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Old 7th Sep 2008, 09:09
  #41 (permalink)  
 
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FFF - you are quite right, but since when was this new fangled thing called the INTERNET a part of PPL syllabus?



A PROB needs to be supplemented by radar or similar data but only if people know about it. The availability is only a recent development - Meteox has been around only a year or two.

And, once outside one's home or club environment, how many airfields have a public PC with internet on it? Mine certainly doesn't. And the vast majority of pilots have no mobile internet and therefore no means of getting supporting info on weather once away from home.

I doubt anybody saying the forecast is duff will be able to support it with data - not because they are wrong but because getting the evidence (other than one for one's local area) is never easy. And anytime there is a PROB in there, you are wasting your time totally.
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Old 7th Sep 2008, 10:09
  #42 (permalink)  
 
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The fact that Met office don't think there is a problem is the problem. No doubt they would prefer people send them their data individually. It can then be ignored. Forums like this are the closest we can get to "Watchdog" like embarrassment of large monoliths so keep plugging away at this. Making our points here as many above have done is the best way to bring about a change. As has been said before Met office can and I'm sure do check what happens against what they predict so they DO know. Forget the ins and outs of TAFS etc. That is a red herring. It's all starts from the synoptic forecasts.

Save of copy of this NOW: http://www.meteonet.nl/aktueel/brackall.htm. Then as the week develops see what actually happens.

Like many other pilots I do this all the time in the hope that I can get to that weekend fly-in etc. IMHO there appears to be a fundamental problem with the weather models used in that they always predict lows will track farther east than they end up doing. Take this weekend. According to the above it was predicted to track up the English channel into France. In fact as we saw it tracke across the mid west of the mainland. When you look at what they actually do they invariably turn north as they get to the UK. This happens over and over again and in fact we all learned about it during our PPL (Coriolis effect). It is common sense that If you can't predict where the centre of a pressure will end up is then anything forecast based on that will be wrong. My 2p Steve
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Old 7th Sep 2008, 10:11
  #43 (permalink)  
 
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The local TAF gives a prob40 of the cloud base being 1,000 with viz of 4K, less in showers. The area forecast supports the terminal forecast. The majority of the time the base is 1,800 with viz of 6K. As a PPL with a hundred hours are you happy to be flying in the prob40 bit or relying on the weather being better?

So when there are parts of the forecast that are on your margins - do you not fly because of those parts, and if those parts turn out to be better than forecast are you upset at the loss of a days flying in consequence.

My point. It is the forecast with a component on your margin that are the ones you don’t like - the stay on the ground, go scenario. You don’t like them because of the marginal component. If the marginal component wasn’t there you would be happy, until you were pi**ed in the air when it turned out it should have been in the forecast.

I am not making excuses for the (in)accuracy of forecasts.

I am simply observing that we all have are own personal limits but the trouble is forecasts will often straddle our limits, so we like the good bits, not the bad. The reality is whenever you are near your margin it is very unlikely you will see just the good bits if you are flying any sort of distance.

I can think of a couple examples. On a recent flight the passenger wanted to enjoy the scenery. The forecast predicted scud running would work fine for most of the route and the forecast proved correct. However the margin between low level flying and remaining legal was small particularly over the route which included some higher ground. On a few occasions the decision had to be made whether to work around the low cloud or give the scenery bit up as a bad job and go IFR. With 100 hours I know I would not have been happy working my way around the low bits, not being sure how far left or right of track I would end up.

I had an occasion last year when I knew my passenger was not that comfortable a flyer. We ideally wanted to get back. The forecast was for strong winds but I anticipated the landing would be just within my limits. Never the less I planned a diversion. As it turned out the wind ended up being over 40 knots with the whole lot being cross wind and to make matters worse, very gusty. The whole flight was thoroughly unpleasant with light to moderate turbulence. In so far as the wind was concerned the forecast was wrong, but in hind sight probably by only around 20% in terms of the strength and 20% in direction. The turbulence was to be expected but perhaps not as bad as it was.

I don’t know, but say I don’t like 10% of the forecasts if I need to go somewhere. That means 90% of forecasts even if they prove a little inaccurate I don’t really think about. For example if the cross wind is 5 knots more than predicted I suspect it doesn’t really register. However when I didn’t like 40% of the forecast there were more occasions when I thought the forecaster had got it wrong because smaller changes in the actual weather put me closer to my personal limits.

And so, my point is, when the weather is on your margin you don’t go flying because you know marginal weather usually contains a forecast of bits that are below your personal limits and because marginal weather is rarely uniform (low bases are rarely exactly 1,200 feet over the entire area) there are almost always bits below your limits. Having decided not to go you watch the progress of the weather and note that none of the marginal bits turned up. Of course you understand that the forecast predicted this was likely but we still like to convince ourselves that had we gone flying we wouldn’t have run into any of the marginal bits either.

In short I am not saying you didn’t understand the forecast, or weren’t qualified to understand but at least on some occasions you did the sensible thing but of course wished you had gone aviating!
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Old 7th Sep 2008, 10:50
  #44 (permalink)  
 
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If issues are raised with CAA (or BOSE), then the Met Office cannot ignore comments.

Regarding use of the longer range charts for planning booking of aircraft/planning trips, it is a simple fact that the further out you look the less accurate it is going to be, but again actually think about the magnitude of the problem. Even for a front or low that is moving steadily with no changes, if the rate of movement is only 1 KT/hr in error, then in 120 hours the front/low will be incorrectly placed by 120 miles. That says nothing for developing systems that accelerate/decelerate or features that dont even exist on the analysis.

Look where all the lows are on the charts SN referred to. How much surface data is there out there in the Atlantic? Satellite fills in the gaps, but there are many unknowns.

Jetstreams drive the weather, and if they are wrong there will be downstream consequences in days to follow. Airliners crossing the Atlantic report winds but western bound ones will avoid the strongest headwinds (so denying data that would be very useful to fine tune models). Even those heading east and riding the wind may well avoid the strongest winds to avoid the associated turbulence.

There are plenty of other models out there to consult and compare, they will suffer the same issues.

I don't think the MO are out there to deliberately spoil your flying or you barbeques. When I see that many lows floating around to the west over the next few days perhaps the 'hint' is that perhaps conditions will be too changeable to plan anything for certain - paint the front room instead ;-)
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Old 7th Sep 2008, 14:27
  #45 (permalink)  
 
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Well just back from the Guernsey Air Rally where the weather was as forecast and just catching up on this.

I am not sure where the comments about the MO ignoring complaints are coming from. Every time I have asked for a complaint to be investigated it has been done so with good humour and accurate responses. The MO are VERY keen to provide a first class service and do not ignore any feedback in my experience to date.

But moaning about forecasts on forums without providing any FACTS does not constitute making a complaint to the MO which is then 'ignored'. Like I have said a few times already, provide hard facts and let me have them or complain direct to the MO with an MOR and they WILL be acted on.

EGHH 070602Z 070716 29013KT 9999 FEW031 BKN048 TEMPO 0716 28015G25KT PROB30 TEMPO 0716 8000 SHRA

Many pilots, especially novices, would look at the PROB30 TEMPO 0716 8000 SHRA, and interpret that as meaning that there could be rain, and associated low visibility, at any point during the day, so they'd stay on the ground.
Which would be the correct interpretation, but it is the pilot making the decision not to fly not a problem with the forecast. 8000m is legal VFR and I know my aircraft does not stop working when it gets wet. So if a pilot chooses to misinterpret the forecast how does it make the forecast wrong?
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Old 7th Sep 2008, 14:32
  #46 (permalink)  
 
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Which would be the correct interpretation, but it is the pilot making the decision not to fly not a problem with the forecast. 8000m is legal VFR and I know my aircraft does not stop working when it gets wet. So if a pilot chooses to misinterpret the forecast how does it make the forecast wrong?

Interesting that you would use the term 'misinterpret the forecast' here. Perhaps they interpreted as being outside their personal limits.

One of my group aircraft did fly through a Prob 30 shower and damn near wrecked the wooden prop. That was more down to airmanship than weather interpretation, but subsequent to that we all got very nervous flying the new prop in any sort of rain - for a bit, anyway.
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Old 7th Sep 2008, 14:36
  #47 (permalink)  

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Bose-x,

Glad you had a good day out in Guernsey, and welcome back to the debate. I think you have missed my point, though.

I agree that the forecast weather is VMC, but it may well be below what many pilots would be happy flying in VFR (as well as robin's very valid point about wooden props, or perhaps you might not want to fly in rain in your open-cockpit aircraft because it's not fun), so I think that debate can be put to one side for now. Let's asume personal limits at the planning stage of the flight, for whatever reason, of 10k viz and no precipitation.

The issue is with the interpretation of the weather information. You said that my interpretation of the TAF was correct. However, my issue is that, just by looking at the Metform 215 and the rainfall radar, I was able to produce a better forecast than the TAF. The TAF said might rain, I said it won't rain. I've been sitting in my living room, 4nm from the airfield, for the whole of the period of the TAF.... and guess what? It hasn't rained. So my question is, if I knew it wasn't going to rain, why didn't the Met Office?

FFF
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Old 7th Sep 2008, 15:22
  #48 (permalink)  
 
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So my question is, if I knew it wasn't going to rain, why didn't the Met Office?
Or perhaps you thought it was not going to rain and it didn't. The MO thought it might rain so gave a probability that it might happen but at Prob30 it was a low probability?


Now if they had not put the likelihood of rain in and it did rain we would complain the forecast was wrong......
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Old 7th Sep 2008, 15:29
  #49 (permalink)  
 
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Taking a look at the radar imager for 1100 Local (1000 UTC) on the Met Office public web site (sorry, haven't figured out how to insert images), shows rain/showers just north and west of Southampton - and not very far from Bournmouth at all. FFF I take "won't" as meaning 0% possible, but really with rain so close (and also some further NW) I don't really believe the possibitlity was 0%. Seems to me they knew showers would develop in the area, but cannot predict the track of every one.

Southampton reported -DZ and -SHRA at 1020 UTC And 1050 UTC.

Seems to me Met O were alerting to a realistic alternative, without going overboard and forecasting truly awful vis and drastically lowered cloud base. In fact the cloud cover was very variable at Bournmouth, and actually lower than the 0716 TAF predicted, but all within the 'leeway' allowed for in ICAO's and CAA's rules.


EGHH 071350Z 28013KT 9999 FEW010 BKN021 16/12 Q1008=
EGHH 071320Z 29011KT 9999 FEW010 BKN021 16/12 Q1008=
EGHH 071250Z 32013KT 9999 FEW018 BKN022 16/12 Q1008=
EGHH 071220Z 31011KT 9999 BKN021 16/12 Q1007=
EGHH 071150Z 31010KT 9999 SCT022 BKN028 16/12 Q1007=
EGHH 071120Z 31012KT 9999 SCT021 BKN022 16/12 Q1007=
EGHH 071050Z 31012KT 9999 SCT021 BKN028 16/12 Q1007=
EGHH 071020Z 31014KT 9999 FEW009 BKN022 16/12 Q1006=
EGHH 070950Z 30011KT 9999 FEW009 BKN019 15/12 Q1006=
EGHH 070920Z 30013KT 9999 FEW010 BKN019 15/11 Q1006=
EGHH 070850Z 29014KT 9999 SCT024 15/12 Q1005=
EGHH 070820Z 30013KT 9999 SCT030 15/12 Q1005=


TAF EGHI 071159Z 071322 26008KT 9999 BKN025=
TAF EGHI 070906Z 071019 25008KT 9999 BKN025 PROB30 TEMPO 1016 8000 -SHRA=
TAF EGHI 070638Z 070716 29013KT 9999 SCT020 TEMPO 0714 28015G25KT PROB30 TEMPO 0716 8000 SHRA=


EGHI 071150Z 26006KT 230V300 9999 FEW020 BKN024 14/11 Q1006=
EGHI 071120Z 26006KT 230V300 9999 FEW020 BKN024 14/11 Q1006=
EGHI 071050Z 26006KT 230V300 9999 -SHRA FEW020 BKN024 14/11 Q1006=
EGHI 071020Z 25006KT 220V290 9999 -DZ FEW018 BKN022 14/10 Q1006=
EGHI 070950Z 25006KT 220V290 9999 FEW018 BKN022 14/10 Q1005=
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Old 7th Sep 2008, 16:02
  #50 (permalink)  
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As I hinted at before, it's all about (artistic?!) interpretation and as FFF unwittingly highlighted, maybe too high a reliance on TAF's as opposed to the bigger picture in some quarters? I would suspect a failing during a pilot's practical training. How many times does an airfield receive telephone calls from potential visitors and club members asking about the weather?

The TAF is an aid, one of the many available (including simply looking out the bloody window but don't get me started on that!) for a pilot to determine if the WX conditions appear favourable for their particular journey. The TAF in no way absolves a pilot from responsibility does it? So why do some place their entire decision making process for a flight on it? As FFF stated, it is but one peice of information in the bigger picture and for what it's worth is more right than wrong, even in todays ever more unpredictable climate, when I check it five times a week for my patch.

My advice would be to continue the interest in Met following the written exam and past simply a fixation with TAF's. I flew for a whole year without ever looking at a TAF and avoided bad weather quite easily! lol

VFE.
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Old 8th Sep 2008, 08:53
  #51 (permalink)  
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Ken Wells

Any progress in identifying precise dates/times where the Met Office made a Horlicks of it, so that bose-x can get them to have a look ??
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Old 10th Sep 2008, 17:15
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will do, away till next week.
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Old 11th Sep 2008, 20:53
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OK - how about the sequence of the synoptics for, say, tomorrow.

During the week I have been monitoring the synoptics (not the BBC) with a view to a cross-channel trip. The forecast for tomorrow has showed a ridge building and a possibly good day, but in a number of the charts there were troughs indicated on the French side.

This morning, the chart showed the ridge stronger than before, but without the troughs. I spent the day planning and arranging the flight but late this afternoon we find the troughs back and an occluded front.

I'll be watching to see how the overnight charts develop as my optimism has started to plummet.
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Old 11th Sep 2008, 21:09
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If you are asking for advice on whether you can do your flight tomorrow, then looking at the forecast I would go.

The trough is way SW in France and it looks like during the day there will be a nice gap in the weather.

Where you going, LFAT? Want some company?
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Old 11th Sep 2008, 21:46
  #55 (permalink)  
 
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No Cherbourg - and the trough is sitting nicely in that area......
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Old 12th Sep 2008, 09:03
  #56 (permalink)  
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then looking at the forecast I would go.
The sort of silly comment that as an 'instructor' you should not be coming out with, especially on a website like this where you don't have all the facts about destination, aircraft equipment, pilot qualifications, etc etc...

Tut tut!

VFE.
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Old 12th Sep 2008, 10:11
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Good Discussion, and some GREAT new websites for my favorites folder. I can see my morning weather routine being somewhat longer now. Some of the satellite images on www.sat24.com are stunning (linked from meteox).

One website I use a lot and very few powered pilots seem to be aware of:

www.xcweather.co.uk

Make sure you go into preferences menu and turn raw data on, then you will see that each station provides the current METAR. This gives a very quick overview of the regional situation upwind or downroute or whatever you like.

Cheers SF
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Old 12th Sep 2008, 11:02
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Quote:
then looking at the forecast I would go.
The sort of silly comment that as an 'instructor' you should not be coming out with, especially on a website like this where you don't have all the facts about destination, aircraft equipment, pilot qualifications, etc etc...

Tut tut!

VFE.
What???? For a VFR flight the aircraft type is irrelevant. One would assume that the pilot holds a PPL. The question was answered with the assumption that it was a basic PPL doing a VFR flight. Therefore anything else does not come into the equation.

The conditions are VFR, the current METARS support VFR as do the TAFS for that region.

You really do have a bug up your ass with me at the moment don't you.
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Old 12th Sep 2008, 11:17
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Bose

As it turned out looking at the weather radar plenty of heavy showers along the north French coast this morning although the Cherborough penisula, rather than LFAT, was pretty clear.
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Old 12th Sep 2008, 12:17
  #60 (permalink)  
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Assumption = the mother of all cock ups.

And yes I do have a bug with you at the moment.

VFE.
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