How useful is sectorised visibility?

[Reggy Stirred Yuza]

Hi,

 

Just wondering what others think of sectorised visibility reports in metars. I think it is a bit confusing trying to work out what they mean and how to interpret the data for take off and landing. How many people know where they are doing these reports from? How do you take into account the displacement from them to where you're taking off from?

 

Any tips or tricks or do you ignore them and work out your own version of vis?

 

 

[TAA Student Pilot]

I generally look out the window. The only weather I get is just on the net, four day/sat piccie and actual radars will do me. To be honest I can't be bothered trying to decifer 6 pages of dribble they send through naips. However if going into somewhere that there's a chance of a ramp check I do carry the latest weather from naips along with a load print out. Have never been ramp checked, there's always a first time though.

 

 

[Guest 3rd dimension]

If you read AIP GEN 3.5 Met Services it explains all you need to know

 

Hope this helps

 

 

[Guest 3rd dimension]

I generally look out the window. The only weather I get is just on the net, four day/sat piccie and actual radars will do me. To be honest I can't be bothered trying to decifer 6 pages of dribble they send through naips. However if going into somewhere that there's a chance of a ramp check I do carry the latest weather from naips along with a load print out. Have never been ramp checked, there's always a first time though.

Student pilot

 

By the sound of that, it means you pretty much "wing" the weather on your flights.

 

Pretty stupid

 

 

[Coop]

I generally look out the window. The only weather I get is just on the net, four day/sat piccie and actual radars will do me. To be honest I can't be bothered trying to decifer 6 pages of dribble they send through naips. However if going into somewhere that there's a chance of a ramp check I do carry the latest weather from naips along with a load print out. Have never been ramp checked, there's always a first time though.

When I read the weather (I get my forecasts from AOPA's website- saves mucking about with NAIPS) I have a copy of the PCA next to the computer so that I can check to see where the various fronts, troughs, etc are going to be located and at what times. I find this makes the official forecasts much more understandable. I find these forecasts to be quite accurate, and so they should be, as they are only looking a few hours ahead. The four-day forecasts are nothing like as precise, because they are looking much further ahead.

 

Another really useful formula (that the met people use) is the following:

 

Cloudbase = (Temperature - Dewpoint) * 400.

 

(eg: (38 degrees - 30 degrees) *400 = 3200 feet.) This explains why a low cloudbase in the morning often gets higher as the day warms up.

 

You can get current dewpoint from many of the web weather sites. If you are flying towards rising ground, then knowing where the cloudbase is likely to be in that area is very useful.

 

Finally, while I appreciate your sentiment in trying to avoid a penalty from a ramp check- all a ramp check will do (if you are found wanting) is cost you some money. Flying into deteriorating weather because you didn't get a good forecast can be a whole lot more expensive....

 

In over 30 years of GA I've never been ramp checked (touch wood) but then I've generally stayed away from the really big GA fields. However, I have flown in some quite marginal conditions and discovered that the met bureau generally do a good job.

 

As for "sectorised visibility"- what the hell is that? :-)

 

Regards

 

Coop

 

 

[Reggy Stirred Yuza]

By "sectorised visibility" I mean when they report things like "4000m SW 9999" in metars or specis. They report how far they can see and in what direction but it doesn't seem to represent what we see on the runway. Sometimes they report speci conditions because of reduced visibility where they are but the aerodrome is relatively clear. I am wondering how others deal with this info? I suppose most people simply ignore the reports and work out visibility for themselves?

 

 

[TAA Student Pilot]

Student pilotBy the sound of that, it means you pretty much "wing" the weather on your flights.

 

Pretty stupid

Maybe so. What do you folks do in remote areas where you can't access weather?

 

 

[TAA Student Pilot]

In over 30 years of GA I've never been ramp checked (touch wood) but then I've generally stayed away from the really big GA fields. However, I have flown in some quite marginal conditions and discovered that the met bureau generally do a good job.

Coop

I have been flying for a while and find the opposite, they are getting better though.

Where abouts are you in SA Coop? I might get down that way in the next month or two.

 

 

[Guest aviatrix27]

While I download weather reports for most of my flying, when possible (sometimes it just can't be done - just try getting an internet connection with your you-beaut Next G modem at Birdsville), I've found that more often than not, the information contained in the report bears little resemblance to actual conditions.

 

These days, there is absolutely no excuse for anything other than plain English reporting. The reason for the abbrieviations used to be cost, that was in the days of telegraph and telex. I haven't operated a telex machine in 25 years or more. Weight limitations preclude most of us carrying full AIPs with us. As for "4000m SW 9999" that could mean almost anything including but not limited to the location of the observations being 4000m SW of the aerodrome and visibility is greater than 10 km at that place.

 

I'm a VFR pilot and fly purely for fun. I have one basic rule when it comes to weather. If I can't see 20 miles (37 km, several times the VFR minima), I don't go. Period. If visibility falls below 20 miles in flight, I find an alternate and land. I don't care what the weather report says, I rely on what I can see, hear and feel. Several times in the last year, weather reports have indicated winds of 35 knots plus, so instead of flying we took the car. Each time the weather reports were wrong, but we were better off safe than sorry. I once departed from an airport and just as I was about to change to area frequency, I heard an RPT say he was conducting a straight-in approach on the reciprocal runway to that I had just used. I called and told him that wind on the ground favoured the other end and got a curt reply saying he had the METAR. I replied with "your call". Actual wind on the ground was approximately 20 knots, and in the opposite direction to the information he had been given. It wasn't long before I heard him announce, in a shaky voice, that he was joining downwind for the runway I had just used. Another time, I was flying in company with a friend, he accessed weather reports in flight and was panic-stricken about reported thunderstorms at Griffith. We were in that area, there was not one cloud visible - anywhere. I did tell my friend to look out the window...

 

As for anyone referring to another person or their decisions on this forum as "stupid", I consider this to be unproductive and extremely close to flaming. That doesn't happen here, please don't resort to name-calling.

 

 

[TAA Student Pilot]

Bewdy, good onya K :biggrin:

 

 

[Coop]

I have been flying for a while and find the opposite, they are getting better though.Where abouts are you in SA Coop? I might get down that way in the next month or two.

Live in Adelaide. Keep the aeroplane out of town, but .

 

Had an occasion where they forecast thunderstorms "north of a line Tibooburra to Cobar" when we got to Cobar- there they were. We had to fly between a couple to get in to Cobar.

 

Likewise they frequently forecast cloud in a direction beyond a line from A to B and I usually find that they are pretty well spot on (give or take a couple of miles).

 

Cloud bases are also usually pretty accurate in my experience. The least accurate figure is usually the wind speed/direction. But that rarely poses a safety risk, and once you are out on track you pretty well know what it really is anyway, and can adjust your plan accordingly.

 

However, I guess some areas are easier to forecast than others, maybe SA's weather is a little easier to model than areas around Sydney or Melbourne.

 

Coop

 

 

[Coop]

While I download weather reports for most of my flying, when possible (sometimes it just can't be done - just try getting an internet connection with your you-beaut Next G modem at Birdsville), I've found that more often than not, the information contained in the report bears little resemblance to actual conditions.These days, there is absolutely no excuse for anything other than plain English reporting. The reason for the abbrieviations used to be cost, that was in the days of telegraph and telex. I haven't operated a telex machine in 25 years or more. Weight limitations preclude most of us carrying full AIPs with us. As for "4000m SW 9999" that could mean almost anything including but not limited to the location of the observations being 4000m SW of the aerodrome and visibility is greater than 10 km at that place.

 

I'm a VFR pilot and fly purely for fun. I have one basic rule when it comes to weather. If I can't see 20 miles (37 km, several times the VFR minima), I don't go. Period. If visibility falls below 20 miles in flight, I find an alternate and land. I don't care what the weather report says, I rely on what I can see, hear and feel. Several times in the last year, weather reports have indicated winds of 35 knots plus, so instead of flying we took the car. Each time the weather reports were wrong, but we were better off safe than sorry. I once departed from an airport and just as I was about to change to area frequency, I heard an RPT say he was conducting a straight-in approach on the reciprocal runway to that I had just used. I called and told him that wind on the ground favoured the other end and got a curt reply saying he had the METAR. I replied with "your call". Actual wind on the ground was approximately 20 knots, and in the opposite direction to the information he had been given. It wasn't long before I heard him announce, in a shaky voice, that he was joining downwind for the runway I had just used. Another time, I was flying in company with a friend, he accessed weather reports in flight and was panic-stricken about reported thunderstorms at Griffith. We were in that area, there was not one cloud visible - anywhere. I did tell my friend to look out the window...

 

As for anyone referring to another person or their decisions on this forum as "stupid", I consider this to be unproductive and extremely close to flaming. That doesn't happen here, please don't resort to name-calling.

G'Day aviatrix,

 

I couldn't agree more with respect to weather codes- they are no longer needed and we should be provided with the option of coded or plain english weather. I hate them, but I still use them because they are a good source of information. I think the reason they stick with coded weather is to maintain consistency with ICAO who have to set standards for world-wide operations, and some places may still be using teletype machines (although I doubt it).... Its probably just that such a wide-ranging change has to be approved across so many countries that it would take ages to achieve, and maybe they have other priorities. Anyway, that's my guess.

 

As for accuracy- I think once you get the hang of reading the weather reports, they contain a great deal of useful, and usually accurate, information. But remember, they are forecasts, not necessarily a statement of what the weather is right now. Pay attention to their period of validity, and bear in mind that they are forecasting for an area, not just one location. Could it be possible that what you have seen was either out of the validity period, or only present in a part of the area?

 

Which winds were being forecast at 35 knots? The aviation forecasts don't give winds at ground level (which is what you would see from your car)- they start at 2000'. It's not unusual for significant differences between what's on the ground and what is forecast at altitude. If you are flying, I presume you would want the winds at your altitude, unless you go in for worm-burning....:tongue:

 

A pilot who ignores a local report from another pilot is a mug- as you so rightly observed. He'll probably pay more attention next time. Some of these folks are too "professional" for their own good....

 

I also adopt your procedure- I fly for fun too, and if the weather gets too "iffy" I land, like you suggest- usually at an airfield, but we've dropped into good paddocks once or twice to wait out a passing rain band. And I've met some very interesting people as a result of unplanned landings on many occasions. If conditions begin to get marginal, I'll only proceed if I can see that there is an "out" either behind or in front. Sometimes an hour or two on the ground is all it takes for the weather to clear, on other occasions I've simply amended my route to go around the worst of it.

 

In remote areas where no other alternative exists, I'll use a land line to call Airservices and get them to read it to me. I've been to some pretty remote places in Dorothy, and its very rare that I can't get a forecast somehow. These days most places have internet access and most people don't mind letting you use their computer for a few minutes.

 

I'm very surprised at the number of people here who think that the Met Bureau's forecasts are useless. But as I said elsewhere, maybe its got something to do with the area being forecast.

 

Safe flying!

 

Coop

 

 

[Guest aviatrix27]

Which winds were being forecast at 35 knots? The aviation forecasts don't give winds at ground level (which is what you would see from your car)- they start at 2000'. It's not unusual for significant differences between what's on the ground and what is forecast at altitude. If you are flying, I presume you would want the winds at your altitude, unless you go in for worm-burning....:tongue:

Wind at 2000 35 knots, airfield elevations 1000'+. Both ends had private airfields with one runway at each, so we figured we would be up the proverbial creek if either airfield had that wind as a crosswind. Other people flew in the same day and said there was little or no wind up to 5000'. Maybe the forecasts in the eastern States aren't quite as accurate as they are in your parts. Here, they're definitely horoscopes with numbers :biggrin:. Even saying that, they're not TOTALLY useless, sometimes they're reasonably close to the mark, just not as often as they should be.

 

 

[TAA Student Pilot]

I have been flying for a living (And for fun, not just a prostitute) for thirty years now. In that time I can only remember landing off an airstrip once because of weather. I have done a bit of flying (20,000+ hours) in that time in all sorts of Aircraft and not had a weather related accident. My current job is flying on only the worst days weather can throw at us in the summer, it's a matter of reading the weather your flying in. Your quite welcome to get any weather predictions you want, I will look at the windsock, clouds and go and do my job.

 

SP

 

 

[Coop]

I have been flying for a living (And for fun, not just a prostitute) for thirty years now. In that time I can only remember landing off an airstrip once because of weather. I have done a bit of flying (20,000+ hours) in that time in all sorts of Aircraft and not had a weather related accident. My current job is flying on only the worst days weather can throw at us in the summer, it's a matter of reading the weather your flying in. Your quite welcome to get any weather predictions you want, I will look at the windsock, clouds and go and do my job. SP

Hey, I'm not knocking looking at the windsock and clouds. Very useful sources of local information, and to be relied on more for your local airfield's weather than prognostications from an office in the city. But that doesn't tell me what the weather is like 90 miles south of here, and that can be very different (and often is).

 

I've landed off-airfields because of weather on numerous occasions- but then, 20 years as a glider pilot and tug-driver does that to you:biggrin:. Only twice outside of gliding, and both were in the Auster, an eminently paddock-capable aircraft (even better than the Pawnee). There are always risks, which can be minimised, but not entirely eliminated, so its not something I make a habit of (or recommend others do without some training first). More often, I've dropped into airfields when the weather has looked difficult.

 

Curious about the nature of your current job- "flying on only the worst days weather can throw at us in summer"- sounds like fire-bombing, care to elaborate? If that is the case, then your flying would be mainly local as you are trying to keep to a minimum the time between reload and delivery. In such cases local observations would be critical to your operations, but I bet you get the best possible advice from the bureau about the likey timing of the arrival of fronts which are going to generate wind changes, no?

 

I'm sure you know that you can't read the weather hundreds of miles away by looking at your local sky and windsock. And with your level of experience, I bet you still get forecasts when you travel long distances cross-country.

 

Coop

 

 

[Coop]

Hi,Just wondering what others think of sectorised visibility reports in metars. I think it is a bit confusing trying to work out what they mean and how to interpret the data for take off and landing. How many people know where they are doing these reports from? How do you take into account the displacement from them to where you're taking off from?

 

Any tips or tricks or do you ignore them and work out your own version of vis?

Just going back to your original question, Reggy, I find METARS the least useful of the weather reports, and its mainly because of the encoding which makes them difficult to interpret. I guess its also true that the folks are trying to forecast weather at a single point (which is what an airfield is, as far as the Met. people are concerned) and I wouldn't mind betting that is the most difficult forecasting trick to perform, and perhaps the least accurate. I mainly use just the area forecast primarily for cloudbase, winds, and presence of fronts and other nasty stuff.

 

I'll pay attention to a METAR or TAF if it mentions really nasty weather, and it may be the final part of a "no-go" decision (I'm strictly VFR). I'm ignorant of "sectorised visibility", probably beause if it's getting that marginal, I'm probably not going anyway....

 

Regards

 

Coop

 

 

[TAA Student Pilot]

On a long trip as I said I look at the telly weather (ABC news is best), the radars (real time actual developments) and the four day for what is trending/position of fronts etc. And looking at the windsock is not going to tell you what the weather is like hundreds of miles away. I have worked most of this country from top to bottom covering all sorts of country and weather and as I said no problems. It is best if you know your own and your Aircrafts limits and always give yourself an out. This works for me, I'm not suggesting anybody else does this. You do what you feel comfortable with.

 

 

[Reggy Stirred Yuza]

Hi All.

 

Thanks for the interesting replies and info. Metars (and Specis) are reports of CURRENT conditions at the airfield and are not forecasts but might have TAFs of TTFs added to them. I think they can be confusing especially when visibility is reported as something one way and something in another direction. I've read the AIP stuff (and other material) and it seems the met people are reporting visibility from where they are located. If they aren't anywhere near the runways, then what they see can be very different to what us in the real world see. Seems kinda dumb to bother doing this when it has no relevance to what a pilot needs to know. I guess the end result is pilots need to work it out for themselves. I was just wondering how others do this. As far as I know, there are no publications that tell us where the met office is located and therefore if we don't know where they are we can't possibly work out what they are tellings us if they say visibility is reduced to 4000m South of them (for eg). I agree that plain language messages would be easier to understand and probably a bit shorter too.

 

 

[Guest Chainsaw]

Great thread guys. I have enjoyed reading and have learnt...thanks :)