query on 500 hpa chart

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oystercatcher
Posts: 6
Joined: 19 Dec 2010 16:57

query on 500 hpa chart

Post by oystercatcher » 14 Feb 2011 16:57

my location is us pacific coast, I post screenshot of the zgrib data matrix being download.

after I select 500 hpa altitude I see that I have to remove check for isobars (MSL)
otherwise I see two sets of pressure labels. I am mostly interested in the 500 hpa
and surface winds but not very knowledgeable about weather science but trying
to learn for sailing.
It seems there is no manual for zygrib at this time, is that correct?
zygrib 3.9.7 from source on fedora fc14
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SYO2
Posts: 45
Joined: 12 Dec 2010 10:57

Re: query on 500 hpa chart

Post by SYO2 » 04 Mar 2011 20:27

Hi,
have a look at one of my post
viewtopic.php?f=4&t=272
Hope it helps ...but nobody seem very interested.
Anyway please feel free....
73·s
ON3CHD
Nautiquement vôtre.

oystercatcher
Posts: 6
Joined: 19 Dec 2010 16:57

Re: query on 500 hpa chart

Post by oystercatcher » 10 Mar 2011 17:06

The link to the mariners weather log is appreciated. I saved the article on
the 500 hpa charts for study.

Using zgrib I have a bit of difficultly as compared to the charts noaa make
available for weatherfax.
I probably need to spread out the isobars and it can be difficult to determine
what label say 5640 hpa is associated with a particular isobar line. The 5640
line is dark and bold on the weatherfax versions.
If anyone using zgrib could help out with a tutorial for the 500 hpa data
I would be grateful. I am just a sailor not a meteorologist but zygrib is
great software.

Thanks

SYO2
Posts: 45
Joined: 12 Dec 2010 10:57

Re: query on 500 hpa chart

Post by SYO2 » 10 Mar 2011 19:45

Hi,
Will try.
-open zygib
-select wished area
-then go to FILE - DOWNLOAD GRIB - TICK HP 500 and only this one
-click on download Grib File
once downloaded zygrib should open automatically the file requested by you
then go to ALTITUDE
Tick GEOPENTIAL ALTITUDE 500 HPA and GEOPOTENTIALS LABELS
then go to the SPACING (m) and tick 20
You probably will be 50 % happy.
Now if you wish to be 100 % happy (Thick line for 5640 and 1020 ) use the free e-mail retrieval service named Saildocs and the free reader named Viewfax.
Less info of course but ...what you need if you don·t want to enter into the details of differences of temperature, humidity and so on...
Cheers.
73·s
ON3CHD
Nautiquement vôtre.

oystercatcher
Posts: 6
Joined: 19 Dec 2010 16:57

Re: query on 500 hpa chart

Post by oystercatcher » 14 Mar 2011 19:48

thanks for the suggestion to change spacing. it makes the chart much cleaner.

this is what I have been using from noaa
http://www.nws.noaa.gov/om/marine/nepacificbrief.shtml

01. is it possible to get the wind arrows for the 500 hpa?

02. For surface analysis - how to get the isobars to show?

03. Sometimes wind arrows are white sometimes black - not sure how
to control color of wind arrows and not changing anything. appears to
be random?

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