SYNOP Visibility 00

[xmetman]

It may have been happening for many years so excuse me if has, but in the past when you reported a visibility of 00 (less than 100 metres) in a SYNOP as an observer, you finished the SYNOP with a F80, F60 or whatever to indicate that the visibility wasn't 0 metres but somewhere between 10 and 90 metres. I think that this was changed to some kind of nine group in the 1980's which did the same thing. Maybe it's because UK SYNOPS now start life in a BufR format, and are then converted back to SYNOPs it's down to the convertor that OGIMET or whoever use, that forgets to add this nine group. It looks odd when it's plotted, and this is the first time that I've really noticed it.

 03414 - RAF Shawbury

 United Kingdom 75 M AMSL [52.8 N 2.7 W]

AAXX 31074 03414 41000 91303 10092 20091 30185 40274 56001 74544 89/// 333 55300 20000==

AAXX 31064 03414 17/00 /1201 10090 20088 30183 40272 57004 60002 733// 333 20060 3/003 55000 55300 20000 70000==

AAXX 31054 03414 47/01 /1701 10086 20084 30184 40274 56008 733// 333 55300 20000==

AAXX 31044 03414 47200 /1202 10072 20068 30185 40275 57010 734// 333 55300 20000 87/05 83/67==

AAXX 31034 03414 47919 /0701 10102 20097 30187 40275 58011 710// 333 55300 20000 88/67==

AAXX 31024 03414 47929 /1204 10107 20101 30193 40281 57006 710// 333 55300 20000 88/65==

AAXX 31014 03414 47934 /0902 10108 20102 30195 40284 58006 710// 333 55300 20000 88/64==

AAXX 31004 03414 17940 /1002 10109 20103 30198 40286 58002 60001 710// 333 55/// 20212 88/64==

AAXX 30234 03414 47934 /0000 10103 20099 30199 40288 54000 710// 333 55300 20000 88/64==

AAXX 30224 03414 47949 /0401 10113 20105 30201 40289 53001 710// 333 55300 20000 88/63==

AAXX 30214 03414 47950 /1103 10113 20105 30200 40288 54000 710// 333 55300 20000 88/63==

AAXX 30204 03414 47950 /1001 10107 20099 30199 40288 54000 710// 333 55300 20000 88/63==

AAXX 30194 03414 47957 /1302 10121 20106 30199 40288 54000 704// 333 55300 20000 88/63==

AAXX 30184 03414 17458 /1203 10122 20105 30200 40288 56001 60002 704// 333 10134 55300 20000 84/16 87/64==

AAXX 30174 03414 47459 /1202 10126 20106 30199 40287 56005 704// 333 55300 20045 81/17 87/64==

AAXX 30164 03414 45460 /1602 10131 20106 30199 40287 56009 333 55300 20190 85/14 86/64==

AAXX 30154 03414 45461 /1805 10132 20102 30201 40289 57009 333 55300 20319 88/14==

AAXX 30144 03414 45462 /1906 10132 20099 30205 40292 56012 333 55300 20363 88/16==

AAXX 30134 03414 45461 /1604 10129 20095 30208 40296 57009 333 55300 20494 88/14==

AAXX 30124 03414 17360 /1605 10123 20093 30210 40299 58008 60001 704// 333 55300 20318 88/09==

AAXX 30114 03414 47257 /1601 10118 20104 30217 40305 51001 704// 333 55300 20212 81/06 88/09==

AAXX 30104 03414 47356 /0101 10111 20105 30217 40306 51005 710// 333 55300 20149 88/09==

AAXX 30094 03414 47350 /3401 10107 20104 30218 40307 53005 710// 333 55300 20052 88/09==

[Keith (Southend)]

It might be worth emailing G. Ballester Valor, the webmaster.

webm...@ogimet.com

Keith (Southend)

[xmetman]

Keith

I've done that numerous times and have given up as he never answers my emails.

Bruce.

[Martin Rowley [West Moors/East Dorset]]

... I've had a quick look through the WMO Manuals and I can't find any way of reporting visibility <100 metres (in detail that is): nothing listed under the '9' Gp set certainly.

Martin.

[xmetman]

In the early 1990's the WMO rejigged the reporting codes (for some reason only known to themselves) but I was fairly sure there was a nine group that helped report visibilities less than 100 metres.

At the same time they removed the nine group to stop the reporting of optical phenomena/frontal passages/wind vears/temperature changes which I always try to report.

That WMO change also scuppered the reporting of the aurora which at Kinloss we had always done.

 

When I was observing I don't think I ever reported a visibility of less that 50 metres even in heavy snow showers, although once when we were driving back from Aviemore to Forres (over the Dava Moor) I had to pull the car off the road and get out at one point because the visibility was no more than 5 yards!

[Martin Rowley [West Moors/East Dorset]]

... I'm using the 1998 (amended) version of WMO coding manual so things may have changed since then: I'll have a hunt around later and see if I can chase down what is/is not allowed in the 'modern' SYNOP code - though as you've pointed out, it's all BUFR'd these days :-)

Martin.

[Metman2012]

Bruce, when I was at Heathrow, all the obs book from the start were held in the observing office admin office. It was fascinating to look at the observations in the early 50s when there were smogs. Visibilities of 1, 2 or 3 metres were common. Each ob was slightly different (I wonder if that was real!). I've heard that many weather stations put string or rope up to guide the observers to the screen etc. Driving in  5 yard visibilities is quite frightening - I've done it once.
Clean air act has improved things quite considerably!

[Martin Rowley [West Moors/East Dorset]]

... Based on Manual on Codes: International: Volume I.1, Part A- Alphanumeric Codes
[edition: 2011, updated 2015 / source WMO library web site]

'9' Gps:
00-09: Time and variability
10-19: Wind and squalls
20-29: State of sea, icing phenomena and snow cover
30-39: Amount of PPN or deposit
40-49: Clouds
50-59: Conditions in mountains, passes, valleys etc., (significantly different from station)
60-69: Present and past weather not already covered in '7' Gp.
70-79: Location and movement of phenomena
80-89: Visibility (see under)
90-99: Optical phenomena and 'miscellaneous' (e.g, sudden rise/fall of temperature/humidity)

The only section pertaining to visibility gives:-

Decile 80–89: Visibility
980VsVs Visibility towards the sea
981VV Visibility to NE
982VV Visibility to E
983VV Visibility to SE
984VV Visibility to S
985VV Visibility to SW
986VV Visibility to W
987VV Visibility to NW
988VV Visibility to N
989VbDa Variation of visibility during the hour preceding the time of observation and the direction in which this variation has been observed.

In the coding for VV (visibility), then as you've pointed out, 00 = < 100 m - no 'remarks' to point to a method of reporting lesser visibility . . .

. . . However, in the 'course' reporting section [90-99] of the VV/VsVs code, there are the following . . .
90 <0.05 km [<50m]
91 0.05 km [50 m]
92 0.2 km [200 m]
93 0.5 km [500 m] etc.......
But I'm pretty sure that this section isn't supposed to be used alongside the 00-89 set.

So, at face value, at least in the SYNOP/SHIP code, there is currently no provision to report visibility below 100 m in any detail.

As noted, the '9' Gp section has altered over the years - so there may well have been something before.

Also looked at the 'Regional' and 'National' variants - again nothing to allow a reporting of VIS below 100m (in SYNOP).

Martin.

[Paul Kendall]

Going back to when I used to do obs if vis below 100m we reported at end of ob FOG50 or what ever the vis was. We also used to add COTRA to end if contrails were observed. I think that they were dropped when the codes changed sometime in the eighties.
Paul Kendall

[xmetman]

Martin

I've just emailed an old colleague of mine and he has sent me some extra information.

This snippet is how a reconstituted SYNOP should look like with visibilities less than 100 metres.

And this is what I get from OGIMET which has converted the BufR into SYNOP.

My source says that the visibility at 0300 UTC was plotted as 60M for Kenley.

The 96147 is an amplification of the WW weather group and it looks to me like OGIMET can't handle regional codes and so throws it away and so we don't see it.

Here are the relevant bits in the WMO manual 306 part A manual:-

So that's why they can plot 60M and not 00M. 

The code format is dreadful and was obviously devised by a committee that have never done an observation in their entire lives.

You can only report 96147, 96148 or 91649.

What was the Met Office WMO representative doing on the day they drafted that rubbish?

Why didn't they just have a specific 9 group for visibilities less than 100 metres say 969VV and allow VV to be any integer value between 0 and 99.

So my memory is holding up quite well with the reporting of visibility

Here's the bit for optical phenomena and miscellaneous :-

I thought I was right - you can report such exotic things like a mirage or St Elmo's fire but you can't report an aurora.

Not that any of this matters much anymore because the SYNOP format has been replaced by BufR, which is a crying shame because the SYNOP format (apart from the 9 group stuff above) was readable and concise.

Bruce.

[Martin Rowley [West Moors/East Dorset]]

... dear me! What a mess!!

I bet the youngsters handling these things wish we old-folks who grew up with codes (when I joined the Office, some parts of the world, notably mainland China were using the IMO pre-1949 code) would toddle off to the nearest Hydrogen store and blow ourselves up :-)

Martin.

[Stephen Davenport]

Yep. That's exactly what I used to do as well as an observer (for both fog and contrails) up to about the mid 1980s.

Stephen
Indianapolis IN.