Inaccurate weather forecasting (TAFs)

[fireflybob]

We managed to do a spot of night flying tonight.

With all the modern computing power how can the Met Office get it so wrong?

4 amended tafs within the space of 5 hours:-

FT 23/01/2014 20:17->

TAF AMD EGNX 232017Z 2320/2418 21004KT 9999 FEW015
TEMPO 2320/2322 6000 SHRA
TEMPO 2404/2407 8000 -RA
BECMG 2407/2410 15010KT 8000 -RA BKN010
TEMPO 2408/2418 4000 RADZ BKN008
PROB30 2410/2418 BKN004=

FT 23/01/2014 17:44->

TAF AMD EGNX 231744Z 2318/2418 28011KT 9999 FEW015
TEMPO 2318/2321 28020G35KT 6000 SHRA
BECMG 2401/2404 21004KT
TEMPO 2404/2407 8000 -RA
BECMG 2407/2410 15010KT 8000 -RA BKN010
TEMPO 2408/2418 4000 RADZ BKN008
PROB30 2410/2418 BKN004=

FT 23/01/2014 17:00->

TAF EGNX 231700Z 2318/2418 28011KT 9999 FEW015
BECMG 2401/2404 21004KT
TEMPO 2404/2407 8000 -RA
BECMG 2407/2410 15010KT 8000 -RA BKN010
TEMPO 2408/2418 4000 RADZ BKN008
PROB30 2410/2418 BKN004=

FT 23/01/2014 16:15->

TAF AMD EGNX 231615Z 2316/2412 29013KT 9999 FEW015
PROB40 TEMPO 2316/2318 29020G30KT 4000 SHRAGS BKN010
BECMG 2322/2401 21004KT
TEMPO 2404/2409 6000 RA BKN008
BECMG 2408/2411 15010KT
BECMG 2409/2412 6000 RA BKN008
PROB30 2409/2412 4000 DZ BKN004=

FT 23/01/2014 15:09->

TAF AMD EGNX 231509Z 2315/2412 29013KT 9999 FEW015
PROB40 TEMPO 2315/2316 29017G27KT 4000 SHRAGS BKN010
BECMG 2322/2401 21004KT
TEMPO 2404/2409 6000 RA BKN008
BECMG 2408/2411 15010KT
BECMG 2409/2412 6000 RA BKN008
PROB30 2409/2412 4000 DZ BKN004=

No doubt they will say it's all within their "tolerances". Maybe I am wrong but 9 hour tafs seemed to be a lot better.

[Genghis the Engineer]

They all look pretty similar to me.

G

[TopBunk]

G

Iwas going to say Genghis, the main variable seems o be the short term end of the forecast and not the longer term.

That being the case, how a 9 hour TAF would be better eludes me!

[fireflybob]

Topbunk yes it was the short term forecast (and actual!) that changed quite rapidly. (In the space of 44 minutes).

I agree a 9 hour taf might not make any difference per se but my perception is they were more accurate short term.

In all my experience locally this was one of the worst forecast changes - the local airfield had launched quite a few a/c based on a good taf and then we suddenly found the conditions had changed and they'd hastily issued an amendment. Threat and Error Management?

[Whopity]

With all the modern computing power how can the Met Office get it so wrong?

Because when they got it right, forecasters could draw charts, now they can't and have to rely on gadgets which are only as good as the people who program them.

[Fostex]

Also the reason that we study met in the ATPL exams...

Do you have the 215 for that evening and did you take it into account as well as the TAF?

Because at the end of the day it is up to the FI to make the call if it is safe to fly based on a combination of forecast, knowledge of the local environment, experience and student pilot ability.

[S-Works]

I sit on the MOUF which is the Met Office Users Forum which manages this. If you want to drop me a line with details I will raise it at the next meeting.

[fireflybob]

Do you have the 215 for that evening and did you take it into account as well as the TAF?

Because at the end of the day it is up to the FI to make the call if it is safe to fly based on a combination of forecast, knowledge of the local environment, experience and student pilot ability.

Fostex, yes of course we do. As we are only 10 nm from EMA it also makes sense to use their TAFs which are somewhat more specific than the generic nature of 215.

In the days when ATC had more capacity EMA would often call us on the phone to warn of approaching weather (as they are generally upwind of our location).

[Burnie5204]

Fireflybob,

A few of those changes were because of the rapidly changing weather we were faced with such as sudden onset moderate showers with strong winds (at times up to 300/38kts) which were unforecast by Exeter (thereby causing some minor issues for ATC) and therefore Exeter would we regenerating the TAFs

However, many of those changes correspond with us being issued with weather warnings.

First we had a specific "Strong winds associated with rain showers", this then became a generic Strong Wind warning. This was then joined by an additional "Ground Frost may form" warning and then later the Strong wind warning was extended.

[ShyTorque]

Seems like tactical forecasting again. The aim isn't so much getting the weather right, more of a case of not being seen to have got it wrong.

Same with air trafficking these days. Call any ATC unit and the first thing you're told, even before you get to pass details is "Remain outside controlled airspace" etc etc.

We live in a world where everyone covers their rear end above all else. All responsibity is pushed downhill onto the PIC.

[S-Works]

I have forwarded Fireflybobs message to the MOUF at his request. Its not for another 2 months but I will pass back any comments.

[Steak&Kidney_Pie]

And throughout this thread, no-one give credit to "nature" and the fact it can vary....

The Met Office are quite clearly trying to be accurate, by the amendments. But at the end of the day....it is a calculated PREDICTION. Not a written fact.

[fireflybob]

The Met Office are quite clearly trying to be accurate, by the amendments. But at the end of the day....it is a calculated PREDICTION. Not a written fact.

Agree - for me that's a given but nothing wrong with commenting on a forecast with the Met Office and finding out why things were not as predicted. It's a two way process - that way we all learn more.

In fact I have had had a very helpful email back from the Met Office explaining what happened. It's too long to post here right now.