SIGWX Charts Experts Interpretation?

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SIGWX Charts Experts Interpretation?

Unread post by RudiGreyling » Thu Mar 08, 2018 8:29 am

Good Morning,

Sometimes when the SIGWX Charts get really busy I struggle to interpret them...

I was wondering if others here on avcom has the same problem, and maybe should we post some examples and questions here for us to learn from experts?

Let me know if this is a good idea, and if the experienced guys will assist solving/clarifying them for us?

Kind Regards
Rudi
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Re: SIGWX Charts Experts Interpretation?

Unread post by Goose » Thu Mar 08, 2018 8:54 am

Which website are you using Rudi?
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Re: SIGWX Charts Experts Interpretation?

Unread post by RudiGreyling » Thu Mar 08, 2018 12:51 pm

Goose wrote:Which website are you using Rudi?
http://aviation.weathersa.co.za/#home
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Re: SIGWX Charts Experts Interpretation?

Unread post by Iceberg » Thu Mar 08, 2018 1:08 pm

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Re: SIGWX Charts Experts Interpretation?

Unread post by RudiGreyling » Thu Mar 08, 2018 3:32 pm

Iceberg wrote:Check under "About"

http://196.37.137.194/Docs/SAWS_AviationCodes.pdf
Thanks Iceberg, but that is not really what I was referring to where I have trouble...I mean when the SIQWX chart gets busy with lots of overlapping symbols and areas then I get confused what is applicable where...maybe I should just post an example and ask the questions and see if someone can give clarity....
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Re: SIGWX Charts Experts Interpretation?

Unread post by RudiGreyling » Thu Mar 08, 2018 3:51 pm

OK here is an example..from this morning:

SATELITE IMAGE:
01_Satelite.jpg
BELOW FL100:
01_SIGWX_01_BELOW_FL100.gif
BELOW FL180: (With colours for my Questions)
01_SIGWX_BELOW_FL180_EDITED.gif
ABOVE FL180
01_SIGWX_ABOVE_FL180.gif
Questions:
I get it, the charts build on top of each other, that is why the dashed areas in blue (ISOL EMBD CB) Penetrate all 3 charts, but...

Q1) Does the Green Aera I marked the Cloud [BKN SC 080/040] extend under the RED AREA where the dashes are marked? (Basically from the sea inland for +/- 100km?)
Q2) is the PINK [ISOL EMBD TCU XXX/085] Applicable to the ENTIRE RED area or only localised?
Q3) lastly the dashed area on the BELOW FL100 chart, is that to indicate the area where moderate turbulence can be expected between 080/SFC?

I hope my questions are clear...?
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Re: SIGWX Charts Experts Interpretation?

Unread post by Iceberg » Thu Mar 08, 2018 4:11 pm

RudiGreyling wrote: Questions:
I get it, the charts build on top of each other, that is why the dashed areas in blue (ISOL EMBD CB) Penetrate all 3 charts, but...

Q1) Does the Green Aera I marked the Cloud [BKN SC 080/040] extend under the RED AREA where the dashes are marked? (Basically from the sea inland for +/- 100km?)
Q2) is the PINK [ISOL EMBD TCU XXX/085] Applicable to the ENTIRE RED area or only localised?
Q3) lastly the dashed area on the BELOW FL100 chart, is that to indicate the area where moderate turbulence can be expected between 080/SFC?

I hope my questions are clear...?
Q1
BKN SC 040/080 (not 080/040) means there is broken stratocumulus between 4000 and 8000ft ASL - but this is only south of your red area. In the red area it is SCT SC 040/080 - only scattered and up to the dotted line along the escarpment.

Q2 Entire area

Q3 Yes

Hope that helps
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Re: SIGWX Charts Experts Interpretation?

Unread post by RudiGreyling » Thu Mar 08, 2018 6:42 pm

Thank you, dankie
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Re: SIGWX Charts Experts Interpretation?

Unread post by RudiGreyling » Fri Mar 09, 2018 7:17 am

Good Morning Gents Here is another one from this morning that gets a bit busy in the northern corner of RSA with overlaps. Stacking the 3 charts does not clear up the confusion with the dashed area for me...
02_Satelite.jpg
02_Cloud Top Heights.jpg
02_SIGWX_01_BELOW_FL100.gif
02_SIGWX_BELOW_FL180.gif
02_SIGWX_ABOVE_FL180.gif
Question:
Q1) On the SIGWX Below FL180, I don't understand what the DASHED line (indicated with RED) is supposed to show and what is separated from what, or what is extended up to the DASHED line only. Any help, please?

Kind Regards
Rudi
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Re: SIGWX Charts Experts Interpretation?

Unread post by Iceberg » Fri Mar 09, 2018 9:08 am

RudiGreyling wrote:Good Morning Gents Here is another one from this morning that gets a bit busy in the northern corner of RSA with overlaps. Stacking the 3 charts does not clear up the confusion with the dashed area for me...
Question:
Q1) On the SIGWX Below FL180, I don't understand what the DASHED line (indicated with RED) is supposed to show and what is separated from what, or what is extended up to the DASHED line only. Any help, please?

Kind Regards
Rudi
Hi Rudi

The dotted line separates the two areas of SC - broken on the southern side and scattered in the northern side.

The Broken CU covers the whole area.

The 4000m vis and drizzle is on the escarpment.

Regards

Karl
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Re: SIGWX Charts Experts Interpretation?

Unread post by Hop Harrigan » Sat Mar 10, 2018 1:54 pm

Gents,
I must comment...I have always thought that the SIGWX chart looks a bit like a child has scribbled it...apart from the confusing issues already outlined, it’s very difficult to place ones route on the chart with any accuracy at all. The RSA and Province outlines and placement of major cities are even difficult to identify clearly.
Would it really be so hard to produce a clear, unambiguous chart? Part of the issue I think is that they’re trying to cram the whole country into one A4 (or smaller ) sheet. Maybe it should be spread over a number of pages?
But then these weather okes are a different breed....
Hop
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Re: SIGWX Charts Experts Interpretation?

Unread post by RudiGreyling » Mon Mar 12, 2018 10:54 am

Iceberg wrote: Hi Rudi

The dotted line separates the two areas of SC - broken on the southern side and scattered in the northern side.

The Broken CU covers the whole area.

The 4000m vis and drizzle is on the escarpment.

Regards

Karl
Thanks Karl, the separation between SC Broken and Scatered makes sense...

...but just to clarify what you are saying about the 4000m Vis and drizzle "is on the escarpment".
A) Is it applicable to the whole area (from the coast line) up to the dotted line in RED, or
B) are you saying it is localised along the dotted, just south of that dotted line all along to the top of RSA NE border, or
C) it is just localised in the immediate vicinity of the actual symbol position?

Thank you
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Re: SIGWX Charts Experts Interpretation?

Unread post by Iceberg » Mon Mar 12, 2018 12:42 pm

RudiGreyling wrote:
Iceberg wrote: Hi Rudi

The dotted line separates the two areas of SC - broken on the southern side and scattered in the northern side.

The Broken CU covers the whole area.

The 4000m vis and drizzle is on the escarpment.

Regards

Karl
Thanks Karl, the separation between SC Broken and Scatered makes sense...

...but just to clarify what you are saying about the 4000m Vis and drizzle "is on the escarpment".
A) Is it applicable to the whole area (from the coast line) up to the dotted line in RED, or
B) are you saying it is localised along the dotted, just south of that dotted line all along to the top of RSA NE border, or
C) it is just localised in the immediate vicinity of the actual symbol position?

Thank you
Hi Rudi

Symbols for rain and drizzle are usually placed at the most likely location where it will occur, but technically speaking it can be possible in the rest of the covered area.

I know from experience that the low vis and drizzle occurs mostly on the escarpment and that is where the drizzle symbol can usually be found.

Just a note. Do not try to overanalize the weather and these type of charts (or any weather charts/predictions for that matter). The charts are a compromise, trying to show a general pattern that changes by the minute. It just primes you for what you can expect.
Aviation writer Richard Collins summed it up as follows:
The forecasts are only for deciding whether to go or not.
Once flying, forget about the forecasts and look out the window.
You are now in the best weather office in the world. Deal with the real weather as you encounter it with prudent decisions.
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Re: SIGWX Charts Experts Interpretation?

Unread post by RudiGreyling » Fri Mar 23, 2018 7:56 am

Hi Karl,

thank you very much. I think understanding these charts are important, cause it helps with the initial go / no go decision. I also agree once you are airborne forget the chart, or rather try to remember the areas of better weather, in case you find you need to divert instead of turning back.

Here is another one from this morning:
Q1) I struggle with the dasshed areas in yellow and what they try to group:
Q2) The yellow Rain, drizzle and mist on the RSA / MOZ border is that trying to show localised? We know it is raining cats and dogs this morning in JHB/PTA and those are far away from J & P
sigwx_03.JPG
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Re: SIGWX Charts Experts Interpretation?

Unread post by Iceberg » Mon Apr 02, 2018 2:09 pm

Sorry for only replying now.

The dotted lines refer to the additional info within them. In this case the ISOL CB and ISOL TCU as well as showers. This is over and above the other information applicable to the wider area.

Symbols for drizzle, fog and rain are mostly placed in the areas that they are most likely to occur. Sometimes the word "LOC ESC" are added - localized on the escarpment.
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