Course 5 - Section 14 - Aviation Weather Reports Flashcards
What does METAR stand for?
Aerodrome Routine Meteorological Report
What does TAF stand for?
Terminal Area Forecast
METAR overview
Metar is the most common format in the world for transmitting obersvational weather data. METARs are prepared by staff working onsite at specific aerodromes
A METAR IS NOT A FORECAST – it gives a snapshot of weather through a sequence of codes
In Canada, METARs are generated using computer software and are based on observations taken at either staffed or automatic sites
METARs use international coding standards, but there are some national variations. Most countries, including Canada, report wind speed in knots, as per ICAO standards, but some countries, including North Korea, Russia nd China, report it in metres per second
METAR
Code: MESSAGE TYPE
***
There are two possible message types:
METAR
indicates a scheduled observation taken on the hour (plus or minus ten minutes)
SPECI
indicates an unscheduled or “special” observation reporting weather events that were not previously reported
METAR
Code: Day/Time
- first two digits indicate the day of the month
- last four digits indicate time in UTC/Zulu
METAR
Code: Wind
Direction
- First three digits indicate wind direction to the nearest 10 degrees true (based on an average of two minutes)
- If the wind direction is variable, the direction is coded VRB when speed is less than three knots (eg VRB02KT)
- With a mean wind speed of three knots or greater, if the variation of the wind direction is 60 degrees or more and less than 180 degrees, direction is indicated with a V (eg 180V250)
Speed
-Following two digits indicate mean speed and unit (KT =knots, MPS = metres per second)
- If gusts exceed mean speed by 5 knots ore more and are at least 15 knots, use G followed by maximum speed
- if wind is calm, use 00000KT
METAR
Code: Visibility
Prevailing Visibility
-Prevailing visibility is reported in whole and fractions of statute miles (SM) up to 3 SM and in whole statute miles up to 15 SM
- If the station has visibility markers (such as mountains or large buildings), visibility greater than 15 SM can be reported in increments of 5 SM
- Visibility that is half or less, or double or more of the prevailing visibility is reported in the Remarks section (at the end of the report)
Runway Visual Range
- If prevailing visibility is 1 SM or less AND/OR RVR is 6000 feet or less, RVR is reported
- RVR of P6000 means it is more than 6000 feet, the highest value reported
- RVR of M300 means it is less than 300 feet, the lowest value reported
-Always begins with the letter R, followed by the runway heading
-Last four digits report the visibility in feet - If value has changed by 300 feet or more in 10 minutes, trend is reported (D = Downward, U = Upward, N = No change)
Example
3/4SM R36/4000FT/D
Visibility is 3/4 of a SM and at R36, the RVR is 4000feet and trending downward
METAR
Code: PRESENT WEATHER
- Reported if significant weather is observed
- is broken down into qualifiers and weather phenomena
EXAMPLE
-SN BLSN
Light snow and blowing snow
METAR
Code: SKY CONDITION
- Specifies amount of cloud using abbreviations:
SKC Clear
FEW few
SCT scattered
BKN Broken
OVC overcast - Lists the height of the base of the clouds in FEET AGL
- Is reported for each layer of cloud
Example BKN008 OVC040
broken cloud layer at 800 feet
overcast cloud layer at 4000 feet
METAR
Code: TEMPERATURE/DEW POINT
- given in celcius
- if below zero, will have M in front for minus
- observed values with .5 degree are rounded up to the next warmer degree
Example
M05/M08
Temperature -5 deg C
Dew point -8 deg C
METAR
Code: Altimeter
reported in inches of mercury with decimal point omitted
eg. A2992
29.92 inches of mercury Hg
METAR
Code: RECENT WEATHER
- If applicable, significant weather phenomena observed since the last routine report but not occurring at the time of observation is reported
- Supplemental information on wind shear is provided
example WS RWY36
Wind shear at runway 36
METAR
Code: REMARKS
- Consists of any observations of significance to aviation
- begins with RMK
-includes, in the following order:
Type of cloud layer
Amount (in oktas)
General weather remarks
Sea level pressure
- THE = SIGN indicates the END OF THE METAR
Qualifiers
Qualifiers always go BEFORE the weather phenomenon, no qualifier means moderate
Cloud Cover
(What info does sky condition give you and describe the oktas)
The sky condition codes give you two key pieces of information:
- The amount of cloud cover at each cloud layer
- The height of the base of each cloud layer
The type corresponds to the portion (in eights or oktas) of the sky covered by a layer of cloud. Note that cloud cover is cumulative. This means that each reported layer amount includes the sum of layers below it
(See chart)
Cloud height
Cloud height is reported in hundreds of feet
- If CB or TCU clouds are present, they are reported after the height eg SCT023TCU is reporting scattered TCU clouds at 2300 feet
- Obscured sky is reported as vertical visibility (VV) and is measured in hundreds of feet. eg VV001 is reporting an indefinite ceiling with vertical visibility of 100 feet
-Partially obscured sky is reported as SKC (if there is no cloud) or is included with the first layer
NOTE: From this section of the METAR, you can deduce the ceiling by determining the height of the lowest layer of clouds that are either BROKEN OR OVERCAST
Cloud height example
Look at illustration
- in the first level at 1500 feet, we see clouds covering two of eight oktas of the sky.
FEW015
-in the next level of 3000 feet, there is only one cloud we can see directly, the other one is obscured. to get the code we add the 2 clouds we see at 1500 plus the one cloud at 3000 to get three of eight oktas. This is coded as
SCT030
- In the last layer of cloud at 5000 feet we have an unobscured view of clouds covering to of eight oktas. adding this to the three oktas for the lower level clouds already counted, we get 5 of eight oktas which is coded as
BKN050
Ceiling
Will be the lowest cloud layer reported as BKN or OVC
(VV or SKC may override this, check!)
Sea level pressure
Add a 10 in front and a decimal between last two numbers and you get SLP in hectopascals
SLP134 is 1013.4 hP
TAFs
TAFs describe weather forecast information for a specific period of time
THEY ARE ISSUED AT LEAST FOUR TIMES A DAY, EVERY SIX HOURS, STARTING AT 0000Z
CANADIAN TAFs HAVE VARIOUS VALIDITY PERIODS AND CAN BE VALID FOR UP TO 30 HOURS
TAFs use the same codes and units as METARs
TAF
Code: MESSAGE TYPE
TAF
This is a TAF message type
TAF
Code: Day/Time
- First two digits indicate the day of the month
- last four digits indicate time in UTC/Zulu
This code represents the date and time the TAF was issued or amended
TAF
Code: VALID TIME PERIOD
A TAF can be valid up to 30 hours
- First two digits indicate start date and the following two digits indicate the start hour
- after the slash, first two digits indicate the end date and the last two digits indicate end hour
eg 2714/2802
Starts on the 27th at 1400Z
Ends on the 28th at 0200Z
TAF
Code: INITIAL FORECAST CONDITIONS
What do they describe ?
These are the conditions forecast at the start of the validity period of the TAF
Describes wind, visibility, weather and sky condition
eg 35005KT P6SM SKC
wind blowing from 350 at 5 knots, visibility more than 6 statute miles, sky clear
TAF
Code: CHANGE GROUPS
Change groups indicate that a change in some or all of the elements is expected
TAF
Code: REMARKS
Remarks, errata and comments
BECMG Example
*** NOTE THAT BECOMING MEANS THE CHANGE TAKES PLACE GRADUALLY DURING THE WINDOW SPECIFIED. THE CHANGE IS FINALIZED AT THE END OF THE WINDOW, LOOK AT EXAMPLE
TEMPO Example
TAF Multiple change group example
Remember about TAFs
They will start with INITITIAL CONDITIONS which occur at the beginning of the valid period of the TAF. Those conditions will be in place until a CHANGE GROUP in the TAF modifies them (permanantly or temporarily)
Remember about FM:
It’s a rapid change that is not temporary
