CLASS 20 WMO CODE/FLAG TABLES ASSOCIATED WITH BUFR TABLE B

(Version 16.0.0 – 05/04/2011)

Changes awaiting validation by the WMO are in red (last updated by the WMO 05/04/2011)

(last update of any type 08/23/2017 - not completely up to date)

Notes: In developing code tables associated with BUFR/CREX Table B to specify units of elements, the following principles should be applied:

(a) Code tables specifying the units for an element which is defined, in the Manual on Codes, by a single symbolic letter shall be compatible with the relevant existing WMO code tables;

(b) Code tables combining two or more existing WMO code tables to specify the units for an element which is defined, in the Manual on Codes, by a group of symbolic letters shall be compatible with the combined code figures of the relevant group of symbolic letters;

(c) Code tables combining two or more existing WMO code tables to specify the units for an element which is defined, in the Manual on Codes, by different symbolic letters shall be compatible with the code figures of the relevant symbolic letters, with successive tens or hundreds values added, as different symbolic letters appropropriate;

(d) Code tables and flag tables should only be used for reporting qualitative information. Quantitative information should be reported as observed using entries in Table B.  "Data description operators" from Table C should be applied when a "scale change" or "data width change" is required;

(e) Reference to existing specification(s) and code table(s) in the Manual on Codes, with explanation of possible deviations, shall be given in an additional table annexed to the annexed to the code tables associated with BUFR/CREX Table B.

0 20 003

Present weather

Code figure
00-49				No precipitation at the station at the time of observation
00-19				No precipitation, fog, ice fog (except for 11 and 12), duststorm, sandstorm, drifting or blowing snow at the station* at the time of observation or, except for 09 and 17, during the preceding hour
No Meteors except photometeors	00		Cloud development not observed or not observable							Characteristic change of the state of sky during the last hour
	01		Clouds generally dissolving or becoming less developed.
	02		State of sky on the whole unchanged.
	03		Clouds generally forming or developing
Haze, dust, sand or smoke	04		Visibility reduced by smoke, e.g. veldt or forest fires, Industrial smoke or volcanic ashes
	05		Haze
	06		Widespread dust in suspension in the air, not raised by wind at or near the station at the time of observation
	07		Dust or sand raised by wind at or near the station at the time of observation, but no well-developed dust whirl(s) or sand whirl(s), and no duststorm or sandstorm seen; or, In the case of sea stations and coastal stations, blowing spray at the station
	08		Well-developed dust whirl(s) or sand whirl(s) seen at or near the station during the preceding hour or at the same time of observation, but no duststorm or sandstorm
	09		Duststorm or sandstorm within sight at the time of observation, or at the station during the preceding hour
10			Mist
11			Patches					shallow fog or ice fog at the station, whether on land or sea, not deeper than about 2 meters on land or 10 meters at sea
12			More or less continuous
13			Lightning visible, no thunder heard
14			Precipitation within sight, not reaching the ground or the surface of the sea
15			Precipitation within sight, reaching the ground or the surface of the sea, but distant, i.e. estimated to be more than 5 km from the station
16			Precipitation within sight, reaching the ground or the surface of the sea, near to, but not at the station
17			Thunderstorm, but no precipitation at the time of observation
18			Squalls				at or within sight of the station during the preceding hour or at the time of observation
19			Funnel cloud(s)**
20-29		Precipitation, fog, Ice fog or thunderstorm at the station during the preceding hour but not at the time of observation
20		Drizzle (not freezing) or snow grains									not falling as shower(s)
21		Rain (not freezing)
22		Snow
23		Rain and snow or ice pellets
24		Freezing drizzle or freezing rain
25		Shower(s) of rain
26		Shower(s) of snow, or of rain and snow
27		Shower(s) of hail***, or of rain and hail***
28		Fog or Ice fog
29		Thunderstorm (with or without precipitation)
30-39		Duststorm, sandstorm, drifting or blowing snow
30		Slight or moderate duststorm or sandstorm									- has decreased during the preceding hour
31											- no appreciable change during the preceding hour
32											- has begun or has increased during the preceding hour
33		Severe duststorm or sandstorm									- has decreased during the preceding hour
34											- no appreciable change during the preceding hour
35											- has begun or has increased during the preceding hour
36		Slight or moderate drifting snow									generally low (below eye level)
37		Heavy drifting snow
38		Slight or moderate blowing snow									generally high (above eye level)
39		Heavy blowing snow
40-49		Fog or ice fog at the time of observation
40		Fog or ice fog at a distance at the time of observation, but not at the station during the preceding hour, the fog or ice fog extending to a level above that of the observer
41		Fog or ice fog in patches
42		Fog or ice fog, sky visible									has become thinner during the preceding hour
43		Fog or ice fog, sky invisible
44		Fog or ice fog, sky visible									no appreciable change during the preceding hour
45		Fog or ice fog, sky invisible
46		Fog or ice fog, sky visible									has begun or has become thicker during the preceding hour
47		Fog or ice fog, sky invisible
48		Fog, depositing rime, sky visible
49		Fog, depositing rime, sky invisible
50-99		Precipitation at the station at the time of observation
50-59		Drizzle
50		Drizzle, not freezing, intermittent								slight at time of observation
51		Drizzle, not freezing, continuous
52		Drizzle, not freezing, intermittent								moderate at time of observation
53		Drizzle, not freezing, continuous
54		Drizzle, not freezing, intermittent								heavy (dense) at time of observation
55		Drizzle, not freezing, continuous
56		Drizzle, freezing, slight
57		Drizzle, freezing, moderate or heavy (dense)
58		Drizzle and rain, slight
59		Drizzle and rain, moderate or heavy
60-69					Rain
60					Rain, not freezing, intermittent				slight at time of observation
61					Rain, not freezing, continuous
62					Rain, not freezing, intermittent				moderate at time observation
63					Rain, not freezing, continuous
64					Rain, not freezing, intermittent				heavy at time of observation
65					Rain, not freezing, continuous
66					Rain, freezing, slight
67					Rain, freezing, moderate or heavy
68					Rain or drizzle and snow, light
69					Rain or drizzle and snow, moderate or heavy
70-79					Solid precipitation not in showers
70					Intermittent fall of snowflakes				slight at time of observation
71					Continuous fall of snowflakes
72					Intermittent fall of snowflakes				moderate at time of observation
73					Continuous fall of snowflakes
74					Intermittent fall of snowflakes				heavy at time of observation
75					Continuous fall of snowflakes
76					Diamond dust (with or without fog)
77					Snow grains (with or without fog)
78					Isolated star-like snow crystals (with or without fog)
79					Ice pellets
80-99					Showery precipitation, or precipitation with current or recent thunderstorm
80					Rain shower(s), slight
81					Rain shower(s), moderate or heavy
82					Rain shower(s), violent
83					Shower(s) of rain and snow mixed, slight
84					Shower(s) of rain and snow mixed, moderate or heavy
85					Snow shower(s), slight
86					Snow shower(s), moderate or heavy
87					Shower(s) of snow pellets or small hail, with or without rain or rain and snow mixed				- slight
88									- moderate or heavy
89					Shower(s) of hail, with or without rain or rain and snow mixed, not associated with thunder				- slight
90									- moderate or heavy
91					Slight rain at time of observation				Thunderstorm during the preceding hour but not at time of observation
92					Moderate or heavy rain at time of observation.
93					Slight snow, or rain and snow mixed or hail*** at time of observation.
94					Moderate or heavy snow, or rain and snow mixed or hail*** at time of observation.
95					Thunderstorm, slight or moderate, without hail*** but with rain and/or snow at time of observation				Thunderstorm at time of observation.
96					Thunderstorm, slight or moderate, with hail*** at time of observation.
97					Thunderstorm, heavy, without hail***, but with rain and/or snow at time of observation.
98					Thunderstorm combined with duststorm or sandstorm at time of observation.
99					Thunderstorm, heavy, with hail*** at time of observation.
Present weather reported from an automatic weather station
100					No significant weather observed
101					Clouds generally dissolving or becoming less developed during the past hour
102					State of sky on the whole unchanged during the past hour
103					Clouds generally forming or developing during the past hour
104					Haze or smoke, or dust in suspension in the air, visibility equal to, or greater than, 1km
105					Haze or smoke, or dust In suspension in the air, visibility less than 1 km
106-109					Reserved
110					Mist
111					Diamond dust
112					Distant lightning
113-117					Reserved
118					Squalls
119					Reserved
Code figures 120-126 are used to report precipitation, fog (or ice fog) or thunderstorm at the station during the preceding hour but not at the time of observation
120					Fog
121					PRECIPITATION
122					Drizzle (not freezing) or snow grains
123					Rain (not freezing)
124					Snow
125					Freezing drizzle or freezing rain
126					Thunderstorm (with or without precipitation)
127					Blowing OR DRIFTING SNOW OR SAND
128					Blowing or drifting snow or sand, visibility equal to, or greater than, 1 km
129					Blowing or drifting snow or sand, visibility less than 1 km
130					FOG
131					Fog or ice fog In patches
132					Fog or ice fog, has become thinner during the past hour
133					Fog or ice fog, no appreciable change during the past hour
134					Fog or ice fog, has begun or become thicker during the past hour
135					Fog, depositing rime
136-139					Reserved
140					PRECIPITATION
141					Precipitation, slight or moderate
142					Precipitation, heavy
143					Liquid precipitation, slight or moderate
144					Liquid precipitation, heavy
145					Solid precipitation, slight or moderate
146					Solid precipitation, heavy
147					Freezing precipitation, slight or moderate
148					Freezing precipitation, heavy
149					Reserved
150					DRIZZLE
151					Drizzle, not freezing, slight
152					Drizzle, not freezing, moderate
153					Drizzle, not freezing, heavy
154					Drizzle, freezing, slight
155					Drizzle, freezing, moderate
156					Drizzle, freezing, heavy
157					Drizzle and rain, slight
158					Drizzle and rain, moderate or heavy
159					Reserved
160					RAIN
161					Rain, not freezing, slight
162					Rain, not freezing, moderate
163					Rain, not freezing, heavy
164					Rain, freezing, slight
165					Rain, freezing, moderate
166					Rain, freezing, heavy
167					Rain (or drizzle) and snow, slight
168					Rain (or drizzle) and snow, moderate or heavy
169					Reserved
170					SNOW
171					Snow, slight
172					Snow, moderate
173					Snow, heavy
174					Ice pellets, slight
175					Ice pellets, moderate
176					Ice pellets, heavy
177					Snow grains
178					Ice crystals
179					Reserved
180					SHOWER(S) or intermittent PRECIPITATION
181					Rain shower(s) or intermittent rain, slight
182					Rain shower(s) or intermittent rain, moderate
183					Rain shower(s) or intermittent rain, heavy
184					Rain shower(s) or intermittent rain, violent
185					Snow shower(s) or intermittent snow, slight
186					Snow shower(s) or intermittent snow, moderate
187					Snow shower(s) or intermittent snow, heavy
188					Reserved
189					Hail
190					THUNDERSTORM
191					Thunderstorm, slight or moderate, with no precipitation
192					Thunderstorm, slight or moderate, with rain showers and/or snow showers
193					Thunderstorm, slight or moderate, with hail
194					Thunderstorm, heavy, with no precipitation
195					Thunderstorm, heavy, With rain showers and/or snow showers
196					Thunderstorm, heavy, with hail
197-198					Reserved
199					Tornado
Present weather (In addition to present weather report from either a manned or an automatic station)
Decile 200-209
200					Not used
201					Not used
202					Not used
203					Not used
204					Volcanic ash suspended In the air aloft
205					Not used
206					Thick dust haze, visibility less than 1 km
207					Blowing spray at the station
208					Drifting dust (sand)
209					Wall of dust or sand in distance (like haboob)
Decile 210-219
210					Snow haze
211					Whiteout
212					Not used
213					Lightning, cloud to surface
214-216					Not used
217					Dry thunderstorm
218					Not used
219					Tornado cloud (destructive) at or within sight of the station during preceding hour or at the time of observation
Decile 220-229
220					Deposition of volcanic ash
221					Deposition of dust or sand
222					Deposition of dew
223					Deposition of wet snow
224					Deposition of soft rime
225					Deposition of hard rime
226					Deposition of hoarfrost
227					Deposition of glaze
228					Deposition of ice crust (ice slick)
229					Not used
Decile 230-239
230					Duststorm or sandstorm with temperature below 0^0C
231-238					Not used
239					Blowing snow, impossible to determine whether snow is falling or not
Decile 240-249
240					Not used
241					Fog on sea
242					Fog in valleys
243					Arctic or Antarctic sea smoke
244					Steam fog (sea, lake or river)
245					Steam log (land)
246					Fog over ice or snow cover
247					Dense fog, visibility 60-90 m
248					Dense fog, visibility 30-60 m
249					Dense fog, visibility less than 30 m
Decile 250-259
250					Drizzle, rate of fall	less than 0.10 mm h^-1
251						0.10-0.19 mm h^-1
252						0.20-0.39 mm h^-1
253						O.40-0.79 mm h^-1
254						O.80-1.59 mm h^-1
255						l.60-3.19 mm h^-1
256						3.20-6.39 mm h^-1
257						6.4 mm h^-1 or more
258					Not used
259					Drizzle and snow
Decile 260-269
260					Rain, rate of fall	less than 1.0 mm h^-1
261						1.0-1.9 mm h^-1
262						2.0-3.9 mm h^-1
263						4.0-7.9 mm h^-1
264						8.0-15.9 mm h^-1
265						16.0-31.9 mm h^-1
266						32.0-63.9 mm h^-1
267						64.0 mm h^-1 or more
268-269					Not used
Decile 270-279
270					Snow, rate of fall	less than 1.0 cm h^-1
271						1.0-1.9 cm h^-1
272						2.0-3.9 cm h^-1
273						4.0-7.9 cm h^-1
274						8.0-15.9 cm h^-1
275						16.0-31.9 cm h^-1
276						32.0-63.9 cm h^-1
277						64.0 cm h^-1 or more
278					Snow or Ice crystal precipitation from a clear sky
279					Wet snow, freezing on contact
Decile 280-299
280					Precipitation of rain
281					Precipitation of rain, freezing
282					Precipitation of rain and snow mixed
283					Precipitation of snow
284					Precipitation of snow pellets or small hall
285					Precipitation of snow pellets or small hail, with rain
286					Precipitation of snow pellets or small hail, with rain and snow mixed
287					Precipitation of snow pellets or small hail, with snow
288					Precipitation of hail
289					Precipitation of hail, with rain
290					Precipitation of hall, with rain and snow mixed
291					Precipitation of hail, with snow
292					Shower(s) or thunderstorm over sea
293					Shower(s) or thunderstorm over mountains
294-299					Not used
300-507					Reserved
508					No significant phenomenon to report, present and past weather omitted
509					No observation, data not available, present and past weather omitted
510					Present and past weather missing, but expected
511					Missing value

Notes:

(1) The middle portion of this code table (code figures 100‑199) includes terms on several levels to cover simple and increasingly complex automatic stations.

(2) Generic terms for weather (e.g. fog, drizzle) are intended for use at automatic stations capable of determining types of weather but no other information. Generic terms are included in the code table using all capital letters.

(3) Code figures for generic precipitation (code figures 140-148) are arranged in order of increasing complexity. For example, a very simple station that can sense only the presence or absence of precipitation would use code figure 140 (precipitation). At the next level, an automatic station capable of sensing amount but not type would use code figure 141 or 142. An automatic station capable of sensing gross type (liquid, solid, freezing) and amount would use code figures 143-148. An automatic station capable of reporting actual types of precipitation (e.g. drizzle rain), but not the amount, would use the appropriate whole decile number (e.g. 150 for generic drizzle, 160 for generic rain).

---

* The expression "at the station" refers to a land station or a ship.

** Tornado cloud or waterspout.

*** Hail, small hail, snow pellets

0 20 004 / 0 20 005

Past weather (l) and (2)

Code figure
0	Cloud covering 1/2 or less of the sky throughout the appropriate period
1	Cloud coverIng more than 1/2 of the sky during part of the appropriate period and covering 1/2 or less during part of the period
2	Cloud covering more than 1/2 of the sky throughout the appropriate period
3	Sandstorm, duststorm or blowing snow
4	Fog or ice fog or thick haze
5	Drizzle
6	Rain
7	Snow, or rain and snow mixed
8	Shower(s)
9	Thunderstorm(s) with or without precipitation
10	No significant weather observed
11	Visibility REDUCED
12	Blowing phenomena, visibility reduced
13	FOG
14	PRECIPITATION
15	Drizzle
16	Rain
17	Snow or ice pellets
18	Showers or intermittent precipitation
19	Thunderstorm
20-30	Reserved
31	Missing value

Note: The weather descriptions in code figures 10 to 19 are progressively complex, to accommodate the different levels of weather discrimination capability of various automatic stations. Stations having only basic sensing capability may use the lower code figures and basic generic descriptions (shown in capital letters). Stations with progressively higher discrimination capability shall use the more detailed descriptions (higher codes).

0 20 008

Cloud distribution for aviation

Code figure
0	Sky Clear
1	Few
2	Scattered
3	Broken
4	Overcast
5	Reserved
6	Scattered/Broken	(Many forecasts use Scattered/Broken or
7	Broken/Overcast	(Broken/Overcast followed by cloud type(s))
8	Isolated	(Used on aviation charts to describe the cloud type Cb)
9	Isolated embedded	(Used on aviation charts to describe the cloud type Cb)
10	Occasional	(Used on aviation charts to describe the cloud type Cb)
11	Occasional embedded	(Used on aviation charts to describe the cloud type Cb)
12	Frequent	(Used on aviation charts to describe the cloud type Cb)
13	Dense	(Used on aviation charts to describe cloud that would cause sudden changes in visibility (less than 1000m))
14	Layers
15	Obscured (OBSC)
16	Embedded (EMBD)
17	Frequent embedded (EMBD)
18-30	Reserved
31	Missing value

0 20 009

General weather indicator (TAF/METAR)

Code figure
0	Reserved
1	NSC Nil Significant Cloud
2	CAVOK
3	SKC Sky Clear
4	NSW Nil Significant Weather
5-14	Reserved
15	Missing value

0 20 011

Cloud amount

Code figure
0	0	0
1	1 okta or less, but not zero	1/10 or less, but not zero
2	2 oktas	2/10 - 3/10
3	3 oktas	4/10
4	4 oktas	5/10
5	5 oktas	6/10
6	6 oktas	7/10 - 8/10
7	7 oktas or more, but not 8 oktas	9/10 or more, but not 10/10
8	8 oktas	10/10
9	Sky obscured by fog and/or other meteorological phenomena
10	Sky partially obscured by fog and/or other meteorological phenomena
11	Scattered
12	Broken
13	Few
14	Reserved
15	Cloud cover is Indiscernible for reasons other than fog or other meteorological phenomena, or observation is not made

Notes:

(1) For use of code figure 15, see Regulation 12.1.4.

(2) `Clear' and `overcast' are coded by 0 and 8 respectively.

0 20 012

Cloud type

Code figure
0	Cirrus (Ci)
1	Cirrocumulus (Cc)
2	Cirrostratus (Cs)
3	Altocumulus (Ac)
4	Altostratus (As)
5	Nimbostratus (Ns)
6	Stratocumulus (Sc)
7	Stratus(St)
8	Cumulus (Cu)
9	Cumulonimbus (Cb)
10	No CH clouds
11	Cirrus fibratus, sometimes uncinus, not progressively invading the sky
12	Cirrus spissatus, in patches or entangled sheaves, which usually do not increase and sometimes seem to be the remains of the upper part of a Cumulonimbus; or Cirrus castellanus or floccus
13	Cirrus spissatus cumulonimbogenitus
14	Cirrus uncinus or fibratus, or both, progressively invading the sky; they generally thicken as a whole
15	Cirrus (often in bands) and Cirrostratus, or Cirrostratus alone, progressively invading the sky; they generally thicken as a whole, but the continuous veil does not reach 45 degrees above the horizon
16	Cirrus (often In bands) and Cirrostratus, or Cirrostratus alone, progressively Invading the sky; they generally thicken as a whole; the continuous veil extends more than 45 degrees above the horizon, without the sky being totally covered
17	Cirrostratus covering the whole sky
18	Cirrostratus not progressively invading the sky and not entirely covering It
19	Cirrocumulus alone, or Cirrocumulus predominant among the CH clouds
20	No CM clouds
21	Altostratus translucidus
22	Altostratus opacus or Nimbostratus
23	Altocumulus translucidus at a single level
24	Patches (often Lenticular) of Altocumulus translucidus, continually changing and occurring at one or more levels
25	Altocumulus translucidus in bands, or one or more layers of Altocumulus translucidus or opacus, progressively Invading the sky;these Altocumulus clouds generally thicken as a whole
26	Altocumulus cumulogenitus (or cumulonimbogenitus)
27	Altocumulus translucidus or opacus In two or more layers, or Altocumulus opacus In a single layer, not progressively Invading the sky, or Altocumulus with Altostratus or Nimbostratus
28	Altocumulus castellanus or floccus
29	Altocumulus of a chaotic sky, generally at several levels
30	No CL clouds
31	Cumulus humilis or Cumulus fractus other than of bad weather^*, or both
32	Cumulus mediocris or congestus, Towering cumulus (TCU), with or without Cumulus of species fractus or humilis or Stratocumulus, all having their bases at the same level
33	Cumulonimbus calvus, with or without Cumulus, Stratocumulus or Stratus
34	Stratocumulus cumulogenitus
35	Stratocumulus other than Stratocumulus cumulogenitus
36	Stratus nebulosus or Stratus fractus other than of bad weather^*, or both
37	Stratus fractus or Cumulus fractus of bad weather^*, or both (pannus),usually below Altostratus or Nimbostratus
38	Cumulus and Stratocumulus other than Stratocumulus cumulogenitus, with bases at different levels
39	Cumulonimbus capillatus (often with an anvil), with or without Cumulonimbus calvus, Cumulus, Stratocumulus, Stratus or pannus
40	CH
41	CM
42	CL
43	Clear
44	Liquid water
45	Supercooled Liquid Water
46	Mixed Phase
47	Optically Thick Ice
48	Optically Thin Ice
49	Multilayered Ice
50-58	Reserved
59	Cloud not visible owing to darkness, fog, duststorm, sandstorm, or other analogous phenomena
60	CH clouds Invisible owing to darkness, fog, blowing dust or sand, or other similar phenomena, or because of a continuous layer of lower clouds
61	CM clouds Invisible owing to darkness, fog, blowing dust or sand, or other similar phenomena, or because of continuous layer of lower clouds
62	CL clouds invisible owing to darkness, fog, blowing dust or sand, or other similar phenomena
63	Missing value

^* "Bad weather" denotes the conditions which generally exist during precipitation and a short time before and after.

0 20 017

Cloud top description

Code figure
0	Isolated cloud fragments of clouds
1	Continuous cloud	flat tops
2	Broken cloud - small breaks
3	Broken cloud - large breaks
4	Continuous cloud	undulating tops
5	Broken cloud - small breaks
6	Broken cloud - large breaks
7	Continuous or almost continuous waves with towering clouds above the top of the layer
8	Groups of waves with towering clouds above the top of the layer
9	Two or more layers at different levels
10-14	reserved
15	Missing value

0 20 018

Tendency of runway visual range

Code figure
0	Increasing (U)
1	Decreasing (D)
2	No distinct change (N)
3	Missing value

0 20 021

Type of precipitation

Bit No.
1	Precipitation-unknown type
2	Liquid precipitation not freezing
3	Liquid freezing precipitation
4	Drizzle
5	Rain
6	Solid precipitation
7	Snow
8	Snow grains
9	Snow pellets
10	Ice pellets
11	Ice crystals
12	Diamond dust
13	Small hail
14	Hail
15	Glaze
16	Rime
17	Soft rime
18	Hard rime
19	Clear ice
20	Wet snow
21	Hoar frost
22	Dew
23	White dew
24-29	Reserved
All 30	Missing value

Note: Mixed precipitation is indicated by setting to one the bits of all the observed single types of precipitation

0 20 022

Character of precipitation

Code figure
0	No precipitation
1	Continuous
2	Intermittent
3	Shower
4	Not reaching ground
5	Deposition
6-14	Reserved
15	Missing value

0 20 023

Other weather phenomena

Bit No.
1	Dust/sand whirl
2	Squalls
3	Sand storm
4	Dust storm
5	Lightning - cloud to surface
6	Lightning - cloud to cloud
7	Lightning - distant
8	Thunderstorm
9	Funnel Cloud not touching surface
10	Funnel cloud touching surface
11	Spray
12	Water-spout
13	Wind shear
14	Dust devils
15-17	Reserved
All 18	Missing value

0 20 024

Intensity of phenomena

Code figure
0	No phenomena
1	Light
2	Moderate
3	Heavy
4	Violent
5	Severe
6	Very severe
7	Missing value

0 20 025

Obscuration

Bit No.
1	Fog
2	Ice fog
3	Steam fog
4-6	Reserved
7	Mist
8	Haze
9	Smoke
10	Volcanic ash
11	Dust
12	Sand
13	Snow
14	Cloud
15	Precipitation
16	Impossible to determine whether snow is falling or not
17-20	Reserved
All 21	Missing value

0 20 026

Character of obscuration

Code figure
0	No change
1	Shallow
2	Patches
3	Partial
4	Freezing
5	Low drifting
6	Blowing
7	Increasing
8	Decreasing
9	In suspension in the air
10	Wall
11	Dense
12	Whiteout
13	Drifting and blowing
14	Reserved
15	Missing value

0 20 027

Phenomena^* occurrence

Bit No.
1	At time of observation
2	In past hour
3	In time period for past weather W1W2
4	In time period specified
5	Reserved
6	Below station level
7	At the station (see Note 1)
8	In the vicinity (see Note 2)
All 9	Missing value

^* Phenomenon in 0 20 027 means any phenomenon, including precipitation and obscuration.

Notes:
(1) In conjunction with the observation of water spouts or funnel clouds i.e. within 3 km of station.
(2) In conjunction with the observation of water spouts or funnel clouds i.e. more than 3 km from station.

0 20 029

Rain flag

Code figure
0	No rain
1	Rain
2	Reserved
3	Missing value

0 20 032

Rate of ice accretion

Code figure
0	Ice not building up
1	Ice building up slowly
2	Ice building up rapidly
3	Ice melting or breaking up slowly
4	Ice melting or breaking up rapidly
5-6	Reserved
7	Missing value

0 20 033

Cause of ice accretion

Bit No.
1	Icing from ocean spray
2	Icing from fog
3	Icing from rain
All 4	Missing value

0 20 034

Sea ice concentration

Code figure
0	No sea ice In sight
1	Ship in open lead more than 1.0 nautical mile wide, or ship in fast ice with boundary beyond limit of visibility
2	Sea ice present In concentrations less than 3/10 (3/8) open water or very open pack ice	Sea ice concentration is uniform in the observation area	Ship in ice or within 0.5 nautical mile of ice edge
3	4/10 to 6/10 (3/8 to less than 6/8), open pack ice
4	7/10 to 8/10 (6/8 to less 7/8), close pack ice
5	9/10 or more, but not 10/10 (7/8 to less than 8/8), very close pack ice
6	Strips and patches of pack ice with open water between	Sea ice concentration is not uniform in the observation area
7	Strips and patches of close or very close pack ice with areas of lesser concentration between
8	Fast ice with open water, very open or open pack Ice to seaward of the ice boundary
9	Fast ice with close or very close pack ice to seaward of the boundary
10-13	Reserved
14	Unable to report, because of darkness, lack of visibility, or because ship is more than 0.5 nautical mile away from ice edge
15-30	Reserved
31	Missing value

0 20 035

Amount and type of ice

Code figure
0	No ice of land origin
1	1-5 icebergs, no growlers or bergy bits
2	6-10 icebergs, no growlers or bergy bits
3	11-20 Icebergs, no growlers or bergy bits
4	Up to and Including 10 growlers and bergy bits - no icebergs
5	More than 10 growlers and bergy bits - no Icebergs
6	1-5 icebergs, with growlers and bergy bits
7	6-10 icebergs, with growlers and bergy bits
8	11-20 icebergs, with growlers and bergy bits
9	More than 20 Icebergs, with growlers and bergy bits - a major hazard to navigation
10-13	Reserved
14	Unable to report, because of darkness, lack of visibility or because only sea ice is visible
15	Missing value

0 20 036

Ice situation

Code figure
0	Ship in open water with floating ice in sight
1	Ship In easily penetrable ice; conditions improving
2	Ship In easily penetrable ice; conditions not changing
3	Ship in easily penetrable ice; conditions worsening
4	Ship in ice difficult to penetrate; conditions improving
5	Ship in ice difficult to penetrate; conditions not changing
6	Ship in ice difficult to penetrate and conditions worsening. Ice forming and floe freezing together
7	Ship in ice difficult to penetrate and conditions worsening. Ice under slight pressure
8	Ship in ice difficult to penetrate and conditions worsening. Ice under moderate or severe pressure
9	Ship in ice difficult to penetrate and conditions worsening. Ship beset
10-29	Reserved
30	Unable to report, because of darkness or lack of visibility
31	Missing value

0 20 037

Ice development

Code figure
0	New ice only (frazil ice, grease ice, slush, shuga)
1	Nilas or ice rind, less than 10 cm thick
2	Young ice (grey ice, grey-white ice), 10-30 cm thick
3	Predominantly new and/or young ice with some first-year ice
4	Predominantly thin first-year ice with some new and/or young ice
5	All thin first-year ice (30-70 cm thick)
6	Predominantly medium first-year ice (70-120 cm thick) and thick first-year ice (>120 cm thick) with some thinner (younger) first-year ice
7	All medium and thick first-year ice
8	Predominantly medium and thick first-year ice with some old ice (usually more than 2 metres thick)
9	Predominantly old ice
10-29	Reserved
30	Unable to report, because of darkness, lack of visibility or because only ice of land origin is visible or because ship is more than 0.5 nautical mile away from ice edge
31	Missing value

0 20 041

Airframe icing

Code figure
0	No icing
1	Light icing
2	Light icing In cloud
3	Light icing In precipitation
4	Moderate icing
5	Moderate icing in cloud
6	Moderate icing in precipitation
7	Severe icing
8	Severe icing in cloud
9	Severe icing in precipitation
10	Trace of icing
11	Trace of icing in cloud
12	Trace of icing in precipitation
13-14	Reserved
15	Missing value

0 20 042

Airframe icing present

Code figure
0	No icing
1	Icing present
2	Reserved
3	Missing value

0 20 045

Supercooled large droplet (SLD) conditions

Code figure
0	No SLD conditions present
1	SLD conditions present
2	Reserved
3	Missing value

0 20 050

Cloud index

Code figure
0	Reserved
1	1st  low cloud
2	2nd low cloud
3	3rd low cloud
4	1st medium cloud
5	2nd medium cloud
6	3rd medium cloud
7	1st high cloud
8	2nd high cloud
9-254	Reserved
255	Missing value

0 20 056

Cloud phase

Code figure
0	Unknown
1	Water
2	Ice
3	Mixed
4	Clear
5	Supercooled liquid water
6	Reserved
7	Missing value

0 20 062

State of the ground (with or without snow)

Code figure
0	Surface of ground dry (without cracks and no appreciable amount of dust or loose sand)	without snow or measurable ice cover
1	Surface of ground moist
2	Surface of ground wet (standing water in small or large pools on surface)
3	Flooded
4	Surface of ground frozen
5	Glaze on ground
6	Loose dry dust or sand not covering ground completely
7	Thin cover of loose dry dust or sand covering ground completely
8	Moderate or thick cover of loose dry dust or sand covering ground completely
9	Extremely dry with cracks
10	Ground predominantly covered by ice
11	Compact or wet snow (with or without ice) covering less than one-half of the ground	with snow or measurable ice cover
12	Compact or wet snow (with or without ice) covering at least one-half of the ground but ground not completely covered
13	Even layer of compact or wet snow covering ground completely
14	Uneven layer of compact or wet snow covering ground completely
15	Loose dry snow covering less than one-half of the ground
16	Loose dry snow covering at least one-half of the ground (but not completely)
17	Even layer of loose dry snow covering ground completely
18	Uneven layer of loose dry snow covering ground completely
19	Snow covering ground completely; deep drifts
20-30	Reserved
31	Missing value

Notes:

(1) The definitions in code numbers 0 to 2 and 4 apply to representative bare ground and numbers 3, 5 to 9 and 10 to 19 to an open representative area.

(2) In all instances the highest code figures applicable are to be reported.

(3) In the above code table, whenever reference is made to ice, it also includes solid precipitation other than snow.

0 20 063

Special phenomena

Code figure
0	Reserved
1	Highest wind speed gusts greater than 11.5 m/s
2	Highest mean wind speed greater than 17.5 m/s
3-6	Reserved
7	Visibility greater than 100000 m
8-9	Reserved
10-19	Mirage
10	Mirage - No specification
11	Mirage - Image of distant object raised (looming)
12	Mirage - Image of distant object raised clear above the horizon
13	Mirage - Inverted image of distant object
14	Mirage - Complex, multiple images of distant object (images not inverted)
15	Mirage - Complex, multiple images of distant object (some images being inverted)
16	Mirage - Sun or moon seen appreciably distorted
17	Mirage - Sun visible, although astronomically below the horizon
18	Mirage - Moon visible, although astronomically below the horizon
19	Reserved
20-22	Day darkness, worst in direction specified
20	Day darkness, bad, worst in direction specified
21	Day darkness, very bad, worst in direction specified
22	Day darkness, black, worst in direction specified
23-30	Reserved
31-39	Coloration and/or convergence of clouds associated with a tropical distrubance
31	Slight coloration of clouds at sunrise associated with a tropical disturbance
32	Deep-red coloration of clouds at sunrise associated with a tropical disturbance
33	Slight coloration of clouds at sunset associated with a tropical disturbance
34	Deep-red coloration of clouds at sunset associated with a tropical disturbance
35	Convergence of CH clouds at a point below 45° forming or increasing and associated with a tropical disturbance
36	Convergence of CH clouds at a point above 45° associated with a tropical disturbance
37	Convergence of CH clouds at a point below 45° dissolving or diminishing and associated with a tropical disturbance
38	Convergence of CH clouds at a point above 45° associated with a tropical disturbance
39	Reserved
40-43	Hoar frost or colored precipitation
40	Hoar frost on horizontal surfaces
41	Hoar frost on horizontal and vertical surfaces
42	Precipitation containing sand or desert dust
43	Precipitation containing volcanic ash
44-49	Reserved
50-59	Nature and/or type of squall
50	Calm or light wind followed by a squall
51	Calm or light wind followed by a succession of squalls
52	Gusty weather followed by a squall
53	Gusty weather followed by a succession of squalls
54	Squall followed by gusty weather
55	General gusty weather with squall at intervals
56	Squall approaching station
57	Line squall
58	Squall with drifting or blowing dust or sand
59	Line squall with drifting or blowing dust or sand
60-69	Variation of temperature during the period specified, associated with glaze or time
60	Temperature steady
61	Temperature falling, without going below 0°C
62	Temperature rising, without going above 0°C
63	Temperature falling to a value below 0°C
64	Temperature rising to a value above 0°C
65	Irregular variation, oscillations of temperature passing through 0°C
66	Irregular variation, oscillations of temperature not passing through 0°C
67	Variation of temperature not observed
68	Not allocated
69	Variation of temperature unknown owing to lack of thermograph
70-79	Variation of visibility during the period specified
70	Visibility has not varied (sun^* visible) towards direction specified
71	Visibility has not varied (sun^* invisible) towards direction specified
72	Visibility has increased (sun^* visible) towards direction specified
73	Visibility has increased (sun^* invisible) towards direction specified
74	Visibility has decreased (sun^* visible) towards direction specified
75	Visibility has decreased (sun^* invisible) towards direction specified
76	Fog coming from direction specified
77	Fog has lifted, without dissipating
78	Fog has dispersed without regard to direction
79	Moving patches or banks of fog
80-89	Optical phenomena
80	Brocken specter
81	Rainbow
82	Solar or lunar halo
83	Parhelia or anthelia
84	Sun pillar
85	Corona
86	Twilight glow
87	Twilight glow on the mountains (Alpenglühen)
88	Mirage
89	Zodiacal light
90	St. Elmo's fire
91-1022	Reserved
1023	Missing value

^* Or sky (if sun is low), or moon or stars at night.    

0 20 071

Accuracy of fix and rate of atmospherics

Code figure	Accuracy of fix (estimated error)	Repetition rate
0	No assessment	No assessment
1	Less than 50 km	Less than 1 per second
2	Between 50 and 200 km	Less than 1 per second
3	More than 200 km	Less than 1 per second
4	Less than 50 km	1 or more per second
5	Between 50 and 200 km	1 or more per second
6	More than 200 km	1 or more per second
7	Less thank 50 km	Rate so rapid number cannot be counted
8	Between 50 and 200 km	Rate so rapid number cannot be counted
9	More than 200 km	Rate so rapid number cannot be counted
10-14	Reserved
15	Missing value

0 20 090

Special clouds

Code figure
0	Reserved
1	Nacreous clouds
2	Noctilucent clouds
3	Clouds from waterfalls
4	Clouds from fires
5	Clouds from volcanic eruptions
6-14	Reserved
15	Missing value

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