Unfamiliar METAR coding
 

Saw this on another website and couldn't find the answer in the NOAA FMH.

What does the modifier "MM" mean when appended to TS?

Example:

METAR KHDC 180138Z AUTO 00000KT 10SM TSMM SCT110 26/20 A2993 RMK AO2 LTG DSNT S THRU N

I have had a very good look at various ref's and I can't find an answer. I can find plenty of US metar's that are using it. I used the NOAA translation function and it just ignores the MM. Must be a US thing although like you say NOAA and the FAA don't use it in their manuals.

Chance are that it is something very simple like how the TS were observed, an automated system perhaps?
Any US domestic dispatchers able to answer this one?
Someone ring the local met bloke.

wild guess- moderate..??

I don't think it means moderate. Moderate activity is noted by the absence of the light prefix "-" and the heavy prefix "+". So a moderate thunderstorm is just TS.

I've only seen this in automatic METARs, so it may have some meaning related to that.

Any more input? This is a head-scratcher...

'MM' looks like some kind of precipitation identifier, as it's in the correct sequence in the METAR. The +/- intensity identifier usually prefixes the wx phenomenon. Thats my 2p ............

l5otg

Could be a typo, never seen MM but am familiar with MI which is shallow.

google TSMM metar and you will find references to a number of US airports using it. But like you say could be a typo.

And yet, it's on a cached page from the NOAA site...

http://64.233.167.104/search?q=cache...lnk&cd=1&gl=us

Hi all...

Ive had a cursory look at other stations with either the TSMM or even VCTSMM and they are all from AUTO stations - meaning there is no human input into their creation. Mind you, that does not mean that it cannot be created by the coder.

Mammatus Cloud is coded as CBMAM so thats not it, and TSNO stands for Thunderstorms with no information....

I had a thought that it could indicate some sort of macro or microburst in the area, but Im not sure if an Auto station would have the ability to track that sort of data.

Anyone want to halt our speculation????

While we are on the subject, I saw 'FLA' on a D ATIS the other night. Any suggestions?

Personally, I think Lauderdale has already give the answer to the MM conundrum.

I've been unable to find a definitive answer anywhere, so here's my speculation!:

This is a type 2 auto ATIS that specifies precipitation type ie RA/GR/PL. This is where the MM is so could be the discriminator needs maintenance. I know this is usually indicated by a $ sign for the whole system, but could this just be the discriminator part? :hmm:



Either that or storms originating in Mexico FIR. :ugh:

Solved
 

I emailed America and just got this back

MM - missing data

TSMM thunderstorm sensor missing.


Ron Jones
Internet Projects Specialist
National Weather Service
Office of the CIO
Silver Spring, MD 20910

Grasscarp,

Thanks a lot. Great minds think alike. Here's my response from NOAA.

"In METAR, MM would be considered missing; so while one would expect TSRA for thunderstorm and rain, the MM indicates a missing precipitation value. While this is certainly not standard, I would assume that there might have been a problem with the present weather sensor and as such that value was missing."

thats too cool...
never even saw the A02 code...jeez!

almost felt like being at work! hahaha

AO2
 

Morning all,

The AO2 remark is just stating that the METAR was produced by an automatic surface observation station (ASOS) that has a precipitation sensor/discriminator, plus in this case it also has a lighting detection system which produces the notes in the RMK section.

The AUTO designator in the METAR means that the reports are generated and distributed without any human oversight. When there is no AUTO it just means the met man/woman is in the building to check the auto-generated reports before they are issued, and can add any RMKs he/she sees fit.

If the system requires maintenance the whole report will be appended with a dollar "$" sign as B777FD says.

Buzzz

TSMM in METARS
 

TSMM indeed means thunderstorm sensor is missing. It is used almost exclusively in automated METARS when TS activity is noted in the remarks when such activity is derived from the National Lightning Detection Network system. In other words, some ASOS airports do not have local TS sensors (TSNO) but, do have TS activity posted in the METAR remarks.

gh