Weather Routing

Weather routing across oceans is often refered to as a Dark Art, full of mystery and intrigue. In reality it is simply number crunching, which is done by some very clever and powerful computer software. There are many different routing software packages out there. At Ocean Race Logistics, we use some of the best, tried and tested first hand. Which program we use depends on what the challenge or project is, from a rowing boat crossing the Atlantic, right up to high tech Grand Prix yachts racing around the world.

Grib file showing different routing options

The first, and most important, thing with any routing is to have an accurate Polar for the boat being routed. A polar is a numerical representation of a boats expected performance capability in any given conditions. Without accurate polars, weather routing is just simply weather forecasting – you cannot route effectively without polars. At Ocean Race Logistics we can work with teams and help them build their polars so that the routing we then offer actually means something.

Polar for a typical sailing yacht

The next most important thing after the polars, is the actual weather forecast used. At Ocean Race Logistics we have access to very high resolution models as well as the low resolution models readily accessible on the internet (such as Windy.com). The low res models are great for getting a large scale feel for what is happening, but the high res models give the real detail and can make the difference between winning or getting the record, or not. Typical low resolution files average the weather over a 100km x 100km grid and compute up to every 3 hours. The highest resolution files we use can show weather over a 1km x 1km grid and up to every 1 hour, which means there are up to 10,000 individual forecasts compared to just one low resolution one in a 100km x 100km area, giving unprecedented accuracy.

HOWEVER, weather forecasting is just that – a forecast. The skill comes in interpreting the weather locally and working with your weather router to get maximum effect out of the data.

We offer bespoke services depending on the project and the teams requirements. as an example, for a typical Atlantic crossing we offer the following:

Ocean Race Logistics work with you and your team to build and collate your polars, then we will route you with a daily email – This package is typically in the region of £3500

We use the following models when weather routing:

GFS: Stands for Global Forecast System from NCEP. This is used by most other weather websites/apps. We now use the GFS-FV3 model. It’s the first significant upgrade to GFS in about 40 years. Unlike the previous GFS model, GFS-FV3 is able to simulate vertical movements such as updrafts, a key component of severe weather, at very high resolution. So far, tests suggest that the FV3 model has more accurate five-day forecasts, as well as better predictions of hurricane tracks and intensification. Although the new FV3 core has shown improvements over GFS it remains ranked 3rd for accuracy behind ECMWF(1st) and UKMO(2nd).

ECMWF: Stands for European Center for Medium-Range Weather Forecasts and is highly regarded by Meteorologists and top Navigators around the world. The ECMWF High RES model consistently rates as the top global weather model from a national weather service with the highest rating scores. In March 2016 ECMWF increased the resolution of their model to a record-breaking 9 km resolution, which is currently the highest resolution global model available. ECMWF data has a very high acquisition cost, and this is why the data is not widely used by many weather websites, and has been traditionally used only by top yacht racing teams and meteorologists.

SPIRE: Is a truly innovative company with the largest nanosatellite network in space. Spire uses a unique technique of measuring the earth’s atmosphere with 3x more radio occultation data than any other commercial entity. This gives an advantage in forecast accuracy for remote locations. The Spire model is #1 for wind speed and direction accuracy using data from offshore weather buoys. It is #2 behind the ECMWF for land-based weather stations.

UKMO: Otherwise known as the “Unified Model” by the UK Meteorological Office has a long reputation as a market leader in forecast modelling. UKMO has very similar accuracy to the ECMWF model offshore, and is slightly behind the ECMWF & Spire models for the land based weather stations.

HRRR: Stands for High-Resolution Rapid Refresh and is an NOAA real-time 3-km resolution, hourly updated, cloud-resolving, convection-allowing atmospheric model, initialized by 3 km grids with 3 km radar assimilation. Radar data is assimilated in the HRRR every 15 min over a 1-h period adding further detail to that provided by the hourly data assimilation from the 13 km radar-enhanced Rapid Refresh.

NAM: Stands for North American Mesoscale Forecast System and is one of NOAA’s major weather models, which in this case covers most of North America. NAM is a mesoscale model, which means that the numerical analysis is able to model land, and other features, at a higher resolution than in a global model, leading to improved forecast accuracy.

AROME: Is a small scale numerical prediction model, operational at Meteo-France since December 2008. It was designed to improve short-range forecasts of severe events such as intense Mediterranean precipitations (Cévenole events), severe storms, fog, urban heat during heat waves. This model is highly regarded by top racing navigators and beats the ECMWF forecast.

PWG: Uses the NCEP global initial conditions, processed through the CSIRO CCAM model to generate the PWG forecast.

PWE: Uses the ECMWF global initial conditions, processed through the CSIRO CCAM model to generate the PWE forecast.