Weather Symbols

While Beaufort code may be used to make a record of the weather, on synoptic charts weather types are usually shown by a set of international symbols.

The tables below show both Beaufort Code and Weather symbols. One might expect there to be a corresponding Beaufort Letter for each symbol, and vice-versa - but unfortunately this is not the case.

Hydrometeors - Water and Ice
Letter Symbol Description
r symbol for rain Rain (drops of water >0.5mm diameter)
rx freezing rain symbol Freezing Rain (i.e. rain which freezes on contact with the ground and vegetation)
d drizzle symbol Drizzle (drops of water <0.5mm diameter)
dx freezing drizzle symbol Freezing Drizzle (i.e. drizzle which freezes on contact with the ground and vegetation)
s snow symbol Snow (ice crystals, often branched into 'flakes' in 'warmer conditions', temperatures >-5oC
h snow pellet symbol Snow Pellets (often referred to as 'soft hail', and typical of wintry showers, especially in coastal regions; white and spherical or conical, 2 to 5mm; fall only from cumulus and cumulonimbus clouds )
h large hail symbol Hail (transparent or opaque particles , usually spheroidal, but sometimes conical; over 5mm; can fall as larger aggregated lumps in heavy thunderstorms; most larger hailstones show evidence of concentric layering)
h hail symbol Small Hail (as above but consisting of snow pellets encased in a thin layer of clear ice, not easily crushable; under 5mm; very common in showery weather in Britain; falls only from cumulus and cumulonimbus clouds)
h ice pellet symbol Ice Pellets (spherical, conical or irregular transparent ice particles <=5mm; fall mainly from altostratus and nimbostratus clouds)
h diamond dust symbol Diamond Dust (tiny ice crystals which fall from a clear sky; requires very cold weather; rare in Britain; common in polar regions)
sh snow grain symbol Snow Grains (white opaque particles <1mm; fall usually from low stratus and stratocumulus clouds)
f fog symbol Fog (Visibility <1km)
fx none Freezing Fog (water droplet fog, that freezes on contact with solid objects)
fe ice fog symbol Wet Fog (damp fog which deposits a film of water on exposed solid surfaces)
fs none Shallow Fog Patches (fog limited to a depth of 2 metres or less; if it is a continuous layer, the lower line of the symbol is continuous, but the Beaufort code stays the same)
m mist symbol Mist (Visibility 1 to 2 km; there are a variety of definitions of mist; the British Met Office also require a relative humidity between 95 and 100%)
ks drifting snow symbol Drifting Snow (snow raised to heights below eye level - 1.8 metres; no overall reduction in visibility)
ks blowing snow symbol Blowing Snow (snow raised to a great height above the land surface causing severe reduction of visibility, e.g. a 'white-out'; strong winds needed; usually limited to upland areas in Britain)
  spray symbol Spray (limited to sea area, large lakes, coastal regions) (limited to sea area, large lakes, coastal regions)
w Dew (produced by night-time radiation cooling
w advection dew symbol Advection Dew (caused by condensation on upright surfaces, usually after a cold spell as warm moist air blows against cold surfaces)
w white dew symbol White Dew (frozen dew drops, as opposed to hoar frost)
x hoar frost symbol Hoar Frost (the 'usual' white frost, produced by radiation cooling; takes the form of small needles, scales, feathers or fans)
x advection hoar frost symbol Advection Hoar Frost (forms in the same way as advection dew, but with temperatures still below freezing)
  rime symbol Rime (a deposit of ice formed on 'solid' objects by freezing fog)
  soft rime symbol Soft Rime (fragile deposit of needles and scales of ice on upright surfaces; limited to temperatures <-8oC and calm or light wind conditions; the deposit can be easily shaken off objects)
  hard rime symbol Hard Rime (As above but hard granular and crystalline ice; forms in strong winds with temperatures -2oC to -10oC; the deposit is difficult to shake off objects)
  clear ice symbol Clear Ice (Similar to glaze, but formed by supercooled water droplets freezing on exposed surfaces; unlike the above two, clear ice lacks air pockets)
  glaze symbol Glaze (a deposit of clear ice produced by freezing rain)
  water spout symbol Water Spout (tornado over sea or lake)

 

Mixed Precipitation
Letter Symbol Description
dr drizzle and rain symbol Drizzle and rain
rs sleet symbol Rain and snow (Sleet)
hs hail and snow symbol Hail and snow
hr hail and rain symbol Hail and rain

 

Lithometeors
Letter Symbol Description
h haze symbol Haze (the presence of microscopic particles in the air in sufficient quantities to give the sky an opalescent appearance; visibility is often reduced; most common in calm anticyclonic weather in summer in Britain, when pollen, dust and pollution contaminate the air)
  dust haze symbol Dust Haze (common in desert regions and in downwind areas, which can stretch for over 1000km)
  smoke symbol Smoke (suspension of mainly carbon and hydrocarbon particles produced by combustion; much reduced in Britain since the Clean Air Acts; common where forest fire occur)
  drifting or blowing dust Drifting or Blowing Dust or Sand (associated with turbulent winds in deserts, dunes and  drought-stricken areas)
  drifting dust or sand symbol Drifting Dust or Sand (dust and sand not rising above eye-level: 1.8 metres)
  blowing dust or sand symbol Blowing Dust or Sand (dust and sand rising to greater heights; it may be enough to veil the sky or sun at times)
  dust or sandstorm symbol Duststorm or Sandstorm (sand or dust raised to great heights by strong turbulent wind; visibility <1km; desert and drought-stricken areas only)
  dust or sand wall symbol Wall of Sand or Dust (common at the leading edge of a duststorm or sandstorm)
  dust devil symbol Dust Whirl or Sand Whirl - 'Dust Devil' (swirling cloud of dust/sand raised from the ground in a vortex; caused when air at ground level becomes very unstable, e.g. by rapid heating in strong sunshine; usually short lived < 60 seconds)

 

Photometeors
Photometeors are luminous optical phenomena caused by the refraction of light due to passage through ice crystals (especially in cirrus clouds), rain, water droplets, etc. There are no Beaufort Letters for photometeors.
Letter Symbol Description
  solar halo symbol Solar Halo - a ring of bright light around the sun, usually white, but sometimes running from reddish nearer the sun to yellow, green or even violet on its outer edge.  The 22o halo is most common and often 'complete'.  The 46o halo is rarer and almost always incomplete.
  lunar halo symbol Lunar Halo - as above but surrounding the moon
  solar corona symbol Solar Corona - one or more sequences of coloured rings of small diameter - 5o for the inside ring ; the inside of each ring is violet or blue and the outside red; solar coronae can only be seen if the sun is much dimmed due to cloud cover; coronae are caused by passage of light through very small water droplets
  lunar corona Lunar Corona - as above, but for the moon, and much more frequently seen
  irisization symbol Irisation - colours, often resembling mother of pearl, appearing on clouds, especially in bands parallel to their margins; the effect is usually to be seen within 10o to 40o of the sun
  glory symbol Glory - one or more sequences of coloured rings seen by an observer around his/her own shadow on a cloud; occurs frequently on mountains when there is mist or cloud on one side of the observer but not on the other; the phenomena is similar to a corona feature, but the light is refracted backwards; when the shadow is large it is often described as a Brocken Spectre, after the German mountain where it was first described
  rainbow symbol Rainbow - a group of concentric arcs with colours ranging from violet to red; caused by refraction of light by precipitation; Inside the primary rainbow, the brightest one, their may be further, fainter, supernumerary rainbows; viewed from above, rainbows appear as complete circles
  fog bow symbol Fog-bow - With fine and very small water droplets < 0.05 mm all the colours except perhaps violet are lost.  Artificial fogbows can sometimes be seen on dark foggy nights when you stand with a streetlight to your back.  They appear like ghostly arches over a darker core.  Natural fogbows are best seen when the sun is very low and red, e.g. dusk or dawn.
  bishops ring symbol Bishop's Ring - a whitish ring centred on the sun or moon, bluish on the inside and reddish brown on the outside; inner radius 10o; outer radius 20o; very rare - they tend to occur after violent volcanic eruptions, e.g. Krakatoa 1883, and after the impact of meteorites, e.g. Siberia 1908, or close passes of comets; they therefore seem to be associated with the passage of light through very fine high altitude dust
  mirage symbol Mirage - an image, usually wavering, of distant objects, which appear distorted, often inverted; mirages are caused by large temperature gradients in the air immediately above the ground producing different refractive indices
  zodiacal light Zodiacal Light - This occasional appears a cone shaped area above the horizon in the position where the sun has just set, or in the position where it is just about to rise.  The light can remain visible with the stars in an otherwise dark sky; it is extremely rare outside the tropics

 

Electrometeors
Electrometeors are phenomena associated with electrical discharges in the atmosphere
Letter Symbol Description
tl thunderstorm symbol Thunderstorm - thunder must be audible at the site before a thunderstorm can be recorded
l lightning symbol Lightning - there are three common types: ground discharge - where the lightning strikes the ground; it is often in a branched form, hence the name 'forked' lightning; cloud discharge - lightning that is within the cloud - its channel is often indistinguishable and we normally refer to it as 'sheet' lightning; air discharge - often sub-horizontal, it runs from cloud to air outside the cloud; sometimes called 'streak' lightning; a fourth an rare form is ball lightning, which appears near the ground usually after a ground discharge; it varies between 10cms and 1 metre in diameter, 'floats' around for several seconds and usually dissipates with a violent explosion
  saint elmos fire symbol Saint Elmo's Fire - a rare bluish-purplish white electrical discharge that 'coats'   projecting objects, e.g. church spires, masts, aircraft wings, etc. causing them to glow; it only occurs in thundery weather when very strong electrical field develop
  polar aurora symbol Polar Aurora - luminous arcs, bands, drapes and curtains of light, that form due to the impact of electrically charged particles from the sun impacting on rarefied gases high in the atmosphere, between 60 and 1000 km; concentrated over the magnetic poles; rarely visible in southern Britain

 

Miscellaneous
Letter Symbol Description
j   Within Sight - used as a suffix for other phenomena, e.g. pj = shower within sight, but not over the recording station
  within sight near symbol Within Sight and within 5 km - i.e. if the phenomena is 'close' to the station; in this case the symbol means 'rain within sight'
  within sight far symbol Within Sight and beyond 5 km - i.e. if the phenomena is 'far' to the station
  precipitation evaporating symbol Precipitation not reaching the ground - in this case, rain; this is a common occurrence in showery weather when the relative humidity is low, e.g. in cool polar maritime air over Britain, trails of falling rain or snow can be seen beneath clouds, but the air is so dry that they evaporate before touching the surface
e   Wet Air - wet air, but without rain falling
y   Dry Air - relative humidity < 60%
u   Ugly Threatening Sky - e.g. before the onset of a thunderstorm
v   Abnormally good visibility - e.g. over 50 miles
p shower symbol Shower - a relatively short period of precipitation; the type is indicated by additional letters or symbols

 

Surface Wind
Letter Symbol Description
g gale symbol Gale - wind speed averaging between 34 and 47 knots for a period of 10 minutes or more
G storm symbol Storm - wind speed averaging over 47 knots for a period of 10 minutes or more
q squall symbol Squall - a strong wind that rises suddenly and lasts for at least a minute then dies away relatively quickly; an increase of 16 knots to a speed over 22 knots is required
kq line squall symbol Line Squall - as above but occurring along the line of a cold front and accompanied by a roll shaped cloud with a horizontal axis and a sharp fall in temperature