusive OR             16|
       9 | B  in Record                  | Z  Checksum                   |
         |_______________________________|_______________________________|
       1 |                                                             32|
       0 | A  Reference value, REAL*4 floating point                     |
         |_______________________________________________________________|
       1 | 13 P 4 # of  4|  reserved   08|    Scaling value            16|
       1 | Marker add.rec|               | n  (INTEGER*2)                |
         |_______________|_______________|_______________________________|
       1 |                                                             32|
       2 | Reserved                                                      |
         |_______________________________________________________________|
       1 |                             16|                             16|
       3 | Data point 1                  | Data point 2                  |
         |_______________________________|_______________________________|
       1 |                             16|                             16|
       4 | Data point 3                  | Data point 4                  |
         |_______________________________|_______________________________|
           In word 6, first byte indicates source of GES ...
                   0 = AVN run      1 = FNL run

           In word 11, byte 2 is used by VSAM for logical records
              that exceed 32,768 bytes


       88-01-01                   35                   NMC Office Note 84