Spot Weather Forecasts (Aug 22, 2006)
Sailocs provides "spot forecasts" which are text forecasts for a single lat-lon point. This is the same data available in a "grib" file, but is a simpler presentation and an alternative to a grib-file over a very small area. The data is extracted from NOAA's "GFS" and "WWW3" global computer models and provides wind-speed, surface pressure and sea-state information for any point on the globe. (Note: this is the same as a "virtual buoy" forecast but that name can be confusing-- there is no buoy, just a computer forecast from a global weather model).
The default forecast is for 5 days at 6-hour intervals, and longer or shorter is available. As an example, to request a forecast for 25N 150W send an email to: query@saildocs.com with the following message-text:
send spot:25N,150W
Do not include any spaces between "spot:" and the lat-lon, spaces are used by Saildocs as separators. What you will get back is a forecast for wind speed and direction, height of significant swell, primary wave direction, and wave period (if available- seastate data is only available for offshore waters).
Latitude and longitude can also be specified as fractional degrees. Model data is available on a grid (0.5-degree for wind, 1 x 1.25 deg for waves), and is interpolated between points. For example to request a forecast for 25-30'N, 150-15'W send the following command:
send spot:25.5N,150.25W
The default forecast is for 5 days. Shorter or longer periods can be specified, out to the limit of the model at 16 days-- but the realistic limit is somewhere between 4 and 7 days and forecasts beyond this are increasingly speculative. The default interval is 6 hours, but can also be changed to 3 hours (for a longer forecast with more detail), or changed to 12 or 24 hours to create a shorter report with less detail. Saildocs can provide data to the nearest 3-hour interval. For example to request a forecast for four days at a 3-hour interval send the following command:
spot:25N,150W|4,3
The "|" character is the same vertical-bar character used with grib-requests, and is upper-case "\" (above the "Enter" key) on US-format keboards, or AltGr and "-" on most international keyboards. Alternately the "/" or "¦" characters can be used.
Subscriptions- Spot forecasts can also be a "subscription" which means that it will be sent each day shortly after 00:00 unless some other time is specified. (The model data is updated 4 times a day, just before 00:00z and every 6 hours).
For example, to subscribe to a spot forecast for 25N 150W, to be delivered each day shortly after 12:00 utc, send the following command:
sub spot:25N,150W time=12:00
More info about Saildocs and subscriptions is available by sending a (blank) email to: info@saildocs.com
NOTES:
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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 1.5x and possibly 2x higher-- so when you see "12 kts" read this as "12-18 kts possibly gusting to 24". 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 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.
North-American "COAMPS" Data:
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Spot-forecast wind data is normally extracted from NOAA's GFS global model. This is one of the best computer models available, but is limited for coastal waters where land effects can dominate. An alternative for coastal waters is the US Navy COAMPS model, which is a higher-resolution meso-scale model that can more accurately model land effects. Coverage is limited to North American and Carib waters generally between 160W in the Pacific to 060W in the Atlantic, and south to the equator (for specific areas send a blank email to:gribmodels@saildocs.com).
The COAMPS data only goes out 48 hours (72 for the west-Atlantic) at 6-hour increments, and is updated every 12 hours at 00z and 12z (available at 06z and 18z). Data includes wind and pressure only, no sea-state data. To request a COAMPS spot-forecast replace "Spot" with "Spot(coamps)". For example, to request a COAMPS forecast for 50N,128W, use the following format:
send spot(coamps):50N,128W
WARNINGS:
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Spot-forecasts are 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- carefully read the notes attached to the first spot-forecast reply that you receive. These are only sent once and repeated occasionally, but are available at any time by sending a (blank) email to: spotwarning@saildocs.com
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Saildocs is an automated service which is offered without charge on an as-is basis, without any warranty or assurances that it will work, be useful, or that the information delivered will be correct. Saildocs is a computer system which is subject to a variety of hardware problems and software errors, and also depends on internet communications with other computers with all the same limitations. Saildocs has no control over the content of the information from other sources, and in particular, weather forecasts may be missing, incorrect or out of date. You may only use the Saildocs service if you understand and accept these limitations.
Please send comments or questions to: support@saildocs.com
Good sailing,
Jim