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METAR RAINFALL

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MissSoph created the topic: METAR RAINFALL

Hi everyone....I’m really not getting how they work out the time for the rainfall in the METAR....

P133... following
METAR YBMK 291300Z 00000KT 1200NW 8000 -RA BKN012 24/18 Q1020 RMK
RF02.0/002.0

Ok....so the report is done at 1300UTC on the 29th...
2mm has fallen in the last 10mins..
But I don’t get how they are saying that no other rainfall has fallen since 9.00 local time
I don’t have the AIP yet as there is a new update to be included.. so the lady said wait to buy it do I get in included.. is there a section in there that talks about how to work out the rainfall message ... how do they get that it’s 9.00 local? Mackay is UTC +10?
#1

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Carello replied the topic: METAR RAINFALL

Here is a link to the Bureau of Met (BoM) web that you should find helpful - Metar-Speci

The YBMK METAR reports -RA and that 2.0 mm of rain has fallen in the preceding 10 mins leading up to the time of the report. The METAR also states that 2.0 mm has fallen since 9am local time. This means that it has just started to rain.

Just as a point of interest, the MK METAR vis groups look wrong. The prevailing vis. of 8000 should be listed first, followed by the min sector vis. of 1200NW - see pdf link above.

The METAR should look like this:

METAR YBMK 291300Z 00000KT 8000 1200NW -RA BKN012 24/18 Q1020 RMK
RF02.0/002.0
#2

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MissSoph replied the topic: METAR RAINFALL

Thanks for the help.. so it’s just a bom thing that they record the rainfall at 9 local time ...when the office opens ;) and in the metar it will always be that the rainfall is recorded at 9 local....?
#3

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Carello replied the topic: METAR RAINFALL

"so it’s just a bom thing that they record the rainfall at 9 local time ...when the office opens"

Yes, historically rainfall was read at the General Post Office - hence the 9am reading for the 24hr rainfall.

With the introduction of automation (ie the AWS), there was some talk within the BoM of shifting the 24 hr rainfall reading to midnight to better align with the calendar day - the idea was squashed because of the impact on the historical record. This may change some day, but for now the METAR/SPECI/TTF observations still record the cumulative rainfall from 9am to 9am in the last rainfall group.

FYI, the BoM attributes the 24 hr rainfall read at 9am to the previous day - eg if 2.0 mm was read at 9am Sunday, the BoM records this as 2.0 mm on Saturday. This is of no real significance to you as a pilot.

I hope this helps!
#4
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