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GRAMET (merged thread)

Today, both GFS and ICON GRAMET forecasts (done yesterday) are completely useless. The actual TS are several hours ahead of schedule

ECMWF (windy.com) is right though

Clearly what is needed is an ECMWF GRAMET Windy.com does produce one but the depiction is capped vertically to 10k feet.

Administrator
Shoreham EGKA, United Kingdom

Just been doing the AR GRAMET for a flight tomorrow dep 0700Z

EGKA XORBI PERON BILGO REM DIKOL VATRI RLP RESPO LUL HR HOC DITON RIPUS GERSA SOSON DEGAD ODINA SRN DESIP PEXUG LEGLO OSKOR NEVNI NOBMI ELTAR IDREK ADOSA UPXUF ALBET CHI AGOMO LABIN PUL LOS LDLO

GFS: July 11 2023, 06:00Z
ICON Global: July 11 2023, 12:00Z
ICON EU: July 11 2023, 12:00Z

GFS:

ICON:

One or the other is BS, since the type of wx being forecast is totally different.

Looking at the MSLP I’d say the ICON one is the BS one:

Administrator
Shoreham EGKA, United Kingdom

Wout wrote:

Do you perhaps know the answer on my 2nd question too?

I guess cloud cover? White is clear sky? The cloud cover circles in the white area are all white.

ELLX
Wout wrote:
On the GRAMET I see a ‘brown’ coloured area. I cannot find the explanation of these colours. Where can I find it?
https://www.autorouter.aero/wiki/gramet/#Strong_Winds_and_Turbulence

Values of E between 80 and 160 are considered moderate turbulence and values above 160 severe turbulence. If E is above 80, the areas inside the corresponding isotachs are shaded in brown.

So in short, the brown shaded areas are turbulence.

Thank you Lionel! I missed it in the text. Do you perhaps know the answer on my 2nd question too?

Wout wrote:

On the GRAMET I see a ‘brown’ coloured area. I cannot find the explanation of these colours. Where can I find it?

https://www.autorouter.aero/wiki/gramet/#Strong_Winds_and_Turbulence

Values of E between 80 and 160 are considered moderate turbulence and values above 160 severe turbulence. If E is above 80, the areas inside the corresponding isotachs are shaded in brown.

So in short, the brown shaded areas are turbulence.

ELLX

On the GRAMET I see a ‘brown’ coloured area. I cannot find the explanation of these colours. Where can I find it?

The same for the chart in the briefing with the METAR plots, what does the background colour white or grey mean?

I’ve been telling for some time that ICON is the worst of these models. I’ve never seen accurate forecast produced by it.

LDZA LDVA, Croatia

I did a couple of gramets from the AR, 24hrs ahead.

Curiously the GFS one is not far off what it actually was in terms of the rain at the departure end, though the layers don’t relate to reality. The ICON gramet is way off and totally useless; it shows basically nice wx and it was horrible, with low cloud, bad vis and heavy rain. Normally GFS is less accurate than the other models (which are now available on windy.com) but not with this source, in this case.

GRAMET_EGHE_EGKA_GFS_pdf
GRAMET_EGHE_EGKA_ICON_pdf

Administrator
Shoreham EGKA, United Kingdom

Posts moved to existing thread.

We are debating a nebulous issue, due to not enough info posted.

The original “gramet” is from the Univ of Granada and can be found here. This is GFS derived, with some computation on top. Then the Autorouter brought out a similar presentation, also GFS derived (now with an ICON option but that works only about 30hrs ahead – discussed above), and again with computation on top.

Much of the presentation in these charts is “artistic” e.g. what shape of cloud you paint depends on things like the lapse rate… you will never see the same thing from two different sources.

I find the accuracy of particularly cloud layers to be poor. There is simply no really good forecasting source for a lot of stuff.

The best source today is windy.com although it has a tendency to result in a lot more cancelled flights

Administrator
Shoreham EGKA, United Kingdom

In EU, choose ICON

Flying Finn living in Switzerland.
LSZL LOcarno, Switzerland
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