Meteorological Codes for use at Observing Stations codes.pdf · SYNOP CODE WW Present weather (manned station) WW=00-49 No precipitation at the station* at the time of observation

Meteorological Codes for use atObserving Stations

SYNOP CodePresent WeatherPresent Weather Symbols

VisibilityCloud Type

Estimating wind speed using Beaufort CodeThe Construction of the 5-digit SYNOP codeDecode for Buoy observations in SSVX bulletins

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SYNOP CODE

WW Present weather (manned station)

WW=00-49 No precipitation at the station* at the time of observation

WW=00-19 No precipitation, 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 preceeding hour

00 Cloud development not observed or observable }characteristic

Weather Symbols

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01 Clouds dissolving or becoming less developed }state of sky 02 State of sky on the whole unchanged }during the 03 Clouds generally forming or developing }past hour 04 Visibility reduced by smoke haze 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 the wind at or near the station at the time of the observation, but no well-developed dust whirl(s), and no sandstorm seen: or, in the case of ships, 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 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 of } shallow fog or ice fog 12 More or less continuous } less than 2 m on land or 10 m at sea 13 Lightning visible, no thunder heard 14 Precipitation within sight, not reaching the ground or surface of sea 15 Precipitation within sight, reaching 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 19 Funnel cloud(s) or tuba1 } the preceding hour or ) at time of observation

WW=20-29 Precipitation, fog, ice fog or thunderstorm at the station during the preceeding hour but not at the time observation

20 Drizzle (not freezing) or snow grains } 21 Rain (not freezing) } Not 22 Snow } falling 23 Rain and snow or ice pellets } as shower(s) 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)

WW=30-39 Duststorm, sandstorm, drifting or blowing snow

Weather Symbols


30 }Slight or { has decreased during the preceding hour 31 }moderate duststorm { no appreciable change during the preceding hour 32 }or sandstorm { has begun or increased during the preceding hour 33 }Severe { has decreased during the preceding 34 }duststorm { no appreciable change during the preceding hour 35 }or sandstorm { has begun or increased during the preceding hour 36 Slight or moderate drifting snow } Generally low 37 Heavy drifting snow } (below eye level) 38 Slight or moderate blowing snow } Generally high 39 Heavy blowing snow } (above eye level)

WW=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 43 Fog or ice fog, sky obscured } preceding hour 44 Fog or ice fog, sky visible } no appreciable change 45 Fog or ice fog, sky obscured } during the preceding hour 46 Fog or ice fog, sky visible } has begun or has become thicker 47 Fog or ice fog, sky obscured } during the preceding hour 48 Fog or ice fog, sky visible 49 Fog or ice fog, sky obscured

WW=50-59 Drizzle

50 Drizzle, not freezing, intermittent } slight at time 51 Drizzle, not freezing, continuous } of observation 52 Drizzle, not freezing, intermittent } moderate at time 53 Drizzle, not freezing, continuous } of observation 54 Drizzle, not freezing, intermittent } heavy (dense) at time 55 Drizzle, not freezing, continuous } of observation 56 Drizzle, freezing, slight 57 Drizzle, freezing, moderate or heavy (dense) 58 Drizzle and rain, slight 59 Drizzle and rain, moderate or heavy

WW=60-69 Rain

60 Rain, not freezing, intermittent } Slight at time 61 Rain, not freezing, continuous } of observation 62 Rain, not freezing, intermittent } Moderate at time 63 Rain, not freezing, continuous } of observation 64 Rain, not freezing, intermittent } Heavy at time

Weather Symbols


65 Rain, not freezing, continuous } of observation 66 Rain, freezing, slight 67 Rain, freezing, moderate or heavy 68 Rain or drizzle and snow, slight 69 Rain or drizzle and snow, moderate or heavy

WW=70-79 Solid precipitation not in showers

70 Intermittent fall of snowflakes } slight at time 71 Continuous fall of snowflakes } of observation 72 Intermittent fall of snowflakes } moderate at time 73 Continuous fall of snowflakes } of observation 74 Intermittent fall of snowflakes } heavy at time 75 Continuous fall of snowflakes } of observation 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

WW=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 }- slight 88 } with or without rain or rain and snow mixed }- moderate or heavy 89 } Shower(s) of hail, with or without rain or }- slight 90 } rain and snow mixed, not associated with thunder }- moderate or heavy

WW=91-94 Thunderstorm during the preceeding hour but not at time of observation

91 Slight rain at time of observation 92 Moderate or heavy rain at time of observation 93 Slight snow, or rain and snow mixed, or hail2 at time of observation 94 Moderate or heavy snow, or rain and snow mixed, or hail1 at time of observation

WW=95-99 Thunderstorm at time of observation

Weather Symbols


95 Thunderstorm, slight or moderate, without hail2 but with rain and or snow at time of observation 96 Thunderstorm, slight or moderate, with hail2 at time of observation 97 Thunderstorm, heavy, without hail2 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 hail2 at time of observation

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

1 Tornado cloud or waterspout 2 Hail, small hail, snow pellets

Return to Codes Index.

Weather Symbols




SYNOP CODE

WW Present weather (manned station)

WW=00-49 No precipitation at the station* at the time of observation

WW=00-19 No precipitation, 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 preceeding hour

00 Cloud development not observed or observable }characteristic 01 Clouds dissolving or becoming less developed }state of sky 02 State of sky on the whole unchanged }during the 03 Clouds generally forming or developing }past hour 04 Visibility reduced by smoke haze 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 the wind at or near the station at the time of the observation, but no well-developed dust whirl(s), and no sandstorm seen: or, in the case of ships, 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 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 of } shallow fog or ice fog 12 More or less continuous } less than 2 m on land or 10 m at sea 13 Lightning visible, no thunder heard 14 Precipitation within sight, not reaching the ground or surface of sea 15 Precipitation within sight, reaching 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 19 Funnel cloud(s) or tuba1 } the preceding hour or ) at time of observation

WW=20-29 Precipitation, fog, ice fog or thunderstorm at the station during the preceeding hour but not at the time observation

Table 11:

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20 Drizzle (not freezing) or snow grains } 21 Rain (not freezing) } Not 22 Snow } falling 23 Rain and snow or ice pellets } as shower(s) 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)

WW=30-39 Duststorm, sandstorm, drifting or blowing snow

30 }Slight or { has decreased during the preceding hour 31 }moderate duststorm { no appreciable change during the preceding hour 32 }or sandstorm { has begun or increased during the preceding hour 33 }Severe { has decreased during the preceding 34 }duststorm { no appreciable change during the preceding hour 35 }or sandstorm { has begun or increased during the preceding hour 36 Slight or moderate drifting snow } Generally low 37 Heavy drifting snow } (below eye level) 38 Slight or moderate blowing snow } Generally high 39 Heavy blowing snow } (above eye level)

WW=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 43 Fog or ice fog, sky obscured } preceding hour 44 Fog or ice fog, sky visible } no appreciable change 45 Fog or ice fog, sky obscured } during the preceding hour 46 Fog or ice fog, sky visible } has begun or has become thicker 47 Fog or ice fog, sky obscured } during the preceding hour 48 Fog or ice fog, sky visible 49 Fog or ice fog, sky obscured

WW=50-59 Drizzle

50 Drizzle, not freezing, intermittent } slight at time 51 Drizzle, not freezing, continuous } of observation 52 Drizzle, not freezing, intermittent } moderate at time

Table 11:


53 Drizzle, not freezing, continuous } of observation 54 Drizzle, not freezing, intermittent } heavy (dense) at time 55 Drizzle, not freezing, continuous } of observation 56 Drizzle, freezing, slight 57 Drizzle, freezing, moderate or heavy (dense) 58 Drizzle and rain, slight 59 Drizzle and rain, moderate or heavy

WW=60-69 Rain

60 Rain, not freezing, intermittent } Slight at time 61 Rain, not freezing, continuous } of observation 62 Rain, not freezing, intermittent } Moderate at time 63 Rain, not freezing, continuous } of observation 64 Rain, not freezing, intermittent } Heavy at time 65 Rain, not freezing, continuous } of observation 66 Rain, freezing, slight 67 Rain, freezing, moderate or heavy 68 Rain or drizzle and snow, slight 69 Rain or drizzle and snow, moderate or heavy

WW=70-79 Solid precipitation not in showers

70 Intermittent fall of snowflakes } slight at time 71 Continuous fall of snowflakes } of observation 72 Intermittent fall of snowflakes } moderate at time 73 Continuous fall of snowflakes } of observation 74 Intermittent fall of snowflakes } heavy at time 75 Continuous fall of snowflakes } of observation 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

WW=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 }- slight 88 } with or without rain or rain and snow mixed }- moderate or heavy

Table 11:


89 } Shower(s) of hail, with or without rain or }- slight 90 } rain and snow mixed, not associated with thunder }- moderate or heavy

WW=91-94 Thunderstorm during the preceeding hour but not at time of observation

91 Slight rain at time of observation 92 Moderate or heavy rain at time of observation 93 Slight snow, or rain and snow mixed, or hail2 at time of observation 94 Moderate or heavy snow, or rain and snow mixed, or hail1 at time of observation

WW=95-99 Thunderstorm at time of observation

95 Thunderstorm, slight or moderate, without hail2 but with rain and or snow at time of observation 96 Thunderstorm, slight or moderate, with hail2 at time of observation 97 Thunderstorm, heavy, without hail2 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 hail2 at time of observation

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

1 Tornado cloud or waterspout 2 Hail, small hail, snow pellets


Table 11:




DECODE FOR METEOROLOGICAL DATA IN BUOY OBSERVATIONSWMO CODE FM 18-X BUOY

The header SSVX identifies bulletins of observations coded in FM 18-X.Note: This code form replaced the former FM 18-IX Ext DRIFTER code.

Observations from buoys similar to observations from ships are encoded in theSHIP code, FM 12 or FM 13, and are included in bulletins headed SMV/, SIV/ etc.

For a full decode please refer to the WMO Manual on Codes, Volume I.1 Part A: Alphanumeric codesWMO Publication No 306, available from: The WMO Secretariatat PO Box 2300, CH-1211 Geneva 2, Switzerland, price Sw Fr 130.- (February 1998)

The following Sections are only included if there are data available SECTION 0 Identification, time and position data MiMiMjMj A1bwnbnbnb YYMMJ GGggiw QcLaLaLaLaLa LoLoLoLoLoLo (6QiQt//)

SECTION 1 Meteorological and other non-marine data (111QdQx 0ddff 1snTTT 2snTdTdTd OR 29UUU 3P0P0P0P0 4PPPP 5appp

SECTION 2 Surface marine data (222QdQx 0snTwTwTw 1PwaPwaHwaHwa ..... .....

SECTION 3 Temperatures, salinity and current (when available) at selected depths 333Qd1Qd2 ..... .....

SECTION 4 Information on engineering and technical parameters including quality control data) 444 (1QpQ2QTwQ4) ..... .....

INTERPRETATION

SECTION 0 (Identification, time and position data)

MiMiMjMj Always coded as ZZYY

A1bwnbnbnb The buoy number or identifier

A1bw The WMO Region and sub-region in which the

buoy was deployed, eg 62 includes the seas around the UK and to the west and south-west of the British Isles. nbnbnb Type and serial number of the buoy (500 is added to

the serial number when the buoy is a drifting buoy)

YYMMJ YY Date MM Month J Last digit of the year

Decode for Buoy observations in SSVX bulletins

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GGggiw GGgg Time of the observation

iw Indicator for source and units of wind speed

0 or 1: Wind speed metres/sec; 3 or 4: Wind speed knots

QcLaLaLaLaLa Qc Quadrant of the globe

N hemisphere: 7 is degrees West, 1 is degrees East S hemisphere: 5 is degrees West, 3 is degrees East LaLaLaLaLa Latitude (eg 54126 decoded as 54.126 degrees, 54.12/

decoded as 54.12 degrees and 541// as 54.1 degrees)

LoLoLoLoLoLo Longitude (eg 132463 decoded as 132.463 degrees, 05621/

decoded as 56.21 degrees, and 1458// as 145.8 degrees

(6QiQt//) Quality control indicators (see WMO Manual on Codes)

SECTION 1 (Meteorological and other non-marine data)

111QdQx Quality control indicators for the section

0ddff 0 Indicator dd Wind direction in tens of degrees ff Wind speed in knots or m/s

1snTTT 1 Indicator

sn Sign of temperature - 0: positive or zero, 1: negative

TTT Dry-bulb temperature in tenths of a degree Celsius

2snTdTdTd 2 Indicator

sn Sign of temperature

TdTdTd Dew-point temperature in tenths of a degree Celsius

OR

29UUU 2 Indicator 9 Relative humidity follows UUU Relative humidity expressed as a percentage: first figure zero except when UUU is 100 percent

3P0P0P0P0 3 Indicator

P0P0P0P0 Pressure at station level, in tenths

of a millibar, omitting the thousands digit

4PPPP 4 Indicator PPPP Mean sea level pressure, in tenths of a millibar, omitting the thousands digit

5appp 5 Indicator



a Characteristic of pressure change ppp Pressure change over last three hours in tenths of a millibar

Created by MWS: 15th February 1998





SYNOP CODE

VV Horizontal visibility at surface

Code km m Code km m Code km m Code km Code km mfigure figure figure figure figure

00 <0.1 <100 20 2.0 2000 40 4.0 4000 60 10 80 30 01 0.1 100 21 2.1 2100 41 4.1 4100 61 11 81 35 02 0.2 200 22 2.2 2200 42 4.2 4200 62 12 82 40 03 0.3 300 23 2.3 2300 43 4.3 4300 63 13 83 45 04 0.4 400 24 2.4 2400 44 4.4 4400 64 14 84 50 05 0.5 500 25 2.5 2500 45 4.5 4500 65 15 85 55 06 0.6 600 26 2.6 2600 46 4.6 4600 66 16 86 60 07 0.7 700 27 2.7 2700 47 4.7 4700 67 17 87 65 08 0.8 800 28 2.8 2800 48 4.8 4800 68 18 88 70 09 0.9 900 29 2.9 2900 49 4.9 4900 69 19 89 >70 10 1.0 1000 30 3.0 3000 50 5.0 5000 70 20 90 <0.05 <50 11 1.1 1100 31 3.1 3100 51 71 21 91 0.05 50 12 1.2 1200 32 3.2 3200 52 72 22 92 0.2 200 13 1.3 1300 33 3.3 3300 53 not used 73 23 93 0.5 500 14 1.4 1400 34 3.4 3400 54 74 24 94 1 1000 15 1.5 1500 35 3.5 3500 55 75 25 95 2 2000 16 1.6 1600 36 3.6 3600 56 6 76 26 96 4 4000 17 1.7 1700 37 3.7 3700 57 7 77 27 97 10 18 1.8 1800 38 3.8 3800 58 8 78 28 98 20 19 1.9 1900 39 3.9 3900 59 9 79 29 99 >=50

Notes

: (1) If the visibility is between two of the distances given in the table, the code figure for the lower distance is reported e.g. a

Synop Visibility Code:

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visibility of 470 m is reported as 04 (2) When VV=00 the actual visibility is reported by the extra group 1V'f'/V'f'f' in Section 5


Synop Visibility Code:

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SYNOP CODE

CL, CM, CH Cloud Type Codes

Table 13: CL Form of Low Cloud

Codefigure

0 No Stratocumulus, Stratus, Cumulus or Cumulonimbus

1 Cumulus with little vertical extent and seemingly flattened, or ragged Cumulus other than of bad weather*, or both

2 Cumulus of moderate or strong vertical extent, generally with protuberances in the form of domes or towers, either accompanied or not by other Cumulus or by Stratocumulus, all having their bases at the same level

3 Cumulonimbus the summits of which, at least partially, lack sharp outlines, but are neither clearly fibrous (cirriform) nor in the form of an anvil; Cumulus, Stratocumulus or Stratus may also be present

4 Stratocumulus formed from the spreading out of Cumulus; Cumulus may also be present

5 Stratocumulus not formed from the spreading out of Cumulus

6 Stratus in a more or less continuous sheet or layer, or in ragged shreds, or both, but no Stratus fractus of bad weather*

7 Stratus fractus of bad weather* or Cumulus fractus of bad weather or both (pannus), usually below Altostratus or Nimbostratus

8 Cumulus and Stratocumulus other than that formed from the spreading out of Cumulus; the base of the Cumulus is at a different level from that of the Stratocumulus

9 Cumulonimbus, the upper part of which is clearly fibrous (cirriform), often in the form of an anvil; either accompanied by Cumulonimbus without anvil or fibrous upper part, by Cumulus, Stratocumulus, Stratus or pannus

0 Stratocumulus, Stratus, Cumulus and Cumulonimbus invisible owing to

Synop Cloud Type Code:

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darkness, fog,blowing snow, dust or sand, or other similar phenomena

* ‘Bad weather’ denotes the conditions which generally exists during precipitation and a short time before and after.

Table 14: CM Form of Medium Cloud

Codefigure

0 No Altocumulus, Altostratus or Nimbostratus

1 Altostratus, the greater part of which is semi-transparent; through this part the sun or moon may be weakly visible - as through ground glass

2 Altostratus, the greater part of which is sufficiently dense to hide the sun or moon, or Nimbostratus

3 Altocumulus, the greater part of which is semi-transparent; the various elements of the cloud change only slowly and are all at a single level

4 Patches (often in the form of almonds or fishes) of Altocumulus, the greater part of which is semi-transparent; the clouds ocurr at one or more levels and the elements are continually changing in appearance

5 Semi-transparent Altocumulus in bands, or Altocumulus in one or more fairly continuous layers (semi-transparent or opaque), progressively invading the sky; these Altocumulus clouds generally thicken as a whole

6 Altocumulus resulting from the spreading out of Cumulus (or Cumulonimbus)

7 Altocumulus in two or more layers, usually opaque in places, and not progressively invading the sky; or opaque layer of Altocumulus, not progressively invading the sky; or Altocumulus together with Altostratus or Nimbostratus

8 Altocumulus with sproutings in the form of small towers or battlements, or Altocumulus having the appearance of cumuliform tufts

9 Altocumulus of a chaotic sky, generally at several levels

/ Altocumulus, Altostratus and Nimbostratus invisible owing to darkness, fog,blowing snow, dust or sand, or other similar phenomena, or more often because of the presence of a continuous layer of lower clouds

Table 15: CH Form of High Cloud

Codefigure



0 No Cirrus, Cirrocumulus or Cirrostratus

1 Cirrus in the form of filaments, strands or hooks, not progressively invading the sky

2 Dense Cirrus, in patches or entangled sheaves, which usually do not increase and sometimesseem to be the remains of the upper part of a Cumulonimbus; or Cirrus with sproutings in the form of small turrets or battlements, or Cirrus having the appearance of cumuliform tufts

3 Dense Cirrus, often in the form of an anvil, being the remains of the upper parts of Cumulonimbus

4 Cirrus in the form of hooks or filaments, or both, progressively invading the sky; they generally become denser as a whole

5 Cirrus (often in bands converging towards one point or two opposite points of the horizon) and Cirrostratus, or Cirrostratus alone; in either case they are progressively invading the sky, and generally growing denser as a whole, but the continuous veil does not reach 45 degrees above the horizon

6 Cirrus (often in bands converging towards one point or two opposite points of the horizon) and Cirrostratus, or Cirrostratus alone; in either case they are progressively invading the sky, and generally growing denser as a whole, the continuous veil extends more than 45 degrees above the horizon, without the sky being totally covered

7 Veil of Cirrostratus covering the celestial dome

8 Cirrostratus not progressively invading the sky and not completely covering the celestial dome

9 Cirrocumulus alone, or Cirrocumulus accompanied by Cirrus or Cirrostratus, or both, but Cirrocumulus is predominant

/ Cirrus, Cirrocumulus or Cirrostratus invisible owing to darkness, fog,blowing snow, dust or sand, or other similar phenomena, or more often because of the presence of a continuous layer of lower clouds

Persistent aircraft condensation trails and clouds formed from them are reported as cloud using the appropriate CH code figure. Rapidly dissipating condensation trails are not reported.

Table 19: C Type of Cloud

Codefigure

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 Cumulus9 Cumulonimbus (Cb)/ Cloud not visible owing to darkness, fog, duststorm, sandstorm, or other analogous phenomena





THE BEAUFORT WIND SCALE

One of the first scales to estimate wind speeds and the effects wascreated by Britain's Admiral Sir Francis Beaufort (1774-1857). Hedeveloped the scale in 1805 to help sailors estimate the winds viavisual observations. The scale starts with 0 and goes to a force of 12.The Beaufort scale is still used today to estimate wind strengths.

The Beaufort scale:

For use on land

For use at sea

BEAUFORT SCALE: Specifications and equivalentspeeds for use on landFORCE EQUIVALENT SPEED DESCRIPTION SPECIFICATIONS FOR USE ON LAND 10 m above ground miles/hour knots0 0-1 0-1 Calm Calm; smoke rises verticall.1 1-3 1-3 Light air Direction of wind shown by smoke drift, but not by wind vanes.2 4-7 4-6 Light Breeze Wind felt on face; leaves rustle; ordinary vanes moved by wind.3 8-12 7-10 Gentle Breeze Leaves and small twigs in constant motion; wind extends light flag.4 13-18 11-16 Moderate Breeze Raises dust and loose paper; small branches are moved.5 19-24 17-21 Fresh Breeze Small trees in leaf begin to sway; crested wavelets form on inland waters.6 25-31 22-27 Strong Breeze Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty.7 32-38 28-33 Near Gale Whole trees in motion; inconvenience felt when walking against the wind.8 39-46 34-40 Gale Breaks twigs off trees; generally impedes progress.9 47-54 41-47 Severe Gale Slight structural damage occurs

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(chimney-pots and slates removed).10 55-63 48-55 Storm Seldom experienced inland; trees uprooted; considerable structural damage occurs.11 64-72 56-63 Violent Storm Very rarely experienced; accompanied by wide-spread damage.12 73-83 64-71 Hurricane --

For use on land

For use at sea Top of page

BEAUFORT SCALE: Specifications and equivalentspeeds for use at seaFORCE EQUIVALENT SPEED DESCRIPTION SPECIFICATIONS FOR USE AT SEA 10 m above ground miles/hour knots0 0-1 0-1 Calm Sea like a mirror1 1-3 1-3 Light air Ripples with the appearance of scales are formed, but without foam crests.2 4-7 4-6 Light Breeze Small wavelets, still short, but more pronounced. Crests have a glassy appearance and do not break.3 8-12 7-10 Gentle Breeze Large wavelets. Crests begin to break. Foam of glassy appearance. Perhaps scattered white horses.4 13-18 11-16 Moderate Breeze Small waves, becoming larger; fairly frequent white horses.5 19-24 17-21 Fresh Breeze Moderate waves, taking a more pronounced long form; many white horses are formed. Chance of some spray.6 25-31 22-27 Strong Breeze Large waves begin to form; the white foam crests are more extensive everywhere. Probably some spray.7 32-38 28-33 Near Gale Sea heaps up and white foam from breaking waves begins to be blown in streaks along the direction of the wind.8 39-46 34-40 Gale Moderately high waves of greater length; edges of crests begin to breakinto spindrift. The foam is blown in well-marked streaks


along the direction of the wind.9 47-54 41-47 Severe Gale High waves. Dense streaks of foam along the direction of the wind. Crests of waves begin to topple, tumble and roll over. Spray may affect visibility.10 55-63 48-55 Storm Very high waves with long over- hanging crests. The resulting foam, in great patches, is blown in dense white streaks along the direction of the wind. On the whole the surface of the sea takes on a white appearance. The 'tumbling' of the sea becomes heavy and shock-like. Visibility affected.11 64-72 56-63 Violent Storm Exceptionally high waves (small and medium-size ships might be for a time lost to view behind the waves). The sea is completely covered with long white patches of foam lying along the direction of the wind. Everywhere the edges of the wave crests are blown into froth. Visibility affected.12 73-83 64-71 Hurricane The air is filled with foam and spray. Sea completely white with driving spray; visibility very seriously affected.

For use on land

For use at sea Top of page

Extracted from the Observers Handbook, Met Office




SYNOP CODE

SECTION 0 iii iRixhVV

SECTION 1 Nddff 1snTTT 2snTdTdTd 4PPPP 5appp 6RRRtR 7wwW1W2 8NhCLCMCH

SECTION 3333 1snTxTxTx (at 1800 UTC) 2snTnTnTn (at 0600 UTC) 3EsnTgTg (at 0600 UTC) 4E'sss (at 0600 UTC) 8NsChshs 9SpSpspsp

SECTION 5555 1V'f'/V'f''f'' 2snTwTwTw iiirrr

Interpretation

SECTION 0iii Station Number

iRixhVV iR Inclusion or omission of precipitation data (Table 1) ix Inclusion or omission of weather group (Table 2) h Height of base of lowest cloud (Table 3) VV Horizontal visibility (Table 4)

SECTION 1Nddff N Total Cloud amount (Table 5) dd Wind direction in tens of degrees (Table 6) ff Wind speed in knots (Table 7)

1snTTT 1 Indicator sn Sign of temperature (Table 8) TTT Dry-bulb temperature in tenths of a degree Celsius

2snTdTdTd 2 Indicator sn Sign of temperature (Table 8) TdTdTd Dew-point temperature in tenths of a degree Celsius

4PPPP 4 Indicator PPPP Last four figs. of air pressure (reduced to mean sea level) inmillibars and tenths

5appp 5 Indicator a Characteristic of pressure change (Table 9) ppp Pressure change over last three hours in millibars and tenths

6RRRtR 6 Indicator RRR Amount of rainfall (Table 10) tR Duration of period of RRR in units of six hours. Main hours only At 0001 and 1200 UTC tR=1 At 0600 and 1800 tR=2

Synop Code

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7wwW1W2 7 Indicator ww Present weather, manned station (Table 11) W1W2 Past weather, manned station (Table 22)

8NhCLCMCH 8 Indicator Nh Amount of low cloud, or medium cloud if no low cloud present(Table 5) CL Form of low cloud (Table 13) CM Form of medium cloud (Table 14) CH Form of high cloud (Table 15)

SECTION 3333 Regional Indicator1snTxTxTx 1 Indicator sn Sign of temperature (Table 8) TxTxTx Maximum temperature 0600-1800 UTC in tenths of a degree

2snTnTnTn 2 Indicator sn Sign of temperature (Table 8) TnTnTn Minimum temperature 1800-0600 UTC in tenths of a degree

3EsnTgTg 3 Indicator E State of ground without snow or measurable ice cover (Table 16) sn Sign of temperature (Table 8) TgTg Grass minimum temperature rounded to nearest whole degree

4E'sss 4 Indicator E' State of ground with snow or measurable ice cover (Table 17) sss Depth of snow (Table 18)

8NsChshs 8 Indicator Ns Amount of individual cloud layer (Table 5) C Form of cloud(Table 19) hshs Height of base of cloud layer (Table 20)

Up to four layers of significant cloud can be reported (using 8NhChshs groups).The rules for the selection of significant cloud layers are:

1. The lowest layer of any amount 2. The next lowest layer of 3 oktas (eighths) or more. 3. The next lowest layer of 5 oktas or more. 4. Any cumulonimbus cloud not already reported under 1, 2 or 3 above, regardless of amount.

Clouds are reported in order of ascending height.Cumulonimbus cloud reported under rule 4 above would be inserted between theother groups at its correct height level - regardless of the amount ofCumulonimbus being reported.

9SpSpspsp 9 Indicator This group is included when necessary to report specialphenomena.

Synop Code


SECTION 5555 National indicator (This section is not sent when there are no datato report)1V'f'/V'f''f'' 1 Indicator V'V' Visibility in metres (reported when visibility is less than100 m) (f')f'f' Speed in knots of the maximum gust in the past hour(>33 kts)

2snTwTwTw 2 Indicator sn Sign of temperature (Table 8) TwTwTw Sea temperature in tenths of a degree

CODE TABLES

Table 1:iR Indicator for inclusion or omission of precipitation data

CodeFigure Precipitation data are reported: Group 6RRRtR is:1 in Section 1 included2 in Section 3 included3 in none of the two Sections 1 and 3 omitted (precipitation amount =0)4 in none of the two Sections 1 and 3 omitted (precipitation amount notavailable)

Note: UK practice only, code figures 1,3 and 4 to be used

Table 2:ix Indicator for type of station operation (manned or automatic) and for present and past weatherCodefigure Type of station operation Group 7wwW1W2 or 7wawaWa1Wa2 is:1 manned included2 manned omitted (no significant phenomena to report)3 manned omitted (not observed, data not available


Synop Code




Documents

Meteorological Codes for use at Observing Stations codes.pdf · SYNOP CODE WW Present weather (manned station) WW=00-49 No precipitation at the station* at the time of observation