Weather charts at different atmospheric levels.

[SYO2]

Hi,
zyGrib is giving us the chance to download from the WWW (ok ...it does not happen frequently to sailors...but who knows one day maybe...) some interesting information.
It is my opinion that sharing our experience on how we use it can only be fruitful to all of us.
This is why I open this post and I hope you will enjoy it.
In order not to fly too high to start with I suggest that we limit ourselves in a first stage to the 500 millibar chart interpretation.
My "open the door"in this matter is:
http://www.vos.noaa.gov/MWL/dec_08/milibar_chart.shtml
Let me have your comment about this paper.

[frank singleton]

My view as a sailor and as a one time professional meteorologist is that these upper air charts are interesting but not very useful. In the past, when I was a young forecaster, they were of fundamental importance in helping us to understand what was happening and to predict. Our problem was that we could only apply the ideas subjectively.

Numerical weather prediction does the sums for us. There is no way that we humans with our brain power can improve on the general patterns ie the movements of lows, highs, fronts etc. The best that we can do is to is to apply our local knowledge, experience and wit to interpret the computer modesl for short term, local effects.

Use the GRIBs for planning - up to 5 days ahead they are pretty good. Llisten to the VHF and use your NAVTEX to hear short term interpretations of the model output and then add your own local knowledge.

There is a fair amount on my site, http://weather.mailasail.com/Franks-Weather/Home, about forecasts, limitations on accuracy and so on.

[oystercatcher]

In another post I was wondering how to get a 500 hpa chart from zygrib
similar to what is available on the nws site.
http://www.nws.noaa.gov/om/marine/nepacificbrief.shtml

Please correct if my interpretation of your comments is wrong.
01. zygrib data comes directly from a mathematical model (GFS) and
the short term 2-3 days forecasts for sea level conditions are useful to sailors

02. the 500 hpa chart from noaa at the link above is from observations
and the mathematical model output from gfs is not reliable. It seems
that gfs does output 500 hpa data and zygrib can produce a chart from it.

Thanks for the explanation and I hope I have a better understanding of what
gfs grib data and zygrib have to offer.