بسم الله الرحمن الرحيم
إسمحولي أقدم لكم درس عن ال METAR
وطبعا الشرح بيكون بالإنجليزي وبحاول اني اترجم الأشياء الي أقدر عليها
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METAR
What is a "METAR" ?
- It stands for METeorological Aerodrome Report issued every half hour for pilots as a part of a pre-flight weather briefing
بمعنى انه تقرير عن حاله الجو في مطار وفي نطاق معين وفي وقت معين
يصدر كل نصف ساعة
وهنا شرح مفصل عن كيفية قراءته بالنسبه لـ :
1. Wind
Wind is given as direction in degrees true followed by the average wind speed.
Example:24015KT - indicates that the wind is blowing from the southwest at 15 kts..
Note: KMH (Kilometres per hour) or MPS (Metres per second) may also be found in this group e.g 34025KPH.
If the wind is gusting this will be shown by a further group of figures preceded by the letter G.
Example: 24015G27KT - indicates that the average wind is 240 at 15 kts but gusts to 27 kts are recorded.
If the wind is calm then 00000KT will be shown.
A variable wind direction will be shown by VRB.
Example: VRB02KT would indicate that the wind was only 2 kts but would not be blowing from any fixed direction.
If the wind is greater than 3 kt and the direction is varying by 60 degrees or more then the actual values must be recorded.
Example: 31015G27KT 280V360 - shows that the wind is blowing from the northwest at 15 kts with gusts to 27 kts but that the wind direction is varying from 280 to 360 degrees. Not very nice...
2. Visibility
Visibility is recorded as a four figure group in metres (2000 metres is roughly 1 nm).
If 0000 is shown it would indicate that the visibility is less than 50 metres.
If 9999 is shown it indicates that the visibility is 10 km or more.
If local conditions vary greatly then two groups may be displayed showing the visibility variation in different sectors.
Example: 1000NW 6000S - shows that the visibility to the northwest of the aerodrome is only 1000 metres but is 6 km to the south.
3. RVR (Runway Visual Range)
Runway Visual Range is an indication of the real visibility as measured down the runway either electronically or manually. RVR is taken when the Met visibility drops below 1500 metres and it will therefore only be shown occasionally in METAR reports. RVR visibility will always be prefixed by the letter R followed by the runway for which the value has been taken. Example:
R24/1200 - RVR for runway 24 is 1200 metres
The RVR value recorded is significant for pilot operations. If the RVR value is below that published for the approach procedure then the aircraft CANNOT MAKE AN APPROACH. The aircraft must either remain in the holding pattern until the weather improves or it must divert.
4. Weather
Weather is identified by one or more two letter groups. The full list is not very long so I shall include them all here - even the more obscure phenomena <g>...
DZ
Drizzle RA
Rain SN
Snow GR
Hail SQ
Squalls GS
Small Hail SG
Snow Grains IC
Diamond Dust PE
Ice Pellets BR
Mist FG
Fog FU
Smoke HZ
Haze
VA
Volcanic Ash DU
Widespread dust SA
Sand SS
Sandstorm DS
Duststorm FC
Funnel Cloud
MI
Shallow BC
Patches DR
Drifting BL
Blowing SH
Showers TS
Thunderstorm FZ
Supercooled (Freezing) Slight or heavy conditions may also be described by a
- or + sign before the two letter code.
RA
= Rain SHRA
= Rain Showers FZFG
= Freezing fog -DZ
= Slight Drizzle +SHSN
= Heavy snow showers MIFG
= Shallow fog CB
Cumulonimbus TCU
Towering CB
5. Cloud
Usually this is a six figure group and one that most of you will already recognise. The group consists of three letters that describe the cloud cover followed by three figures for cloud height ABOVE AERODROME LEVEL.
Cloud amount is given as;
FEW
Few. This indicates 1 or 2 oktas of cloud.
SCT
Scattered. This indicates 3 or 4 oktas of cloud.
BKN
Broken. This indicates 5 to 7 oktas of cloud.
OVC
Overcast. This indicates 8 oktas (solid cloud cover).
Cloud height is given by the next three figures which show the altitude in hundreds of feet. i.e. 040 is 4000 ft, 004 is 400 feet, 200 is 20,000 ft. Examples:
SCT020 - Scattered at 2000 ft.
BKN005 - Broken cloud at 500 feet.
OVC250 - Overcast at 25,000 feet.
A METAR may contain several cloud layers so you may get: SCT025 BKN070 BKN120 -
showing scattered cloud at 2500 ft, broken cloud at 7000 feet and again at 12,000 feet.
SKC - (Sky Clear) will be used if no cloud layers are observed.
CAVOK - Used if no cloud exists below 5000 ft AND the visibility is greater than 10 km AND there is no fog, precipitation or snow.
CB - Used to emphasise Cumulonimbus formation - BKN015CB
TCU - Used to signify Towering CB formation.
NSC - Signifies that no significant cloud exists above 5000ft.
In conditions of fog when the cloud cover cannot be seen then the vertical visibility will be reported using VV as the code.
e.g. VV003 = vertical visibility 300 feet.
If the fog is so bad that no measurement can be taken then you may possibly see VV/// in a METAR.
6. Temperature and Dew Point
Temperature and Dew Point are both measured in Centigrade. A minus value is preceded by the letter M. Examples:
25/12 = Temp 25°C, Dew Point 12°C, or
00/M02= Temp 0°C, Dew Point -2°C.
7. QNH (Barometric Pressure)
QNH is rounded down to the next whole millibar and reported as a four figure group preceded by Q. If the value is less than 1000mbs then the first digit will be 0.
Examples;
Q0996, Q1030.
To explain this further may I just add that if you set the QNH value on your altimeter then the height displayed on the instrument will be your height above sea level. If you are on the ramp then your altimeter should read airport elevation.
One other side factor of pressure is on aircraft performance. If QNH is low then an aircraft will perform much more badly (less lift, slow climb, poor engine performance) because it is operating in less dense air.
8. Recent Weather
This may be included if appropriate using the weather codes above, prefixed with RE (for recent).
Example RERA for recent rain..
9. Wind Shear
Again this will only be included if appropriate. The code WS is used followed by the runway affected.
Example:
WS LDG RWY28L or WS TKOF RWY08
10. Trend
This is only available at selected airfields. It is intended to indicate significant changes of weather in the two hours after the observation is made. If the change is temporary then TEMPO is used followed by the predicted conditions. If the change is permanent them BECMG (Becoming) will be used. Example:
TEMPO 3000 SHRA = temporary visibility 3000 metres with rain showers.
BECMG 33035KT = becoming 35 kts of wind from 330.
NOSIG = no significant changes in weather.
وهنا مثال عن الـ METAR
وتتم قرائته كالتاالـي: *( من اليسار لليمين)
رمز المدينة
تاريخ إصدار التقرير
وقت إصداره بالنسبه للتوقيت العالمي Zolo أو UTC
جهة هبوب الريح
سرعة الرياح
مدى تفاوت اختلاف الرياح
ال 9999 تدل على مستوى الرؤية جيده بمدى يفوق ال 10 كيلومتر
FEW030 تعني وجود FewCouds بمقياس 1-2 Oktas على إرتفاع30ألف قدم
06/12 تعني ان TEmprature is 12 c & the Dewpoint is 6
Q1013 means that the QNH reading is 1013
QNH* the aerodrome pressure
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وهذا كان الدرس رقم 1 من تقدمة أخوكم ( طيران الإمارات )
والي عندي عنده أي إستفسار انا حاضـر....
وترقبوا جديدي من الدروس.....