4/20/23 

AIM 

(c)  (Type). 

If Towering Cumulus Clouds (TCU) or Cumulonimbus Clouds (CB) are present, they are 

reported after the height which represents their base. 

EXAMPLE

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(Reported as) SCT025TCU BKN080 BKN250 (spoken as) “TWO THOUSAND FIVE HUNDRED SCATTERED 

TOWERING CUMULUS, CEILING EIGHT THOUSAND BROKEN, TWO FIVE THOUSAND BROKEN.” 

(Reported as) SCT008 OVC012CB (spoken as) “EIGHT HUNDRED SCATTERED CEILING ONE THOUSAND TWO 

HUNDRED OVERCAST CUMULONIMBUS CLOUDS.” 

(d)  Vertical Visibility (indefinite ceiling height). 

The height into an indefinite ceiling is preceded by 

“VV” and followed by three digits indicating the vertical visibility in hundreds of feet. This layer indicates total 

obscuration. 

EXAMPLE

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1

/

8 

SM FG VV006 

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 visibility one eighth, fog, indefinite ceiling six hundred. 

(e)  Obscurations

 are reported when the sky is partially obscured by a ground

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based phenomena by 

indicating the amount of obscuration as FEW, SCT, BKN followed by three zeros (000). In remarks, the 

obscuring phenomenon precedes the amount of obscuration and three zeros. 

EXAMPLE

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BKN000 (in body)  . . . . . . . .  “sky partially obscured” 

FU BKN000 (in remarks) . . .  “smoke obscuring five

−

 to seven

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eighths of the sky” 

(f) 

When sky conditions include a layer aloft, other than clouds, such as smoke or haze the type of 

phenomena, sky cover and height are shown in remarks. 

EXAMPLE

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BKN020 (in body) 

. . . . . . . .  

“ceiling two thousand broken” 

RMK FU BKN020  . . . . . . . .  “broken layer of smoke aloft, based at two thousand” 

(g)  Variable ceiling. 

When a ceiling is below three thousand and is variable, the remark “CIG” will be 

shown followed with the lowest and highest ceiling heights separated by a “V.” 

EXAMPLE

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CIG 005V010  . . . . . . . . . . . .  “ceiling variable between five hundred and one thousand” 

(h)  Second site sensor. 

When an automated station uses meteorological discontinuity sensors, remarks 

will be shown to identify site specific sky conditions which differ and are lower than conditions reported in the 

body. 

EXAMPLE

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CIG 020 RY11  . . . . . . . . . . .  “ceiling two thousand at runway one one” 

(i)  Variable cloud layer. 

When a layer is varying in sky cover, remarks will show the variability range. 

If there is more than one cloud layer, the variable layer will be identified by including the layer height. 

EXAMPLE

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SCT V BKN  . . . . . . . . . . . . .  “scattered layer variable to broken” 

BKN025 V OVC  . . . . . . . . .  “broken layer at two thousand  five hundred variable to overcast” 

(j)  Significant clouds. 

When significant clouds are observed, they are shown in remarks, along with the 

specified information as shown below: 

(1) 

Cumulonimbus (CB), or Cumulonimbus Mammatus (CBMAM), distance (if known), direction 

from the station, and direction of movement, if known. If the clouds are beyond 10 miles from the airport, DSNT 

will indicate distance. 

EXAMPLE

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CB W MOV E . . . . . . .   “cumulonimbus west moving east” 

CBMAM DSNT S  . . . .   “cumulonimbus mammatus distant south” 

(2) 

Towering Cumulus (TCU), location, (if known), or direction from the station. 

EXAMPLE

−

 

TCU OHD  . . . . . . . . .   “towering cumulus overhead” 

TCU W  . . . . . . . . . . . .   “towering cumulus west” 

Meteorology 

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