9 Meteorology

METAR

Interpreting METARs and TAFs is a very important activity in the life of a pilot and controller, and this explanation will be prove that this task is not at all as daunting as it may seem.

There is more information at IVAO HQ under the Training department and our South African weather website .

The following is an example of a METAR, a surface observation, from O.R. Tambo International airport, Johannesburg. Just click on any of the cells to go to the help dealing with that particular section. For the actual current weather in our division, go here .

Type ID Time Wind Vis Wx Sky T/TD Altimeter Remark
METAR FAJS 091800Z 19020G26KT 5000 +SHRA BKN070 12/08 Q1027 BECMG CAVOK

 

METAR –           Type

METAR is the scheduled observation taken at the end of each half hour or hour.

SPECI is an observation taken at an unscheduled time due to certain criteria that is met such as low visibility, low clouds, frozen precipitation, or thunderstorms.

FAJS –           ICAO Station ID

In this example, F refers to a Southern Africa and A refers to South Africa, JS is the 2 letter id for O.R. International Airport, Johannesburg.

091800Z –           Time and Date

  • The 09 represents the day of the month
  • The 1800 represents the time at which the observation went out
  • The Z represents that the time is in ZULU or UTC (Universal Time Code).

19020G26KT –           Surface Winds

  • 190 (the first three digits) is the direction of the winds in TRUE degrees from 0 to 360 degrees (although you will never see 360 because after 359, it goes back to 0).
  • 20 (next two numbers) is the speed of the surface wind in knots.
  • G26 represents the wind gusts. In this case the gusts are 26 knots. Gust will not always be on here. There is criteria which must be met in order to have a gust. Simply, unless it’s windy, you are not going to see gusts in the observation.
  • The KT simply means knots. It will always be at the end.
  • For winds speeds below 7 knots, you might see VRB005KT which means the wind direction is variable. This is the idea of “light and variable” that you might see in a forecast.
  • For winds greater than 6 knots you might see 18015KT 150V210. The winds are from 180 degrees at 15 knots, but the direction is actually varying between 150 degrees and 210 degrees. In order to be variable above 6 knots, the winds must have at least a 60 degree variation.

5000 –           Horizontal Visibility

The 5000 simply means horizontal visibility is average 5000 meters, the highest value is 9999 means, meaning better than 10kms. This is the highest/best visibility measured. Visibility less than 10kms is usually shown then in increments of thousands of meters, e.g. 1000 or 5000 showing 1000m or 5000m visibility.

+SHRA –           Present Weather and Obscuration

  • This value shows the weather conditions and obscuration (if any).
  • ‘+’ is the designator for heavy. Precipitation will either be light ‘-‘, moderate has nothing or heavy ‘+’ based on certain criteria that must be met. For more info on that criteria, please see the FMH-1 link at the bottom of this page. For now, just understand that it is simply the intensity of the snow, rain, hail, sleet, or freezing rain.
  • +SHRA thus showing Heavy Showers and Rain
Qualifier Weather phenomena
1. Intensity or Proximity 2. Descriptor 3. Precipitation 4. Obscuration 5. Other
– Light

Moderate (Note 2)

+ Heavy

VC Vicinity (Note 3)

 MI Shallow

PR Partial

BC Patches

DR Low Drifting

BL Blowing

SH Showers

TS Thunderstorm

FZ Freezing

 DZ Drizzle
RA Rain
SN Snow
SG Snow Grains
IC Ice Crystals
PL Ice Pellets
GR Hail
GS Small Hail and/or Snow Pellets
UP Unknown Precipitation		 BR Mist
FG Fog
FU Smoke
VA Volcanic Ash
DU Widespread Dust
SA Sand
HZ Haze
PY Spray		 PO Well-developed Dust/Sand Whirls
SQ Squalls
FC Funnel Cloud Tornado Waterspout (see note 3)
SS

BKN070 –           Cloud Cover

  • BKN represents a broken sky. (The clouds cover 5/8 to 7/8 of the sky)
  • 070 represents the clouds are at 7,000 feet above the airfield
  • The cloud cover will either be FEW (1/8 to 2/8 cloud coverage), SCT (SCATTERED, 3/8 to 4/8 cloud coverage, BKN (5/8 to 7/8 coverage), and OVC (OVERCAST, 8/8 Coverage).
  • You will often have more than 1 designator (i.e. SCT035 BKN090 OVC140)
  • An indefinite ceiling caused by fog, rain, snow, etc., will require a designator as VV (Vertical Visibility). VV is the how high you can see vertically into the indefinite ceiling.
  • Significant Clouds such as TCU (Towering Cumulus), CB, (Cumulonimbus, or a shower/thunderstorm), or ACC (Altocumulus Castellanus) will be found on the en of a category (i.e. SCT035TCU)

12/08 –           Temperature and Dewpoint

  • 12 represents the air temperature in Celsius
  • 08 represents the dewpoint in Celsius
  • If the temperature or dewpoint falls below 0 there will be an “M” before it (i.e. 03/M02). “M” means minus.

Q1027 –           Altimeter / Pressure

Q stands for QNH, measured in Hectopascals (hPa). This is used for your altimeter setting.

1027 means 1027HPa for the airfield’s AMSL adjusted pressure.

RMK BECMG CAVOK –           Remarks

RMK simply means REMARKS and marks the end of the standard meteorology observation and the beginning of the remarks that are put in as necessary.

BECMG means ‘Becoming’. Weather is changing and becoming. What follows is the expected weather.

CAVOK means Ceiling And Visibility OK. This means clear skies and horizontal visibility better than 10kms.

There are many more remarks. Use the link at the top of this page to the HQ training site for more.