This chart shows the track of Cirrus from Start (green ball) as a red line, whereby the big, round, red dots represent Cirrus' positions as reported during the roll calls. From the last known postion a red line with red diamonds begins which ends at the Finish (yellow ball). This diamond line is the projected best route for Cirrus given the weather situation and Cirrus' performance in dependance of wind speed and wind angle (also known as "her polars"). There may be additional diamond lines in other colors, which are the 2nd, 3rd,... best choices for sailing. There may also be square dots in red and other colors. For an explanation look at the historic data with interpretation examples.

The black lines, sometimes shaped like half-circles but mostly quite irregular, are the "isochrones". These are lines connecting all the locations which Cirrus could reach within 1, 2, 3,... days (the thin black lines are fractions of a day) beginning at the point where the routing starts. In the ideal case the best route crosses these isochrones where their separation is widest, i.e. the distance crossed is greatest. But not always! Cirrugator can figure out wether an early sacrifice will be rewarded later, and vice-versa.

The thin red arrows represent the true wind speed and true wind direction; the longer the arrow the higher the wind speed. This is the wind which Cirrus would experience if she were sailing the best route at the forecasted speed, as this wind is calculated from the true wind field determined from the grib files. It is called "moving grib" in Cirrugator parlance.

The bottom graph shows boatspeed, and true/apparent wind speed/direction along the projected best route. Look for situations where the apparent wind angle (blue round dots) reaches deep angles marked by the (light-)blue bands at the bottom and top ends of the graph. This is the famous DDW - Dead Down Wind - situation, which is not only difficult and dangerous to drive, but also NOT the fastest course. Cirrugator can be configured to avoid such bad courses for most of the times, avoiding the tendency for "sailing on the edge".

This graph shows wind arrows overlaid on a chart, whereby the arrow direction gives the wind direction and the length the wind speed. The information is transferred in computer files, called GRIB (Gridded Binary) files for the technology on how to condens information into these files. The data result from huge global weather calculation programs run by the US Weather Service, of which we take the portion relevant to us. The data are calculated at a specific time (GRIB Reference Date), and are valid for a specific time (GRIB Valid Date).

We obtain these files by sending an email request to a server (from Sailmail, or directly from NOAA), and the server responds by returning an email to us with the requested grib file attached. The file is then decoded by Cirrugator and used in the routing calculation. We use a forecast range of up to 10 days, i.e. we get one file with a single Valid Date chart for each of 10 consecutive days. Although, as is well known, the forecast quality of the later days leaves a bit to be desired, this is still the best information available.

Find more details on the Cirrugator Help site.

These are the 'Pacific Surface Analysis' and '48-hour Surface Forecast' weather faxes, which are sent out by the US National Weather Service with an update every 6h and 12h, resp.. They are key sources of weather information, complementing the grib files shown above.

They are indeed sent as a fax by shortwave radio, with the typical chirping noise of a fax machine coming from the loudspeaker. We record it via the sound-input of a computer. They are also available on the internet but due to the size of the files, and our VERY slow internet connection both via radio and satellite phone (remember the days of 1200 baud modems? We wish we were as fast as that!), we prefer the standard fax and use the internet for the grib files.

To download these files yourself find the correct NOAA's marine weather pages and look for the heading SURFACE CHARTS. There you have the analysis (you want Part 1) and forecasts. And a whole lot more under the other headings...

When you compare weather faxes and grib charts, pay attention to the dates: we may not always be able to print matching dates!

See how a particular boat performs over time and trades places with the other boats. This is most easily seen for the reference boat (thick red line with round red dots).