RAREP reader

What is the radar at Palam seeing?

Read a RAREP

Pick a report. The screen draws it straight from the code; tap any group to find it on the screen.

• Palam, a solid area
• A solid area of echo north-west of the radar, increasing, moving towards 150° at 25 km/h, with tops of 9 to 12 km.
• RAREP 42375 15030 270/050 300/060 350/025 280/010 SLD INCG 1525 ALTD 270/09/050 340/10/060 280/12/010 =
• Kolkata, a squall line
• Our own example: a Nor'wester squall line west of Kolkata, points given along the line anticlockwise, racing towards the south-east.
• RAREP 42809 22110 330/120 300/090 270/070 240/060 SQL LN INCG 1240 ALTD 300/14/090 260/16/065 =
• Chennai, a cyclone eye
• Our own example: the eye wall of a cyclone 130 km out to sea, drawn as a closed ring, drifting north-west.
• RAREP 43279 08060 052/142 051/121 060/108 069/121 068/142 060/152 052/142 EYE NO CHG 3010 ALTD 060/15/150 =
• Widely scattered
• Our own example: an area less than 1/8 covered, starting from the northernmost point and closed by repeating it. Dying out, so no heights are given.
• RAREP 42182 05090 350/180 300/160 330/120 020/150 350/180 WDLY SCT DEC 0515 =

Memory hook: bbb/rrr is a point, ALTD is how high: a RAREP is a drawing sent as numbers.

Takeaway: Station and time, then the outline of the echo as azimuth/range points, then what it is (SLD, SQL LN, EYE...), whether it is growing, where it is going, and after ALTD, how high the tops reach.

How does a RAREP turn into a picture?

A RAREP, group by group

An example from Palam, plotted step by step. Tap Next.

1. Who and when RAREP 42375 15030: a radar report from station 42375 (Palam, Delhi) on the 15th at 0300 UTC (YYGGg). RAREPs are normally sent at the synoptic hours, with extra reports if observations break or echoes develop fast.
2. The outline Each bbb/rrr group is a point on the edge of the echo: azimuth in degrees, range in km. Joined up they outline the area. The rule: areas start at the northernmost point and go round anticlockwise, repeating the first point to close the area. Not every real report keeps to it; the screen closes the area anyway. Lines, spiral bands and eye walls: points along the line, anticlockwise.
3. Character and tendency SLD: an area fully covered with echo. INCG: its intensity is increasing (DEC decreasing, NO CHG no change).
4. Movement 1525: dsds = 15, the direction it is moving towards in tens of degrees (150°), and fsfs = 25 km/h.
5. Heights ALTD announces the heights: bbb/HtHt/rrr, so 270/09/050 is a top of 9 km amsl at 270°, 50 km. Here the tops reach 9, 10 and 12 km. Heights are only given within 200 km of the radar. Bright band and anomalous propagation (AP) go in plain language.

Memory hook: RAREP · station · YYGGg · bbb/rrr… · character · tendency · dsdsfsfs · ALTD bbb/HtHt/rrr.

Takeaway: A RAREP is a drawing sent as numbers: station and time; the echo outline as azimuth/range points (bbb/rrr, km); the character (SLD) and tendency (INCG); movement as direction in tens of degrees and speed in km/h (1525 = towards 150° at 25 km/h); then after ALTD the tops as azimuth/height/range (km amsl).