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20020124: 20011210: GEMPAK: mismatched BR and MIFG symbols?

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  • Subject: 20020124: 20011210: GEMPAK: mismatched BR and MIFG symbols?
  • Date: Fri, 25 Jan 2002 13:15:23 -0700
Christian,

The explanation I received:

>Some info...
>I have determined that 3-bar fog is for when the sky is obscured by the
>fog. It is from the time when people actually took the obs, not
>machines. 2-bar fog is for when the fog is all around horizontally, but
>not above the observer. It really has nothing to do with visibility.
>Also, from what I have found, there was no way to generate 3-bar fog in
>an SA report nor in a METAR report. The only way to get 3-bars in from
>the Synoptic coding where a distinction is made between 2-bar and 3-bar
>by WMO code number.


The 3 bar fog mentioned is what you refer to as WMO #45.

From the metar quick reference card, I find that BR has visibility
>= 5/8 SM, and FG is < 5/8 SM. But, the WMO table differences
you refer to are for differences in vertical, not horizontal.

I differ from NCEP's interpretation in that I read code table 4677
symbol 44 represents sky visible, and 45 represents sky obscured.
Since the observation included BKN001, I would assume #44 is
in order and not #45. This will take code development to
take into account sky coverage observations.

Steve Chiswell
Unidata User Support





>From: Christian Page <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200201250320.g0P3KPx15464

>
>Hi Steve,
>
>Any news from NCEP about the BR and FG problems?
>
>Thanks a lot for you support,
>
>Christian Page
>address@hidden    http://meteocentre.com/
>
>Agent de recherche et de planification +1 514 987 3000 ext. 2376
>Departement des Sciences de la Terre et de l'Atmosphere UQAM
>
>On Thu, 20 Dec 2001, Steve Chiswell wrote:
>
>>
>> Christian,
>>
>> The WMO table 4677 explanation of code "45" is fog with the sky coverage
>> obscurred. That seems to contradict the BKN001 observation below.
>> There isn't necessariliy a 1 to 1 correlation between METAR weather
>> observations and Synoptic codes. I have asked NCEP for their input on how to
>> deal with BR and FG and the associated plotting codes that are returned.
>>
>> Steve Chiswell
>> Unidata User Support
>>
>> On Tue, 11 Dec 2001, Christian Page wrote:
>>
>> >
>> > Hello again,
>> >
>> > There is still a problem. The FG symbol is plotted as the BR symbol.
>> > Example, today, 14Z:
>> >
>> > EBLG 111350Z 34002KT 0300 R23L/0350N FG BKN001 02/02 Q1036 NOSIG
>> >    EBLG    011211/1400     10.00
>> >
>> > So FG should have been plotted as 45 if I recall well, not 10. 10 is for B
> R, not
>> > FG.
>> >
>> > So:
>> >
>> > MIFG and BR are plotted correctly.
>> > FG is plotted as BR, which is wrong.
>> >
>> > Thanks again,
>> >
>> > Christian Page
>> > UQAM
>> >
>> > On Mon, 10 Dec 2001, Steve Chiswell wrote:
>> >
>> > >
>> > > Christian,
>> > >
>> > > It appears that there needs to be an update to the ptwnmt.f routine.
>> > >
>> > > Attatched is a copy that will change the encoding of MIFG to GF (12)
>> > > and BR to F (10).
>> > >
>> > >
>> > > Place the attatched ptwnmt.f file in $GEMPAK/source/gemlib/pt. Then
>> > > update the gemlib with:
>> > >
>> > > cd $GEMPAK/source/gemlib/pt
>> > > make clean
>> > > make all
>> > > make clean
>> > >
>> > > Then relink the dcmetr decoder so that it recognizes this change:
>> > >
>> > > cd $GEMPAK/source/programs/dc/dcmetr
>> > > make clean
>> > > make all
>> > > make install make clean
>> > >
>> > > Thanks,
>> > >
>> > > Steve Chiswell
>> > > Unidata User Support
>> > >
>> > >
>> > > On Mon, 10 Dec 2001, Unidata Support wrote:
>> > >
>> > > >
>> > > > ------- Forwarded Message
>> > > >
>> > > > >To: <address@hidden>
>> > > > >From: Christian Page <address@hidden>
>> > > > >Subject: GEMPAK: mismatched BR and MIFG symbols?
>> > > > >Organization: UCAR/Unidata
>> > > > >Keywords: 200112101021.fBAALHN03989
>> > > >
>> > > >
>> > > > Hi,
>> > > >
>> > > > I just noticed today that when using sfmap to plot METAR data, I get:
>> > > > MIFG -> symbol 10
>> > > > BR -> symbol 12
>> > > >
>> > > > Shouldn't it be the reverse?
>> > > >
>> > > > Christian Page
>> > > > UQAM
>> > > >
>> > > >
>> > > >
>> > > > ------- End of Forwarded Message
>> > > >
>> > >
>> >
>>
>>
>