Quality of UK Met office forecasting.

[roundwego]

Not sure if this strictly comes under "Tech Log" but couln't find anywhere more suitable.

Is it just my imagination or has the ability of the met office to provide useful forecasts been reducing year on year over the last 15 or so years?

Here is a typical TAF randomly picked off the list today.

1322 10014KT 6000 -RA FEW004 BKN009 TEMPO 1322 3000 -RADZ BKN004 PROB30 TEMPO 1322 1000 RADZ OVC002 PROB30 TEMPO 1322 9999 NSW BKN015

This TAF is no good to man nor beast as it effectively says;-

"The weather will be poorish but it might be bloody awful on the other hand it might be a fine flying day"

My view is that this is the Met Office's way off keeping their statistical accuracy high. Instead of working to produce more accurate forecasts, they widen the goalposts so wide they can't miss. Alternatively, have their legal advisors told them to cover all eventualities?

Anyone else of a similar mind? Would be particularly interested in the views of any Met Officers.

[APRIANA]

Hahaha,

the usual TAF. I would however take it from that one that the weather would be pretty poor, but may give some scope for a short local flight, or circuits.

I do agree that they seem to produce a TAF with so much scope that at some point they will have to hit the nail on the head.

[fireflybob]

I think part of this is a symptom of the demise of local forecasters of considerable experience as opposed to relying on a computer. I can recall the days in the early 80s flying out of Manchester and Birmingham where one was personally briefed by a local forecaster!

By that I do not mean that I am against computers! But a local forecaster was worth his/her weight in gold who was often privy to more anecdotal data than any "computer".

Remember going into Faro many years ago at night. At top of descent we heard the other company aircraft ahead of us diverting to Lisbon due fog at Faro. I decided to continue to overhead and was able to complete a visual approach in CAVOK conditions. After we had shutdown the agent came on the flight deck and I asked him where the fog was to which he replied "Oh fog never lasts more than 30 minutes here!". This is is the sort of local knowledge which can make a difference and he wasn't even a forecaster.

When I fly GA in the Midlands we talk about "Trent Valley" effect which has a tremedous effect on the local weather which is often at variance with the local weather.

[HEATHROW DIRECTOR]

<<But a local forecaster was worth his/her weight in gold >>

Wise and true words. There are half a dozen internet sites I visit for forecasts, plus we watch forecasts on the Beeb, ITV and Channel 5. The difference between them is often quite astonishing even though I assume that they are all working with info supplied by the Met Office... or am I wrong? One thing they can never get right is the forecast temperature: "It'll be around 5 degrees tonight"... next morning there's an inch of ice on the pond and the car won't start!

[SIGMET nil]

I can't really comment on the forecasting accuracy of the Royal Met Office, as I don't work in the UK. I stumble every now and then over one of their TAFs, when briefing pilots for flights to the UK and my experience so far has been, that UK TAFs are decent enough and often lean a bit towards the pessimistic side - just like ours. :}

With regard to the mentioned TAF - when I saw it, I at first thought it was a fake, because I can't seem to remember a TAF with so many overlapping TEMPO groups. However, I had a closer look and thought it looked like a situation with low stratus and warm advection aloft.

As I'm writing I still have some UK surface observations and some vertical soundings from the 30th available on my workstation. To me it looks like a vast part of England and the better parts of Wales and Scotland (except of some regions on the leeward/western side of some prominent hillridges) were covered with low stratus. In the Newcastle area it reached up to 5000 ft msl at noon, with other layers higher above. Indeed a southeasterly current e.g. at 5000 ft msl brought warmer air to the UK.
This weather pattern often is associated with drizzle falling out of the low stratus - with rapidly changing intensity and equally rapid changes in visibility and cloud base.
So I can understand, what was the motivation behind this TAF. A pity I don't know for which airport it was made. My guess would be Aberdeen, but I will probably err on this. Else I could have told you, what really happened in that period.

The highly complex computer models, that try to anticipate the state of the atmosphere ahead in time are fairly good in predicting the shifting and change of large weather structures, but at least the ones that are available to me do a poor or at best mediocre job in understanding, what will go on in the boundary layer of the atmosphere, say below 5000 ft above ground. Especially with regard to haze, mist, fog, low stratus and drizzle or snow grains.
So sometimes a forecaster can only recognize the potential for hazardous conditions, such as heavy drizzle with poor visibility, but he hasn't got a reliable guidance as to when this phenomenon may occur precisely. As others have already said, local experience may be of help, though.

Anyway, I don't agree with you, that this TAF is useless.

APRIANAs interpretation is spot on in my opinion. The MOST PROBABLE weather condition is expected to be 6 km visibility and 900 ft ceiling at this location.
So with the first group that states the basic weather conditions you already have a good idea that crosscountry flying VFR in a fixed wing plane may be problematic in this area. Especially in somehow hilly terrain. The various TEMPO groups offer quite a range for deterioration, so such a flight maybe outright dangerous as visibility and ceiling may drop even below the legal limits.
An IFR pilot however, who wants to operate into this field and has a limit of say 800 m and 200 ft ceiling can expect a pretty low chance, that conditions will be below his limit and also good chances, that conditions will be significantly better than that.
Somebody, who is desperate to practice some VFR patterns at the field may deduct from this TAF some chance to be able to do so, but as it is just PROB30 that cloud base will be better than 1000 ft agl chances are, that he or she will waste a lot of time, while waiting for sufficient conditions.

I think an individual weather briefing taylored to your special demands could in this situation shed more light on expected conditions for your flight, than this TAF can. In Germany, we still offer such briefings, mainly via telephone. The feedback from pilots so far has been encouraging.

One final note with regard to computers - 12 years ago work as a MET officer - at least here - was still exclusively a paper and pencil job. I just want to talk for myself, but since the advent of modern computer workstations I have been able to visualize weather data and which enabled me to absorb a vastly higher amount of weather related information in a very short time. This has improved my understanding of weather patterns enormously. I daresay, this has also considerably improved the quality of my forecasts and briefings in the past 8 years. More than can be accounted to the improvements in resident numerical modelling, to choose my words very carefully. :} I hear the same from other colleagues, that I regard as competent.

I'd be also highly interested in feedback to the original question from pilots and meteorologists alike.

[SIGMET nil]

With regard to HEATHROW DIRECTOR's comment on temperature forecasts:

- The source of weather information for the mass media may vary indeed. The quality of their weather forecasts will depend on the quality of their raw data and even more on the compentence of their in house staff to process the information and prepare it for broadcast.

- Often the media don't allow enough time for a detailed forecast in their weather transmissions.

- Making good temperature forecasts is not a trivial task. You either need a lot of local experience in a forecaster, which is expensive as any manpower is.
The output of the numerical models is of limited use, as, see my above posting, the boundary layer near the surface is not simulated with sufficient accuracy.
However a strong combination is to make a statistical approach to the numerical data. So you need to build a lot of preferredly fully automatic weather stations and make a statistical approach to their temperature measurements with regard to the various weather patterns.
After a couple years the system can say 'This particular weather pattern will probably yield this temperature at this particular location'
That is an automated way of gaining 'local experience'. A private company here in Germany is doing this, and from what I can tell with great success.

[SIGMET nil]

Another hint for private use ..

why not make your own forecast ?
At least for domestic purposes ...

Here you can find a lot of numerical weather information:

http://www.wetterzentrale.de/topkarten/fsavneur.html

(Bodendruck = surface pressure, Mittl. Wolken = medium level clouds, Niederschlag = precipitation, Taupunkt = dew point, Stromlinien = stream lines, other words like 'Temperatur' are self explaining I hope)

Here you get this in higher resolution, at least for England and Wales:

http://www.wetterzentrale.de/topkarten/fsgfsmeur.html

The modelling is done by the Yanks and it is at least worth a try - they do a very good job for Southern Germany.

[Linton Chilcott]

Can any of you met guys clarify how the "PROB 30 / 40" info is defined and even derived?

They seem to me to have a rather nebulous definition. I have been unable to find a written resource that explains precisely what they mean. To me, "PROB 30" could mean:

1. AT ANY GIVEN MOMENT, there is a 30% chance of ...

or

2. There is a 30% chance of ... occurring AT SOME STAGE throughout the period.

Two slightly different possibilities. In general, it probably doesn't make a lot of difference, I know - in effect it means "a feeling in our water suggests that ... might happen". However, somewhere in this highly defined business of ours, there must surely be a clear definition of what it means and how it is derived. Or not.

Thanks.

Also, about once a fortnight or so, I find myself comparing a METAR with a TAF covering the period of the METAR, and find the METAR to be already worse than anything in the TAF. (But I guess it's a black art, as much as a science!) Certainly, while JAR permits ignoring certain PROB items in a TAF while selecting the Alternate, these occurences make me think it is a very good idea to temper this with common sense!

[bookworm]

The syntax of PROBs is defined in the WMO Manual of Codes in FM51 (TAF) 51.9. Unfortunately it leaves the application somewhat open to interpretation. Here's mine:

PROB30 TEMPO <change group>

means that there is a 30% chance of the weather described in the change group occuring at some time within the period in circumstances that would fit TEMPO (i.e. less than an hour in each instance and no more than 1/2 the period)

PROB30 <change group>

means that there is a 30% chance of the weather described in the change group occuring at some time within the period in circumstances that would not fit TEMPO. That means that either the weather described in the change group, if it occurs, is expected to persist for more than 1/2 the period, or that it will last for more than an hour at a time.

Thus even in the second case, the chance of it occuring at any given moment may be much less than 30%.

(IANAMG)

[SIGMET nil]

@ Linton Chilcott's question:

I browsed several documents such as the ICAO Annex 3 and the NWS regulations for TAF production and couldn't find a specified definition on how prob30 is defined.

Annex 3 - 6.2.10 reads:

Recommendation: The probability of occurence of an alternative value of a forecast element or elements should be indicated, as necessary, by use of the abbreviation "PROB" followed by the probability in tens of per cent and the time period during which the alternative value(s) is (are) expected to apply. The probability information should be placed after the element or elements and be followed by the alternative value of the element or elements. The probability of a forecast of temporary fluctuations in meteorological conditions should be indicated, as necessary, by use of the abbreviation "PROB" followed by the probability in tens of per cent, placed before the change indicator "TEMPO" and the associated time group.
A probability of an alternative value or change of less than 30 per cent should not be consiedered to be sufficiently significant to be indicated. A probability of an alternative value or change of 50 per cent or more, for aviation purposes, should not be considered a probability but insetad should be indicated, as necessary, by use of the change indicators "BECMG" or "TEMPO" or by subdivision of the validity period using the abbreviation "FM". The probability should group should not be used to qualify the change indicator "BECMG" nor the time indicator "FM".

PROB30 means the probability at a given time. Else the probability for something to happen in a PROB30 group for say a 2 hour period would be higher in comparison to that in a PROB30 group for a 4 hour period. If probability for certain weather conditions becomes higher than 50 %, these conditions are considered to be prevailing weather, temporary or persistent respectively ...