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What is WindGURU?

WindGURU is a service specialized for forecasting weather, mostly for windsurfers and kitesurfers (but not only...). Forecasts are based on data produced by weather forecast models. Windguru is able to provide forecast for any place on planet Earth. The main reason to create this site was the idea to get the forecasts quickly and easily without wild clicking the mouse while searching for meteomaps throughout the internet.

Important: The forecasts you can see on this website are definitelly not official forecasts, Windguru was developed in order to help people in forecasting. What you see is only raw model data in human readable format, it's up to you how to interpret it. Please note that models are only models..., predicting weather is extremely difficult task and these models are very complicated, if the forecasts are not perfect, it's normal.

The forecasts are displayed in tables which show how the weather will develop on a certain location in the next few days. Sure that the wind speed and direction are the most important, but it also shows temperature, precipitation, cloud cover and waves (for ocean spots). Of course this is not the only thing you can see on this website, there are also wind archives, tide predictions, some forecast maps, "Top forecast" search, a simple forum for users... and I hope other new features will appear later. But, all in all, the basis of windguru will always be the forecast tables:

Forecast tables

Every forecast table shows a model initialization time (top left corner) which is in UTC (GMT), all the other times are in local time. The last row of the forecast shows coordinates, altitude and timezone of the spot - if the timezone is set correctly it should automatically adjust daylight savings time if it is active. Next to the little sun icon are the times of sunrise and sunset in local time (these are really sunrise and sunset, NOT dawn and twilight). Ocean spots also show sea surface temperature (more info below). A little legend for the forecasts:

Wind speed: wind speed in 10 meters above surface

Modified windspeed: The idea of "modified wind" is to estimate how good the wind will be at locations which are more senstitive to wind directions but the model does not realize it. Because of the landscape around your spot the wind may be better when it blows from one direction but worse when it blows from the other. You can find more info about wind modifications in a special help section

Wind direction: most will understand this :) but after all I still sometimes get questions about it, so to be clear to everyone: Nthis is NORTH wind, it is the wind which blows FROM north. Other example: south-west wind:SW

Temperature: temperature in 2 meters above ground

*Temperature: temperature in 2 meters above ground with correction to real altitude of the spot. The temperature is a parameter which varies by altitutude. The model only has a limited resolution so it only calculates with a smoothed terrain. In more variable terrain the difference between model and real height of the spot can be significant. Because we can determine the difference between altitudes we can adjust the temperature forecast to fit the real height of the spot by interpolating forecast data from different levels. By default we show this adjusted forecast instead of original model temperature where available, registered users can turn this off in user settings or choose to show both model and adjusted temperatures. (available at GFS, NAM, HRW)

The temperature adjustements can only work right if we know the real altitude of the spot. Windguru uses GTOPO30 and SRTM data sets as source of altitude data. GTOPO30 is a global digital elevation model with 30 arc seconds = approximately 1 kilometer resolution by USGS (U.S. Geological Survey). SRTM (Shuttle Radar Topography Mission) consisted of a specially modified radar system that flew onboard the Space Shuttle Endeavour during an 11-day mission in February of 2000, it generated the most complete high-resolution digital topographic database of Earth in most land areas. Both these databases provide pretty accurate altitudes for specified coordinates but users can also enter altitudes of their custom spots manually.

Wind chill: is the apparent temperature felt on exposed skin due to wind. The degree of this phenomenon depends on both air temperature and wind speed. The wind chill temperature (often popularly called the wind chill factor) is always lower than the air temperature for values where the wind chill formula is valid. Wind chill is only defined for temperatures at or below 10 °C (50 °F) and wind speeds above 3 knots. (optional, hidden by default, registered users can enable this parameter)

0° isotherm: altitude in meters in which the temperature is at 0 degrees Celsius (freezing level). By default we show this only if the model predicts temperatures below 5 °C. Registered users can change this in settings. (available at GFS, NAM)

Relative humidity: relative humidity in percent. Hidden by default but registered users can choose to show this parameter.

Pressure: mean sea level presure (pressure reduced to sea level) in hPa. Hidden by default but registered users can choose to show this parameter. (Values above 1000 hpa are printed as x-1000 to save space in the table).

Cloud cover: high / middle / low cloud cover in percent (available at GFS, NAM, WRF). Optionaly, registered users can choose to only view total cloud cover as one value (low, middle and high clouds all together). HRW model only offers total cloud cover.

Precipitation: Precipitation in milimeters. Models that offer forecasts for every 3 hours show accumulated precipitation for last 3 hours, models that have hourly forecasts show precipitation for last hour. For better comparison the background color indicating intensity will be same for both 1 or 3-hourly models. Some of the models can also indicate snowfall - with bold blue numbers.. (available at GFS, WRF 9 km (Europe), WRF 3 km (CZ)). Snow/rain type of precipitation is estimated according to altitude of the spot and forecasted freezing level height. 1 mm of rain could transform into approx. 1 cm of snow so when you see blue numbers you can consider these values as centimeters of snow per hour (or 3 hours) instead of milimeters of rain.

Windguru rating: How good the windsurfing conditions will be? I suppose all you are interested in is the windspeed :) only low temperature can be a limit sometimes... exact numbers of stars depend on your user settings but default should mean something like this:

= It should be OK, but big sails only (7.x meter sails)
= Very good wind. Don't leave your 5.x meter sails at home!
= Superb! It's a crime to ignore such a day!
123 Blue stars instead of yellow appear when cold weather is expected (default is 10 deg C or lower temperature, but you can adjust this in user settings)

Yes, others than windsurfers have different preferences, for example for paraglider 30 knots is not the best day... I hope to prepare some other ratings for other users too.

For most ocean locations also wave forecast is available. This is based on NWW3 model (NOAA wave watch III)

Wave: Significant wave height in meters. It is the average height (from wave crest to trough) of the one-third highest waves at a location.

Wave period: Peak wave period in seconds. It is the period of the dominant wave system derived from the wave energy spectrum. This can either be the locally generated "wind sea" (in cases with strong local winds) or swell that is generated elsewhere.

Wave direction: Direction of the dominant waves.

Please note that the wave data are general for "around that area", on the open sea... not for your local reef inside your small bay (forecasts are based on coarse NWW3 data). You have to think about what waves come to your beach based on what waves are forecasted.

Sea surface temperatures come from NOAA Real-Time Global Sea Surface Temperature analysis (RTG_SST_HR dataset), the source is satellite data and also buoy and ship observations. The resolution of the SST dataset is 0.083 degree (approx. 8 km) so remember that local differences are always possible. Temperatures are only valid for oceans and large lakes. Data update once per day. More information at NOAA website.

Colors used in forecasts:


Graphical version of the forecast.

Now you can also see the forecasts as graphs, simply click the graph icon on the second tab of any forecast table.

WG forecast graph

Since the beginning of this site, the core of Windguru was the forecast displayed as colorful table with a lot of numbers. I think it will stay like this in future too because despite one can consider it a bit oldschool, the table shows a lot of info with high detail on a small space and still looks clear and uncluttered. But why not to offer alternative display option? Forecast graph offers another view, more eye candy :-) and some people will prefer it.

If you like to have the graphical view as your default, you can set it using the "options tab" on the main page.

Important notice: Your browser must support SVG graphics in order to display the graphical forecast. All good browsers (Chrome, Firefox, Opera, Safari, IE 9) are OK, but if you have Internet Explorer 8 or older it will not work, please switch to better browser if this is your case.

The positive thing is that all the graphs are not plain images that require additional data download, instead they are drawn by your browser, so it is also bandwith friendly for those with slower connections.

Graph example

What you see below is the first version of the graphical forecast (probably not final, we expect to fine-tune it over time).

There are two main sections of the graph, the upper part is dedicated to the most important = wind, it scales depending on how much wind is predicted, if strong wind is forecasted it is bigger, if there is not much wind it becomes smaller.

The bottom part shows the "less important" parameters like temperature, clouds, precipitation, pressure and humidity - all drawn into one section to save space. The cloud cover display is a little special so it needs a little more explanation: low clouds are the dark grey area that is drawn from bottom of the graph, high clouds are light grey drawn from the top of this graph section and middle clouds (medium grey) are drawn from the center both up and downwards. If any of these fill all the area then it means 100% cloud cover for given cloud layer. Because all the cloud layers are semi-transparent if there is a lot of clouds in all layers the whole cloud graph turns almost black indicating a lot of clouds, the darker it is the more clouds are forecasted and you can still see how much each layer participate.

Right now the units for wind speed and temperature are taken from the classic table forecast, if you want to switch them temporarily, go back to the normal forecast, change units to what you prefer and then open the graph tab again, it will redraw with selected units.

WG forecast graph example

Future plans are to use the graphical display for visualizing temperature profile and wind in higher levels. We also plan to allow users to customize graph appearance because not only wind addicted people watch Windguru and they probably have other preferences.

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