Abbreviations and Codes Used in the Observer’s Diary

While the notation has varied over the centuries, a standard for meteorological abbreviations and codes used in the observer’s diary has been slowly established. Below are tables with modern versions of such codes, which can help you better understand the comments accompanying the daily measurements.

Table 1: Code for wind direction

All directions are from true (not magnetic) North. When the wind is calm, enter 00 for direction.

COMPASS POINT (from which the wind is blowing)CODED ENTRY
North36
North-north-east02
North-east05
East-north-east07
East09
East-south-east11
South-east14
South-south-east16
South18
South-south-west20
South-west23
West-south-west25
West27
West-north-west29
North-west32
North-north-west34

Table 2: Code for wind speed

SpecificationBeaufort ForceCoded Entry (equivalent speed at 10 m in knots)
Calm: smoke rises vertically000
Light air: direction of wind shown by smoke drift but not by wind vanes102
Light breeze: wind felt on face; leaves rustle; ordinary vane moved by wind205
Gentle breeze: leaves and small twigs in constant motion; wind extends light flag309
Moderate breeze: raises dust and loose paper; small branches are moved413
Fresh breeze: small trees in leaf begin to sway; crested wavelets form on inland waters519
Strong breeze: large branches in motion; umbrellas used with difficulty624
Near gale: whole trees in motion; inconvenience felt when walking against the wind (Force 7 is not regarded as a gale)730
Gale: breaks twigs off trees; generally impedes progress837
Strong gale: slight structural damage occurs (chimney pots and slates removed)944
Storm: seldom experienced inland; trees uprooted; considerable structural damage occurs1052
Violent storm: very rarely experienced; accompanied by widespread damage1160
Hurricane: extremely rare; widespread damage and loss of life1268

Table 3: Present weather code and appropriate Beaufort letters or symbols

Even more detailed tables, with all of the associated symbols, can be found in this PDF file from the Met Office.

Miscellaneous phenomena
* must be occurring at the time of the observation
† must have occurred in the preceding hour
*† at the time of the observation OR in the preceding hour

CodeDescriptionBeaufort
Total Cloud:
0 - 2/8clear sky b
3/8 - 5/8partly cloudy bc
6/8 - 8/8 cloudy c
8/8 total cloudUniform thick layer completely covering sky (overcast) o
State of Sky:
01† Clouds generally dissolving or becoming less developed
02†State of sky generally unchanged
03†Clouds generally forming or developing
04*Visibility reduced by smoke (e.g. industrial smoke, forest fires)
05* Haze z
06* Widespread dust in suspension in the air (NOT raised by wind) at or near station
07† Dust or sand raised by the wind but no well developed dust- or sand-whirl(s), at or near station
08*†Well developed dust- or sand-whirl(s) at or near station, but no dust- or sand-storm seen
09*† Dust- or sand-storm within sight of the station jkz
10*Mist m
*Shallow fog (or ice fog) at station, not deeper than 2m. over land or 10m. over sea...fs
11 ... in patches
12... more or less continuous
13Lightning seen (but NO thunder heard)
*Precipitation in sight (but not at station)...jp
14... NOT reaching the ground or surface of sea
15... reaching the ground or surface of the sea, but at a distance of not less than about 3 miles
16 ... reaching the ground or surface of the sea near to (but not at) the station
17*Thunderstorm WITHOUT precipitation at the stationt
18*†Squalls at or within sight of the stationq
19*† Funnel cloud(s) (e.g. water-spout, tornado cloud) at or within sight of the station

Phenomena Ceased During Preceding Hour

CodeDescription
20 Drizzle (not freezing) OR snow grains
21Rain (not freezing)
22Snow (in flakes)
23Rain and snow (sleet) OR ice pellets
24Freezing drizzle OR freezing rain
25Shower(s) of rain
26Shower(s) of snow (in flakes) OR of snow and rain (sleet)
27Shower(s) of hail, small hail OR of rain and hail
28Fog (or ice fog), i.e., visibility LESS THAN 1000m due to water particles or ice crystals
29Thunderstorm (with OR without precipitation)

SAND or DUST STORMS

CodeDescriptionBeaufort
Slight...kzₒ
...or Moderate:kz
30has decreased in the past hour
31no appreciable change
32has begun or increased in the past hour
Severe:KZ
33has decreased in the past hour
34no appreciable change
35has begun or increased in the past hour

DRIFTING or BLOWING SNOW

CodeDescriptionBeaufort
36Slight...↓ksₒ
...or Moderate drifting snow, generally low↓ks
37Heavy drifting snow, generally low↓KS
38Slight...↑ksₒ
...or Moderate blowing snow, generally high↑ks
39Heavy blowing snow, generally high↑KS

FOG (or ICE FOG)

Fog denotes visibility LESS THAN 1000m due predominantly to water droplets (or ice crystals).

The Beaufort letter for fog depends upon its density: 0 m – 199 m = F ; 200 m -999 m = f

CodeDescriptionBeaufort
40Fog at a distance (not at station in past hour) jf
41Fog in patchesif
Fog has become THINNER in past hour:F or f
42sky/clouds discernible
43sky/clouds obscured
No appreciable change in fog in preceding hour:F or f
44sky/clouds discernible
45sky/clouds obscured
Fog has formed or become THICKER in preceding hour:F or f
46sky/clouds discernible
47sky/clouds obscured
FOG DEPOSITING RIME:
48 sky/clouds discernible
49sky/clouds obscured

Precipitation from stratiform clouds

CodeDescriptionBeaufort
DRIZZLE
Slight
50intermittentidₒ
51continuousdₒdₒ
Moderate
52intermittentid
53continuousdd
Heavy
54intermittentiD
55continuousDD
FREEZING DRIZZLE
56slight
57moderate
DRIZZLE with RAIN
58slight dₒrₒ
59moderate...dr
...or heavyDR
RAIN
Slight
60intermittentirₒ
61continuousrₒrₒ
Moderate
62intermittentir
63continuousrr
Heavy
64intermittentiR
65continuousRR
FREEZING RAIN
66slight
67moderate or heavy
RAIN (or drizzle) WITH SNOW (SLEET)
68
69slightrₒsₒ or dₒsₒ
SNOW (FLAKES)moderate...rs or ds
...or heavyRS or DS
Slight
70intermittentisₒ
71continuoussₒsₒ
Moderate
72intermittentis
73continuousss
Heavy
74intermittentiS
75continuousSS
SNOW GRAINS, ICE PELLETS etc.
76Ice prisms
77Snow grains sh
78Isolated star-like snow crystals
79Ice pellets

Precipitation from cumuliform clouds only
† The intensity refers to thundery conditions not to the precipitation
* Hail here includes hail, small hail and snow pellets

CodeDescriptionBeaufort
SHOWERS...
...of RAIN
80slight prₒ
81moderate...pr
...or heavyPR
82violentPR
...of RAIN and SNOW (SLEET)
83slightprₒsₒ
84moderate...prs
...or heavyPRS
...of SNOW (FLAKES)
85slightpsₒ
86moderate...ps
...or heavyPS
...of SNOW PELLETS, or SMALL HAIL with or without rain or sleet
87slight
88moderate or heavy
of HAIL with or without rain or sleet
89slightphₒ
90moderate...ph
...or heavyPH
THUNDERY CONDITIONS:
A thunderstorm without any precipitation is reported by code figure 17
Thunderstorm CEASED in past hour: PRECIPITATION CONTINUING
91slight rain
92moderate/heavy rain
93slight snow/sleet/hail
94moderate/heavy snow/sleet/hail
THUNDERSTORM WITH PRECIPITATION both at time of observation
†Thunderstorm with ...
95rain and/or snow (flakes), slight...tlrₒ(sₒ)
...or moderatetlr(s)
96hail*, slight...tlhₒ
..or moderatetlh
97 rain and/or snow (flakes), heavyTLR(S)
98dust- or sand-stormtlkz
99hail*, heavyTLH

Table 4: Code for observing and reporting visibility

The viewpoint for most objects is inside the Met Enclosure by the Stevenson screen (or the nearest location from which the object is visible) unless otherwise specified. Objects marked with asterisk (*) are not visible from the ground and may require a higher vantage point.

Coded EntryGeneral DescriptionVisibility Range (inclusive)Standard DistanceActual DistanceName of ObjectBearing
XDENSE FOG0 - 24 yards / 0 - 19 metres
EDENSE FOG25 - 44 yd / 20 - 39 m22 yd / 20 m22 yd / 20 mCalver DomeNE
0THICK FOG45 - 104 yd / 40 - 99 m44 yd / 40 m38 yd / 35 mRobinson Memorial DomeNNW
1THICK FOG105 - 210 yd / 100 - 199 m110 yd / 100 m76 yd / 69 mObservatory (Troughton) DomeNNW
2FOG220 - 430 yd / 200 - 399 m220 yd / 200 m219 yd / 200 mHypercube (Viewpoint: Stone Calendar)NW
3MODERATE FOG440 - 1090 yd / 400 - 999 m440 yd / 400 m443 yd / 405 m; 666 yd / 609 m; 728 yd / 666 m;St Mark's Church Tower; Catholic Cathedral; Church of Ireland CathedralSE; W; SW
FOG LIMIT
4VERY POOR VISIBILITY1100 - 2190 yd / 1000 - 1999 m1100 yd / 1000 m830 yd / 760 m; 902 yd / 825 mPolice Station Radio Mast; Armagh City HotelS; SSW
5POOR VISIBILITY2200 - 4390 yards / 2000 - 3999 metres2200 yd / 2000 m1870 yd / 1710 m Armagh DAB Radio Mast*SW
6MODERATE VISIBILITY3 - 6 miles / 4 - 9 kilometres2.5 mi / 4 km; 4.7 mi / 7 kmn/a; 4.3 mi / 6.9 kmn/a; Vicar's Cairn*n/a; SSW
7GOOD VISIBILITY7 - 12 mi / 10 - 19 km6.25 mi / 10 km8.6 mi / 13.8 kmCarrigatuke HillSSE
8VERY GOOD VISIBILITY13 - 24 mi / 20 - 39 km12.5 mi / 20 km; 18.7 mi / 30 km12.1 mi / 19.4 km; 18.3 mi / 29.4 kmMullyash Mountain*; Slieve Gullion*SSE; SSW
9EXCELLENT VISIBILITY25 miles or over / 40 kilometres or over25 mi / 40 kmn/an/an/a

Table 5: Code for state of ground

WITHOUT SNOW OR ICE CODED ENTRYWITH SNOW OR ICE
Surface of ground dry (without cracks and no appreciable amount of dust or loose sand)0Ground predominantly covered by ice
Surface of ground moist 1Compact or wet snow (with or without ice) covering less than one-half of the ground
Surface of ground wet (standing water in small or large pools on surface)2Compact or wet snow (with or without ice) covering at least one-half of the ground but ground not completely covered
Ground flooded3Even layer of compact or wet snow covering ground completely
Surface of ground frozen 4Uneven layer of compact or wet snow covering ground completely
Glaze on ground 5Loose dry snow covering less than one-half of the ground
Loose dry dust or sand not covering ground completely 6Loose dry snow covering at least one-half of the ground (but not completely)
Thin layer of loose dry dust or sand covering the ground completely 7Even layer of loose dry snow covering ground completely
Moderate or thick cover of loose dry dust or sand covering ground completely8Uneven layer of loose dry snow covering ground completely
Extremely dry with cracks9Snow covering ground completely; deep drifts

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