Chapter 27
RADAR REPORT (RAREP), SIGMET MESSAGE
& SATELLITE BULLETIN
DGCA CPL/ATPL Study Notes — Aviation Meteorology
📡
Compiled by Capt. Pankaj Pahil
DGCA CPL/ATPL Study Notes — Aviation Meteorology
1. Radar Report (RAREP) — Introduction & Code
RAREP = Radar Report. Reports the location, intensity, movement, and height of radar echoes (precipitation areas, thunderstorms) from a ground-based weather radar station.
RAREP is normally reported only at synoptic hours. In case of any break in observations or rapid development, additional messages are transmitted as necessary.
RAREP Code Form
RAREP FEBB liiiii YYGGg
CHARACTER (b.b.b.b.b.f.t.t) b.b.b.h.h./f.t.t.
Intensity Tendency: d.d.f.f. ALTD (bbb/H.H/rrr)
Code Elements Explained
| Code | Meaning |
|---|
| RAREP | Radar Report identifier |
| FEBB | Station Index number |
| YYGGg | Date and time of RAREP |
| liiiii | Station Index number |
| bbb | Azimuth in three digit degrees of points on the periphery of an echo area |
| rrr | Range: three digit in kilometres |
| ALTD | Indicator of Echo Height Information |
| H.H. | Height of Top of Echo amsl in km (may be repeated as required) |
| d.d. | Direction in tens of degrees in which echo is moving |
| f.f. | Speed in km per hour of the echoes |
2. RAREP — Character of Echoes & Intensity Terms
Character of Echoes
| Code | Character | Description |
|---|
| EYE | Eye | An echo of eye wall of a tropical cyclone |
| SPRL BAND | Spiral Band | A continuous or broken curved line of echoes of spiral band associated with a cyclone |
| SQL LN | Squall Line | Having length 60 km or more and length to width ratio about 10 to 1 |
| BRKN LN | Broken Line | Broken line of echoes |
| SLD | Solid | An area fully covered with echoes |
| BRKN | Broken | An area 4/8 to 7/8 covered with echoes |
| SCT | Scattered | An area 1/8 to 4/8 covered with echoes |
| WDLY SCT | Widely Scattered | An area less than 1/8 covered with echoes |
| ISLTD | Isolated | Isolated solid mass of echo |
| ECHO ALOFT | Echo Aloft | Echoes seen only at elevations higher than the beamwidth |
Intensity Tendency
| Code | Meaning |
|---|
| INCG | Increasing |
| DEC | Decreasing |
| NO CHG | No Change |
Bright Band & Anomalous Propagation (AP) are reported in plain language.
Bright Band = A radar echo caused by enhanced reflectivity of partially melted snowflakes — occurs at the melting level.
AP (Anomalous Propagation) = False echoes caused by abnormal bending of radar beam near the ground (temperature inversions etc.)
3. RAREP — Important Notes
- Groups within brackets () are repeated as many times as necessary.
- To define the shape of line echoes, spiral bands and eye wall: as many bbb/rrr points as necessary are used. Points given along the line in anticlockwise direction.
- To define the shape of areas: as many bbb/rrr points as necessary. Points given in anticlockwise order starting from the northernmost point. The first point is repeated as the last point to indicate it is a closed area.
- If an echo system with a distinct characteristic is partly or wholly embedded in another, the two systems are reported in separate groups.
- Reports of heights are restricted to a maximum range of 200 km from the station.
4. RAREP Decoded Examples
Example 1
RAREP 42375 15030 270/050 300/060 350/025 280/ 010 SLD INCG 1525 ALTD
270/09 050 340/10/060 280/12/ 010 =
Radar Report for 42375 (International Identification No.) (say) Palam Date 15th at 0300
UTC Area of Solid echo from and 270 deg 50, 300 deg 60 km, 350 deg 25 km, 280 deg 10 UTC
Area of Solid echo Moving in 150 direction with speed of 25 KMH
Altitude of echoes in 270 direction 9 km at 50 km
In 340 direction 10 km at 60 km; in 280 direction 12 km at 10 km = Intensity: INCREASING
Example 2
RAREP 43003 10143 270 / 030 / 330 / 040 050 / 020 MDT INCG RPD NW / 012 ALTD
260/ 15 / 030 BRIGHT BAND 280 / 30 AP 300/ 330 /150 Angles between the Azimuth
270° to 340° Range 15 to 20 nm (AP – Anomalous Propagation)
Station 43003, Date 10th at 14:30 UTC
Echo area defined by azimuths 270°/030 km, 330°/040 km, 050°/020 km (anticlockwise from northernmost)
MDT INCG RPD NW/012 → Moderate intensity, Increasing Rapidly, Moving NW at 012 km/h
ALTD 260/15/030 → Echo height: At azimuth 260°, top at 15 km, at 030 km range
BRIGHT BAND 280/30 → Bright Band at 280° azimuth, 30 km range
AP 300/330/150 → Anomalous Propagation between azimuth 270° to 340°, Range 15–20 nm
5. SIGMET Message
SIGMET = Significant Meteorological Information
Prepared in abbreviated plain language using ICAO approved abbreviations. Contains information about significant en-route weather hazards.
SIGMET for subsonic aircraft is identified as SIGMET SST.
SIGMET for supersonic aircraft is identified as SIGMET SST (separate series of sequence numbers).
SIGMET information is disseminated to all forecasting offices in India and also transmitted on AFTN under D/D priority to MWOs in neighbouring countries within a distance of 1100 NM from the boundaries of local FIRs.
6. SIGMET Content & Structure
flowchart TD
A[SIGMET Message Contains] --> B[Identification of MWO\neg. VECC]
A --> C[Message ID and Sequence No.\neg. SIGMET 2 = 2nd SIGMET]
A --> D[Date-Time Group\nValidity Period in UTC\neg. VALID 221215/221600]
A --> E[Description of Phenomenon\neg. SEV FRQ]
A --> F[Phenomenon for which issued\neg. TURB, TS]
A --> G[Observed or Forecast + expected\ncontinue time\neg. OBS AT 1150 UTC, FCST AT 1000 UTC]
A --> H[Location\nLat/Lon or geographic feature\neg. FCST TOPS FL390 S OF 54 DEG N\nor OVER KOLKATA AT FL250]
A --> I[Movement\neg. MOVE E 25 KT]
A --> J[Change in intensity\neg. INTSF, WKN or NC]
A --> K[Volcanic ash outlook\nbeyond validity period\neg. VABB SIGMET 3 VALID 221600/222000]
| SIGMET Element | Abbreviation | Meaning |
|---|
| Sequence | SIGMET 2 | 2nd SIGMET = 2nd SIGMET in series |
| Validity | VALID 221215/221600 | Valid from 22nd 1215 UTC to 22nd 1600 UTC |
| Severity | SEV | Severe |
| Frequency | FRQ | Frequent |
| Observed/Forecast | OBS / FCST | Observed at time / Forecast at time |
| FL | FL250, FL390 | Flight Level (×100 ft) |
| Tops | TOPS FL390 | Cloud/echo tops at FL390 |
| Intensity change | INTSF / WKN / NC | Intensifying / Weakening / No Change |
| Movement | MOVE E 25 KT | Moving East at 25 knots |
| No CB | OT LK | Outside cloud tops? (no CB) |
7. SIGMET Examples
TS SIGMET Examples
VECC SIGMET 4 VALID 161200/101600 TC OBS 20.2N 89.2E AT 1130 UTC FRQ
TS TOPS FL350 W 150NM OF CENTRE MOV NW 10 KT OTLK TC CENTRE
110300 21N 87.9E 111200 21.5N 86.4E.
VABB SIGMET 3 VALID 151600/152200 SEV TS TOPS FL400 W 150NM OF CENTRE
MOV NW 10 KT NC.
VECC SIGMET 3 VALID 151600/152000 TC FCST 20.2N 89.2E AT 1200 UTC FRQ
TS TOPS FL500 W 150NM OF CENTRE MOV NW 10 KT NC OTLK TC CENTRE
160300 21N 87.9E 161200 21.5N 86.4E.
1603001 21N 87.9E 16200 21.5N 86.4E.
Decoded (first SIGMET):
VECC SIGMET 4 → Met Watch Office Kolkata, SIGMET number 4
VALID 161200/101600 → Valid from 16th 1200 UTC to 16th 1600 UTC
TC OBS 20.2N 89.2E AT 1130 UTC → Tropical Cyclone Observed at 20.2N 89.2E at 1130 UTC
FRQ TS → Frequent Thunderstorm
TOPS FL350 → Cloud tops at FL350 (35,000 ft)
W 150NM OF CENTRE → Within 150 NM west of cyclone centre
MOV NW 10 KT → Moving NW at 10 KT
OTLK TC CENTRE 110300 21N 87.9E → Outlook: TC centre forecast at 0300 UTC on 11th at 21N 87.9E
111200 21.5N 86.4E → At 1200 UTC on 11th at 21.5N 86.4E
SIGMET Sub-types — Key Phenomena:
| Phenomenon | Code in SIGMET |
|---|
| Thunderstorm | TS |
| Severe Turbulence | SEV TURB |
| Severe Icing | SEV ICE |
| Tropical Cyclone | TC |
| Volcanic Ash | VA |
| Severe Mountain Wave | SEV MTW |
| Widespread Sand/Dust Storm | DS, SS |
| Marked Mountain Wave | MTW |
8. Satellite Bulletin
Satellite imageries are analysed and supplied as Bulletins in abbreviated form.
Format: SAT BLTN BASED ON METSAT PIC OF YYGGgg UTC
Satellite Bulletin Abbreviations
| Abbreviation | Meaning |
|---|
| CONVTE | Convective |
| CLDS | Clouds |
| EMBDD | Embedded |
| MOD | Moderate |
| INT CONVTN | Intense Convection |
| SKM | Srikakulam |
| EC BAY | East Coast Bay (of Bengal) |
| AFSN PAK | Afghanistan Pakistan |
| RPT | Repeat |
| IDS | Islands |
| COT | Coast |
| ADJ | Adjoining |
| EXT | Extending |
| S AREA | Sea Area |
| BET LAT | Between Latitude |
| LONG | Longitude |
| W COT | West Coast |
| SB | Scattered to Broken (cloud coverage) |
9. Satellite Bulletin Decoded Example
Original Satellite Bulletin (coded)
SAT BLTN BASED ON METSAT PIC OF 271200 UTC.
THE CONVTE CLOUDS CURVED BANDS OF VORTEX OVER EC BAY HAS REDUCED NOW
CENTERED OVER 16.5N/91.0E RPT 16.5N/91.0E(.) INTENSITY T REDUCED MOV
1.5 RPT T 1.5 (.) ASSTD BKN LOW MED CLOUDS EMBDD SCT MOD TO INT CONVTN
(AT10.5N TO 14.0N LONG 85.5E TO 91.5E AND LAT 14.0N TO 18.5N EAST OF
LONG 87.5E ARAKAN COT AND S MYANMAR(.) SCT M/LAYERED CLOUDS OVER NW JK
AND AREA BET LAT 37.0N TO 16.0N LONG 60.0E TO 100.0E(.) SCT LOW /MED
CLOUDS OVER SKM NE STATES BAY IDS KER(.) SCT MED/HIGHCLOUDS OVER AFSN
PAK REST JK HP UTRCL PJB AND NW GUI(.) SCT TO BKN LOW/MED CLOUDS EMBDD,
MOD TO INT CONVTN OVER S AREA BET LAT 5.0N TO 14.8N LONG 60.0E TO 68.0E
SE ARSEA ADJ INDIAN OCEAN BET LAT 2.0N TO 8.0N LONG 69.0E TO 76.0E S
SRILANKA GULF OF MARTABAN SUMATTRA ADJ W COT BORNEO JAVA IDS AND SEA
EXT. N MADAGASCAR(.)=
Interpretation (Plain Language)
Satellite Bulletin based on METSAT picture of 27th day at 1200 UTC:
The convective clouds — curved bands of vortex over East Central Bay (of Bengal) — has reduced. It is now centred over 16.5N/91.0E. Repeat 16.5N/91.0E. Intensity 1.5. Associated broken low and medium clouds embedded, scattered to moderate to intense convection at 10.5N to 14.0N long 85.5E to 91.5E and lat 14.0N to 18.5N east of long 87.5E — Arakan coast and S Myanmar.
Scattered medium layered clouds over NW J&K and area bet lat 37.0N to 16.0N long 60.0E to 100.0E. Scattered low/medium clouds over Sikkim, NE states, Bay Islands, Kerala. Scattered med/high clouds over Afghanistan, Pakistan, rest J&K, HP, Uttaranchal, Punjab and NW Gujarat.
Scattered to broken low/medium clouds embedded, moderate to intense convection over sea areas between lat 5.0N to 14.8N long 60.0E to 68.0E, Arabian Sea, adjoining Indian Ocean between lat 2.0N to 8.0N long 69.0E to 76.0E, S Sri Lanka, Gulf of Martban, Sumatra, adjoining west coast of Borneo, Java, islands and sea extending N of Madagascar.
10. Master Reference & Quick Revision
RAREP Key Reference
| Parameter | Key Value |
|---|
| SQL LN length | ≥ 60 km, length:width ratio ≈ 10:1 |
| SLD echo coverage | Fully covered |
| BRKN echo coverage | 4/8 to 7/8 |
| SCT echo coverage | 1/8 to 4/8 |
| WDLY SCT coverage | Less than 1/8 |
| Max RAREP height range | 200 km from station |
| Area shape direction | Anticlockwise from northernmost point |
| Line shape direction | Anticlockwise direction |
| Intensity INCG / DEC / NO CHG | Increasing / Decreasing / No Change |
| Bright Band / AP | Reported in plain language |
SIGMET Key Reference
| Parameter | Key Value |
|---|
| SIGMET for subsonic aircraft | SIGMET (plain) or SIGMET SST |
| SIGMET for supersonic aircraft | Identified as SIGMET SST |
| SIGMET dissemination to neighbours | Within 1100 NM of FIR boundaries |
| SIGMET transmission priority | D/D priority on AFTN |
| Intensity codes | INTSF (intensifying) / WKN (weakening) / NC (no change) |
| Observed vs Forecast | OBS AT time / FCST AT time |
SIGMET Phenomena Quick Reference
| Phenomenon | SIGMET Code | Significance |
|---|
| Thunderstorm | TS (FRQ/EMBD/SEV) | Major icing, turbulence, lightning hazard |
| Tropical Cyclone | TC | Extreme winds, rain, turbulence |
| Severe Turbulence | SEV TURB | Structural damage risk |
| Severe Icing | SEV ICE (non-FZ or FZRA) | Control surface icing |
| Volcanic Ash | VA | Engine damage, windshield abrasion |
| Mountain Wave | SEV MTW | Extreme turbulence & downdrafts |
Quick Revision — Chapter 27:
RAREP: Radar Report at synoptic hours; echoes plotted anticlockwise; max height reports within 200 km; AP and Bright Band in plain language.
SIGMET: En-route hazard information; in abbreviated plain language; SIGMET SST for supersonic; disseminated to MWOs within 1100 NM; INTSF/WKN/NC for intensity change.
SAT Bulletin: Based on Metsat pictures; abbreviated form; describes cloud coverage, convective activity, vortex positions; identifies geographic areas using standard abbreviations.
RAREP Echo Coverage Mnemonic: "Widely-Scattered-Broken-Solid"
WDLY SCT <1/8 → SCT 1–4/8 → BRKN 4–7/8 → SLD 8/8 (full coverage)
Capt. Pankaj Pahil