Meteorology

To allow you to interpret weather information and assess the actual weather occurring and make decisions based on what you see.

The Met Office Learning Centre

The Met Office Interpreting weather maps

The Met Office Weather charts

The Met Office Guide to Weather Chart Symbols

The Met Office Weather abbreviations

The Met Office have information on Air masses and fronts

Metar - Explanation

The Metar report for Southend will look something like the list below.

SOUTHEND EGMC 032250Z 01008KT 5000 -DZ BR BKN005 08/06 Q1028

Name of Airport Location Indicator Date & Time Wind Visibility Present Weather Cloud Temperature & Dew Point QNH
Self explanatory EGMC is the ICAO indicator
for Southend
Date & Time
03 - Date
2250Z
10.50pm zulu or UTC time
Wind Direction & Speed
010degrees/08 Knots
Visibilty
0000 = 'less than 50 metres'
9999 = 'ten kilometres or more'.
No direction is required.
DZ=Drizzle
BR=Mist

See list below
BKN=Broken
005 = 500feet


See list below
Temperature & Dew Point

M indicates a negative value
M003/M002
QNH
Q indicates the sea level pressure millibars.
If the letter A is used QNH is in inches and hundredths.

 

Present Weather
+ = Heavy (well developed in the case of +FC and +PO); - = Light; no qualifier = Moderate.
BC=Patches BL=Blowing BR=Mist DR=Drifting
DS=Duststorm DU=Dust DZ=Drizzle FC=Funnel cloud
FG=Fog FU=Smoke FZ=Freezing GR=Hail (>5mm)
GS=Small hail or snow pellets HZ=Haze IC=Ice crystals MI=Shallow
PL=Ice pellets PO=Dust devils PR=Banks RA=Rain
SA=Sand SH=Showers SG=Snow grains SN=Snow
SQ=Squalls SS=Sandstorm TS=Thunderstorm VA=Volcanic ash
VC=In vicinity      
Up to three groups may be present, constructed by selecting and combining from the above. Group omitted if no weather to report.

 

Cloud
SKC=Sky clear (0 oktas) FEW='few' (1-2 oktas) SCT='Scattered' (3-4 oktas) BKN='Broken' (5-7 oktas) OVC='Overcast'.
There are only two cloud types reported; TCU=towering cumulus and CB=cumulonimbus. VV///='state of sky obscured' (cloud base not discernable): Figures in lieu of '///' give vertical visibility in hundreds of feet. Up to three, but occasionally more, cloud groups may be reported.

Cloud heights are given in feet above airfield height

 

CAVOK

Visibility greater or equal to 10 km, no cumulonimbus, no cloud below 5000 ft or highest MSA (greater) and no weather significant to aviation.

 

Trends
ExampleExplanationFurther info
BECMG FM1100 23035G50KT TEMPO FM0630 TL 0830 3000 SHRA 'becoming from 1100, 230 degrees 35 KT , max 50 KT, temporarily from 0630 until 0830, 3000 metres, Moderate rain shower's
BECMG=Becoming TEMPO=Temporarily NOSIG=No sig change
NSW=No sig weather AT=At FM=From
TL=Until NSC=No sig cloud  
Any of the wind forecast, visibility, weather or cloud groups may be used, and CAVOK. Multiple groups may be present.

*CAVOK will replace visibility and cloud groups

Dew point - The temperature at which the air, when cooled, will just become saturated.

Hoar frost is composed of tiny ice crystals and is formed by the same process as dew, but when the temperature of the surface falls below freezing point.

Water drops larger than 0.5 mm in diameter are classed as rain.

Precipitation will fall as snow when the air temperature is below 2 C.

The official definition of fog is a visibility of less than 1,000 metres.


Military Aerodrome colour codes

In addition to a normal TAF or METAR, military aerodromes may use a colour code, which is a form of shorthand for their crews to reinforce the information in the main message. The meaning of each colour is listed below. PPL holders without instrument qualifications are advised that any code except "blue" or "white" may indicate serious problems, and even "white" is no guarantee that the weather is good, even at the time of the report.

Colour Code

Minimum base of lowest cloud
(SCT or more)above aerodrome level

Minimum reported visibility

Blue

2500 feet

8km

White

1500 feet

5km

Green

700 feet

3700 m

Amber

200 feet

800 m

Red

Below 200 feet (or sky obscured)

below 800 m

Black

Aerodrome unavailable for reasons other than cloud or visibilty