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12/09/2017 2:07 pm  #1


NAM Grib from Squid not Consistent with NOAA Data

Looking at a section of Hi Res NAM data over Connecticut this morning, there is an obvious difference in the data obtained from Squid vs. NOAA.  Same hour of the same run from both.

While the wind velocity is consistent across the geography, the wind angle is clocked about 16 degrees in the Squid data vs. the NOAA data.  At least as displayed in Expedition.

Really now, what's 16 degrees between friends? Not much, unless they are sailing upwind against each other!

So somewhere in the labyrinth of software somewhere between France, the USA and New Zealand a bit has been flipped that needs to be unflipped.

Unless I've flipped out.

But study the attached picture and see what I mean. Look closely at any one place on both screens. It helps to look at the wind orientation next to a prominent letter such as the "B" in Boston.  You will see the difference in wind direction.

DM

 

12/10/2017 11:51 am  #2


Re: NAM Grib from Squid not Consistent with NOAA Data

The same problem as described above with NAM data from NOAA vs. from Squid, as viewed in Expedition, happens with HRRR data.  The wind directions on the Expedition chart are different between the two sources.

My guess is that old man Lambert, as in "Lambert conformal conic projection" is in the middle of this muddle.  He is either being invoked when he shouldn't, or vice-versa is my hunch.

But whatever the issue, it would sure be nice to get consistent results in Expedition no matter the source.  

I am reluctant to see if GFS data has the same problem.  And then it raises the question of the myriad other GRIB files and GRIB sources floating around out there -- will somebody please check them all? Shouldn't take more than a week or so of your time. When we are floating around on the ocean it's nice to know which way the wind might be blowing.

Thanks,

DM

DM

     Thread Starter
 

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