Flight planning with this patchy weather
Join Date: Jul 2010
Location: UK
Posts: 156
Likes: 0
Received 0 Likes
on
0 Posts
What is needed is knowing how to directly use the various internet-sourced weather data to make practical go/no-go decisions. I am not aware of anybody doing that.
Well, why don't you run an evening at Shoreham? You're seriously more clued-up than most of us and can sift out the b-****. I'll run the booking.....
Well, why don't you run an evening at Shoreham? You're seriously more clued-up than most of us and can sift out the b-****. I'll run the booking.....
Join Date: May 2001
Location: UK
Posts: 4,631
Likes: 0
Received 0 Likes
on
0 Posts
VMC
Its only partly about the weather.
Weather radar, METARs, and TAFs are without doubt the best sources for buidling a picture of the weather, and build a picture you should. It isnt of course just about the weather along your track, but the whats happening to the windward of your track that will give you a feel of how things might develop. Equally important is an assessment of your escape routes along your track - where do you go to get quickly on the ground if necessary and how might the terrain impact on your decision.
I find it interesting how often pilots plan for trouble. For example consider a typical trip from the south of England to Scotland - there are plenty of possible routes but why would you select a route over high ground if the weather is marginal - add on the extra miles and route up the coast.
and its also a lot about your piloting ability.
So many pilots seem very uncomfortable flying low level - is it stories of the dangers of scud running or other reasons? It takes time to be comfortable flying low level but once you are comfortable in reality it is very rare you cant stay under the weather in the UK. I can think of very few trips that I have wanted to do VFR that werent possible. Yes, that may well mean a circuitous route and there may be occasions when it clearly isnt possible or wise.
I would of course recommend time spent with an instructor or another pilot who is comfortable flying in these sort of conditions, the usual health warnings apply.
As to second guessing the professional forecasts I am less certain they are as consistantly accurate as some would have you believe. I can think of one pilot I know well who has a better than 90% record of predicting what the actual weather will be in those circumstances when he thinks it will be different from the met office forecast. More often that not it is better, but to be fair I can think of a few occasions when we have rightly predicted it would be worse.
Of course in these days of computerised weather forecasts local knowledge is particularly useful. There has been more than one occasion my flying partner(s) have been anxious to depart based on good TAFs - On a few of those I have been much more cautious and asked them to be certain that they really dont mind a train journey on our return to collect the car. Sure enough the fog has rolled in and all movements for the rest of the day have stopped.
Its only partly about the weather.
Weather radar, METARs, and TAFs are without doubt the best sources for buidling a picture of the weather, and build a picture you should. It isnt of course just about the weather along your track, but the whats happening to the windward of your track that will give you a feel of how things might develop. Equally important is an assessment of your escape routes along your track - where do you go to get quickly on the ground if necessary and how might the terrain impact on your decision.
I find it interesting how often pilots plan for trouble. For example consider a typical trip from the south of England to Scotland - there are plenty of possible routes but why would you select a route over high ground if the weather is marginal - add on the extra miles and route up the coast.
and its also a lot about your piloting ability.
So many pilots seem very uncomfortable flying low level - is it stories of the dangers of scud running or other reasons? It takes time to be comfortable flying low level but once you are comfortable in reality it is very rare you cant stay under the weather in the UK. I can think of very few trips that I have wanted to do VFR that werent possible. Yes, that may well mean a circuitous route and there may be occasions when it clearly isnt possible or wise.
I would of course recommend time spent with an instructor or another pilot who is comfortable flying in these sort of conditions, the usual health warnings apply.
As to second guessing the professional forecasts I am less certain they are as consistantly accurate as some would have you believe. I can think of one pilot I know well who has a better than 90% record of predicting what the actual weather will be in those circumstances when he thinks it will be different from the met office forecast. More often that not it is better, but to be fair I can think of a few occasions when we have rightly predicted it would be worse.
Of course in these days of computerised weather forecasts local knowledge is particularly useful. There has been more than one occasion my flying partner(s) have been anxious to depart based on good TAFs - On a few of those I have been much more cautious and asked them to be certain that they really dont mind a train journey on our return to collect the car. Sure enough the fog has rolled in and all movements for the rest of the day have stopped.
Join Date: Sep 2003
Location: Retford, UK
Posts: 476
Likes: 0
Received 0 Likes
on
0 Posts
One thing which seems to put a lot of people off is the ubiquitous PROB30 SHRA+ that we often get. It's not a 30% chance that you will get caught in a CB though. I guess most people build up enough experience to look at the F215, the rain radar and a range of TAFS/METARS and relate it to previous days.
Join Date: Dec 2011
Posts: 2,460
Likes: 0
Received 0 Likes
on
0 Posts
I find the F215 to be almost useless, because the forecaster chucks in everything he can think of.
The PROB30 has been degraded by the fact that only PROB30 & PROB40 are permitted under ICAO.
So PROB30 is now a shorthand for "a small chance of it happening but pretty unlikely" and normally you find that anytime there is a trough on the MSLP chart (see the link I posted) that appears as a PROB30 TEMPO TSRA in the TAFs.
PROB40 means that he thinks it will happen, probably.
What makes a massive difference is using GPS and doing things the "modern way". If you cannot navigate in haze then (sorry to say this) you are wasting your time doing a PPL, because you can be grounded for much of the summer.
The PROB30 has been degraded by the fact that only PROB30 & PROB40 are permitted under ICAO.
So PROB30 is now a shorthand for "a small chance of it happening but pretty unlikely" and normally you find that anytime there is a trough on the MSLP chart (see the link I posted) that appears as a PROB30 TEMPO TSRA in the TAFs.
PROB40 means that he thinks it will happen, probably.
What makes a massive difference is using GPS and doing things the "modern way". If you cannot navigate in haze then (sorry to say this) you are wasting your time doing a PPL, because you can be grounded for much of the summer.
Join Date: Jul 2010
Location: london
Posts: 23
Likes: 0
Received 0 Likes
on
0 Posts
Cloud tops
I do find myself envying the rich guys in Barons with weather radar, but this kind of extended CB activity is less usual that just yer regular low-level clag.
As a holder of a year-old IMC rating, my more common concern is the cloud tops, which are very hard to establish. I know that 1000' cloud will inevitably mean some IMC work leaving under the 2500' Class A that sits over my N London airfield, but having cleared that, if I was able to climb into clear air at, say 4,000' heading west I'd be out of it within 10 mins. But if it was XXX all the way to Wales or Cornwall, that would mean a great deal of hard work and, with no TCAS and without even a radar service in parts, I may not feel entirely relaxed flying blind all that way. But of course the 215 is far too general to give any real planning accuracy as to cloud tops over that distance.
As a holder of a year-old IMC rating, my more common concern is the cloud tops, which are very hard to establish. I know that 1000' cloud will inevitably mean some IMC work leaving under the 2500' Class A that sits over my N London airfield, but having cleared that, if I was able to climb into clear air at, say 4,000' heading west I'd be out of it within 10 mins. But if it was XXX all the way to Wales or Cornwall, that would mean a great deal of hard work and, with no TCAS and without even a radar service in parts, I may not feel entirely relaxed flying blind all that way. But of course the 215 is far too general to give any real planning accuracy as to cloud tops over that distance.
That's what skew-Ts are for (see above.)
You get a picture of the relative humidity of the atmosphere at various levels, & can use that to assess the amount of cloud.
You can also see the stabilty of the atmosphere & use the dry & saturated adiabatic lines to forecast the base & tops of convective cloud.
You get a picture of the relative humidity of the atmosphere at various levels, & can use that to assess the amount of cloud.
You can also see the stabilty of the atmosphere & use the dry & saturated adiabatic lines to forecast the base & tops of convective cloud.
Join Date: Jul 2010
Location: london
Posts: 23
Likes: 0
Received 0 Likes
on
0 Posts
Cloud tops
Yes, perhaps I should make a concerted attempt to find a reliable source of t-skews and an even more concerted attempt to understand and interpret them. But wouldn't be nice if some met guys with a bloody great computer did it for us by providing a map of Britain witha cloud thickness forecast...
Join Date: Dec 2010
Location: Sheffield
Posts: 113
Likes: 0
Received 0 Likes
on
0 Posts
Flight Cancelled
Well I am sat here feeling very frustrated, as I have just cancelled my planned flight today from Gamston to Leicester. The forecast today is very similar to that of yesterday, and certainly here in Sheffield, the day turned out better than expected. The bit that concerns me on the TAF's is the threat of thunderstorms en-route. During my training, I was advised that TS is a no-no.
My decision is also based on the fact that I would be taking two passengers (who I do not know), so their reaction to turbulence is unknown.
I have about 100 hours in my log book now, and have just completed the IMC, so I am still a relative novice. I would appreciate others opinions from the forecasts. Am I being over-cautious ??
My decision is also based on the fact that I would be taking two passengers (who I do not know), so their reaction to turbulence is unknown.
I have about 100 hours in my log book now, and have just completed the IMC, so I am still a relative novice. I would appreciate others opinions from the forecasts. Am I being over-cautious ??
Join Date: Jul 2010
Location: London
Age: 53
Posts: 55
Likes: 0
Received 0 Likes
on
0 Posts
"Am I being over cautious?"
No.
I'm in exactly the same position as you; I stayed on the ground today, too. I WANT to regret it, but I made my decision from the local TAFs. It's sunny and blue out the window, but it's also gusty, and those clouds look awfully tall...
I'm in exactly the same position as you; I stayed on the ground today, too. I WANT to regret it, but I made my decision from the local TAFs. It's sunny and blue out the window, but it's also gusty, and those clouds look awfully tall...
Join Date: Jun 2008
Location: England & Scotland
Age: 63
Posts: 1,413
Likes: 0
Received 0 Likes
on
0 Posts
I liked Fuji Abound's post 25.
I am a PPL(H) so most likely more comfortable than many posting here about flying under the weather. The ability to drop into a farmer's field and wait out the weather is also an important difference.
I have a minima rule that I have not so far broken (and I don't intend to); visibility to maintain 60knt airspeed and 600ft height OR turn back, divert or stick it in a field right now.
My normal airspeed is 110-120knt so I am aware of reducing speed to maintain VIZ, and I have a radar altimeter set to chime at 700 ft to remind me that things are getting tight.
I do take account of whether my direction of travel is with, or into, the oncoming weather.
PROB 30 I take note of but the likelihood is low. So, like FA's on Saturday 21 I headed to the airfield, and had a full day. Occasional heavy rain, with hail and gusting winds, to steer well clear of but nothing that caused problems, or even concerns given my fuel state and divert options.
So far, in total I have had 2x turn-back and give in, 1x land in a field for 40 minutes to wait for the weather to change, and no divert to alternate field. In addition, there have been a couple of times flying West to East when I have stayed on the ground waiting for a front to go through, and then lifted in the clear air ahead of the next wave of clouds to fly along with the clear air to my destination.
I do like to follow the METARs that are up-weatehr so I can get a more accurate understanding of what is going to hit me. Seeing airfield METARs dropping in succession also gives a clear view of the speed of advance.
Finally, on long N / S strips (EGKR to the Western Highlands) I have a number of alternate routes to provide for low-level options both West and East coast, depending on weather.
I am a PPL(H) so most likely more comfortable than many posting here about flying under the weather. The ability to drop into a farmer's field and wait out the weather is also an important difference.
I have a minima rule that I have not so far broken (and I don't intend to); visibility to maintain 60knt airspeed and 600ft height OR turn back, divert or stick it in a field right now.
My normal airspeed is 110-120knt so I am aware of reducing speed to maintain VIZ, and I have a radar altimeter set to chime at 700 ft to remind me that things are getting tight.
I do take account of whether my direction of travel is with, or into, the oncoming weather.
PROB 30 I take note of but the likelihood is low. So, like FA's on Saturday 21 I headed to the airfield, and had a full day. Occasional heavy rain, with hail and gusting winds, to steer well clear of but nothing that caused problems, or even concerns given my fuel state and divert options.
So far, in total I have had 2x turn-back and give in, 1x land in a field for 40 minutes to wait for the weather to change, and no divert to alternate field. In addition, there have been a couple of times flying West to East when I have stayed on the ground waiting for a front to go through, and then lifted in the clear air ahead of the next wave of clouds to fly along with the clear air to my destination.
I do like to follow the METARs that are up-weatehr so I can get a more accurate understanding of what is going to hit me. Seeing airfield METARs dropping in succession also gives a clear view of the speed of advance.
Finally, on long N / S strips (EGKR to the Western Highlands) I have a number of alternate routes to provide for low-level options both West and East coast, depending on weather.
Thread Starter
Join Date: Nov 2010
Location: UK
Posts: 148
Likes: 0
Received 0 Likes
on
0 Posts
You have expressed exactly what I was thinking in my original post, and I have about the same number of hours. I cancelled when faced with the same situation, and sure enough there were others at the airfield who would have flown. I can only say I was happy with my decision once the initial disappointment dissipated (and once I saw the actual weather which unfolded at my destination). I'm going to do the trip when the weather permits - the destination is still there.
If you had flown and had a bad experience, you would really have kicked yourself. And your passenger probably took comfort from knowing that you are the sort who is cautious.
At our level of experience, I think this is the sort of decision which becomes more tricky to make and others may have views on whether we worry too much. But, aside from mere disappointment, is there really any downside to erring on the side of caution? I guess it's more difficult if your flying is constrained to weekends. This weather has got to shift soon and we have some bank holiday s coming up, courtesy of HRH.
If you had flown and had a bad experience, you would really have kicked yourself. And your passenger probably took comfort from knowing that you are the sort who is cautious.
At our level of experience, I think this is the sort of decision which becomes more tricky to make and others may have views on whether we worry too much. But, aside from mere disappointment, is there really any downside to erring on the side of caution? I guess it's more difficult if your flying is constrained to weekends. This weather has got to shift soon and we have some bank holiday s coming up, courtesy of HRH.
Join Date: Nov 2000
Location: Cambridge, England, EU
Posts: 3,443
Likes: 0
Received 1 Like
on
1 Post
During my training, I was advised that TS is a no-no.
If the forecast is for embedded CBs I stay on the ground. If you can't see them you can't avoid them.
If the forecast is for isolated CBs, which you have a reasonable chance of seeing and avoiding, then I go flying. And on occasion have had to change my planned route to avoid thunderstorms, which I've seen from many many miles away.
It's in between that's harder - when they don't actually use the "embedded" word but also give the impression that there are more of the things closer together than justifies "isolated".
Join Date: Dec 2011
Posts: 2,460
Likes: 0
Received 0 Likes
on
0 Posts
If forecast skew-ts were accurate, they would be fantastic.
And weather forecasting would be exact too
In reality, these thermodynamic diagrams are just graphics which are generated from the same GFS computer model.
There is no magic here. The forecasters use these diagrams too, to generate their PROB30 TEMPO +TSRA etc. There is nothing a pilot can do with these things which will produce a more accurate TAF - unless the forecaster has done a cockup which is very rare.
The wx we have been having the last few days has indeed been unstable and this shows up on the skew-ts but the weather model itself is far too coarse to predict bases and (especially) tops accurately. This is why I use IR satellite images (and other data) to get an idea of what is really out there, before the flight.
And weather forecasting would be exact too
In reality, these thermodynamic diagrams are just graphics which are generated from the same GFS computer model.
There is no magic here. The forecasters use these diagrams too, to generate their PROB30 TEMPO +TSRA etc. There is nothing a pilot can do with these things which will produce a more accurate TAF - unless the forecaster has done a cockup which is very rare.
The wx we have been having the last few days has indeed been unstable and this shows up on the skew-ts but the weather model itself is far too coarse to predict bases and (especially) tops accurately. This is why I use IR satellite images (and other data) to get an idea of what is really out there, before the flight.
If you're looking for a bit more detailed overview of UK/European weather, especially when it come to making go/no-go decisions, then I would recommend TopMeteo as a good service to subscribe to.
You get all the normal charts, METARS, TAFS, etc. but they also run models geared to light aviation on their servers and I have have found their predictions of cloudbase, wind, precipitation, cloud layers, etc. to be amazingly accurate.
You get all the normal charts, METARS, TAFS, etc. but they also run models geared to light aviation on their servers and I have have found their predictions of cloudbase, wind, precipitation, cloud layers, etc. to be amazingly accurate.
That is yet another GFS site.
In the last week or two's unstable airmasses, the showers have developed pretty much where they said they would - I was able to plan and successfully complete a fairly big flight in the UK by taking the forecast at face value, altering routings by as little as 20nm to stay clear of predicted adverse weather. This sort of precision hasn't been available at low cost to the average GA pilot until quite recently.
Incidentally I wonder why they split the clouds into low medium and high? It is really a continuous spectrum, a lot of the time.
When I did the ATPL, those were the standard definitions (I think!)
I tend to think of low cloud being associated with the surface in some way, either by convection or orographic influence, medium cloud as not being convectively connected and high as completely crystalline in content. Then you get a Cb which spans all three categories.
Join Date: Aug 2003
Location: Surrey
Posts: 1,217
Likes: 0
Received 0 Likes
on
0 Posts
If forecast skew-ts were accurate, they would be fantastic.
And weather forecasting would be exact too
In reality, these thermodynamic diagrams are just graphics which are generated from the same GFS computer model.
....
The wx we have been having the last few days has indeed been unstable and this shows up on the skew-ts but the weather model itself is far too coarse to predict bases and (especially) tops accurately.
And weather forecasting would be exact too
In reality, these thermodynamic diagrams are just graphics which are generated from the same GFS computer model.
....
The wx we have been having the last few days has indeed been unstable and this shows up on the skew-ts but the weather model itself is far too coarse to predict bases and (especially) tops accurately.
