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Loaded weather for Liverpool early this evening, this is the METAR

 

EGGP 131650Z 32010KT 280V340 9999 VCSH FEW024 06/M03 Q1013

 

In FSX however I had major lightning strikes and very gusty conditions at 2,500ft.

 

No indications in the METAR for TS nor out of the window in Manchester nor were ther any indications of gusty winds.

 

SP2 Build 4815

 

Any thoughts from Hi-Fi?

 

Dave

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A non-HiFi thought...

 

Take a look at nearby EGNR (using the same build as you)... it is showing thunderstorms (EGNR 131720Z 33008KT 290V010 9999 VCSH FEW022CB 05/M02 Q1013)

 

And still is... http://www.aviationweather.gov/adds/metars/?station_ids=EGNR&std_trans=translated&chk_metars=on&hoursStr=past+3+hours&submitmet=Submit

 

so yes... very interesting...

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The problem is that the METAR specifies "CB", which in the US indicates thunderstorms but in other parts of the world does not. CB in the METAR will trigger thunderstorms.

 

In AS2012, under Cloud Options, check the box for "Prevent thunderstorms when CB reported" to get rid of the thunderstorms.

 

Hook


Larry Hookins

 

Oh! I have slipped the surly bonds of Earth
And danced the skies on laughter-silvered wings;

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The problem is that the METAR specifies "CB", which in the US indicates thunderstorms but in other parts of the world does not.

 

It is in the UK when describing Sky Condition (along w/ cloud bases).

 

See: UK Met Office

 

 

 

check the box for "Prevent thunderstorms when CB reported" to get rid of the thunderstorms.

 

Btw Hook... you can go there now (Met Office) an see in METARs, CBs being reported now for Northern England

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To paraphrase Will Rogers, all I know is what I read in the manual.

 

Prevent Thunderstorms When CB Reported: Check to Prevent Thunderstorms with CB reports. USA tends to report CB when Thunderstorm activity is imminent while in other countries it may be routinely used for more normal (not significantly-convective) conditions.

I checked the METARS with the first link you provided before posting. While that one METAR didn't specify CB, others did. Occasionally, nearby METARS will influence what you see in the game.

 

Hook


Larry Hookins

 

Oh! I have slipped the surly bonds of Earth
And danced the skies on laughter-silvered wings;

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I checked the METARS with the first link you provided before posting. While that one METAR didn't specify CB, others did.
 
Little confused here... EGGP showed for me as Vulcan posted... ENGR was still showing CBs (similar to the METAR I posted).
 

 

Occasionally, nearby METARS will influence what you see in the game.
 
Yes... this is what I was getting at in my first post.
 
 
This statement:
 

 

The problem is that the METAR specifies "CB", which in the US indicates thunderstorms but in other parts of the world does not.
 
is quite different than this statement:
 

 

Prevent Thunderstorms When CB Reported: Check to Prevent Thunderstorms with CB reports. USA tends to report CB when Thunderstorm activity is imminent while in other countries it may be routinely used for more normal (not significantly-convective) conditions.
 
 
And I don't like this statement:
 

USA tends to report CB when Thunderstorm activity is imminent while in other countries it may be routinely used for more normal (not significantly-convective) conditions.

 
 
 
A Thunderstorm needs 3 components to develop:
 
  • Moisture
  • Unstable lapse rate
  • Lifting Mechanism
 
Without all three you won't get a thunderstorm.  With all three you may still not get a thunderstorm.  It can be "imminent" when all three conditions are present and visible by observing e.g. Tower Cu.
 
You see a stroke of lightning or hear thunder... that is, by definition, a Thunderstorm.
 
I do not think the "imminent" part is correct unless it is referring to conditions required for  "significantly convective" thunderstorms i.e. Intense or Severe Thunderstorms (as defined by the WSO)... something that would require other conditions not listed above.
 
In that case, I have a hard time believing (based on experience) a Thunderstorm would not be reported in a METAR because any Thunderstorm can be a hazard to flight.
 
 

USA tends to report CB when Thunderstorm activity is imminent while in other countries it may be routinely used for more normal (not significantly-convective) conditions.

 
Where I can see this statement somewhat making sense... in the U.S. (at least previously to METAR adoption)  and iirc weather reporting was for 5 miles around the airport (although current reporting "VC" is up to 10sm).  This could make the case for a Thunderstorm being "imminent" (not in growth or required elements but in location re: the airport)... whereas in "other parts of the world" I have read reporting maybe be 10 miles or even more... akin to the U.S. of "DSNT" (Distant) which would be U.S. beyond 10sm to 25sm.
 
-Rob

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Rob, I was responding to the original poster who was wondering why he was seeing thunderstorms when there was no apparent indication in the METAR that he thought should have been in effect. I told him why, and how to fix it, based not on Real World weather but how AS2012 interprets METARS.

 

I will add that the CB indication may not be a binary switch that turns on or off the presence of thunderstorms, but is handled in a similar manner to icing or turbulence, where AS2012 looks at prevailing conditions and generates an appropriate weather situation. From everything I've seen, AS2012 usually does an outstanding job, but occasionally the interpolation functions can get confused and render something unexpected. Sometimes this results in pleasant surprises, other times makes you scratch your head.

 

Hook


Larry Hookins

 

Oh! I have slipped the surly bonds of Earth
And danced the skies on laughter-silvered wings;

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Not to mention that the "gusty wind" condition can be triggered by the known weather bug in FSX simply from the variable wind direction " 280V340" - i.e. wind direction shifting more than 30 degrees (in this case 60 degrees) from the average 310 degrees direction. Also note - surface wind speed of 10 knots at surface, whereas by 3000 feet the wind forecast is 23 knots. Using FSUIPCs wind smoothing feature for wind direction and/or speed helps, but will not totally solve the issue there.


___________________________

Kenneth E Wood Jr  🌪️🌩️

ex AG1, USN (14yr Vet) Weather Foecaster

 

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Rob, I was responding to the original poster who was wondering why he was seeing thunderstorms when there was no apparent indication in the METAR that he thought should have been in effect.

 

Yes... I was too Hook... at least when I read my post(s) that is what I thought I was doing.

 

And I thought my explanation how "vicinity" is handled "here" vs. "there" would provide some clue along that line - and might explain what was written in the manual about CB handling.  That this really is not something "unexpected" or necessarily AS2012 improperly handling the METAR data.

 

And based on that info I certainly wouldn't want "the fix".  In fact, I find it "very cool" the program did this.  I reckon good to know the option exists to nix it out.

 

 

From everything I've seen, AS2012 usually does an outstanding job, but occasionally the interpolation functions can get confused and render something unexpected. Sometimes this results in pleasant surprises, other times makes you scratch your head.

 

RW Wx certainly like this too in the sense it can depart wildly from what was expected or forecast. :P

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OK, first sorry for the delay in replying, for some reason I didn't get my usual email notifictaion.

 

G Ozzie, I'm surprised that EGNR was reporting CB givien how close it is to EGGP but that seems a good explanation for TS south of EGGP. However I would have expected VCTS or VCCB instead of VCSH.

 

 

@Hook, I don't understand your "The problem is that the METAR specifies "CB"," in post #3, CB is not mentioned anywhere in the EGGP METAR I posted.

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I'm surprised that EGNR was reporting CB givien how close it is to EGGP but that seems a good explanation for TS south of EGGP. However I would have expected VCTS or VCCB instead of VCSH.

 

I agree with you on both points.

 

Must have been outside the "vicinity" of EGGP to report that way... but iirc it was getting on toward evening i.e. easier to see at EGGP.

 

-Rob

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OK, first sorry for the delay in replying, for some reason I didn't get my usual email notifictaion.

 

G Ozzie, I'm surprised that EGNR was reporting CB givien how close it is to EGGP but that seems a good explanation for TS south of EGGP. However I would have expected VCTS or VCCB instead of VCSH.

 

 

@Hook, I don't understand your "The problem is that the METAR specifies "CB"," in post #3, CB is not mentioned anywhere in the EGGP METAR I posted.

Hook was responding to post #2.

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