"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 VVhShShS 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.
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