Language:

Here I collected some information on weather models for the benefit of fellow sailors. I hope it may be of some interest to all lovers of the sea. The list is certainly not exhaustive and I am happy for all suggestions and ideas (Paolo) about expanding and improving this review of weather models.

Weather and navigation

It is wise and desirable to plan any navigation in function of the weather conditions that we expect to meet and to do so even before casting off.

Cruises are always prepared before the actual navigation and the success of each voyage and every holiday are dependent on the care dedicated to study weather and sea conditions that will be expected to meet. The choice of anchorages, landing ports, and destinations of every navigation all depend on weather conditions. We look for favorable winds for a comfortable, easy and fast navigation in order to throw anchor in a protected anchorage to be safe through the night without having to worry about the safety of our mooring. Weather, wind and sea are the decisive factors for the success of any navigation. Looking at the weather and understanding changes in the future is essential for all sailors who want safely navigate, by sail or motor.

In planning a cruise we car relay on a countless number of weather forecasts to which we easily have access when we are still on the ground. Among the information available there are valuable weather models, now accessible with a computer, a tablet or with a phone.

Weather models

Fortunately for sailors and navigators weather models used to produce weather forecasts are becoming more accurate and reliable over time. Many of them are now accessible to the general public free of charge. With the improvement of technology and the ease of internet access even when sailing, it is possible for the average sailor to gather a number of weather resources and weather information as it was unthinkable only a decade ago.

Numerical weather predictions

In the dissemination and transmission of data and weather information one of the most established standard is the GRIB (gridded binary) format that allows an Internet transmission of compressed file whose contents can be easily viewed on a computer, a tablet or a mobile phone.

GRIB files can contain a variety of meteorological parameters: pressure, wind, precipitation, waves and many more. These data are produced automatically from the different computers that process the various weather models. These files contains weather information that was not reviewed and vetted by professional meteorologists and hence they have to be used as a complement to the weather forecasts that are made available to mariners by the various institutions dealing with marine forecast for navigation.

Information about GRIB files

Here are some examples of what we can achieve thanks to today’s technologies:

High resolution WAM model for the Aegean (wind and pressure) in GRIB format

High resolution WAM model for the Aegean (temperature) in GRIB format

Many of the analyzes produced by the various weather models are now distributed in GRIB format and data access services range from free to paid service, with local or global coverage, high, medium and low resolution.

The software that display information in GRIB format offer the possibility to download data in a convenient way. Unfortunately, the data offered often refer to a limited number of models, often the only GFS. It is important to know that we can retrieve the information we care, often at no cost. In the following review of weather models links and references to every model will be provided. Who is willing to contribute with additional information is welcomed.

There are many weather models available, and none is more valuable than the others. They serve different purposes and each model evaluates differently a lot of different factors. low-resolution models are used to assess major variables involved on a large scale, but are ineffective for determining weather forecasts in coastal areas, or where the influence of geography and morphology of the land induces significant changes in the weather dynamics. Other models have a high resolution to capture the best local phenomena, but they have limited validity in the future. A comparison of different models is of great help and can be comforting when all of them converge to the same conclusions. Instead we should be very wary of the weather when models are providing conflicting data between them.

At this point, before describing the different weather models, I think it is important the reference to a parameter often provided by many of them: it is the Convective Available Potential Energy (CAPE), which measures the potential energy in the air. The values ​​of CAPE, in Joules per kilogram allow us to get an idea of ​​the potential for development of storm cells of a specific area. I mention if here because of its importance in navigation.

The following CAPE values provide an indication of the level of instability in an air mass:

0001-1000 J / kg: Marginally Unstable

1000-2500 J / kg Moderately Unstable

2500-3500 J / kg: Very Unstable

3500 J / kg and higher: Extremely Unstable

Below weather models relevant and of interest for sailors are summarized, in alphabetical order. Some of these are also available in GRIB format and can then be downloaded with an internet or wireless connection.

Aire Limitée Adaptation dynamique Développement InterNational (ALADIN)

Consortium sponsored by Météo-France with several countries of Central and Eastern Europe. The consortium managing ALADIN initiated in 2005 a partnership with the consortium in charge of HIRLAM (High Resolution Limited Area Model), another high-resolution model (up to 2 km) used in Europe. The goal of the two consortia is to arrive at an integrated management of the two models.

Wind and pressure, ALADIN – Croazia

Link to the ALADIN consortium website

AROME

Model managed by Meteo France to improve short term forecasts of high intensity weather events in the Mediterranean region. Five-day forecast.

Wind, AROME – France

Link to AROME

ARPEGE

Global weather model managed by Météo-France

Wind, ARPEGE – Europe

Link to ARPEGE

Advanced Scatterometer data (ASCAT)

ASCAT does not refer to a weather model but is a satellite system for real-time analysis of the wind on seas of the globe. Instead of the classic wind forecasts, ASCAT provides us with the wind real values, as read by satellite, for all the world’s seas. The data is collected every hour and have global coverage. This information is also available in GRIB format.

Wind, from ASCAT, 25Km resolution

Link to ASCAT

Atlantic operational Real Timer Ocean Forecasting System (RTOFS)

Forecasting model of Atlantic ocean currents maintained by the US National Weather Service.

Current, Atlantic Ocean

Data from RTOFS model

Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS)

Regional weather model managed by the American Navy. It covers certain regions bordering the United States. Forecasts up to two days. Resolution at 12 Km.

Wind and pressure, COAMPS – California

Information about COAMPS

 European Center for Madium-Range Weather Forecasts (ECMWF)

European global weather model. According to many more accurate than the American GFS model. Unfortunately, the data in GRIB format are not accessible to all, being a paid service. Many providers of paid weather information service base their analysis on this model.

Pressure, ECMWF – Europe

Information about ECMWF 

GDPS-GEM (Global Environmental Multiscale model)

Managed by the Canadian Meteorological Service. Medium and long-term weather forecasts.

Pressure, GEM – United States

Information about GDPS-GEM

GRIB data for GDPS-GEM 

Global Forecast System (GFS)

This is the most known global weather model in use. Updated every six hours by the American meteorological service, with forecasts of up to sixteen days. However, after 4-5 days any model lose confidence and should be used as a general indication fo the future weather. GFS data are available in GRIB format.

Hugh altitude analis

High altitude analysis (500 hPa) GFS – Europe

Information about GFS

GRIB data from the GFS weather model

Navy Global Environmental Model (NAVGEM)

Global weather model run by the US Navy. Equivalent to the GFS, useful to compare the validity of the models.

Pressure, NAVGEM – Europe

Information and data about NAVGEM

North American Mesoscale Model (NAM)

Regional weather model of the state of the atmosphere, produced by the American Weather Service. It takes into account the small-scale weather phenomena and therefore much more effective than other global models as the GFS. High resolution data but valid for a short period of time: 2/3 days.

Wind, NAM – Nord America

Information about NAM

GRIB NAM weather data

Ocean Surface Current Analysis – Realtime (OSCAR)

Analysis of the global sea currents. The data is calculated through satellite measurements, and model forecasts cover five days. Data available in GRIB format.

GRIB data from OSCAR model with representation of the Gulf Stream

Skiron

High-resolution weather model (grid 5 Km) by the University of Athens. The data in GRIB format are available for the Mediterranean, with forecasts up to five days.

Wind, SKIRON – Balearic

GRIB weather data from SKIRON

Weather Research and Forecasting (WRF)

This weather model covers different areas of the globe and offers high-resolution forecasts that take into account local conditions. The model is used by various institutions and organizations to perform predictive analysis covering certain areas. Useful and reliable in the short-term weather forecasts that take into account the geography and the local topography.

Wind and pressure, WRF – Italy

Information about WRF

GRIB weather data of Mediterranean sea from WRF 

Wave Watch 3 (WW3)

Wave model managed by the American meteorological department. Updated four times a day, with forecast data up to 180 hours.

Wave heights, WW3 – Atlantic Ocean

WW3 model data at the link

Where to get weather information in GRIB format?

The data of many of these models are available in GRIB format free of charge. Here are summarized the main sources that can be accessed.

ling to: GDPS-GEM

link to: GFS

link to: Gribfiles (paid service)

link to: Mailasail

Mailasail offers an interesting service for free access to a variety of weather information. The instructions to access their free services are located at this link

link to: Meteoconsult

link to : NAM dal sito NOAA

link to: Openskiron

Openskiron covers the entire Mediterranean with useful high-resolution data. GRIB files can be downloaded from the site.

link to: Saildocs

Saildocs provides a service similar to mailasail and allows to access multiple weather information from their archives by sending an email.

For general information on the Saildocs service send a blank email to: info

For information on GRIB files available at Saildocs send a blank email to: grib

Information on available weather models at Saildocs can be received by sending a blank email to: models

link to: Norway Meteorogical Service