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Mastering Aviation Weather Reports: A Comprehensive Guide for UK Pilots

Windsock

Weather plays a critical role in aviation, and pilots need to be well-versed in interpreting various weather services to ensure safe flight operations. This guide will provide an overview of essential aviation weather services for UK pilots, including METARs, TAFs, SIGMETs, and AIRMETs. We’ll also discuss how to interpret each weather service to help you make informed decisions while flying.

METARs (Meteorlogical Aerodrome Reports)

What are METARs?

METARs are aviation routine weather reports generated by meteorological stations at airports worldwide. They provide pilots with up-to-date, concise information on the prevailing weather conditions at a specific location. METARs are issued every 30 minutes or hourly, depending on the airport, and can be critical when planning a flight.

 

How to read and interpret METARs

METARs use a standard format to convey information, including wind direction and speed, visibility, weather conditions, cloud cover, temperature, dew point, and altimeter setting. Here’s a step-by-step guide to interpreting METARs:

Report type: Identify whether it’s a routine METAR or a special weather report (SPECI).

Station identifier: A four-letter ICAO airport code.

Date and time: A six-digit group (in UTC) followed by a ‘Z’ for Zulu time.

Wind: Wind direction (in degrees) and speed (in knots), followed by ‘KT’. Variable wind direction is indicated by ‘VRB’.

Visibility: Prevailing horizontal visibility in meters or statute miles.

Weather: Weather phenomena, such as rain, snow, or fog, using standard abbreviations.

Clouds: Cloud cover and height, represented by three-letter abbreviations (e.g., FEW, SCT, BKN, OVC) and a three-digit height in hundreds of feet.

Temperature and Dew Point: A two-part group separated by a slash, with temperature first and dew point second (both in degrees Celsius). Negative values are indicated with an ‘M’ prefix.

Altimeter setting: A four-digit group prefixed with ‘Q’ or ‘A’, representing the atmospheric pressure at sea level in hPa or inches of mercury, respectively.

 

Common METAR abbreviations and codes

Some standard METAR abbreviations include:

RA: Rain

SN: Snow

BR: Mist

FG: Fog

HZ: Haze

TS: Thunderstorm

GR: Hail

FEW: Few clouds (1/8 to 2/8 sky coverage)

SCT: Scattered clouds (3/8 to 4/8 sky coverage)

BKN: Broken clouds (5/8 to 7/8 sky coverage)

OVC: Overcast (8/8 sky coverage)

Keep in mind that METARs can include additional information, such as runway visual range (RVR), recent weather, and other remarks. Familiarising yourself with these abbreviations will help you quickly understand the weather conditions at your destination or departure airport.

 

Example

Here’s an example of a METAR for London Heathrow Airport (EGLL):

METAR EGLL 261120Z 27010KT 9999 SCT030 12/06 Q1019 NOSIG
 
Now, let’s break down this METAR:

METAR: Indicates it’s a routine weather report.

EGLL: The ICAO airport code for London Heathrow Airport.

261120Z: Date and time of the report, in this case, the 26th day of the month at 1120 UTC (Zulu time). 

27010KT: Wind direction and speed, showing a wind from 270 degrees at 10 knots.

9999: Visibility, which is 9999 meters, indicating excellent visibility (usually 10 km or more).
SCT030: Scattered clouds at 3,000 feet above ground level.

12/06: Temperature and dew point, 12 degrees Celsius for the temperature and 6 degrees Celsius for the dew point.

Q1019: Altimeter setting, indicating an atmospheric pressure of 1019 hPa (hectopascals) at sea level.

NOSIG: No significant change in weather conditions is expected for the next two hours.

This METAR shows that the weather at London Heathrow Airport at the time of the report was generally favourable, with scattered clouds, good visibility, and light winds.

METARs can be found on the Met Office Aviation page, here

Airplane on a sunny day

TAFs (Terminal Aerodrome Forecasts)

A Terminal Aerodrome Forecast (TAF) is a concise statement of the expected meteorological conditions at an airport during a specified time period. TAFs are typically issued every 6 hours and have a forecast period of 24 hours, with some larger airports issuing 30-hour forecasts. They are used by pilots to plan flights, taking into consideration the weather conditions at their departure and destination airports.

 

How to read and interpret TAFs

A TAF consists of several parts, including the forecast time period, wind direction and speed, visibility, weather phenomena, and cloud cover. Here’s a breakdown of the components of a TAF:

Forecast Time Period: Indicates the valid time period for the TAF, typically ranging from 24 to 30 hours.

Wind Direction and Speed: Represents the expected wind direction and speed during the forecast period.

Visibility: Describes the expected horizontal visibility in meters or kilometers.

Weather Phenomena: Indicates any significant weather events that may occur, such as rain, snow, or thunderstorms.

Cloud Cover: Specifies the cloud coverage and altitude of the cloud base.

 

Common TAF codes and abbreviations

TAFs use specific codes to represent various weather phenomena and conditions. Here’s a list of some common TAF codes and their meanings:

TEMPO: Indicates temporary fluctuations in the weather conditions, typically lasting less than an hour.

BECMG: Stands for ‘Becoming,’ which means a gradual change in the weather conditions is expected.

PROB: Represents the probability of specific weather phenomena occurring, usually followed by a two-digit number (e.g., PROB30 means a 30% probability).

FM: Stands for ‘From,’ indicating a rapid change in the weather conditions at a specific time.

-RA: Light rain

RA: Moderate rain

+RA: Heavy rain

SN: Snow

TS: Thunderstorm

SCT: Scattered clouds

BKN: Broken clouds

OVC: Overcast clouds

FEW: Few clouds

CAVOK: Ceiling and visibility okay, meaning no significant weather, visibility 10 km or more, and no clouds below 5,000 feet or the highest minimum sector altitude.

Keep in mind that this is not an exhaustive list, but it covers some of the most common codes you’ll encounter in TAFs. By familiarizing yourself with these codes, you’ll be better prepared to understand and interpret TAFs for your flights in the UK.

 

Example

Here’s an example of a UK TAF:

TAF EGCC 260500Z 2606/2712 24012KT 9999 SCT025
TEMPO 2606/2610 7000 -RA BKN014
BECMG 2612/2615 27008KT
FM270600 33012KT 9999 BKN018
PROB30
TEMPO 2709/2712 7000 -SHRA
 
This TAF is for Manchester Airport (EGCC) and covers the period from 06:00 UTC on the 26th day of the month to 12:00 UTC on the 27th day of the month. It provides the following information:

Initial conditions: Wind from 240 degrees at 12 knots, visibility 9999 meters, and scattered clouds at 2500 feet.

Temporary conditions (TEMPO) between 06:00 and 10:00 UTC: Visibility reduced to 7000 meters with light rain (-RA) and broken clouds at 1400 feet.

Becoming (BECMG) between 12:00 and 15:00 UTC: Wind shifts to 270 degrees at 8 knots.
From (FM) 06:00 UTC on the 27th: Wind from 330 degrees at 12 knots, visibility 9999 meters, and broken clouds at 1800 feet.
30% probability (PROB30) of temporary conditions (TEMPO) between 09:00 and 12:00 UTC on the 27th: Visibility reduced to 7000 meters with light rain showers (-SHRA).

By understanding these codes and their meanings, you’ll be able to decipher TAFs and make informed decisions about your flights in the UK.

Man stood under wing of airplane on a rainy day

SIGMETs (Significant Meteorlogical Information)

What are SIGMETs?

SIGMETs (Significant Meteorological Information) are weather advisories issued by meteorological watch offices. They provide information about significant weather events that could affect the safety of aircraft operations, such as severe turbulence, severe icing, thunderstorms, volcanic ash, or sandstorms. SIGMETs are issued for specific areas and are valid for a certain period, usually up to 4 hours.

 

Common SIGMET codes and abbreviations

To read a SIGMET, you’ll need to understand the abbreviations and codes used in the message. Some common SIGMET abbreviations and codes include:

WS: SIGMET for severe turbulence, severe icing, or severe mountain waves

WV: SIGMET for volcanic ash

WU: SIGMET for tropical cyclones

WZ: SIGMET for severe thunderstorms

EMBD: Embedded (used with thunderstorms)

FRQ: Frequent (used with thunderstorms)

ISOL: Isolated (used with thunderstorms)

 

Example

Here’s an example of a UK SIGMET:

WS EGRR LONDON FIR/UIR
EGRR SIGMET 01 VALID 080400/080800 EGRR-
LONDON FIR/UIR SEV TURB FCST WI N5710 W01000 – N5600 W00300 –
N5300 W00300 – N5210 W01000 – N5710 W01000 SFC/FL100 STNR NC=


This SIGMET from London FIR/UIR (EGRR) is for severe turbulence. It is the first SIGMET of the day (01) and is valid from 04:00 UTC to 08:00 UTC. The affected area is described by the coordinates N5710 W01000, N5600 W00300, N5300 W00300, N5210 W01000, and back to N5710 W01000. The turbulence is forecasted from the surface (SFC) up to flight level 100 (FL100). The weather phenomenon is stationary (STNR) and there are no changes (NC) expected during the validity period.

By understanding these codes and their meanings, you’ll be able to interpret SIGMETs and make informed decisions about your flights in the UK.

airplane being deiced

In conclusion, understanding and interpreting aviation weather reports such as METARs, TAFs, and SIGMETs is an essential skill for pilots flying in the UK. These reports provide crucial information about current and forecasted weather conditions, allowing pilots to make informed decisions and plan their flights safely and efficiently. By familiarizing yourself with the common codes, abbreviations, and formats of these weather reports, you’ll be better equipped to navigate the ever-changing weather patterns in UK airspace. Keep practicing your interpretation skills, and you’ll become more confident in using these vital tools to ensure safe and enjoyable flights.

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