News

Long-range Weather Forecasting for the Caribbean

24 February 2009By Chris Tibbs

With so many yachts down island, let’s take a look at weather forecasting for the Caribbean.

Local forecasts are broadcast on the radio, available by fax and posted in marina offices, and they also can be found on a number of websites, including www.caribwx.com, a general site for the Caribbean, and www.srh.noaa.gov/sju/Forecast/index.php,
which covers Puerto Rico and the USVI.

But it's good practice to find out what's going on over a larger area and for a few days into the future. You need to know the bigger picture.

The first place to start is the U.S. National Oceanic and Atmospheric Administration (NOAA) and the National Weather Service (NWS) at www.weather.noaa.gov/fax/gulf.shtml for synoptic and forecast charts. This will indicate where the Azores (Bermuda) High is, along with any troughs, fronts or tropical waves. As well as synoptic charts, NWS also posts forecast charts for 24, 48 and 72 hours out, along with wind and wave charts.

So now you have a good idea what to expect from the weather, and on a fairly large scale. The high sea forecasts are also available on the same website, which helps to clarify the situation, particularly if you're a bit rusty at reading synoptic charts.

We're used to seeing satellite pictures and these are available from a host of servers, but will all be from the same U.S. satellites. The vast majority of pictures are from the geostationary satellite GOES East, which covers the Caribbean. The better-resolution polar orbiting satellites are not so readily available. Although, for a moderate cost, a receiver can be carried on board to download pictures directly from these satellites. This proves most useful for high-latitude and remote sailing, but an unnecessary luxury for most yachts cruising in the Caribbean.

The website www.goes.noaa.gov/ is the place to begin for satellite imagery, with links to pictures of the Caribbean and around the world. With practice, matching satellite pictures with synoptic charts can greatly increase your understanding of the weather and helps to build a 3-D picture. The satellite images also will help you to get an idea of squall frequency.

No look at Caribbean weather would be complete without a visit to the U.S. National Hurricane Center, www.nhc.noaa.gov/index.shtml. Even though we're out of the hurricane season, it's always worth a quick look to be sure you’re in the clear. Additionally, there is a link to the Tropical Weather Discussion and Outlook. Whilst this can be a bit heavy going, it contains a considerable amount of information and is useful for predicting the likelihood of squalls.

In addition to the sites listed, you can add a GRIB file for wind speed and direction. I use UGrib software; however, the majority of GRIB files available are all from the GFS model, so while there are a number of suppliers of the files, most provide the same information. GRIB files give an indication what the wind strengths will be away from land and away from any squalls.

One of the most asked questions on board is, “What is the weather going to do?” There's a lot of information on the web and now that most boats have access to it, it’s not difficult to get into a daily routine of keeping one step ahead of the weather both in the short term and over the length of the cruise.

Chris Tibbs is a meteorologist who previously worked as a skipper in the yachting industry. He is the author of the Onboard Weather Handbook (McGraw-Hill).