I’m sitting here at my computer looking at tomorrow’s Terminal Aerodrome Forecast, or TAF for short. These are very important for determining whether you fly which is good, just think about flying which is bad, or fly and soon realize it would have been a much better idea to stay on the ground which is really, really bad. These forecasts are a wonderful example of pilot jargon that was developed in the days of telegraphs and teletype as they convey a day’s worth of weather information in one or two lines. They are a fine example of a data communications anachonism in today’s internet age when if you want to know the weather in West Bend, Oregon you can get it straight from the satellite along with the last 50 years of minute-by-minute dew point records. There have been efforts to get these forecasts amended to plain language but they have endured in their current concentrated form mostly I think because Pilots like them. I know I do because when I see the mystified faces of my friends and family when I show them one if gives me a smug feeling of superiority because I’m part of a part of an elite fraternity; a group of intrepid men and women who can decipher the magical code.
It’s a code that can make you gleeful or morose, and they can change pretty radically in the UK because all of its weather forces. Today has been a disgusting, slimy, semi-frozen morass of a day. It started off wet and cold, developed into wet and cold, and then later developed to become wet and cold and dark. I wouldn’t have needed to fly today to get into the clouds, all I would have had to do is step outdoors. I’m waiting for the midnight forecast to come out that will cover all of tomorrow as I’m hoping beyond hope that I can get some flying time in before I go away to New York for Christmas.
It’s here, I’ll put it below so you can read it and I can feel a smug sense of superiority when you go “huh?”
LONDON/STANSTED EGSS 132323Z 1400/1506 10010KT 6000 -RA BKN005 BECMG 1400/1403 VRB06KT TEMPO 1400/1506 2000 BR BKN002 PROB30 TEMPO 1410/1418 BKN010 PROB40 TEMPO 1421/1506 1200 BKN000
They’re not all this long. Usually when it stretches 2 full lines it’s bad. My favorite abbreviation is NSW, for No Significant Weather. That’s always nice to see. I’ll break it down for you:
EGSS – the international code for Stanstead, an international airport NE of London near where I fly from
132323Z – this forecast was sent out on the 13th of December at 2323 UTC, ie 11:23pm Greenwich Mean Time
1400/1506 – the forecast is from 00:00 UTC on Dec 14th to 06:00 on the 15th
10010KT – winds 100 degrees 10 Knots, that’s just fine
6000 – visibility 6000 meters, about 4 miles. That’s kinda minimal, but it’s perfectly legal
-RA – Light rain (no shit sherlock, it’s been -RA all day)
BKN005 – Cloud Broken (almost overcast) at 500 feet – don’t take off unless you have a full instrument rating and an airplane with lots of expensive instrument landing equipment
BECMG 1400/1403 VRB06KT – between 00:00 and 03:00 winds will become variable 06 knots
TEMPO 1400/1506 2000 BR BKN0002 – oh great, for a 30 hour period between midnight and 06:00 Monday there will be temporary periods where visibility will drop to 2000 meters in mist with broken clouds at 200 feet – Don’t fly unless you have a full instrument rating and a multi-million dollar computer guided blind landing system
PROB30 TEMPO 1410/1418 BKN010 – there’s a 30% probability that temporarily between 10am and 6pm tomorrow the cloud will raise to 1000 feet. Wow, you could fly in that if it wasn’t for the bit above
PROB40 TEMPO 1421/1506 1200 BKN000 – there’s a 40% probability that between 9pm tomorrow and 6am Monday that visibility will drop to less than a mile and the cloud will be literally down at ground level. – don’t fly unless you have x-ray vision. the difference between PROB 30 and PROB 40 in the UK is that PROB 30 means it isn’t likely to happen but could, and PROB 40 means that it probably will, it’s just the met office don’t have the courage to say 60% because the weather in the UK is so hard to predict
In other words tomorrow is going to be another filthy, stinking morass, a complete toxic waste dump of a Sunday fit only for ironing and swearing.
What is it with the weather in England this year? My flying group had 17 days of flyouts planned and we actually got to do 6 with the rest canceled because of weather. Time after time it’s something. Last Sunday it was mist, the weekend before rain. Cmon! What do I have to do here?! Gimme some love, goddammit! All I ask is for is just one decent weekend day, and instead I get a weekend where as far as I know the sun has gone to the pub for a beer. I am not a mushroom!!
You know what, I think we can condense the forecasts more no problem. Rather than expand it I can concentrate tomorrow’s forecast into a much more efficient space:
EGSS 132323Z 1400/1506 CMPLT SHT