Significant Wind Levels The beginning of section 6 may be identified in the coded  message  by  the  indicator  group  21212.  This section  is  used  to  report  winds  at  "significant  wind levels."  All  observers  on  U.S.  Navy  ships,  Marine Corps, and naval upper-air observers operating outside WMO Region IV report significant level winds in this section,  and  need  not  report  any  information  in  the PILOT  reporting  code.  Synoptic  stations  and  other  land or mobile land stations within WMO Region IV do not include this group in the TEMP coded report. Instead, the Fixed Regional Level Winds are reported using the appropriate PILOT code message Parts B and D. Data for each significant wind level is contained in two  groups  of  five-digit  numbers,  nnPPP  and  ddfff, which  are  repeated  for  each  level  selected.  The  first group for each level is used the same as in the significant temperature levels:    it contains the level identifier nn and the pressure level PPP. The second group, ddfff, is the wind direction and speed. Encoding is the same as in part  A  of  the  code.  Levels  of  missing  wind  data  are reported  similarly  to  missing  significant  levels  of temperature and humidity. System Status and Seawater Temperature 1-28 Section  7  (Table  1-9),  31313  s_rr_ar_as_as_a  8GGgg 9s_nT_wT_wT_w,  contains  information  on  the  rawinsonde system used for the observation, the actual launch time of  the  instrument,  and  the  seawater  temperature.  The 31313 is the section identifier. In the second group,  s_rr_ar_as_as_a,  the s_r  is the solar and  IR  radiation  correction,  found  from  WMO  Code Table 3849. MRS systems use code figure 4, solar and IR  radiation  corrected  automatically  by  system.  The r_ar_a is the code for the rawinsonde system used and is obtained  from  WMO  Code  Table  3685.  The  current MRS system is reported by code 61 for the "Vaisala RS- 80  Marwin."   The  s_as_a  is  the  tracking  technique  and system status, from WMO Code Table 3872. Code 05 is used  with  MRS  equipment  using  VLF-Omega frequencies.   GPS   equipped   systems   will   use   code figure 08. The actual UTC time of the radiosonde release is entered in the fourth group following the 8 indicator. If the  radiosonde  instrument  is  released  at  1120Z,  the group would read 81120. The  seawater  temperature  group  is  only  reported  by ships, and is deleted in reports from other stations. It is in the fourth group, which begins with the indicator 9. The s_n, the sign of the temperature (0 for positive and 1 for  negative)  is  followed  by  the  water  temperature (T_wT_wT_w) in tens, units and tenths of a degree Celsius. Cloud Data Section 8 (Table 1-9) reports cloud information in one  group  following  the  41414  indicator  group.  The N_hC_LhC_MC_H is the cloud group. The N_h is the sum of all  the  low-etage  clouds  present,  or  if  no  low-etage clouds are present, the sum of all the mid-etage clouds present, in oktas (WMO Code Table 2700), and h is the coded height above the surface of the lowest cloud layer (WMO  Code  Table  1600).  The  C_L,  C_M,  and  C_H represent, respectively, the predominant type of low-, mid-, and high-etage clouds from WMO Code Tables 0513, 0515, and 0509. Regional Codes Regional codes are added to the international code following the regional code indicator groups. In WMO Region IV, the required regional codes are specified in the FMH-3. In Region IV, all regional data is reported in “additional” data groups, commonly called the 101- groups, following the 51515 Regional code indicator. Other  countries  may  use  different  regional  codes following  any  of  the  other  regional  code  indicator groups 52525, 53535, . . ., 59595, and national codes 61616, 62626, . . .,  or  69696.  Regional  and  national codes  for  other  countries  are  found  in  WMO Publication   306,   Manual   On   Codes,   Volume   II, Regional Codes and National Coding Practices. The 101 -groups are five-digit groups following the format  101  A_dfA_df.  The  A_dfA_df  indicates  the  type  of data being reported as listed in table 1-6. Actual data may  follow  a  "101-group"  in  additional  code  figure groups. Only data pertaining to the sounding below the 100-hPa level is reported with 101-groups in Part B. These  groups  can  be  used  to  report  doubtful  data, corrected  data,  or  early  transmission  data.  If  the sounding   terminates   below   the   100-hPa   level,   the reason for termination is also entered in this section. PART C - UPPER MANDATORY LEVELS Part  C  of  the  TEMP  codes  contains  reports  for mandatory  levels  above  the  100-hPa  level.  The mandatory levels reported in this section are the 70-hPa, 50-hPa,  30-hPa,  20-hPa,  and  10-hPa  levels.  This section uses the same format as Part A of the TEMP code message, including identification data, mandatory level data for the levels above 100 hPa, tropopause data