Transatlantic flights & weather

[KelvinD]

I have always assumed that on days like today I see a lot US bound flights taking the southerly option and heading out via Southampton, it was because there must be some unfavourable weather in the Atlantic. Today there have been flights of different airlines passing over Basingstoke heading for Miami, New Orleans, Newark etc. Just now, a Virgin en route to Boston passed overhead here. The next departure from Heathrow seemed to be a United flight to Newark yet that one has gone westerly toward Bristol etc. Do different airlines have different views on the weather and how it affects their flight plans?
As I write, another Virgin flight, coincidentally bound for Newark is overhead my location.
Incidentally, another United flight ex LHR is currently doing laps off the Swansea area. The flight is UA959, N654UA and was bound for Chicago.

[Ace Beer Charlie]

Looks like UA959 is now heading back to LHR!

[KelvinD]

Yes, it seems to be heading in the general direction of Ockham. After circuits around the Gower Peninsula, the passengers and crew should be speaking Welsh by now!

[DaveReidUK]

The route a US-bound flight takes over the UK will be determined by which NAT Track it is flight-planned to follow. Those tracks vary from day to day and do indeed take account of the weather, in particular the winds.

[KelvinD]

Thanks Dave. What puzzled me was the United and Virgin flights, both heading for Newark and both on different tracks.

[wiedehopf]

Might have filed for different altitudes and the "optimal track" is not available at their altitude. Then there is reduced lateral separation minima on the tracks, but they should both be capable.
And yes i believe dispatch departments have different strategies. Some might route around possible forecast turbulence more than others.

Then they might have tried to file for the same track but one was first and the track was "full" so they got booted off to the next track.
Different wind speeds at different altitudes might also offset detours that would otherwise not make sense.

[kcockayne]

Thanks Dave. What puzzled me was the United and Virgin flights, both heading for Newark and both on different tracks.Accurate answers to this situation have already been given & I won’t expand on them - except to illustrate what regularly happens with the DLH daily flights to eastern South America. Quite often the 2 Brazilian flights from Frankfurt take a more southerly route eg over Paris, NTS, STG, Canaries, west of Senegal, NE Brazil, whilst the Buenos Aires flight takes a track well north of this - despite the “ natural” track on paper being the same as the one taken by the Brazilian flights.

[KelvinD]

I appreciate the answers given and won't argue with them. I would point out though that my original query was based on the assumption that flights to the US, at the time I wrote, were taking a southerly route, presumably because of weather in the Atlantic. It is only when there is adverse weather en route that we see flights to Miami, New York etc passing overhead my part of the world. Yet is appeared that if the Virgin flight to Newark took this route due to the weather, it seemed odd that a following United flight to the same destination chose a more northerly route.

[kcockayne]

I appreciate the answers given and won't argue with them. I would point out though that my original query was based on the assumption that flights to the US, at the time I wrote, were taking a southerly route, presumably because of weather in the Atlantic. It is only when there is adverse weather en route that we see flights to Miami, New York etc passing overhead my part of the world. Yet is appeared that if the Virgin flight to Newark took this route due to the weather, it seemed odd that a following United flight to the same destination chose a more northerly route.
Well,, that is why I gave the illustration of the Brazil/Argentina flights - by the same company. This is what happens. Trans Atlantic traffic tend to take more southerly routes when you get an anticyclone centered to the north of Eire/west of UK. This gives an easterly wind to the southwest of the UK/ south of Eire ie a tailwind.Even though the distance flown to destination may be longer than the Great Circle route. But, the demand for the optimum tracks across the Atlantic is so great that not every aircraft can have the optimum route. Some will have to take a track to the south or north of these tracks. That is why two aircraft going to the same place may take different routes (ATC cannot accomodate them on the same route); even though the flights are operated by the same airline. Many years ago I used to work out the NAT track system at Prestwick using a slide rule - great fun which really re-Inforced the importance of your contribution to the operation of trans Atlantic operations.

[Doors to Automatic]

Kelvin - you can see the current position of the Jet Stream here https://www.netweather.tv/charts-and-data/jetstream

At present it is situated in the northern part of the Atlantic, which would explain why everything going West is routing on more Southerly tracks. There would still be several tracks available, with the departures routing over Bristol and S Wales taking the more Northerly tracks.

Flights going to the West Coast were taking routes over Greenland to avoid the Jetstream to the North; these would be taking an initial path directly to the North after departure, rather than a more NW track over Belfast.

[rog747]

a few times when i was working we routed out over lands end and azores to miami or orlando st lucia - usually in summer (like now)

4 engines mind

[KelvinD]

Thanks for all the replies. I shall now consider myself educated! (Well, semi educated at least!)

[rog747]

Thanks for all the replies. I shall now consider myself educated! (Well, semi educated at least!)

quite rightly -you are fine lol was a good question

most TA a/c for west and east coasts follow a great circle route that will track north as far as possible (being the shortest distance) even over the north Pole for some west coast or Japan flights but depending on the weather and headwinds forecast and in the case of Big twins (ETOPS) MEL's then the route will be adjusted accordingly
if its favorable to go south then they will as seen this week - but I think in going south there is an area that ETOPS twins cannot go - maybe someone here will remind me

Westbound flights are normally into the prevailing headwinds and eastbounds (back to the UK) will see strong tailwinds and jetstreams often knocking an hour or more off the flight time - these winds are on the northerly tracks usually

[Groundloop]

I doubt many flights follow great circle routes as headwinds/tailwinds tend to be the most important factor. I don't think there are any areas of the Atlantic nowadays which are outside ETOPS limits these days.

[rog747]

Great Circle Mapper (http://www.gcmap.com/mapui?P=BIKF,LPLA&R=120min@(BIKF,LPLA,BGSF,CYQX)&RS=s&MP=rect)

the great circle mapper is used for ETOPS rules and ETOPS alternates

under 120 mins rules there is still a small triangle in mid-atlantic which is a no-go but under 138 mins (120 +15%) that is removed

currently RR 787's affected by the engine issues are limited to 60 mins ETOPS I gather, so any TA ops are impossible

[MCDU2]

There are significant savings to be made avoiding radar control and utilising High Level Airspace (HLA) as well subject to winds and sig wx. Many flights will avail of the WATRS routes into the SE parts of the US (eg: MIA/MCO/TPA) from Ireland/UK/Near Europe.

[pax britanica]

Over three decades i clocked up a great many trips from London to Bermuda (32N 64W approx 700nm SE of JFK) during that time flying on 747 classics, DC10s, tristars and 777s I have flown over the Azores and Iceland en route and pretty much everywhere in between including coasting out over Lands End and not being over land again until 50ft over the lights at BDA .
Atlantic weather can certainly cause a huge variation in tracks and as has been said thats before Shanwick have to sort out everyone wanting the same few tracks and flight levels -of course there was always Concorde to JFK which was literally above all of that.

Also had some extra ordinary variations in block times too including close to ten hours westbound once (1011-500) and 5 hours 5 mins back a couple of days later

[WHBM]

Very roughly, the westbounds tend to go further north than the eastbounds, due to common weather patterns. Not always the case of course. This is even more pronounced across the Pacific, where New York to Tokyo tends to head north, virtually over the North Pole, where returning they come across the Pacific and British Columbia.

Anadyr, in the Russian Far East, to Moscow, a domestic flight, can be routed westbound just a little further north than the Great Circle and pass over the North Pole itself.

I've done London to Miami over Prestwick and Newfoundland, and next trip direct, overhead Bermuda. I've also just once returned from SFO to London and never crossed Canada, overhead Chicago and we coasted out around Bangor ME.

[India Four Two]

I once flew Los Angeles to Bangkok and we didn’t fly over any part of the Pacific! There were two massive lows over the Aleutians and the Bering Sea, that had 150 knot westerly winds!

Our route was north over California, Oregon, Washington, British Columbia and the Yukon. We coasted out over the Beaufort Sea, coasted in over Siberia and flew over Kamchatka, the Sea of Okhotsk, China and Thailand.

[wiggy]

There are significant savings to be made avoiding radar control and utilising High Level Airspace (HLA) as well subject to winds and sig wx. Many flights will avail of the WATRS routes into the SE parts of the US (eg: MIA/MCO/TPA) from Ireland/UK/Near Europe.

Indeed, it’s always just down to best winds/shortest shortest distance - For example you sometimes see some interesting routings between the U.K. and South America which is due to trying to avoid high navigation services charges associated with some FIRs.

[Reverserbucket]

interesting routings between the U.K. and South America
Look at BA's routings ex-LHR/LGW to Santiago and Lima - some days tracking over the western Sahara and others the Azores. Don't forget the recent PBCS requirement on the NAT OTS; non-compliant a/c can end up flying far less desirable tracks and FL's.

[wiggy]

:ok:

Exactly,...there are now a whole host of variables/factors that the planners plug into the machine these days before generating (possibly) multiple flight plans for one sector and looking at the costs...it is no longer just a case of looking at distance and the average wind, but as you rightly say, comm/nav compliance, navigation charges ( big money in some FIRs), ETOPS acceptability...etc etc

[DaveReidUK]

Indeed, it’s always just down to best winds/shortest shortest distance

Yes, we'd guessed you meant "not always ..." :O

[wiggy]

Yes, we'd guessed you meant "not always ..." :O


Oh,:ugh: yep..thanks for spotting that...I'll leave the offending post as is to save me further confusing matters .

ATB