Download Method
The "download method" in the Offshore App refers to the way you choose to download weather data. You can select from various methods such as "WEB," "Iridium GO!," "GO exec," or others depending on your connection type and preferences .
If you are using a Starlink , Marina Wifi or a 4G/5G connection, you should use the download method "Web" to ensure proper connectivity and data retrieval .
Choosing the correct download method is crucial otherwise you will be unable to download.
Use Offshore Optimised Settings.
The "Use Offshore Optimised Settings" in the Offshore App is a feature designed to help new users download all necessary data efficiently while managing data usage, especially when using satellite connections like Iridium GO! or GO exec. When enabled, it sets default GRIB preferences to 24-hourly intervals, 5-day forecasts, and 100km resolution, including wind, pressure, and rain data. It also selects specific forecast models such as PWG, PWE, ECMWF, GFS, SPIRE, and UKMO, and turns on GMDSS forecasts with graphic forecasts selected. This setup is particularly useful for managing data limits and ensuring you have the essential information for safe voyage planning.
GRIB Intervals
The "GRIB interval" in the Offshore App refers to the time step of the GRIB files you download. This setting determines how frequently the forecast data is updated within the downloaded file. You can choose intervals such as 3, 6, 12, or 24 hours. Selecting a longer interval, like 24 hours, will result in a smaller file size, which is beneficial for low bandwidth connections. The program interpolates data between these time steps, which means it estimates the values for times between the intervals you select. This feature is particularly useful for managing data usage when using satellite connections.
How many days should I download?
When using the Offshore App, the number of days you should download GRIB files for depends on your specific needs and the duration of your passage. The Offshore App allows you to download GRIB forecast maps for up to 7 to 10 days, depending on the models you choose .
For efficient data usage, especially when using satellite connections, it's recommended to download GRIBs with a 3 to 5-day forecast, as this is a common default setting that balances data size and forecast length .
PRO TIP: You should be downloading new weather data on passage every 12 hours when the models have updated. Always bring in the Wind and Pressure GRIBs, of at least 3 to 4 models, 3 days so you can visualise the general synoptic overview. The weather routing is independent of the GRIBs you download, if for example you don't download the UKMO GRIB, you are not missing out on this models information as it is shown in the weather routing results.
What resolution should I download?
When downloading GRIB files in the Offshore App, the resolution you choose should balance detail and file size, especially if you're using a satellite connection.
For satellite connections, a resolution of 100km is recommended to keep file sizes manageable. This is particularly important when downloading over a satellite connection, as higher resolution files can be too large.
If you are not constrained by bandwidth, you might opt for a higher resolution, but for most practical purposes, 100km is sufficient to provide a general synoptic view of the weather patterns.
Adjust the resolution based on your specific needs and the capabilities of your internet connection.
The highest resolution data is always used in the weather routing, if you click anywhere on any of the coloured model route lines, a pop up box will show with the highest resolution data available for that position on the route.
What models should I download?
When choosing models to download in the Offshore App, consider the following:
Available Models: The Offshore App supports multiple weather models, including ECMWF, SPIRE, UKMO, GFS, PWG, and PWE.
You can choose from various models, but selecting fewer models can help reduce the total file size.
Note that SPIRE and UKMO models are encrypted and can only be viewed within the Offshore App and are not compatible with other software.
What forecast options should I download?
You should always download Wind, and Pressure GRIBs at a bare minimum. In addition the other forecast variables such as Gust, Rain, Cloud, Air Temp, Wave, CAPE etc can also be selected to download.
When selecting forecast options in the Offshore App, consider the following:
File Size Management: To keep the file size manageable, it is recommended to select only essential data such as Wind and Pressure initially. You can add more options later if needed . A file size of 150kB for an Iridium GO!, 500kB for the GO exec are a general rule of thumb.
PRO TIP: Wind and Pressure are important , Pressure in the GRIB compare this to your onboard Barometer to help validate the forecast data.
Downloading the Rain, helps identify the potential timing of any frontal activity.
Downloading CAPE is very useful in determining whether or not there is any likelihood of getting any Thunderous activity, High energy the greater change of thunderous cloud activity which is not shown in the Wind GRIBs.
WEATHER ROUTING
When on passage always use Weather Routing and start time now.
Make sure you have moved the green start waypoint to your current GPS position.
PRO TIP: To easily find your current position, use the Snap to tool
On the Weather Routing Map page, open the way points icon, top right.
Click on the arrow with a circle around it beside the start way point, you should see the GPS co-ordinates change to your current position when you tap it. To double-check, move the start way point away from where it is, then click on the arrow again and see if the way point numbers change, and the start way point will snap to your position.
GMDSS
Downloading the GMDSS and understanding the text based output is important prior to departure, This is written by a meteorologist advising of adverse weather conditions. Downloading the GMDSS graphical display, this feature is invaluable for identifying potential weather hazards, particularly during long ocean crossings. The graphical display allows you to see the general synoptic view at a far greater range than a GRIB map.
OBSERVATIONS
When downloading data in the PredictWind Offshore App, it is generally recommended to focus on essential data to keep the file size manageable, especially when using satellite connections. Observations are usually a very large file and can be turned off to reduce the file size. Consider reducing the GRIB area and downloading as a secondary download.
PRO TIP: Observations can also be used to validate the forecast, expecting a SW change in 12 hours time?, has it already occurred on land.
OCEAN DATA
Any weather route or departure plan calculation with either the Standard or Professional Forecast Subscriptions will consider your choice of ocean current data, tidal currents, and wave polars when calculating a route. However, only the Professional will show you these details when viewing the results in the tables and along the routes.
Viewing ocean data GRIBs while offshore can be beneficial, but they are very large file sizes, so if you only have satellite data it is best to download ashore on high speed internet before you leave so it is stored in the Offshore App.
PRO TIP: Consider reducing the GRIB area and downloading ocean data as a secondary download, you only require data 2-3 days in front of the boat.
SATELLITE IMAGERY
Satellite imagery helps validate the positioning of weather fronts and thunderous activity.
TRACKING DATA
GPS tracking download it will upload any pending blog posts. The other main reason you should download GPS tracking data is it allows you to see what friends and family can see ashore on your tracking page, so you can see if your tracking page is updating correctly.
AIS DATA
Downloading AIS Data allows you to see AIS targets within a 300 nautical mile radius of your green start weather routing position. Providing heads up of fishing fleets, shipping lanes and container ships over the horizon.
YB EVENTS ( A Racing or Rally feature)
Downloading YB events allows you to track the entire race fleet or rally that you have set up on the forecast website or in the PredictWind App, providing comprehensive visibility of all participating boats.