Why are heathrow flights cancelled tonight

[Mr_B]

The bbc are reporting flights being cancelled

BBC News - Heathrow cancels 70 flights due to storms (http://www.bbc.co.uk/news/uk-england-london-13569404)

But the wind doesn't look too bad, mamxium 27 knots


Taf


LONDON/HEATHROW EGLL 261701Z 2618/2724 29012KT 9999 SCT025 TEMPO 2618/2622 27017G27KT 7000 SHRA PROB30 TEMPO 2618/2619 TSRA BKN014 BKN020CB PROB30 TEMPO 2704/2708 BKN014

&

Metar


LONDON/HEATHROW EGLL 262020Z 29009KT 9999 BKN037 BKN042 12/08 Q1012 NOSIG

Is it just the thunderstorms which have caused the flights to be cancelled

[Flightman]

Yes, CB's etc

[Skipness One Echo]

Central London was thunder and lightning, very, very frightening, me Galileo Galileo Figaro etc.....

[HeathrowAirport]

That's why....
Omg what a **** off #Thunderstorm - wow!! All #Heathrow fligh... on Twitpic (http://twitpic.com/52syaz)

Excuse the comments at the bottom of it, but those brave pilots (2-3 of them that went through that bugger where brave, most decided they didn't want too - I know that!

I could feel the downdraft rattling against my window, at about the same time that the aircraft on approach pulled off there approach.

If you look at Met Office: London & South East England: latest radar (http://www.metoffice.gov.uk/weather/uk/se/se_latest_radar.html) - it was near enough a downpour.

[Nubboy]

Bearing in mind the name of the forum, here's a bit of info for you.

I wasn't at work yesterday so didn't have a first hand look at it.
However the comment about "brave pilots" does raise a few issues.

First off is that our concerns for our passengers are in three different levels, safety, comfort then covenience (sub divide this into pucntuality then preferred destination). In other words you get to the right destination, on time provided the first two criteria are met. End of. Bravery just doesn't come into it.

We now have two bits of kit that help us do that. Weather radar and windshear prediction. The weather radar is a broad brush approach that shows us where the rain is falling. The display display is colour coded: green, amber, red and magenta. The different colours are calibrated for different size rain drops. Big raindrops need big updrafts to generate them. On a personal basis I find green is no problem, amber is enough to suspend cabin service and have the crew strapped in, red is a no go area by a sensible margin (5 to 20 miles) and don't ever ever contemplate magenta.

Predictive windshear is also radar based and shows areas where the differences in local winds could make the approach unsafe. In extreme circumstances, say the gust front produced by a heavy downpour from a thunderstorm, an aircraft might not be able to to outfly the downdraft and be pushed onto the ground. Has happened and it's not good.

What this means from a practical point of view is that an approach should only be continued if it's safe to do so. Even then I've had to go around from a very low level as gusts have come through and the aircrafty wouldn't have landed in the touch down zone. The crew would have discussed their options prior to making their approach, and would have briefed any conditions requiring them to break off.

Looking at the TAF in the original post, LHR wasn't a cast iron guarantee for clear weather, so for me that would mean an hours holding fuel, plus fuel for a diversion airfield which didn't have the magic term TSRA in the forecast.

Crews don't, as a rule divert lightly. It costs the company shed loads of cash and disrupts the passengers and flying schedule. Also my car is parked at home base. Howver, we don't do brave.

Hope this helps.

[HEATHROW DIRECTOR]

Well said Nubboy...

[dfdasein]

Passengers mutiny on grounded plane - Yahoo! News (http://uk.news.yahoo.com/passengers-mutiny-grounded-plane-141132645.html)

[DX Wombat]

Nubboy, I would not have said you didn't do brave, more like you didn't do stupid and reckless. Who in their right mind would want to fly through one of these?
http://img.photobucket.com/albums/v604/DX_Wombat/P1011447.jpg
Taken at Halfpenny Green a couple of years ago the cloud is probably located somewhere in the region of Shobdon.