Creating TAFs...

[rse]

Best place I can find here for this. Calling all Met trained folks.

How can you tell and what tools do you use to differentiate between the following? What is it that allows you to be this sure, whether it happens or not?

SCT025 - SCT035 - what is it that causes the 1000' difference?
SCT030 - BKN030 - what is it that makes sct 'sct' and not 'bkn'?
RA +RA - presumably much easier here?
SHRA - RA - patchy/less water suspended equals only showers?
BCFG - 150mFG
FG - BR etc etc…
GS - GR - what conditions form the difference between the two? GR is constantly forming in layers below the freezing point so is much harder and more dangerous, whereas GS are just quick-forming non-laminar pellets?

Isobars to wind strength and direction understood but where cloud/precipitation are concerned - specifically to do with the amount of moisture present and the T/DP relationship or is it more than that?

TVM!

[B737900er]

SCT025 - SCT035 - what is it that causes the 1000' difference?

There is a layer of cloud its that simple.

SCT030 - BKN030 - what is it that makes sct 'sct' and not 'bkn'?

Sky coverage based on Oktas .

SKC = Sky Clear = 0/8
Few = 1/8 to 2/8
Scattered = 3/8 to 4/8
Broken = 5/8 to 7/8
OVC = Overcast = 8/8

[MarkerInbound]

I believe the OP was asking how forecasters know which to forecast.

specifically to do with the amount of moisture present and the T/DP relationship or is it more than that?

That's a good starting point. Cloud base can be determined by the difference in surface temperature and dew point, they have different lapse rates. Coverage will be a function of instability and dew point. The amount and intensity of rain fall depends on the available precipitable water and the type of clouds expected to develop. After that I don't know.

[chevvron]

I believe the OP was asking how forecasters know which to forecast.



That's a good starting point. Cloud base can be determined by the difference in surface temperature and dew point, they have different lapse rates. Coverage will be a function of instability and dew point. The amount and intensity of rain fall depends on the available precipitable water and the type of clouds expected to develop. After that I don't know.
In the UK, forecasters no longer prepare TAFs, they're all computer generated.

[fireflybob]

In the UK, forecasters no longer prepare TAFs, they're all computer generated.

Don't we know it!

I did hundreds of 'em. Over 30 years later, I still have dreams about having forgotten to do the 04-13 and getting in a panic, ha! ha!

I wish we still had the 9 hour TAFs (we could still keep the 18/24 hour ones) which seemed to be more accurate and not full of so much PROB30 that or TEMPO this etc. Also the fact that they were issued every 3 hours meant they could be easily updated and there were less amendments than we seem to get these days.

[HEATHROW DIRECTOR]

Nothing beats the real live forecasters and observers. Thanks guys...

[fireflybob]

In the early 1980s we checked into Met at Manchester for briefing for a night Ibiza. I asked why Palma was forecasting fog but Ibiza wasn't. Without batting an eyelid the forecaster replied "Katabatic drainage off the high ground on the north side of Majorca" - EGQL1964 you guys did a fantastic job for us!