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Fronts (types)

Cloud Cover

High Clouds : type CH

Middle Clouds : type CM

Low Clouds : type CL

Plotted Station (surface analysis)

Plotted Station (upper air analysis)

Significant Weather Prog

Visibility code vs kilometers  (VV)

Weather Symbols used to illustrate the weather  (ww)

Winds

Plotted Station (surface analysis)

sfcplot.gif (2721 octets) CH High Cloud type
CM Middle Cloud type
CL Low Cloud type
N Cloud Cover (portion of the sky covered)
PPP Atmospheric pressure. The pressure is indicated in millibars but only the last three digits are shown. For example, a pressure of 1002.1 will be indicated as 021 whereas a pressure of 1021.1 will be indicated as 211.
PP Indicate the pressure change since the last observation (in millibars).
a Graphical representation of the pressure change
ww Present Weather when the observation is taken
w Past Weather in the past hour at the time of the observation
VV Visibility Code vs kilometers).
TdTd Dew Point (in degrees Celsius).
TT Air Temperature (in degrees Celsius).
station_ex.gif (2017 octets)

Example

Overcast, with an air temperature of 24 degrees Celsius, dew point of 21 degrees Celsius. The wind was from the north-east between 10 and 14 knots. The pressure was 1003.8 millibars decreasing (\) of 1.1 millibars in the last 3 hours (1 1 on the chart). Rain showers with low clouds which were Stratus, the visibility was reduced to less than one kilometre. In the preceding hour of the observation, fog was the weather.

Plotted Station (upper air analysis)

upperplot.gif (1306 octets) hh Height of pressure level in decametres
h2h2 Thickness between two pressure levels (decametres). ex. 500 -1000 mb thickness
TT Air Temperature (in degrees Celsius)
DD Temperature - Dew Point Spread  (in degrees Celsius)
ddd Wind Direction (in tens of degrees)
ff Wind speed (in knots)

Significant Weather Prog

turbmod.gif (91 octets) moderate turbulence
turbsev.gif (114 octets) severe turbulence
turbmod.gif (91 octets)--turbsev.gif (114 octets)cat.gif (1084 octets) moderate to severe turbulence in Clear Air above 10000 feet
icgmod.gif (133 octets) moderate icing
icgsev.gif (134 octets) severe icing

 

Spatial or Time Description Qualitative description for Clouds
Convective Clouds type(s) Convective Clouds tops
format used for convective cloud description
few.gif (1215 octets) few TCU / ACC embedded with tops at 18000 feet
nmrs.gif (1357 octets) numerous TCU / ACC embedded with tops at 24000 feet

 

Cloud Cover in oktas  Cloud Convective Description Top
Base
format used for cloud description
lyr16-18.gif (1205 octets) 6 oktas of cloud in layers with base lower than 10000 feet (or 700 mb) and tops from 16000 to 20000 feet
lyr12-18.gif (1111 octets) 6 oktas of cloud in layers with base at 12000 feet and tops at 18000 feet
ns.gif (1116 octets) 8 oktas of Nimbostratus cloud type with base lower than 10000 feet and tops at 22000 feet

Types of Fronts

ftcold.gif (1122 octets) cold front
ftwarm.gif (1144 octets) warm front
ftstat.gif (1120 octets) stationnary front
ftocclu.gif (1115 octets) occluded front
trowal.gif (1013 octets) Trough of warm air aloft  (TROWAL)

Examples of Symbols used to illustrate the weather  (ww)

61.gif (180 octets) rain 79.gif (331 octets) ice pellets
51.gif (166 octets) drizzle 89.gif (329 octets) hail
80.gif (296 octets) rain shower 5.gif (334 octets) haze
66.gif (382 octets) freezing rain 10.gif (173 octets) mist
71.gif (240 octets) snow 45.gif (185 octets) fog
85.gif (337 octets) snow shower 49.gif (319 octets) fog, depositing rime
82.gif (294 octets) heavy rain shower 17.gif (294 octets) thunderstorm
18.gif (359 octets) squalls 97.gif (403 octets) thunderstorm, heavy, with rain and/or snow
87.gif (347 octets) ice pellets (shower) 99.gif (379 octets) thunderstorm, heavy, with hail
13.gif (261 octets) lightning    

Winds

ws0.gif (1007 octets) less than 5 knots ws30.gif (975 octets) 30 to 34 knots
ws5.gif (955 octets) 5 to 9 knots ws35.gif (993 octets) 35 to 39 knots
ws10.gif (951 octets) 10 to 14 knots ws40.gif (1003 octets) 40 to 44 knots
ws15.gif (976 octets) 15 to 19 knots ws50.gif (888 octets) 50 to 54 knots
ws20.gif (980 octets) 20 to 24 knots ws70.gif (914 octets) 70 to 74 knots
ws25.gif (982 octets) 25 to 29 knots ws105.gif (924 octets) 105 to 110 knots and so on

Cloud Cover

  in oktas (/ 8) in tenths (/ 10)
n0.gif (371 octets) no clouds
n1.gif (454 octets) 1 okta or less 1 tenth or less but with a presence of cloud
n2.gif (409 octets) 2 oktas 2 or 3 tenths
n3.gif (444 octets) 3 oktas 4 tenths
n4.gif (392 octets) 4 oktas 5 tenths
n5.gif (394 octets) 5 oktas 6 tenths
n6.gif (345 octets) 6 oktas 7 or 8 tenths
n7.gif (361 octets) 7 oktas or more but not 8 9 tenths or more but not 10
n8.gif (285 octets) completely overcast
n9.gif (476 octets) Sky completely obscured by a layer at the surface or by a phenomenon with a base not at the surface

High Clouds : type CH

ch1.gif (248 octets) CI (cirrus) in the form of filaments, strands, or hooks, not progressively invading the sky
ch2.gif (262 octets) dense Ci, in patches or entangled sheaves, which usually do not increase
ch3.gif (239 octets) dense Ci, often in the form of an anvil, being the remains of the upper parts of  Cb (cumulonimbus)
ch4.gif (261 octets) Ci  in the form of hooks or of filaments, or both, progressively invading the sky
ch5.gif (236 octets) Ci and Cs (CirroStratus) or Cs 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
ch6.gif (275 octets) Ci and Cs or Cs 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
ch7.gif (300 octets) veil of Cs covering the celestial dome
ch8.gif (240 octets) Cs not progressively invading the sky and not completely covering the celestial dome, Ci and Cc (CirroCumulus) may be present
ch9.gif (418 octets) Cc alone, or Cc accompanied by Ci or Cs, or both, but Cc is predominant

Middle Clouds : type CM

cm1.gif (281 octets) As (AltoStratus), the greater part of which is semi-transparent; through this part the sun or moon may be weakly visible, as through ground glass.
cm2.gif (321 octets) As, the greater part of which is sufficiently dense to hide the sun or moon, or Ns (NimboStratus)
cm3.gif (314 octets) Ac (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 mince
cm4.gif (318 octets) patches (often in the form of almonds or fishes) of Ac, the greater part of which is semi-transparent; the clouds occur at one or more levels and the elements are continually changing in appearance
cm5.gif (399 octets) semi-transparent Ac in bands, or Ac in one or more fairly continuous layers (semi-transparent or opaque), progressively invading the sky; these altocumulus clouds generally thicken as a whole
cm6.gif (430 octets) Ac resulting from the spreading out of Cu (Cumulus)
cm7.gif (391 octets) Ac in two or more layers, usually opaque in places, and not progressively invading the sky; or opaque layer of Ac, not progressively invading the sky; or Ac together with As
cm8.gif (488 octets) Ac with sproutings in the form of small towers or battlements; or altocumulus having the appearance of cumuliform tufts
cm9.gif (425 octets) Ac of a chaotic sky, generally at several levels

Low Clouds : type CL

cl1.gif (359 octets) Cu (Cumulus) with little vertical extent and seemingly flattened
cl2.gif (416 octets) Cu 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 base at the same level.
cl3.gif (467 octets) Cb (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
cl4.gif (336 octets) Sc (StratoCumulus) formed by the spreading out of cumulus; cumulus may also be present
cl5.gif (247 octets) Sc not resulting from the spreading out of cumulus
cl6.gif (189 octets) St (Stratus) or Sf (Stratus Fractus)  in a more or less continuous sheet or layer, or in ragged shreds, or both, but no stratus fractus of bad weather
cl7.gif (196 octets) Sf (stratus Fractus) of bad weather or cumulus fractus of bad weather, or both (pannus), usually below altostratus or nimbostratus
cl8.gif (359 octets) Cu and Sc 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
cl9.gif (413 octets) Cb cumulonimbus, the upper part of which is clearly fibrous (cirriform), often in the form of an anvil; either accompanied or not by cumulonimbus without anvil or fibrous upper part, by cumulus, stratocumulus, stratus, or pannus

Horizontal Visibility Code vs Kilometers  (VV)

Code Km Code Km Code Km
00 : 0 32 : 3.2 67 : 17.6
02 : 0.2 36 : 3.6 69 : 19.2
04 : 0.4 40 : 4 70 : 20.8
06 : 0.6 48 : 4.8 72 : 22.4
08 : 0.8 56 : 6.4 74 : 24
10 : 1 58 : 8 80 : 30.4
12 : 1.2 59 : 9.6 82 : 40
16 : 1.6 61 : 11.2 83 : 44.8
20 : 2.0 62 : 12.8 85 : 56
24 : 2.4 64 : 14.4 86 : 60.8
28 : 2.8 66 : 16 89 : greater than 70.4

 

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Weather data provided by Environment Canada and NAV CANADA