"LSR" for loose snow on runway, "PSR" for packed snow on runway, and "IR" for ice on runway. The code "RCRNR" is used when braking action is impeded but accurate decelerometer readings are not available. For example,   a   runway   with   packed   snow   and   a decelerometer reading of 15 would be reported as PSR15. NAVMETOCCOMINST  3141.2  contains  many additional  examples  of  runway  condition  reports, including descriptive terms used when a decelerometer is not available. Regional Differences Specific   data   that   may   be   included   in   the supplemental  data  section  within  each  WMO  region  are normally described in WMO Publication 306, Manual on Codes, Volume II, Regional Codes and Coding Practices. Within WMO Region IV, North America, at the time of this writing, no decisions have been made on regional  additions  to  the  METAR  code. SPECI CODE OBSERVATION REPORTS The SPECI code is used to report any significant changes in the weather at any time other than the scheduled  hourly  observation.     Both NAVMET- OCCOMINST  3141.2  and  NAVMETOCCOMINST 3144.1  outline  criteria  and  requirements  for  special observations that are reported using the SPECI code. The SPECI code uses the same groups in the same order as reported in the METAR code except that for a special observation,  SPECI  replaces  METAR.  The  time reported in a SPECI report is the time that the change was observed to have occurred, not the time that the report is transmitted. Q19. Q20. Q21. Q22. Q23. Q24. REVIEW  QUESTIONS How should scattered cumulonimbus at 2,500 feet  be  encoded? How should a surface-based partial obscuration (3/8) of fog be encoded? In what situation is the group VVh_Sh_Sh_S used? How should an air temperature of -4.4°C be encoded? What remark in the METAR code is mandatory for  all  observations? What  does  the  additive  data  group  4/006 indicate? Q25. Q26. Q27. The total 24-hour precipitation is reported at what time? What does the additive data remark SLR12 indicate? What   publications   contain   criteria   and requirements  for  SPECI  observation? SHIPBOARD SURFACE AVIATION WEATHER—SHIP AVIATION CODE LEARNING   OBJECTIVES:   Identify   the manuals  that  provide  instructions  for  recording weather elements on the U.S. Ship Aviation Code   observation   form.   Identify   the applications of the U.S. Ship Aviation Code observation form. List the weather elements required on the U.S. Ship Aviation Code form and describe how the elements are entered and encoded. Shipboard  weather  observers  use  CNMOC  Form 3141/3 to record weather observation data in the METAR/SPECI code. Unlike shore sites, the METAR code aboard ship is used only to record data, not to encode data for transmission. For transmission to data collection centers, these observations are encoded into WMO  Code  FM  13-XI,  the  ship  synoptic  code, normally transmitted every 6 hours. The bottom portion of CNMOC Form 3141/3 is used to record the encoded synoptic  observations.  We  will  discuss  the  Ship Synoptic code later in this chapter. In this section, we briefly cover how the data is recorded on the form. The shipboard observation form (fig. 3-2) is very similar to the shore station METAR code form. While some columns for recording weather elements at sea are the same as those used ashore, the elements that are unique to observations at sea are designated with letters. Additionally, all columns are identified with the type of data to enter, and, in many cases, with the system of measurement and the degree of precision required. NAVMETOCCOMINST  3144.1,  Manual  for Ship's  Surface  Weather  Observations,  provides  detailed instructions  for  recording  observed  weather  elements on the form. Remarks that apply to aircraft operations are entered in column 14. Remarks are generally entered  in  the  same  order  that  the  basic  coded information  is  entered. 3-11