What BOM TAF's don't tell you.
 

Hello fellow ppruners.

I would like to raise the issue of aviation weather forecasts and what they DON'T tell you.

Here are today's forecast for Brisbane and surrounding areas issued by the Australian Bureau of Meteorology. I have copied both the Aviation forecasts and also those forecasts issued to the general public.


I've just read the Australian AIP and it says:

So if there is only a 5%, 10%, 20%, or 25% chance of there being thunderstorms, the powers that be deem that information superfluous when it comes to aviation. Does anyone else think this is rather odd? As important as this information is to someone wanting to put the washing out to dry, or a family organising a day at the beach, surely it is even more important to a pilot operating an aircraft, especially one flying IFR with no radar!

Perhaps the requirements for holding fuel could be such that if there is less than a 30% chance of thunderstorms (eg PROB10 TEMPO TS) that holding fuel is discretionary, but please do not filter this information out of the TAF. Allow the pilot to make their own assessment!

Mate

A TAF is a valid forecast for 5nm ONLY around an aerodrome.

Your general weather forecast for Brisbane (you showed later) is a general non aviation forecast for the greater Brisbane area. ie a lot bigger area than the 5nm around the airport.

So if the Met forecasters don't think the storm will get within 5nm, the TAF won't even mention it.

So in theory there could be stationary TS all around the airfield and in theory the TAF does not have to mention it.

That is why an AREA forecast goes hand in hand with a TAF, so you can get the big picture. A SIGWX chart completes the forecast.

Gliderboy

Also TAFs get amended; usually a daily generic city forecast is good enough for the whole day.

If the prob of a TS within the 'TAF area' goes up then it would get mentioned in the amended TAF or next TAF, would it not?

What we do not want is for the forecasters to put on 30/60 holding due TS to cover themselves when it is highly unlikely, but possible that it may occur. This can have a big impact on payloads for contract flying.

A forecast is a best guess of what nature will bring. Sometimes on a clean forecast it may be prudent to put on some for Mum and the kids. For example if the temp/dew point is getting a bit close then alternate fuel may be advisable. Forecasts are not ironclad. Perth would average 3-5 days per year when fog unforecast or formimg a number of hours earlier than forecast occurs. When it does you can tell by the pitch of da' voice on the radio who has not picked it!

This could be the forecast for Brisbane almost everyday through summer!!:ok:

Aviation is an art not a science. Nobody writes it all down on paper for you to follow, chapter and verse. If you need that ,you should have become a lawyer.

You use common sense, animal cunning and past experience along with the forecast to work out what might happen. With weather the word "might" is the operative word. Then you err on the side of caution.

It makes things a lot less stressful.

Ever seen the Perth TAF during the winter?
If there is even the slightest chance of fog it gets a prob 30.
A fair few have been caught out previously so I think it does boil down to risk management!

I went on a tour of the BoM in PH some time years ago, and one of the guys there was mentioning they were working on improving the accuracy of their fog forcasting due to a few serious unexpected fog incidents.
Further in the conversation he mentioned that whenever there is a chance of fog it will be in the TAF.
Just a Perth SOP i take it.

There was a thread a few months back regarding unexpected fog at Perth.


I must add the lower level area briefing is a great product compared to other countries.

thread creep
 

Apologies for the thread divergence but … how readable are BoM aviation forecasts? I assume trainee pilots may take a bit of time to become familiar with them, but is the arcane terminology something that can cause an occasional misunderstanding among experienced pilots?
I’m not a pilot (RAAF pilot son and commercial pilot brother) but have read a few forecasts over the phone to them.
I 'teach' usability and use these forecasts as examples of how the initiated can understand something but the uninitiated just see ‘gibberish’.
just interested
thanks
layman

I think you have answered your own question, Layman.

A private pilot license holder is "initiated." They do a course on meteorology which not only includes an understanding of weather (such as one might gain in high school geography), but also its impact on aircraft operations, and weather services available. That is, how why and where forecasts are produced, how to read them, what they do and don't tell you.

Last time I looked there were exams on met at PPL, CPL and ATPL level. Don't get to exercise the privileges of those licenses if you don't pass those exams!

Take the basic met, read the AIP section on Met, apply experience.... those arcane forecasts tell you a lot. The better you know your met and AIP, the more they tell you.

I've done the study and read the books. I don't think its broke, so please... no fixing it!!

Tip - do yourself a favour and ring the officer in charge of your local BoM office. Tell them you are a pilot and would like to come and meet an aviation forecaster. You will be welcomed with open arms. They are a very professional group of people and you will be most likely impressed with their interest in aviation and the questions they will have for you. We still get the same quality of met info they gave in the old days of face to face briefings. The thing you don't get anymore is the 'feel' for the men and women that put them together. Do yourself a favour. Get on in there!

This forecast variation is quite common in Brisbane. All day today there has been mention of a chance of a late storm by the radio jocks.
No mention on our forecasts.

I see it more as a " cover " for the met guys so if by remote chance a storm does come the public can't winge about not being warned.

I agree with ITCZ, Ring up the BoM. They are a fantastic bunch of people and more than happy to help!

On the ARFOR product if you are unsure of anything, ring the aviation desk number. Most times you actually speak to the bloke who put the forcast together. He can go into any depth you want and will be a wealth of knowledge. I have learnt many things from ringing them up!!

:ok: ITS A FANTASTIC SERVICE!! :ok:

They just get annoyed when people ring up and say ''whats the weather?":ugh:

If you ring up and say ''I have the area xx ARFOR, I have a question about xx" they will bend over backwards! :D

As for the media, many get their weather from 3rd party sources and are not as accurate.

I know here in Perth the ch10 weatherman will go to the BoM and sit and chat to them whats going on. Good Stuff :ok:

Channel 9 on the other hand cannot even draw a synoptic properly. They draw a trough as a cold front! According to them theres been a cold front over the N.T for the last few days thats moving east to west!! :ugh:

really? I wish! :p

A little off the thread but many years ago ( when Flight Service was operating )the Met man in Alice Springs had a sign on his desk -

Bureau of Meteorology - this is a non prophet organization

You might be interested to know that QF has so much faith in the official BOM forecasts that they have hired their own met guys/gals to make their own assessment of the weather and if the BOM forecasts are deemed inadequate QF will issue additional 'OPRISK' requirements to its crews.

The situation in BNE could well result in QF issuing an OPRISK requirement to carry Tempo holding fuel due to 'unforecast TS'.

ITCZ, BrazDriver
thanks for the responses / hints - I'll give BoM a ring
regards
layman

That's quite funny. Thanks for that. :)

Glider boy. Yes I know TAF's only cover 5 nm radius around an aerodrome. You said: Do you really believe a meteorologist has the ability to make that call? Remember we are talking about a FORECAST with a validity period of 6,12, or 24 hour period not a weather REPORT.

And don't you remember them teaching you during your pilot licence theory about thunderstorms and the three things that are required to make them happen. Humidity, Unstable/Conditionally Stable atmosphere, and a trigger that initially pushes up the parcel of air that gets the process started. In this case the trigger was a low level trough. This trough covered a wide area across the state, let alone the Brisbane metropolitan area! A nascent storm could appear anywhere within the trough and then travel a significant distance during its life span of several hours.

With these facts in mind, your statement: although being made to illustrate your point about the 5 nm radius, is rather silly don't you think?

SM4 Pirate said: Sure it would but you are missing the point for a couple of reasons.

1. What if the chances don't increase? What if they remain at 20%? That is a very significant probability. One in five. Even 10% or one in ten is significant!

2. So an increase of only 10% from PROB20 to PROB30 will cause a requirement for TS to suddenly appear on an amended TAF with all the associated operational implications. What about a flight that has already departed and is mid-flight either from a domestic port or from overseas? Surely it would be better for them to have known that there was always a risk of there being a thunderstorm during the given period so that they could have allowed for it if they wanted to.

illusion said: Pass-A-Frozo said: BrazDriver said:Pass-A-Frozo then said: I made the point in my original post that there is no reason why the mention of TS or FOG or anything else for that matter that has a probability of less than 30% should automatically mean that there is a requirement for holding/diversion fuel! Would you please read my post again. If the Bureau of Meteorology determines that there is a 20% chance of thunderstorms, well then there is a 20% chance of thunderstorms regardless of whether or not that is included in the TAF!! There is absolutely no reason why a 20% percent chance of thunderstorms if mentioned on the TAF should automatically require holding/diversion fuel be carried.

Meteorologists should not be forced to make decisions on whether or not there should be a requirement for holding/diversion fuel at an aerodrome. They should simply be telling it how it is. If there is a 20% chance of thunderstorms in Brisbane, or a 10% chance of fog in Perth, well then let them state that in the TAF. It is then up to the aviation industry to determine what the fuel requirements are. If there is less than a 30% chance of some meteorological phenomenon happening, well then the regulations could be written such that the information can be considered as advisory only and that holding/diversion fuel is optional.

It is completely unfair to blame a meteorologist for there being mass diversions and forced autolands below landing minimas at a destination such as Perth because there was only a 5% or 10% chance of there being fog that doesn't rate a mention on the TAF simply because that is the way things are done! Why should a meteorologist be forced to say there is a 30% chance of fog when there is really is only a 5% chance, simply because they don't want there to be no mention of a chance of fog on the TAF and cop the abuse when the fog does roll in that one time in twenty.

Can no-one see the point I am making??

gliderboy said:You will find that overseas carriers and the major domestic ones do not include ARFOR's in the pilot briefing, and the pilots certainly do not have the time and rarely the facilities to seek them themselves.

Bleve said: That is not quite true. My understanding is that they are actually BoM employees seconded to Qantas and imbedded within flight dispatch (the sections that produce the flight plans) and operations control (the section that keeps the world wide operation together).

These OPRISKs you mention can often be the result of these 5%, 10%, 20% PROB's that never get a mention on any TAF. They're not "unforcast TS" but rather "unmentionable TS"!

It can work the other way as well. If you have a long flight that won't allow you to carry the 30/60 holding due TS, a phonecall to met asking them nicely to review the TAF prior to an unwanted fuel stop works wonders. ATC call up with an amended TAF and the calculator is replaced with the newspaper!

Blip yes I think you are correct. However from previous experience the BoM (being a government dept) would have insisted that QF pay for their wages. So the fundamental point remains that QF don't trust the 'vanilla' head office TAFs/TTFs and paying for on site BoM personnel is deemed a sound investment.

then there will be no TS... The point of an amended TAF is to show the changes; there are various requirements (usually alternate management and extra fuel) that puting TS probs on TAFs in terms of complience. If you willy nilly post every % say 10 and above on a TAF then for the 8 times a year a TS hits an aerodrome, it's forecast 250 times...

It's called hazard alerting, if you are within 1 hours flight time as an IFR you gt tld about the amended conditions, if VFR it will be braodcasy on area freq's; and flightwatch have all the info available at the click of a mouse; call them.

Are you suggesting a flight departing WSSS will have the latest on BN on departure and take that as the only time the WX is checked?

We (ATC) assume your wx brief was accurate 1 hour before ATD; after that we are considering the ramifications of change on your operations. Airlines have various operations people assessing these things for their pilots.

If you are on your own, single pilot etc., call flightwatch within a hour of dest and get an update; all sig changes (hazardous) there after will be braodcast on the area freq, or directed to you if you are IFR.

It's not perfect, agreed, but at least it isn't "chick'n little" stuff either.