'Official' station Wind Values: A query for a Professional Meteorologist

Hi,

I’m collecting wind speed, gust, and direction data from two nearby official stations to compare them with readings readings at my own station. I want to determine the extent of the differences for various wind directions, as a first step to understanding the underlying causes; sampling errors in my equipment, influences of local topology etc.

Of course it is critical to compare like with like - otherwise the results are meaningless. I’m confused about exactly what the wind speed information contained in the hourly reports from official stations is. I understand the wind speed data for a given hour is taken sometime in the 10 minutes proceding the hour e.g. between 0950 and 1000 for the 1000 ovservation, but I don’t know whether the reported wind speed is e.g. the ‘average’ in that 10 minute period, the maximum observed in that period or what? Also, in relation to gusts - how is it determined that ‘gusts’ are occurring and should be reported? Quite often no gust information is given in the hourly reports…

I assume there are a set of rules relating to these hourly readings? Can a professional or knowledgeable amateur cast any light on precisely how the wind values in an hourly observation are determined from the recorded anemometer data, so I can apply the same rules when producing the hourly report for my own station?

AFAIK there is no universal set of rules - even ‘official’ values may vary according to the protocols in different countries. In general in the UK for example, 10-minute mean values are used for data from non-aviation sources. But for some airports at least I’ve got a suspicion that 2-minute means may be reported on the basis that aircraft taking off and landing need more up-to-date information than 10-min means allow when conditions are changing quickly. If the peak gust in the preceding averaging period (eg 2- or 10-minutes or whatever) is greater than the mean by >10knots then the gust speed is also reported, but otherwise not.

It sounds like you’re maybe looking at METAR values. There’s a decent guide to decoding these written by a professional meteorologist (for UK use but I doubt that Ireland is very different) at:

http://www.booty.org.uk/booty.weather/metinfo/codes/METAR_decode.htm

prodata,

Many thanks. Of the two stations, one is an airport (EICK) and the other an official Met Eireann observation station (Roches Pt / 32950). I’d concur that UK and Irish observations are most likely done according to the same ‘rules’.

The link you’ve provided certainly moves me closer to a clear answer for EICK. I will be able to clear up quite easily whether EICK samples at 2 or 10 minutes.

The explanation of gust information is noted and clears that up.

In relation to Roches Point, 10 minute mean samples, with gusts > 10 knots in that 10 minute period being reported, would fit my own impressions, but perhaps an email to Met Eireann might be in order just to confirm.

It is almost certainly true that there are different rules for measurement being used in different countries…In the UK the MetOffice has info on [color=red]their website [/color] which corroborates Prodata’s input about an average being taken over a 2 minute period with a handheld anemometer. However, as ideally the anemometer should be at an unobstructed location some 30 ft (10 metres) agl, I believe that the electronic versions on a mast are more likely being remotely viewed and averages taken.

There is a definition of wind gust (as a forecast, not past tense)…Quote; is the maximum 3-second wind speed forecast to occur within a 2-minute interval at a height of 10 meters. Wind gust forecasts are valid at the top of the indicated hour. unquote

There are some active Professional Meterologists on the UKww forum and you may well get an immediate answer from them. If you do, put their answer back here :wink:

Further to my last:…Not unsurprisingly, I was asking similar questions about wind gust definitions a while back on the UKww forum…The thread is quite long but there are answers from the met professionals there which may enlighten you… :wink:

munrobaggins,

Many thanks; the UKWeatherWorld forum posts were indeed very informative. It just goes to show - knowing where to find the information is perhaps even more important than actually knowing it :smiley:

g’luck.