25
METEOROLOGY — CHAPTER 25 · NOTES
Aerodrome Met Reports — METAR, SPECI & TREND
by Ghost Aviator
LECTURE PARTS
Table of Contents
- 1. METAR and SPECI — Introduction
- 2. METAR/SPECI Code Structure
- 3. Reporting Met Elements — Detailed Rules
- 4. CAVOK — Definition and Conditions
- 5. Criteria for Issue of SPECI
- 6. SPECIAL Report (India-specific)
- 7. Explanation of METAR/SPECI Code Groups (Table 25.1)
- 8. TREND Forecast (Landing Forecast)
- 9. W' W' Significant Present & Forecast Weather (Table 25.3)
- 10. hs hs hs Cloud Base Code (Table 25.4)
- 11. Worked METAR/SPECI/TREND Examples
- 12. Practice Q&A
- 13. Master Reference Tables
1. METAR and SPECI — Introduction
METAR = Meteorological Aerodrome Report (routine)
SPECI = Aerodrome Special Met Report (issued when criteria are met)
Both encoded using WMO Manual on Codes (WMO 306). Used by aircrew, operators, and ATC. Both have the same code format.
SPECI = Aerodrome Special Met Report (issued when criteria are met)
Both encoded using WMO Manual on Codes (WMO 306). Used by aircrew, operators, and ATC. Both have the same code format.
- METAR is issued at half hourly or hourly intervals.
- SPECI is issued any time criteria are met — for deterioration immediately, for improvement after 10 minutes.
Full METAR/SPECI Code Form
METAR or SPECI CCCC YYGGggZ ddffGfmfmKT/MPS/KMH dndndnVdxdxdx
VVVVDv VxVxVxVxDv RDRDRi/VRVRVRVRi w'w'
or or
CAVOK RDRDRi/VRVRVRVRi VRVRVRVRVRi
NsNsNshs hshs T'T'/Td'Td' QPhPnPnPn REw'w' WSDRWYDrDr
2. METAR/SPECI Code Structure
| Code Group | Meaning | Example |
|---|---|---|
| METAR or SPECI | Report type identifier | METAR / SPECI |
| CCCC | ICAO location indicator (4-letter) | VIDP (Delhi) |
| YYGGggZ | Date/Time UTC — Day(YY), Hour(GG), Min(gg), Z=UTC | 241130Z = 24th, 11:30 UTC |
| dddff(Gfmfm)KT/MPS/KMH | Wind direction (ddd), speed (ff), gusts (Gfmfm), units | 27010KT, 32020G45KT |
| dndndnVdxdxdx | Variable wind direction (min V max) | 170V050 |
| VVVV or CAVOK | Visibility (metres) or CAVOK | 6000S, CAVOK |
| RDRDRi/VRVRVRVRi | RVR — Runway, instrument, RVR value, tendency | R27/1200D |
| w'w' | Present weather phenomena | +SHRA, TSRA, FZFG |
| NsNsNshs hs hs | Cloud amount (Ns) and base height (hs hs hs) | FEW020, SCT100, BKN250 |
| VV/// | Vertical Visibility (sky obscured) | VV/// |
| SKC or NSC | Sky Clear / No Significant Cloud | SKC, NSC |
| T'T'/Td'Td' | Temperature / Dew Point (°C) | 34/27 |
| QPhPnPnPn | QNH pressure (hPa) | Q0999, A3005 |
| REw'w' | Recent weather | RERA (recent rain), RETS |
| WSDRWYDr | Wind Shear on Runway | WSRWY09, WS ALLRWY |
| (WT/SS) | Sea Surface Temp / State | W19/S4 |
| RMK | Remarks (appended at end) | RMK... |
3. Reporting Met Elements — Detailed Rules
(a) Surface Wind
Direction and Speed reported as: 27010KT/MPS/KMH
Variable wind (speed < 3KT): VRB02KT
Stronger wind — direction changed ≥ 180°: VRB10KT
Calm (less than 1 kt): 00000KT
Gusty wind (30020 gusting 40KT): 30020G40KT
Extreme directions (variation ≥ 60° and ≤ 180°): e.g., 270V050
Wind ≥ 100 KT: reported as 24 0P99KT
Variable wind (speed < 3KT): VRB02KT
Stronger wind — direction changed ≥ 180°: VRB10KT
Calm (less than 1 kt): 00000KT
Gusty wind (30020 gusting 40KT): 30020G40KT
Extreme directions (variation ≥ 60° and ≤ 180°): e.g., 270V050
Wind ≥ 100 KT: reported as 24 0P99KT
(b) Visibility
- Reported in steps of 50 m (when vis 0–800 m), e.g., 50, 100, 150…750, 800 m
- In steps of 100 m when vis is 800 m to 5000 m — e.g., 900, 1000…4900, 5000 m
- In steps of 1 km when vis is 5000 m to 9000 m — e.g., 6000, 7000, 8000, 9000 m
- Reported as 9999 when visibility is ≥ 10 km or more
(c) RVR — Runway Visual Range
RVR observations are made when visibility or RVR < 1500 m. Reported in steps of:
25 m — when RVR is 000–400 m
50 m — when RVR is 400–800 m
100 m — when RVR is 800–2000 m
RVR 1500–2000 m is reported under RMK and not disseminated internationally.
25 m — when RVR is 000–400 m
50 m — when RVR is 400–800 m
100 m — when RVR is 800–2000 m
RVR 1500–2000 m is reported under RMK and not disseminated internationally.
RVR Tendency Code (i): U = Increasing, D = Decreasing, N = No change
| Code i | Meaning |
|---|---|
| R | R = RVR; DR = Runway; i = tendency in last 10 min |
| i as N | Nil — as D (decreased) |
| U | RVR increased |
| D | RVR decreased |
| N | No change |
When RVR > 1500 m: reported as R27P1500U (prefix P = more than)
RVR below assessable (e.g., below 150m by instrument): R27M0150 (prefix M = less than)
(d) Cloud Base — Reported in Steps
- 30 m — up to 3000 m
- 300 m — above 3000 m
(e) Cloud Reporting Terms
| Code | Octas | Meaning |
|---|---|---|
| FEW | 1–2 | Few |
| SCT | 3–4 | Scattered |
| BKN | 5–7 | Broken |
| OVC | 8 | Overcast |
| SKC | 0 | Sky Clear (used at auto stations) |
| NSC | — | No Significant Cloud |
Cloud Layering Rules:
- Lowest layer reported regardless of amount (FEW, SCT, BKN or OVC)
- Next layer reported when cloud amount is 3/8 or more (SCT, BKN or OVC)
- Next layer reported when cloud amount is 5/8 or more (BKN or OVC)
- In addition CB is always reported whenever observed
(f) Temperature
Involving 0.5°C or more are rounded up to next higher value. e.g., +2.5°C reported as 03; −2.5°C as M 02.
(g) Pressure (QNH)
Rounded down to nearest whole hectopascal lower value. e.g., QNH 996.6 hPa reported as QNH 996 hPa. Range of pressure over the world is 850 hPa to 1100 hPa.
(h) Fog (FG)
Reported when visibility is < 1000 m due to water drops or ice crystals or both, except when prefixed by MI, BC, PR or VC.
(i) Mist (BR)
Reported when visibility is 1000 m but not more than 5000 m.
(j) HZ, SA, DU, FU, VA
Reported when visibility is 5000 m or less, except SA when specified by DR (Low Drifting).
(k) Present Weather Phenomena (Full List)
Drizzle (DZ), Rain (RA), Snow (SN), Snow Grain (SG), Ice Pellet (PE), Ice (IC), Hail ≥5mm (GR), Hail <5mm (GS), Fog (FG), Mist (BR), Sand (SA), Dust (DU), Haze (HZ), Smoke (FU), Volcanic Ash (VA), Dust Devil (PO), Squall (SQ), Funnel Cloud (FC), Dust Storm (DS), Sandstorm (SS), Shower (SH), Thunderstorm (TS)
(l) Supplementary Information
Recent significant weather also included in abbreviated plain language. e.g., WIND 32010 KT, WIND AT 60 M 36025 KT IN APCH OR MOD TURB AND ICE IN CLIMOUT, WS RWY 12.
4. CAVOK — Definition and Conditions
CAVOK (pronounced KAV-OH-KAY) = Ceiling And Visibility OK
Issued when ALL three conditions are met simultaneously:
Issued when ALL three conditions are met simultaneously:
- Visibility ≥ 10 km
- No clouds of operational significance
- No weather of significance
Minimum Sector Altitude (MSA): The lowest altitude which may be used which will provide a minimum clearance of 300 m (1000 ft) above all objects located in the area contained within a sector of a circle of 46 km (25 NM) radius centered on a radio aid to navigation.
Exam Tip — CAVOK Mnemonic: "10-No-No"
Vis ≥ 10 km + No significant cloud + No significant weather → CAVOK
Vis ≥ 10 km + No significant cloud + No significant weather → CAVOK
5. Criteria for Issue of SPECI
flowchart TD
A[SPECI Trigger Criteria] --> B[Surface Wind]
A --> C[Visibility]
A --> D[RVR]
A --> E[Present Weather]
A --> F[Clouds]
A --> G[Temperature]
B --> B1["Direction change ≥60° AND speed before/after ≥10kt"]
B --> B2["Mean speed changed by ≥10kt"]
B --> B3["Variation from mean speed by ≥10kt (gust) AND speed before/after ≥15kt"]
C --> C1["Passes through 800, 1500, 3000 or 5000m"]
D --> D1["Changes or passes 150m, 350m, 600m or 800m"]
E --> E1["Onset/cessation/change in FZ precip, FZFG, MOD/HVY precip, drifting/blowing snow, sand, dust, DS, TS, SS, squall, funnel clouds"]
F --> F1["BKN or OVC at 30, 60, 150, 300, 450m"]
F --> F2["Cloud below 450m changes: SKC/FEW/SCT↔BKN/OVC or BKN/OVC↔SKC/FEW/SCT"]
F --> F3["Sky obscured & vertical vis changes/passes 30,60,150,300m (where laser ceilometer installed)"]
G --> G1["Surface temp increases ≥2°C from last observation"]
SPECI Issuance Timing:
For deterioration → issued immediately
For improvement → issued after 10 minutes
For deterioration → issued immediately
For improvement → issued after 10 minutes
6. SPECIAL Report (India-specific)
In addition to SPECI, a SPECIAL Report (in abbreviated plain language) is issued for Height of Base of Clouds and Visibility in India. These are passed to ATC only for their local use and are not disseminated beyond the aerodrome of origin:
- Visibility 2000 or 4000 m
- Cloud base 90 or 120 m, where Ceilograph/Ceilometer exists
7. Explanation of METAR/SPECI Code Groups (Table 25.1 & 25.2)
Visibility Groups
| Code | Meaning | Coded As |
|---|---|---|
| VVVV Dv | Min Visibility 6000m in South | 6000S |
| VxVxVxVxDv | Visibility <1500m in one direction and >5000 in other then: N, NE, NW | 1400SW 6000E / 3000NW |
| CAVOK | Visibility, Cloud Ceiling, Present Wx better than prescribed values | CAVOK |
| 9999 | Visibility 10 km or more | 9999 |
RVR Group
| Code | Meaning | Example |
|---|---|---|
| R | RVR identifier | R |
| DRDRDRi/VRVRVRVRi | Runway, tendency in last 10 min / RVR value / tendency | R27/1200D |
| i = N (nil) | As D — decreased | — |
| U | RVR increasing | R27P1500U |
| D | RVR decreased | R21P1500D |
| RVR >1500m | Has increased: R27P1500U | — |
| RVR below instrument | R27M0150 | — |
Pressure QNH
| Code | Meaning | Example |
|---|---|---|
| QPhPnPnPn | QNH rounded down to whole hPa | Q0999 |
| APhPnPnPn | QNH in inches (US format) | A3005 = 30.05 inches |
Recent Weather (RE)
| Code | Meaning |
|---|---|
| RERA | Recent Rain |
| RETS | Recent Thunderstorm |
Wind Shear
| Code | Meaning |
|---|---|
| WSRWY09 | Wind Shear Runway 09 |
| WS ALLRWY | Wind Shear All Runways |
8. TREND Forecast (Landing Forecast)
TREND = Statement of expected significant changes in any one or more of the weather elements: surface wind, visibility, weather and clouds.
When no significant change is expected: NOSIG
TREND is appended to a METAR or SPECI and is valid for TWO hours.
When no significant change is expected: NOSIG
TREND is appended to a METAR or SPECI and is valid for TWO hours.
TREND Code Form
TTTTT or NOSIG TTGgg ddffGfmfmKT/MPS/KMH VVVV or CAVOK
TTTTT w'w' or NSW NSNS NS hs hs or V/// or SKC or NSC (RMK)
Change Group (TTTTT)
| Code | Meaning |
|---|---|
| BECMG | Becoming — gradual and permanent change (starts at…UTC, completes at…UTC) |
| TEMPO | Temporary change for less than one hour AND aggregate of such changes < half period indicated by GGgg. TEMPO lasts < 1 hour; total TEMPO time < half the TREND period. |
| NOSIG | No Significant Change |
TEMPO Rule: TEMPO lasts for less than one hour and the aggregate of such repeated changes is less than half the period indicated by GGgg.
BECMG: Gradual permanent change — starts at …UTC and completes at …UTC.
BECMG: Gradual permanent change — starts at …UTC and completes at …UTC.
Time of Expected Occurrence of Change (TTGGgg)
| Code | Meaning | Example |
|---|---|---|
| FM (From) | From time TL | — |
| TL (Until) | Until time | — |
| AT (At) | At exact time | — |
| GGgg | Time in Hr and Min | eg. 0430, 0800 |
e.g., BECMG FM1230 TL1300 TEMPO FM0800 | BECMG TL1230 OVC005 | BECMG AT1030 OVC010
Visibility in TREND
Visibility 4000 m in Rain and Showers: 4000 RASH
CAVOK as in METAR
Weather in TREND (NSW)
NSW = No Significant Weather (used to indicate weather has ceased)
9. W' W' Significant Present & Forecast Weather (Table 25.3)
| Qualifier | Description | Precipitation | Obscuration | Other |
|---|---|---|---|---|
| – Light | MI Shallow | DZ Drizzle | BR Mist | PO Dust/Sand Whirl (Dust Devil) |
| Moderate (no qualifier) | BC Patches (random, discontinuous coverage) | RA Rain | FG Smoke | SQ Squall |
| + Heavy (well developed; substantial coverage) | PR Partial (covers part of aerodrome) | SN Snow | VA Volcanic Ash | FC Funnel Clouds (Tornado or Water Spout) |
| VC In the Vicinity (not at station, but within 8 km) | DR Low Drifting | SG Snow Grain | DU Widespread Dust | SA Sand Dunes |
| BL Blowing | IC Ice Crystals, Diamond dust | SA Sand | SS Sandstorm | |
| SH Shower | PL Ice Pellets (Sleet) | HZ Haze | DS Duststorm | |
| TS Thunderstorms | GR Hail ≥5mm | |||
| FZ Freezing | GS Small Hail <5mm |
Key Notes on W' qualifiers:
FZ (super-cooled water droplets or precipitation) is used with RA and DZ;
DR is used with DU, SA, or SN raised by wind to < 2 m agl;
BL is used with DU, SA or SN raised by wind to ≥ 2 m agl;
MI, BC and PR are used with FG only, e.g., BCFG, MIFG, PRFG
FZ (super-cooled water droplets or precipitation) is used with RA and DZ;
DR is used with DU, SA, or SN raised by wind to < 2 m agl;
BL is used with DU, SA or SN raised by wind to ≥ 2 m agl;
MI, BC and PR are used with FG only, e.g., BCFG, MIFG, PRFG
10. hs hs hs Cloud Base Code (Table 25.4)
| hs hs Code | 000 | 001 | 002 | 003 | 004 | etc. | 011 | 009 |
|---|---|---|---|---|---|---|---|---|
| Cloud Base m | <30 | 30 | 60 | 90 | 120 | … | 330 | 2970 |
Each code increment = 30 m. Code 001 = 30 m, Code 004 = 120 m, Code 011 = 330 m.
Exam Tip: hs hs hs in METAR = cloud base in hundreds of feet × 100 (e.g., FEW020 = FEW at 2000 ft). In TREND, hs hs hs code is given as 3-digit code where each unit = 30 m.
11. Worked METAR/SPECI/TREND Examples
Example SPECI Decoded
SPECI VIDP 230300Z 30015G35KT 270V050 1200NW 6000S R27/P1500
+SHRA FEW020 FEW025CB SCT100 BKN250 34/27 Q1004 RERA WS RWY27
Decoded:
SPECI VIDP → Aerodrome Special Met Report for Palam (New Delhi)
230300Z → 23rd day at 0300 UTC
30015G35KT → Surface Wind 300°/15 KT gusting to 35 KT
270V050 → Wind direction varying from 270° to 050°
1200NW → Visibility 1200 m in NW direction
6000S → Visibility 6000 m in South
R27/P1500 → Runway Visual Range R/W 27 more than 1500 m
+SHRA → Weather: Heavy Shower and Rain
FEW020 → Clouds 1–2/8 at 2000 ft
FEW025CB → 1–2/8 CB at 2500 ft
SCT100 → 3–4/8 at 10,000 ft
BKN250 → 5–7/8 at 25,000 ft
34/27 → Temperature 34°C and Dew Point 27°C
Q1004 → QNH 1004 hPa
RERA → Recent Rain
WS RWY27 → Wind Shear Warning for R/W 27
SPECI VIDP → Aerodrome Special Met Report for Palam (New Delhi)
230300Z → 23rd day at 0300 UTC
30015G35KT → Surface Wind 300°/15 KT gusting to 35 KT
270V050 → Wind direction varying from 270° to 050°
1200NW → Visibility 1200 m in NW direction
6000S → Visibility 6000 m in South
R27/P1500 → Runway Visual Range R/W 27 more than 1500 m
+SHRA → Weather: Heavy Shower and Rain
FEW020 → Clouds 1–2/8 at 2000 ft
FEW025CB → 1–2/8 CB at 2500 ft
SCT100 → 3–4/8 at 10,000 ft
BKN250 → 5–7/8 at 25,000 ft
34/27 → Temperature 34°C and Dew Point 27°C
Q1004 → QNH 1004 hPa
RERA → Recent Rain
WS RWY27 → Wind Shear Warning for R/W 27
Example TREND Decoded
TEMPO FM0830 TL0900 24025G45KT 2000 RATS FEW020 FEWCB025 SCT100
BKN250 BECMG FM0930 27005KT 6000 NSW.
TEMPO FM0830 TL0900 → Temporary from 0830 until 0900 UTC:
Surface Wind 240/25 KT Gusting to 45 KT, Visibility 2000 m in Rain and Thunder Shower, Clouds 1–2/8 at 2000 ft, 1–2/8 CB at 10,000 ft, 3–4/8 at 25,000 ft.
BECMG FM0930 → Becoming from 0930 UTC:
Wind 270/5 KT, Visibility 6000 m and No Significant Weather.
Surface Wind 240/25 KT Gusting to 45 KT, Visibility 2000 m in Rain and Thunder Shower, Clouds 1–2/8 at 2000 ft, 1–2/8 CB at 10,000 ft, 3–4/8 at 25,000 ft.
BECMG FM0930 → Becoming from 0930 UTC:
Wind 270/5 KT, Visibility 6000 m and No Significant Weather.
METAR Examples with TREND
METAR VIAM 211500Z 33010KT 6000 FEW040 FEW050CB 29/25 Q1004 NOSIG =
METAR VEGK 1600Z 23015KT 6000 LT FEW010 SCT020CB BKN100 22/Q1002
TEMPO FM 1630 TL 1725 30015G28KT 2500 TSSH SCT020CB OVC150 =
METAR VIJO 1230Z 23015KT 5000 SA SKC 37/18 Q1004 BECMG 1314 24015G28KT
-DS 1500 FEW015 SCT020CB BKN100=
METAR VIAR 1300Z 25015KT 2500 HZ SKC 39/19 Q1001 BECMG AT1400 25010KT CAVOK =
12. Practice Q&A
Based on METAR: VIDP 160230Z 33005KT 290V050 1500S 5000N R15/P1500U BR FEW020 FEW050CB SCT120 BKN300 32/29 Q1003 REFG TEMPO FM0330 22015G25KT 2500 TSSH FEW025CB SCT100 BKN150 BECMG AT0415 25010KT CAVOK=
Use this METAR / TREND for Questions 1–22
METAR VIDP 160230Z 30005KT 290V050 1500S 5000N R15/P1500U BR FEW020 FEW025CB SCT120 BKN300 32/29 Q1003 REFGTEMPO FM0330 22015G25KT 3000 +TSRA FEW010 SCT025CB BKN150 BECMG AT0415 27008KT CAVOK=
Q1. The METAR has been issued on day: (a) 15th (b) 16th (c) 17th
✅ Correct: (b) 16th — YY = 16 in YYGGggZ = 160230Z
❌ (a) 15th and (c) 17th are wrong day codes.
💡 YYGGggZ: first two digits = day of month (UTC).
Q2. The METAR has been issued at: (a) 0630 IST (b) 0230 UTC (c) 0230 IST
✅ Correct: (b) 0230 UTC — GGgg = 0230, Z suffix = UTC
❌ IST = UTC + 5:30 hrs. 0230 UTC = 0800 IST, not 0630 or 0230 IST.
💡 Z always = UTC. IST = UTC + 5h 30min.
Q4. Wind direction is varying from: (a) 290 to 050° (b) 050 to 290° (c) 200 to 050°
✅ Correct: (a) 290 to 050° — Variable wind group: 290V050
❌ The format is always dndndnVdxdxdx = min direction V max direction.
💡 Variable wind direction reported when variation ≥60° and ≤180°; format = minVmax.
Q5. Visibility 1500 m is towards: (a) N (b) S (c) All over the airport
✅ Correct: (b) S — 1500S = 1500 m in South direction
❌ Direction suffix gives compass bearing of minimum visibility: S = South.
💡 When directional visibility varies, the minimum is reported first with its direction letter appended.
Q6. Visibility towards N is: (a) 1500m (b) 5000 m (c) 3000 m
✅ Correct: (b) 5000 m — 5000N = 5000 m in North direction
💡 Second directional vis group 5000N = visibility towards North is 5000 m.
Q7. Height of base of low clouds above station level is: (a) 2000 ft (b) 2500 ft (c) 2500 m
✅ Correct: (a) 2000 ft — FEW020 = FEW at 020 = 2000 ft (heights in METAR are in hundreds of feet)
❌ METAR cloud heights are in hundreds of FEET, not metres.
💡 METAR convention: cloud height code × 100 = feet AGL. 020 × 100 = 2000 ft.
Q8. Runway Visual Range is: (a) 1–2/8 (b) More than 1500m (c) 500–1000m
✅ Correct: (b) More than 1500m — R15/P1500U: P = more than, 1500 = value, U = increasing
❌ P prefix = Plus = more than; M prefix = Minus = less than.
💡 P1500 = RVR exceeds 1500m (instrument upper limit). U = upward tendency.
Q9. RVR is: (a) Decreased (b) Increased (c) Remained same
✅ Correct: (b) Increased — tendency 'U' = Increasing
💡 RVR tendency: U=Up (increasing), D=Down (decreasing), N=No change.
Q10. The poor visibility is due to Present Weather which is: (a) Fog (b) Brown Dust (c) Mist
✅ Correct: (c) Mist (BR) — BR is reported when vis is 1000–5000m
❌ FG = Fog (vis <1000m); BR = Mist (1000–5000m). Here vis = 1500m → BR is correct.
💡 Key split: <1000m = FG (Fog); 1000–5000m = BR (Mist).
Q11. Amount of lowest cloud is: (a) 1–2/8 (b) 2–4/8 (c) 5–7/8
✅ Correct: (a) 1–2/8 — FEW = 1–2 octas
💡 FEW=1–2, SCT=3–4, BKN=5–7, OVC=8 octas.
Q12. Amount of CB cloud is: (a) 1–2/8 (b) 2–4/8 (c) 5–7/8
✅ Answer: (a) 1–2/8 — FEW025CB is a FEW layer of cumulonimbus: FEW means 1–2 oktas.
❌ (b) 2–4/8 and (c) 5–7/8 would be SCT or BKN.
💡 CB is reported as its own group with the usual amount code.
Q13. Height of base of CB is: (a) 2500 m (b) 3000 ft (c) 2500 ft
✅ Answer: (c) 2500 ft — FEW025CB: the cloud base is 025 × 100 = 2,500 ft above the aerodrome.
❌ (a) 2500 m confuses feet with metres. (b) 3000 ft does not match the group.
💡 Cloud heights in METAR and TAF are in hundreds of feet.
Q14. The height of topmost layer of cloud is: (a) 3000 m (b) 30000 m (c) 30000 ft
✅ Correct: (c) 30000 ft — BKN300 = 300 × 100 = 30,000 ft
❌ Cloud codes in METAR are always in hundreds of feet.
💡 BKN300 = Broken at 30,000 ft (approximately 9000 m = FL300).
Q15. The landing forecast appended to any METAR is valid for: (a) 1 hr (b) 2 hr (c) 3 hr
✅ Correct: (b) 2 hr — TREND (landing forecast) is valid for 2 hours
❌ TAF is valid for 9–30 hrs. TREND is only 2 hours.
💡 TREND = 2 hour validity. BECMG starts and completes within those 2 hours.
Q16. The wind in TREND from 0330 UTC is valid up to: (a) 0400 (b) 0430 (c) 0415
✅ Correct: (c) 0415 — TEMPO FM0330, then BECMG AT0415
💡 TEMPO is valid until the next change group. BECMG AT0415 = change at 0415.
Q17. Expected visibility after 0415 UTC is: (a) 6000 m (b) 3000 m (c) 10 km or more
✅ Answer: (c) 10 km or more — After BECMG AT0415 the trend gives CAVOK, which means visibility of 10 km or more, no significant cloud and no significant weather.
❌ (a) 6000 m and (b) 3000 m are not forecast by the trend.
💡 CAVOK = 10 km or more + no significant cloud + no significant weather.
Q18. The difference between TT and TdTd is 3°C. The atmosphere is: (a) Very Dry (b) Moist (c) Saturated
✅ Correct: (b) Moist — TT=32, Td=29, spread=3°C → moist but not saturated
❌ Saturated = T-Td ≈ 0; Very Dry = large spread (>10°C); 3°C spread = moist.
💡 T-Td spread: 0 = saturated; 1–3°C = moist; >5°C = drying; >10°C = very dry.
Q20. Just before METAR issued: (a) Rain at obs (b) Rain during last one hour (c) Fog
✅ Correct: (c) Fog — REFG = Recent Fog, not rain
💡 REFG clearly indicates fog was recent. RERA would indicate recent rain.
Q21. Range of pressure as Q1003 is: (a) 1002.5 to 1003.5 hPa (b) 1003.0 to 1003.5 hPa (c) 1003.0 to 1003.9 hPa
✅ Correct: (c) 1003.0 to 1003.9 hPa — Q1003 means pressure was rounded DOWN to 1003, so actual value is 1003.0 to 1003.9
❌ Pressure is rounded DOWN (not rounded to nearest). So Q1003 = actual 1003.0 to 1003.9.
💡 QNH always rounded DOWN to whole hPa. Q1003 → actual pressure = 1003.0 to 1003.9 hPa.
Q22. Temperature reported as 32°C is: (a) 31.4 to 32.3°C (b) 32.1 to 32.4°C (c) 31.5 to 32.4°C
✅ Correct: (c) 31.5 to 32.4°C — temperature is rounded UP to next higher for 0.5°C increments
💡 Temperature involving 0.5°C or more rounds UP. So "32" represents range 31.5–32.4°C.
Q23. Visibility is reported in steps of 50 m when visibility is: (a) 800 m to 5000 m (b) 0 to 800 m (c) 5000 m to 10 km
✅ Correct: (b) 0 to 800 m — steps of 50 m for 0–800 m range
❌ (a) 800–5000m uses 100 m steps; (c) 5–9 km uses 1 km steps.
💡 Visibility step sizes: 0–800m → 50m; 800–5000m → 100m; 5000–9000m → 1km; ≥10km → 9999.
Q24. Visibility reported in steps of 100 m when visibility is: (a) 800 m to 5000 m (b) 0 to 800 m (c) 5000 m to 10 km
✅ Correct: (a) 800 m to 5000 m
💡 100m steps for the 800–5000m range.
Q25. Visibility reported in steps of 1000 m when visibility is: (a) 800 to 5000 m (b) 0 to 800 m (c) 5000 m to 9999
✅ Correct: (c) 5000 m to 9999 — 1 km steps for 5–9 km range
💡 5000–9000m: 1 km steps. Above 10km → 9999.
Q26. Visibility reported 9999 when visibility is: (a) 800 to 5000 m (b) 9000 to 9999 m (c) 10 km or more
✅ Correct: (c) 10 km or more
💡 9999 is a special code meaning ≥10 km. It does NOT mean exactly 9999 m.
Q27. Temperature +2.5°C is reported as: (a) 02 (b) 03 (c) 2.5°C
✅ Correct: (b) 03 — +2.5°C rounded UP to 3°C = coded as 03
💡 Rule: involving 0.5°C or more → round UP. +2.5 → 3 → coded 03.
Q28. Temperature −12.5°C is reported as: (a) −12 (b) −13 (c) M 12
✅ Answer: (c) M12 — −12.5 °C is rounded to the next higher value, −12 °C, and a negative temperature carries the prefix M: M12.
❌ (a) −12 is the value without the M prefix. (b) −13 rounds the wrong way.
💡 Round .5 upwards (towards zero for negatives), and use M for minus.
Q29. Pressure rounded to nearest whole number in hectopascal: (a) exact value (b) upper value (c) lower value
✅ Correct: (c) lower value — QNH always rounded DOWN
💡 Safety rule: always round DOWN so pilots have slightly lower (safer) pressure value.
Q30. QNH 1002.6 hPa is reported as: (a) Q1002 (b) Q1003 (c) Q1002.6
✅ Correct: (a) Q1002 — rounded DOWN to lower whole hPa
💡 1002.6 → round down → 1002 → Q1002.
Q31. QNH 29.92 inches is reported as: (a) Q2900 (b) A2992 (c) A 3000
✅ Correct: (b) A2992 — A prefix for inches; 29.92 → A2992
💡 Q prefix = hPa (QNH); A prefix = inches of mercury (altimeter setting). A2992 = 29.92 inches.
Q32. Fog is reported when visibility is: (a) <1000 m (b) 1000 m (c) >1000 m
✅ Correct: (a) <1000 m — FG reported when vis <1000 m due to water droplets/ice crystals
💡 FG = <1000m; BR (Mist) = 1000–5000m. This is a key exam boundary.
Q33. Mist is reported when visibility is: (a) <1000 m to 2000 m (b) 1000 to 5000 m (c) >1000 m
✅ Correct: (b) 1000 to 5000 m — BR (Mist) range
💡 BR = British term for Mist = 1000 to 5000 m visibility.
Q34. CAVOK signifies Visibility, Cloud… and present weather better than the prescribed values or conditions: (a) ceiling (b) base (c) amount
✅ Correct: (a) ceiling — CAVOK = Ceiling And Visibility OK
💡 CAVOK full expansion: Ceiling And Visibility OK.
Q35. CAVOK is issued when visibility is: (a) 9–10 km (b) 10 km or more (c) 10 km only
✅ Correct: (b) 10 km or more — CAVOK requires visibility ≥10 km
💡 All three CAVOK criteria must be met simultaneously.
Q36. CAVOK is issued when: (i) Vis 10 km or more; (ii) No cloud below 1500m or below highest MSA; (iii) No CB. (a) Any one condition (b) Any two conditions (c) All the three conditions
✅ Correct: (c) All the three conditions — CAVOK requires ALL criteria simultaneously
💡 CAVOK is only issued when ALL conditions are simultaneously satisfied.
Q37. SPECI is issued when: (a) Change in wind dir ≥60° and speed before/after ≥10 kt; (b) Mean speed changed by ≥10 kt; (c) Variation from mean speed by ≥10 kt and speed ≥15 kt. Options: (a) Any one / (b) Any two / (c) All three
✅ Correct: (a) Any one condition — SPECI issued when ANY one of the surface wind criteria is met
💡 SPECI wind criteria are OR conditions — any single criterion triggers SPECI.
Q38. SPECI is issued when Clouds are BKN or OVC base at 30, 60, 150, 300, 450 m AND cloud amount below 450m changes. (a) Any one condition (b) Any two conditions (c) All the above conditions
✅ Answer: (a) Any one condition — Each cloud criterion for a SPECI is a trigger on its own: any one of them is enough.
❌ (b) and (c) wrongly require two or all of the conditions to occur together.
💡 SPECI criteria are alternatives: any one triggers a report.
Q39. SPECI is issued for vertical visibility, by stations having Ceilograph, when sky is obscured: (a) True (b) False
✅ Correct: (a) True — SPECI is issued when sky is obscured and vertical vis changes or passes 30, 60, 150, or 300 m where laser ceilometer is installed
💡 Vertical visibility SPECI only applies where ceilometer/ceilograph equipment is installed.
Q40. SPECI is issued when surface temperature has increased by: (a) 3°C (b) 4°C (c) 2°C
✅ Correct: (c) 2°C — SPECI when surface temperature increases by ≥2°C from last observation
💡 Temperature SPECI threshold = 2°C increase from last observation.
Q41. WSRWY28 indicates that the wind shear has been reported for: (a) take off path (b) approach path (c) both take off and approach paths
✅ Correct: (c) both take off and approach paths — WSRWY (runway) applies to both
💡 WS RWYnn = wind shear on runway nn — covers both take-off and approach.
Q42. R26/M0150 in a METAR indicates that: (a) maximum RVR is 150 m (b) minimum RVR is 150 m (c) 150 m is the lowest RVR instrument can measure and RVR < 150 m
✅ Correct: (c) 150 m is the lowest the instrument can measure and RVR is <150 m — M prefix = less than/below minimum instrument range
❌ (a) P prefix = maximum instrument range; (b) M = below minimum instrument range.
💡 M = Minus = less than. M0150 = actual RVR <150m (below instrument minimum).
13. Master Reference Tables
Critical Numbers — Quick Reference
| Parameter | Key Value |
|---|---|
| METAR issuance | Half-hourly or hourly |
| SPECI for improvement | After 10 minutes |
| SPECI for deterioration | Immediately |
| TREND validity | 2 hours |
| Fog threshold | Vis <1000 m |
| Mist (BR) range | 1000–5000 m |
| HZ/SA/DU/FU/VA | Vis ≤5000 m |
| CAVOK vis threshold | ≥ 10 km (coded 9999) |
| RVR observations triggered | When vis or RVR <1500 m |
| RVR steps 0–400m | 25 m |
| RVR steps 400–800m | 50 m |
| RVR steps 800–2000m | 100 m |
| Cloud base steps ≤3000m | 30 m |
| Cloud base steps >3000m | 300 m |
| QNH rounding | Always DOWN to whole hPa |
| Temp rounding (≥0.5°C) | UP to next higher |
| SPECI wind dir change | ≥ 60° AND speed ≥10 kt |
| SPECI mean speed change | ≥ 10 kt |
| SPECI gust variation | ≥ 10 kt AND speed ≥15 kt |
| SPECI vis thresholds | 800, 1500, 3000 or 5000 m |
| SPECI RVR thresholds | 150, 350, 600 or 800 m |
| SPECI cloud thresholds | BKN/OVC at 30, 60, 150, 300, 450 m |
| SPECI temp increase | ≥ 2°C |
| SPECIAL (India) vis | 2000 or 4000 m |
| SPECIAL (India) cloud base | 90 or 120 m (where ceilometer exists) |
| MSA clearance | 300 m (1000 ft) above all objects |
| MSA sector radius | 46 km (25 NM) |
| Pressure range world | 850–1100 hPa |
Mnemonic Sheet
CAVOK = "10-No-No": Vis ≥10km + No sig cloud + No sig weather
Cloud cover Mnemonic: "Flock Scatters, Breaks Overcast"
FEW (1-2) → SCT (3-4) → BKN (5-7) → OVC (8)
Vis Steps: "50-100-1k-9999"
0–800m: 50m steps | 800–5000m: 100m steps | 5–9km: 1km steps | ≥10km: 9999
FG vs BR: "Fog Kills (below 1km), Mist is More (1–5km)"
RVR Tendency: "U-D-N = Up-Down-No change"
P prefix = Plus = more than | M prefix = Minus = less than
QNH Always Down, Temp Always Up (for 0.5°C increments)
SPECI Wind Criteria (any ONE): "60-10-10-15"
Dir change ≥60° AND spd ≥10 | Mean spd change ≥10 | Gust var ≥10 AND spd ≥15
Cloud cover Mnemonic: "Flock Scatters, Breaks Overcast"
FEW (1-2) → SCT (3-4) → BKN (5-7) → OVC (8)
Vis Steps: "50-100-1k-9999"
0–800m: 50m steps | 800–5000m: 100m steps | 5–9km: 1km steps | ≥10km: 9999
FG vs BR: "Fog Kills (below 1km), Mist is More (1–5km)"
RVR Tendency: "U-D-N = Up-Down-No change"
P prefix = Plus = more than | M prefix = Minus = less than
QNH Always Down, Temp Always Up (for 0.5°C increments)
SPECI Wind Criteria (any ONE): "60-10-10-15"
Dir change ≥60° AND spd ≥10 | Mean spd change ≥10 | Gust var ≥10 AND spd ≥15
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