An Essential Page for Sailors

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Background information about weather information on the Internet


Related pages -

On this page

Warning

Links to meteorological information on the Internet are not guaranteed and therefore must not be relied upon. Although increasingly reliable, the Internet is not part of an operational service, pages can and do change at no notice - even on National Weather Service sites. In an operational sense, it is supplementary rather than complementary to the Global Maritime Distress and Safety System.

All links on this site are there on a best endeavours basis. They were checked to be correct when provided. I cannot guarantee that they will remain so.

IN PARTICULAR and as a matter of good seamanship sailors should have the correct equipment (Marine VHF/ Radio, LW Radio Receiver, Marine MF/HF SSB receivers or transceivers, NAVTEX and Inmarsat-C/SafetyNETTM) appropriate to their sailing waters and needs to ensure that they are able to receive warnings and forecasts provided as part of the GMDSS.

World Weather Centres

The two main world centres are the UK Met Office and the US National Weather Service, Washington, which provide, by mutual backup, worldwide services to aviation. Their Numerical Weather Prediction models (NWP) probably the most advanced in operational use. That is why many sites lead inevitably to products originating from the UK Met Office or the US NWS.

There are, of course, many other Met Services, see the pages on ECMWF and other Weather Centres and the links to International and National services.

Many of these organisations run NWP models and, for various reasons, output will differ from one to another. Comparison between models is a one way of gaining impressions about the value of a forecast on a particular occasion. Elsewhere in these pages, I advocate comparing successive forecasts from a known, reliable source as a better approach.

More localised Inshore waters forecasts are usually produced by relevant countries and broadcast on marine VHF, sometimes by NAVTEX and on the Internet. National Weather Services producing these forecasts have access to the various NWP models so that these forecasts should be well founded.

The UK Met Office

The Met Office Home page, leads to informative links to

  • Marine and other forecasts,
  • Hourly observations.
  • Some basic synoptic meteorology,
  • Cloud identification and how they are formed.
  • Terms used in forecasts.
  • Research programmes
  • Weather prediction models,
  • Climate change research,
  • Observational techniques.
  • Data archives

With a little delving you can find much of relevance to Yachtmaster, Coastal Skipper or Competent Crew courses.

Some links to Met Office information pages and forecasts are as below.

Weather Charts

Charts come in three forms.

  • First, and most familiar to many, are charts that have some human input in the drawing of the isobars and fronts so that there is experience added to the computer output.
  • Secondly, there are charts which are unadjusted computer output of the predicted pressure fields, but with fronts added by a forecaster.
  • Finally, there are charts which are pure computer output of mean sea level pressure, and various upper air fields, these being un-amended by a human forecaster.

Met Office Charts

The UK Met Office Analyses (ASXX) and 24-hour prognoses (FSXX) for 00, 06, 12 and 18 UTC are issued every six hours. These are available on some four to five hours after data time.

Forecasts for 36 hours to 72 hours are produced every 12 hours and are available some 6 or 7 hours after the data time.

Forecasts for 96 and 120 hours are issued once a day at about 2300 UTC.

All forecast charts are based on Numerical Weather Prediction (NWP) output but amended by forecasters in the light of their knowledge and experience. The 4 and 5-day forecasts are produced using output from other Met Services output, including that from the ECMWF. The end product issued is a “preferred” solution for the fourth and fifth day and may differ considerably from the raw computer output from the UK computer model.

On-line sources

There are several sources for these charts including on this site. . See my page of charts on the Internet. This page also includes links to charts from other centres.

The same page has links to the raw (ie unmodified) computer forecasts from the UK Global Model.

Forecasts beyond 6 days

The ECMWF and the NOAA GFS (Glal Forecast System)0 GRIB both provide forecasts to 10 days at least. At present, these are probably only useful to sailors up to 8 days ahead, at best.

Forecasts in Text

GMDSS

Weather forecasts in text for the open sea are provided under the SOLAS Convention, by nominated countries worldwide. These can be obtained by VHF, MF and HF Radio, NAVTEX, Inmarsat-C and, nowadays, via the Internet.

My GMDSS Texts pages =========================== gives texts from National Met Services. I always advise using texts that I know come from national weather services written for the GMDSS. There are automatically generated forecasts, some from official sources and others from private firms. Generally they will not be grossly misleading but they should not be relied upon for warning purposes. Strong wind strengths are likely to be under-predicted and poor visibility over-predicted. '''

Sailing Forecasts around NW Europe

1. The UK Met Office forecasts provides the definitive marine forecasts for waters around the UK. Other countries' services such as Météo France do likewise for their waters. Go to the GMDSS pages =================================== where there are also links to most marine text forecasts around Europe.

Because many British (and other nationalities) sail in the Baltic and the Mediterranean, this site has pages listing all forecast sources that I believe are useful for the Baltic and the Mediterranean.

Private Met Services

There are a number of sites run by private weather companies where forecasts are available. Sometimes these are free and sometimes they are on repayment. I have always hesitated to give links to such services because I do not know to what extent these forecasts are based on the National Met Service output. Neither do I know the levels of experience and training of the staff. The presentation of forecasts by the private companies are often very good.

Wherever they come from all forecasts from private companies should be used with the same care as those from the National Met Services.


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