Fw: Spot:39N,5W
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Message ID: 81WRIHRKUD20
Date: 2020/04/05 13:58
From: query-reply@saildocs.com
To: EA7OP
Source: SMTP
Subject: Spot:39N,5W
Data extracted from file gfs200405-00z.grb dated 2020/04/05 05:07:18
Data extracted from file ww3euro-20200405-00z.grb dated 2020/04/05 05:46:00
request code: Spot:39N,5W|2,6|WIND,WAVES,PRMSL
Forecast for 39°00N 005°00W (see notes below)
Date Time WIND DIR WAVES DIR PER PRESS
utc kts deg mtrs deg sec hPa
----------- ----- --- ----- --- ---- ------
04-05 12:00 6.6 189 1016.2
04-05 18:00 6.7 204 1014.6
04-06 00:00 4.8 185 1018.5
04-06 06:00 2.6 173 1018.9
04-06 12:00 9.0 216 1020.4
04-06 18:00 2.3 263 1019.9
04-07 00:00 1.7 144 1023.3
04-07 06:00 1.9 109 1023.5
NOTES:
------
In the spot forecast the date/time is always UTC and wind speed is in knots at 10 meters of altitude (the usual nautical convention). This is an average wind speed and gusts will be 1.5 to 2x higher. Wind direction is the direction the wind is blowing from.
Wave information is from the WW3 model and is computed from GFS wind data. Wave estimates are NOT valid near shore. Wave height is in meters and is the "Significant Wave Height", which is the average of the largest 1/3 of all waves. The largest waves will be 1.5 to 2x larger than the significant wave height. Wave direction is "from", same as wind, and is the direction that most waves come from- not necessarily the largest waves. Wave period is the mean wave period in seconds, and of course smaller numbers mean steeper waves. Temperatures (if included) are in degrees Celsius.
For more info about spot-forecasts send a (blank) email to: spotforecasts@saildocs.com
WARNINGS:
---------
This spot-forecast is extracted from a computer forecast model. While such computer data can provide useful guidance for general wind flow, there are limitations which must be understood. What you are receiving is a weather prediction generated by a computer run by NOAA/NCEP (GFS, WW3 models) or the US Navy (comaps, nogaps) and downloaded and processed by Saildocs (a service of Sailmail). The network is complex, and any computer network is subject to hardware and software failures or human error which can effect accuracy or availability of data. In particular, if our servers were not able to download a current data file then the grib-file may be based on old data. The file information is shown above.
Also remember that grib data is not reviewed by forecasters before being made available. You are getting a small part of the raw model data that the forecasters themselves use when writing a forecast, and it is your responsibility to make sure that the data is consistent with your local conditions and with the professionally-generated forecasts (e.g. text bulletins and weather-fax charts).
Grib data also has limitations along shore, where local effects often dominate and may not be adequately modeled. In addition these models cannot provide adequate prediction for tropical systems, frontal activity or convergence zones. For example, while global models can provide useful data on the likely track of hurricanes, they grossly underestimate the strength of hurricanes because of their small size compared to the model grid. For hurricane/cyclone forecasts, carefully monitor the appropriate warning messages and do not rely on grib data from any source.
That all said, spot forecasts can provide useful guidance not available elsewhere. Understand the limitations and use the data carefully. These forecasts should be considered supplemental to professionally-generated charts or forecasts.
And please save a copy of these notes, they are long and won't be repeated for a month or so.
=====
Thanks for using Saildocs, an Internet document retrieval
service for the bandwidth-impaired. By using this service
you agree to the Saildocs terms and conditions (send a
blank email to: terms@saildocs.com for a copy).
Saildocs is a service of Sailmail, a membership-owned email
service built by cruising sailors for cruising sailors.
Sailmail provides world-wide email via marine-band radio,
internet and satellite including support for the Iridium GO!
For more information on SailMail see the web page at sailmail.com
or send a query to the office at sysop@sailmail.com.
More information on Saildocs is available by sending an email to
info@saildocs.com, this will return the how-to document (about 5K).
Message ID: 81WRIHRKUD20
Date: 2020/04/05 13:58
From: query-reply@saildocs.com
To: EA7OP
Source: SMTP
Subject: Spot:39N,5W
Data extracted from file gfs200405-00z.grb dated 2020/04/05 05:07:18
Data extracted from file ww3euro-20200405-00z.grb dated 2020/04/05 05:46:00
request code: Spot:39N,5W|2,6|WIND,WAVES,PRMSL
Forecast for 39°00N 005°00W (see notes below)
Date Time WIND DIR WAVES DIR PER PRESS
utc kts deg mtrs deg sec hPa
----------- ----- --- ----- --- ---- ------
04-05 12:00 6.6 189 1016.2
04-05 18:00 6.7 204 1014.6
04-06 00:00 4.8 185 1018.5
04-06 06:00 2.6 173 1018.9
04-06 12:00 9.0 216 1020.4
04-06 18:00 2.3 263 1019.9
04-07 00:00 1.7 144 1023.3
04-07 06:00 1.9 109 1023.5
NOTES:
------
In the spot forecast the date/time is always UTC and wind speed is in knots at 10 meters of altitude (the usual nautical convention). This is an average wind speed and gusts will be 1.5 to 2x higher. Wind direction is the direction the wind is blowing from.
Wave information is from the WW3 model and is computed from GFS wind data. Wave estimates are NOT valid near shore. Wave height is in meters and is the "Significant Wave Height", which is the average of the largest 1/3 of all waves. The largest waves will be 1.5 to 2x larger than the significant wave height. Wave direction is "from", same as wind, and is the direction that most waves come from- not necessarily the largest waves. Wave period is the mean wave period in seconds, and of course smaller numbers mean steeper waves. Temperatures (if included) are in degrees Celsius.
For more info about spot-forecasts send a (blank) email to: spotforecasts@saildocs.com
WARNINGS:
---------
This spot-forecast is extracted from a computer forecast model. While such computer data can provide useful guidance for general wind flow, there are limitations which must be understood. What you are receiving is a weather prediction generated by a computer run by NOAA/NCEP (GFS, WW3 models) or the US Navy (comaps, nogaps) and downloaded and processed by Saildocs (a service of Sailmail). The network is complex, and any computer network is subject to hardware and software failures or human error which can effect accuracy or availability of data. In particular, if our servers were not able to download a current data file then the grib-file may be based on old data. The file information is shown above.
Also remember that grib data is not reviewed by forecasters before being made available. You are getting a small part of the raw model data that the forecasters themselves use when writing a forecast, and it is your responsibility to make sure that the data is consistent with your local conditions and with the professionally-generated forecasts (e.g. text bulletins and weather-fax charts).
Grib data also has limitations along shore, where local effects often dominate and may not be adequately modeled. In addition these models cannot provide adequate prediction for tropical systems, frontal activity or convergence zones. For example, while global models can provide useful data on the likely track of hurricanes, they grossly underestimate the strength of hurricanes because of their small size compared to the model grid. For hurricane/cyclone forecasts, carefully monitor the appropriate warning messages and do not rely on grib data from any source.
That all said, spot forecasts can provide useful guidance not available elsewhere. Understand the limitations and use the data carefully. These forecasts should be considered supplemental to professionally-generated charts or forecasts.
And please save a copy of these notes, they are long and won't be repeated for a month or so.
=====
Thanks for using Saildocs, an Internet document retrieval
service for the bandwidth-impaired. By using this service
you agree to the Saildocs terms and conditions (send a
blank email to: terms@saildocs.com for a copy).
Saildocs is a service of Sailmail, a membership-owned email
service built by cruising sailors for cruising sailors.
Sailmail provides world-wide email via marine-band radio,
internet and satellite including support for the Iridium GO!
For more information on SailMail see the web page at sailmail.com
or send a query to the office at sysop@sailmail.com.
More information on Saildocs is available by sending an email to
info@saildocs.com, this will return the how-to document (about 5K).
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