Use of RTOFS for Current.Gribs - Gulf of Maine

[rgleason]

In a last attempt to get a decent 1 hour interval (or 3 hr) grib file for the Gulf of Maine for this race, I am wondering if there is good way to convert hourly interval tide information from a PDF file into a useful current grib file, and adjust the time to High tide at St. John since the current charts are based on high water there.

The files that need to be converted are found onOpenCPN File Thingie rguser, rgpass under the directory "Gulf of Maine Currents"

I would be interested in any suggestions as to how best to do this. Thanks.

[did-g]

Originally Posted by rgleason

In a last attempt to get a decent 1 hour interval (or 3 hr) grib file for the Gulf of Maine for this race, I am wondering if there is good way to convert hourly interval tide information from a PDF file into a useful current grib file, and adjust the time to High tide at St. John since the current charts are based on high water there.

The files that need to be converted are found onOpenCPN File Thingie rguser, rgpass under the directory "Gulf of Maine Currents"

I would be interested in any suggestions as to hrtofs ow best to do this. Thanks.

In my understanding there's no tidal current in RTOFS so it's useless for you.

It's possible to convert text to grib with standard tools so once you get current vectors in text adjusting grib time to tide time and range shouldn't be too hard.

Getting speed vectors in text form from a picture? if it's a one-off doing it manually could be the easiest. On the other hand I thing you can buy RTOFS + tides current, likely expensive and quality unknown.

[rgleason]

did-g
Thank you for responding. I believe the RTOFS does try to model tidal surface currents.
See About the Atlantic RTOFS down towards the bottom, Atlantic RTOFS, Model Configuration, HYCOM
Surface Forcing -forcing fields from 3-hour NCEP (GDAS/GFS) model
Tides M2, S2, N2, K1, P1, O1, K2, Q1 tidal modes, Body and boundary tides

I believe the 3hour interval exists, but because of recent changes in NOAA due funding, OSCAR no longer works and has moved to NAS and the 1/3 degree model is here

I believe the surface current data with 3 hour intervals exists for the Gulf of Maine, but I don't know how to extract it from the very big files. If you look down below, I think you'll see what I mean.

I am somewhat handicapped in converting the PDF to a grib file because I don't know grib formatting and protocols, and my impression is that to do it by hand would be a big task. I guess it would require some graphic interpreter that could determine the direction of the and degrees in the shaft, and assign magnitude by using the shaft thickness index. This interpreter would have to then output a grib file. It is very unlikely this exists as it is too specific a problem.

I wonder if there is some way to estimate and manually assign current vectors on a larger scale in a grib file, that could at least be used by the weather_routing plugin.
I notice that the hourly currents in the first 2/3's of the race are actually very moderate and that whole area could be assigned (0.5-1.0) in a certain direction for each hour. It is the last third of the leg across that gets critical because the currents go up to 2.2 and if I could make a grib file of that area, assigning manually a somewhat smaller area, for each hour, it would be ideal. Then I would align the date and time with St. John's from July 8 about July 11

PS: Here is an interesting link about an experimental 1/12 degree RTOFS model for the Gulf Stream and Mid Atlantic that just misses the Gulf of Maine.

[rgleason]

This bottom link is for "Global RTOFS Model and its use for regional and near coastal modeling at NOAA/EMC". It states NAM is better in some cases than GFS.

OSCAR Data now here
https://podaac.jpl.nasa.gov/dataset/...4_OC_third-deg

[rgleason]

Here is the experimental 1/12 degree Hycom link.
HYCOM + NCODA Global 1/12° Analysis

[did-g]

Originally Posted by rgleason

did-g
Thank you for responding. I believe the RTOFS does try to model tidal surface currents.
See About the Atlantic RTOFS down towards the bottom, Atlantic RTOFS, Model Configuration, HYCOM
Surface Forcing -forcing fields from 3-hour NCEP (GDAS/GFS) model
Tides M2, S2, N2, K1, P1, O1, K2, Q1 tidal modes, Body and boundary tides

Yes maybe they have some but if you look at hourly RTOFS or Copernicus' GLOBAL_ANALYSIS_FORECAST_PHY_001_024 they don't have tidal streams you get in your pdf or in OCPN current .

A smaller file from Copernicus data
http://195.154.231.142/HD/maine.grb

Same extracted from RTOFS hourly rtofs_glo.t00z.f024_west_atl_std.grb2
http://195.154.231.142/HD/rtofs_maine.grb

Compare them to your pdf.

[rgleason]

Did-g
You are right! I've checked both an RTOFS (24hour is available not 12hr) downloaded from Saildocs, and the two Hourly Intervals you provided from Copernicus and RTOFS (Those are a good find!). To summarize, I found that the strengths and directions at the end of Nova Scotia are too weak and the directions do not correspond to the the scanned ATLAS OF CURRENTS for Bay of Fundy and Gulf of Maine, using this information for times

http://www.timetemperature.com/tznb/saint-john.shtml

St. John, New Brunswick, CA Atlantic Time Zone (UTC -4)
St. John, is now on Daylight Savings so that also subtracts 1 hour (UTC-3).
UTC - GMT Offset
Saint John, New Brunswick is GMT/UTC - 4h during Standard Time
Saint John, New Brunswick is GMT/UTC - 3h during Daylight Saving Time

Eastern Standard Time is UTC-5
Eastern Standard Daylight Time is UTC-4
So Eastern Standard Daylight Time is one hour greater than St.John

GRIB File is June 29 UTC 12:00
So we subtract 3 hours for St. John Daylight Time = 9:00 am
At St. John Low Tide is 10:54, 2.53ft
Need the table for 1 hour before low water at St. John.

Saint John Tide table:
Thursday 29 June
4:36 AM ADT 8.02 meters (26.31 ft) High Tide
5:39 AM ADT Sunrise
10:54 AM ADT 0.77 meters (2.53 ft) Low Tide

Did-g quote

A smaller file from Copernicus data
http://195.154.231.142/HD/maine.grb

Same extracted from RTOFS hourly rtofs_glo.t00z.f024_west_atl_std.grb2
http://195.154.231.142/HD/rtofs_maine.grb

Compare them to your pdf.

So it appears that even the 1 hour RTOFS and the 1 hour Copernicus on the half hour that you found, do not represent the actual tidal currents found in the Gulf of Maine as shown by the "Atlas of Tidal Currents".

The current velocities are not even close and directions are off particularly for the last 1/3 of the passage from Marblehead to Brazil Rock, Nova Scotia.

Thank you Did-g, you were right...

Now I wonder if I could take on of these 1 hour grib files from Did-g and edit it to correct the directions and velocities?

Is there a graphic tool somewhere that will let me do that?
I'd like to be able to select a square or polygonal area for a certain hour and then be able to change or edit all those gridded points to be a certain direction and velocity. With a tool like that I could fix on of the grib files for a full cycle of tides.

Then I'd like to find a grib tool that would change the entire grib to a different UTC time so I could get it to align with St. John New Brunswick High and Low Tide.

Perhaps someone can suggest such a tool?

[rgleason]

Here are some tools for creating and using Grib files https://disc.gsfc.nasa.gov/hydrology...software-tools

WGrib and GrADS are probably the more current software, but I am not sure either one would allow me to simply edit datapoints in a mass way. The tools appear to be more like extraction tools which provide good ways to analyze the data.

Still looking.

[did-g]

Originally Posted by rgleason

Here are some tools for creating and using Grib files https://disc.gsfc.nasa.gov/hydrology...software-tools

WGrib and GrADS are probably the more current software, but I am not sure either one would allow me to simply edit datapoints in a mass way. The tools appear to be more like extraction tools which provide good ways to analyze the data.

Still looking.

There's also pygrib.

When is your race?
Did you ask Atlas of current producer if they have data in tabular format? Or Maine university?

If you have current vectors in computer readable format, producing grib is not a big problem.

[.Paul.]

Rick and others,

Google found this site:

LuckGrib - Home

They seem to have a GRIB downloader for the MAC that is sold on ITunes.

They talk about access to

RTOFS Global HYCOM. Ocean Currents

which should be of interest for your race.

I am guessing that the LuckGrib people have figured out how to get regional (latitude and longitude) subsets from RTOFS Global.

Paul

[rgleason]

Dear Paul. Thankyou. There is not android app and I don't have Mac. Looks good perhaps a mac user can report.

[rgleason]

I have exported the Atlas of Currents, created jpg files, and rotated each one, and brought it into wxfax as an overlay. This is atenporary less than optimal solution.

[belizesailor]

Have you tried GRIB current data from MyOceans?

I use it for weather routing and can download it directly via SailGRIB WR (Android).

[rgleason]

I have WR SailGrib will check my oceans, but as did-g points out, and as I tested, the base noaa Hycom do not have tidal currents for Gulf of Maine.

[rgleason]

The tidal models are available (U of Maine etc) but have not been incorporated into Rtofs model yet.