When I have to get weather data via SSB/Pactor I don't like getting the typical GRIBs with "wind arrows" because the gridded wind data greatly inflates the file size. Instead I get two separate files:
(1) A GRIB file over a relatively large area with only surface pressure (plus rain if tropical convergence zones are a concern). With 24hr intervals and a 2° x 2° grid size a 10-day forecast over the entire SW-Pazific will still be under Sailmail's 10KB file size limit.
(2) A Spot Forecast that lists a set of forecast parameters for a specific lat/lon position in a tabular text format (under way I request a "moving forecast" for my average course and speed). A file with a few days worth of forecast data will be small (<2KB) even at 6 or 3 hour intervals.
(1) helps to see the big picture and in most cases the wind can be estimated accurately enough from the isobar contours anyway (of course with all the usual health warnings that this is raw computer model output). (2) I find helpful at a micro-level to pick out changes in e.g. wind direction along a timeline.
To make the spot forecast data easier to read, I use the spreadsheet attached at the bottom of this post which turns the terse tabular data into some simple time line charts:
Attachment:
Spot_Forecast.gnumeric - Gnumeric.png [ 178.07 KiB | Viewed 14125 times ]
Using the spreadsheet with spot forecasts is simple:
(1) Send an email with your data request email to
[email protected] with the follwing line in the message body:
Code:
send Spot:18.3S,168.5E|7,6|PRMSL,WIND,WAVES,RAIN,LFTX
Read: "send me surface pressure, wind speed and direction, wave height and direction, precipitation and Lifted Index for position 18°18'S 168°30'E over the coming 7 days in 6-hr intervals".
For a moving forecats you add boat speed in knots and COG in °T to the request:
Code:
send Spot:18.3S,168.5E|7,6|PRMSL,WIND,WAVES,RAIN,LFTX|5.5,215
What you get back in the reply email from saildocs looks like this:
Code:
Data extracted from file gfs130902-12z.grb dated 2013/09/02 17:03:36
Data extracted from file ww3-20130902-12z.grb dated 2013/09/02 16:48:48
request code: Spot:18.3S,168.5E|7,6|PRMSL,WIND,WAVES,RAIN,LFTX
Forecast for 18°18S 168°30E (see notes below)
Date Time PRESS WIND DIR WAVES DIR PER RAIN LFTX
utc hPa kts deg mtrs deg sec mm/h °C
----------- ------ ----- --- ----- --- ---- ---- ----
09-03 00:00 1014.0 8.0 167 1.1 139 7.5 0.0 4.9
09-03 06:00 1012.5 14.2 183 1.1 143 7.5 0.0 3.5
09-03 12:00 1014.4 12.4 160 1.3 145 7.8 0.0 3.4
09-03 18:00 1012.3 11.7 169 1.4 145 8.6 0.1 4.7
09-04 00:00 1014.4 9.6 176 1.4 144 9.3 0.0 5.5
09-04 06:00 1012.2 11.7 176 1.5 143 9.5 0.0 6.2
...
The above is for a stationary forecast. For a moving forecast you would see two additional columns with lat/lon for each data point.
(2) Copy all the lines with data from the response email (starting with "09-03 00:00 ..." and paste them into the "Import" tab of the attached spreadsheet. Pasting the lines will bring up Gnumeric's data import dialog:
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Text Import Configuration_008.png [ 53.28 KiB | Viewed 14125 times ]
(3) With all the newly pasted data selected press the "Sort ascending" button on the Gnumeric toolbar to get rid of the empty lines:
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Import_sort.png [ 62.62 KiB | Viewed 14125 times ]
(4) Copy the sorted data from the tab "Import" into the tab "Stationary" or "Moving" (starting in cell G4), depending on whether your request included course and speed. In cell E2 you can enter the offset of local time vis-à-vis UT in hours (a positive number means you're ahead of UT):
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That's it. The little charts should pick up the new data, providing a good "at a glance" view of what NOAA's GFS model thinks will happen where you are.
The manual copy and paste is not very elegant but it hasn't been enough of a pain for me to come up with a better solution.
Oh - and here's the file:
Attachment:
Spot_Forecast.gnumeric.txt [15.32 KiB]
Downloaded 488 times
Rename it after downloading to get rid of the ".txt" extension (the discussion board doesn't allow attachments that end in "gnumeric")