Clouds

[Old Koreelah]

Can't find a special category for this thread, so here goes. I flew to Clifton last weekend and thought I knew a bit about clouds.

 

I found a cumulus cloud forming almost 1,000 feet below the local cloud base. First time I've seen that.

 

On the way home on Sunday, cloud base west of YWCK was about 7,000'. Half an hour further south near YIVL it was over 8,500.

 

I also learned that trying to climb over an apparently thin layer of scattered cu's is a good way to waste a lot of fuel. With the sun behind you, the depth of clouds up ahead is not apparent and they often extend way beyond 10.

 

I also learned that later in the day, after cu's have completed most of their vertical development, they shade the earth and flying under them can be pretty smooth.

 

 

[facthunter]

Where the cloud base forms depends in the local Relative humidity. A cumulus cloud can be a very local phenomenon and can often form as a result of a river that continues in a particular direction for a while, providing moisture.

 

Active Cu will have changing tops, which are bumpy and unpredictable as to vertical development. There will be an updraft into the base of a developing Cu.

 

Heated earth causes thermal activity, and "bumps", and the small " Cu " in the afternoons are pretty benign.. The greatest energy in a Cu is released from the water vapour content, changing from a gas to a liquid, releasing heat which causes the updraft, which keeps the whole process going. The warmer and more moist the air mass is the greater the possibility of a large Cu or Cb forming. It only needs a trigger. ( Hot paddock or mountain ridge or a convergence of the winds/ frontal activity.) and a suitable adiabatic lapse rate, for the temp in the cloud to stay above the ambient, and it will keep developing. Nev

 

 

[Old Koreelah]

Yep Nev, I was familiar with all that. I just hadn't ever noticed the anomalies mentioned. The implications for little aeroplanes are that when planning a flight we shouldn't extrapolate local conditions across a region. Setting a cruise height clear of clouds locally may take you into them an hour later.

 

 

[Dafydd Llewellyn]

Where the cloud base forms depends in the local Relative humidity. A cumulus cloud can be a very local phenomenon and can often form as a result of a river that continues in a particular direction for a while, providing moisture.Active Cu will have changing tops, which are bumpy and unpredictable as to vertical development. There will be an updraft into the base of a developing Cu.

Heated earth causes thermal activity, and "bumps", and the small " Cu " in the afternoons are pretty benign.. The greatest energy in a Cu is released from the water vapour content, changing from a gas to a liquid, releasing heat which causes the updraft, which keeps the whole process going. The warmer and more moist the air mass is the greater the possibility of a large Cu or Cb forming. It only needs a trigger. ( Hot paddock or mountain ridge or a convergence of the winds/ frontal activity.) and a suitable adiabatic lapse rate, for the temp in the cloud to stay above the ambient, and it will keep developing. Nev

Garn - they were just practicing for the new airspace restrictions when Wellcamp becomes active . . .

 

 

[facthunter]

I don't know where good meteorological references are obtained these days, and I never really know what base people are coming from, when the subject comes up. My comments are a bit basic but a lot of formulae and numbers are quickly forgotten. I have always been fascinated with meteorology and I think the full person to person briefing available years ago was far more useful than what is available today. Knowledge of the real weather is not just a requirement for a ramp check but an aid to safer flight. You can often read the clouds to give warning of an approaching cold front about 500 Kms ahead of it, but that sort of thing doesn't appear to be taught .. The forecasts are not always reliable either, and none of us are immune from the effects of bad weather. Nev

 

 

[Old Koreelah]

... The forecasts are not always reliable either... Nev

You are on the money, Nev. A lot of more experienced weather-watchers, from farmers to sailors, can give a pretty good forecast by looking at cloud patterns. Fear of litigation seems to have infected every agency. Forecasts and NOTAMs are miles long and seem designed to discourage anyone from reading right through them- just like the pages of legalese we routinely accept when we click the "agree" button.

 

 

[Dafydd Llewellyn]

I don't know where good meteorological references are obtained these days, and I never really know what base people are coming from, when the subject comes up. My comments are a bit basic but a lot of formulae and numbers are quickly forgotten. I have always been fascinated with meteorology and I think the full person to person briefing available years ago was far more useful than what is available today. Knowledge of the real weather is not just a requirement for a ramp check but an aid to safer flight. You can often read the clouds to give warning of an approaching cold front about 500 Kms ahead of it, but that sort of thing doesn't appear to be taught .. The forecasts are not always reliable either, and none of us are immune from the effects of bad weather. Nev

Every locality has its own weather "pattern"; one gets to know it by flying in the area and by watching the better TV weather presentations - you can deduce it fairly well from the synoptic chart and the BOM weather radar images - and the world wind map is also pretty good. I used to fly to work every day when I lived near Mittagong and worked for de Havs at Bankstown; it takes a while, but if you look at the sky as you fly, and relate it to a good basic meteorology course plus the other references, you get to know what to expect. That does not absolve one from the legal requirement to get a forecast - but it's often more accurate. I got to know the isiosyncracies of the weather in the Sydney basin pretty well. I'm still learning it for the area around Clifton.

The problem is, that the best prediction available is often indecisive; the weather may or may not allow the flight. Forecasts allow one to decide not to fly, when the conditions are obviously adverse - or to fly when it's CAVOK - but that's about 35% of the time. The other 65% is in the "well, lets go and take a look at it" category - and that's where people come unstuck. Under those conditions, one needs something extra up one's sleeve - and if you do not have the option of going onto instruments and climbing, then the only other option is to be able to land - and sometimes the only available option is in a convenient paddock, or croppie strip. I've done a lot of "scud running" in my time, and it's not pleasant. Gliding - especially cross-country gliding - is possibly the best way to get to understand weather.

 

So forecasts are a legal requirement, but ultimately you have to make decisions based on what you find. The thing is, MAKE a decision - don't just blunder on, hoping it will get better over the next ridge. We should be teaching people how to make the critical VFR weather decision - turn back.

 

 

[frank marriott]

I think the full person to person briefing available years ago was far more useful

 

Absolutely Nev, but with all the user pays crap we lost it. Remember when there was a Flight SERVICE as well.

 

 

[eightyknots]

You are on the money, Nev. A lot of more experienced weather-watchers, from farmers to sailors, can give a pretty good forecast by looking at cloud patterns. Fear of litigation seems to have infected every agency. Forecasts and NOTAMs are miles long and seem designed to discourage anyone from reading right through them- just like the pages of legalese we routinely accept when we click the "agree" button.

Unless you click the Rec Flying "agree" button

 

 

[Oscar]

The guru: http://www.amazon.com/Meteorology-Glider-Pilots-C-Wallington/dp/0719533031.

 

 

[Dafydd Llewellyn]

The guru: http://www.amazon.com/Meteorology-Glider-Pilots-C-Wallington/dp/0719533031.

Guru for English gliding weather; not for Australia - tho his basics are valid anywhere. We almost never see a warm front or an occluded front. I found the old RAAF Manual of meteorology more useful; but nothing beat playing golf with a couple of CSIRO Cloud Seeding Officers; they reckoned the golf course was the ideal spot to keep an eye out for weather suitable for cloud seeding - and I learned more about weather from them than from anything else.

 

 

[Old Koreelah]

So true, Dafydd. Most old met. texts were northern hemisphere-based with much irrelevant stuff like warm fronts and occluded fronts. No wonder most of us switched off.

 

 

[facthunter]

I agree that finding suitable "books/references) is difficult but for some reason I have maintained a BIG interest even when often flying above most of the significant weather. Flying simple light aircraft REQUIRES you to know a fair bit in a practical sense, as well as the legal one, for your own safety's sake. Perhaps this subject needs to be addressed more deeply than just ticking it off on a piece of paper. An "airman"(person?) is another concept of a pilot. Nev

 

 

[Dafydd Llewellyn]

I agree that finding suitable "books/references) is difficult but for some reason I have maintained a BIG interest even when often flying above most of the significant weather. Flying simple light aircraft REQUIRES you to know a fair bit in a practical sense, as well as the legal one, for your own safety's sake. Perhaps this subject needs to be addressed more deeply than just ticking it off on a piece of paper. An "airman"(person?) is another concept of a pilot. Nev

I agree - but one needs to do some reading to comprehend what you're looking at. For example, one often sees a Fohngap at Murrurrundi Gap, and just East of Bathurst, under SE stream conditions. How many RAA pilots know what a Fohngap is - and what it implies if you try to penetrate further upwind? Glider pilots will recognise it.

 

 

[facthunter]

The BEST information I ever obtained was directed at Glider pilots with the exception of Jetstream (upper air) phenomenon( winds of over 200 knots) which is still being researched. While many never venture into that area it affects the weather below and is all part of the big picture. Nev

 

 

[Old Koreelah]

I crossed the Liverpool Range twice at the weekend. Gentle uplift from the northerly airstream created a layer of small cu's which abruptly stopped at the crest of the range. I was wary of rotor effects from air pouring over the top, but turbulence was pretty mild on Saturday. I have met a couple of older blokes who have been rolled sideways in that rotor; their main problem was deciding whether to fight it or continue with the roll until right-side up.

 

 

[Stoney]

I took this photo on a flight to New Zealand a few weeks ago. I thought it gives a nice perspective looking down from the top.

 

 

 

[Jabiru Phil]

Saw this cloud Sunday, looked a bit dangerous at the bottom.

 

Phil

 

 

 

[eightyknots]

You are on the money, Nev. A lot of more experienced weather-watchers, from farmers to sailors, can give a pretty good forecast by looking at cloud patterns. Fear of litigation seems to have infected every agency. Forecasts and NOTAMs are miles long and seem designed to discourage anyone from reading right through them- just like the pages of legalese we routinely accept when we click the "agree" button.

I just clicked the AGREE BUTTON underneath your statement!

 

The result? ...it turned into a green tick.

 

 

[Yenn]

Never heard of a Fohngap. I do know what the fohn effect is and what causes it. maybe someone could explain the fohngap. Or is it just a renaming of something old to fool us old codgers?

 

 

[SDQDI]

I think a fohn gap is where you can't get service and the fohn effect is when you can hear someone from mucha long way away:sorry:

 

 

[Dafydd Llewellyn]

Never heard of a Fohngap. I do know what the fohn effect is and what causes it. maybe someone could explain the fohngap. Or is it just a renaming of something old to fool us old codgers?

See http://www-das.uwyo.edu/~geerts/cwx/notes/chap14/foehn_gap.html

 

 

[Old Koreelah]

Never heard of a Fohngap. I do know what the fohn effect is and what causes it. maybe someone could explain the fohngap. Or is it just a renaming of something old to fool us old codgers?

Dafydd mentioned Murrurundi Gap, where south-bound air spills thru this lowpoint in the Liverpool Range. From the northern side we often see the range covered in froth. Some pilots try to fly under it; I'd rather clear the crest by at least a few hundred feet.

Anyway, for the information of anyone crossing the range, our club has a safe haven for those who decide to turn back until conditions improve.

 

http://www.recreationalflying.com/threads/did-you-do-it-over-the-weekend-who-with-tell-us-about-it.115029/#post-426504 #20

 

 

[kaz3g]

I don't know where good meteorological references are obtained these days, and I never really know what base people are coming from, when the subject comes up. My comments are a bit basic but a lot of formulae and numbers are quickly forgotten. I have always been fascinated with meteorology and I think the full person to person briefing available years ago was far more useful than what is available today. Knowledge of the real weather is not just a requirement for a ramp check but an aid to safer flight. You can often read the clouds to give warning of an approaching cold front about 500 Kms ahead of it, but that sort of thing doesn't appear to be taught .. The forecasts are not always reliable either, and none of us are immune from the effects of bad weather. Nev

BOM used to put out a terrific booklet on weather...I haven't seen mine for quite a while but it was almost a "must have" when doing a PPL back then. Those were the days when such things were "free".

 

Kaz

 

 

[turboplanner]

What's the current training situation? In my training we emerged as a licensed Meteorologist.

 

We covered most cloud forms, but that left two problems.

 

Unexpected changes en route, trying to remember which type of cloud from the many clouds and degrees of clouds we studied.