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Sunday, October 28, 2012

Weatherwise, BVS!


Weather is serious stuff. If there is one thing outside of the boat that could make or break this voyage, it is the weather. You need to read it, interpret it, predict it and play it. One wrong decision could end up with you losing your mast or sanity.

One of the followers of the voyage asked about weather and weather prediction. I have been using BVS (Bon Voyage) for the last three years and I am more than impressed by their weather prediction abilities. They are so accurate in short term that I can set my watch to their predictions.

I asked Jerry Hale to tell my readers more about their software and weather prediction systems. He quickly sent a write up that has made even me sit up and take notice of how they go about their business of weather predicting. Read on!! (for the impatient, there is a video that should explain everything)

AWT appreciates the opportunity to provide some information to those following Abhilash Tomy on this circumnavigation of the world.

AWT is the leading provider of award-winning weather routing products and services. These include: BVS, the industry’s leading onboard voyage management software; GlobalView™ and Fleet Decision Support System, graphical, information rich shore-based fleet management service; as well as a variety of shore-based routing services.

AWT’s BonVoyage System (BVS) is an icon-driven graphical marine voyage optimization system that provides on-board and around-the-clock weather routing information. It has a sophisticated yet user-friendly interface, and is both comprehensive and cost-effective, making it an indispensable tool. Because of BVS’s ease of use, captains are more likely to take advantage of its capabilities. To view a video interview of captains about BVS, click here.

To minimize communication costs, BVS provides the vessel with the most current data by email in a highly-compressed format. BVS generates color-enhanced maps and graphics that allow the captain to easily view and interpret this data.

BVS has state-of-the-art features that place it far above other products. First, AWT enhances weather model wind, current, and weather data to provide highly accurate forecasts. With this data, BVS creates detailed forecasts that enable both tactical and strategic voyage planning. In addition, BVS provides an interactive tool that enables captains to avoid dangerous conditions and determine the best course of action to keep vessels safe. Through its advanced technology, BVS can also optimize voyage routes for time or fuel savings.

Effective weather routing depends on the quality of the data used to determine and predict weather conditions. Weather model data provided by government sources such as NCEP provide a good basis, but it falls short in terms of accuracy of results for tropical storms and the limitation of three-day forecasts.

To address these shortcomings, AWT transforms data with sophisticated, state-of-the-art wave modeling that produces more accurate results and 16-day weather forecasts that show storm trends and weather patterns. AWT modifies the raw model pressure and wind output in a number of locations to achieve the best results. For example, around tropical cyclones we make edits to the isobars around a tropical cyclone to better represent the actual wind speed. This wind data is used to initialize the wave model giving our clients the best possible data around these dangerous systems.

Above, the image on the left shows a raw data model depicting winds of only 50 knots and waves of 4 – 5 meters for a typhoon that in fact had winds of 125 knots. After AWT’s enhancement (on the right), the wind field is more accurately depicted with maximum winds of 125 knots and waves up to 14 meters.

Viewing High-Resolution Data

Not only is AWT data better, but it is also easy to visualize. With BVS, the captain can see high-resolution data in order to get a more accurate view of weather conditions in areas that are most critical to the voyage. When captains request weather data for a geographical area, they can specify regions within that area where they want to see detailed, high-resolution data. With high-resolution data, captains can better see weather and current conditions in the selected regions and take precise tactical action.

The example above shows standard wind data on the right region of the display and high-resolution data on the left.

The example above shows standard current data on the right region of the display and high-resolution data in the left.

Using high-resolution current data, captains can take advantage of positive currents and avoid adverse currents during a voyage. Even small course alterations can save substantial time and fuel.

Another area where AWT modifies the raw model data, to ensure the most accurate information, is around India. The southwest and northeast monsoon conditions are certainly the principle weather events that impact that region. In short, the monsoons are driven by air temperatures over Asia in relation to the sea temperatures. During the summer the air over east/central Asia is hot, the rising air creates surface low pressure drawing in moist air from the Arabian Sea and the Bay of Bengal. The flow in July and August can frequently bring the southwest winds up to Beaufort Force 8-10 across the western Arabian Sea.

The above image is taken from BVS showing an area of enhanced gale force monsoon conditions from 25 July 2012. As you can see in this image the core of the heaviest winds were over the far western Arabian Sea. The long fetch and duration of these conditions however allow significant waves of 4-5 meters to extend all the way to the coast of Pakistan and India.


On the other hand, in winter, when temperatures are cold over east/central Asia the air tends to sink creating surface high pressure. This prevailing area of high pressure results in a dry northeast wind across the waters surrounding India. Generally speaking the northeast monsoon does not generate the same wind strength as the southwest monsoon.

The periods of time between the southwest and northeast monsoon (April, May and June then September, October and November) are marked by light and variable conditions as the gradual transition from one primary wind flow to the other takes place.

While monsoon winds are clearly the primary influence on weather in the waters surrounding India, the impact of tropical cyclones can’t be over looked. Tropical cyclone activity is of concern mainly May through September through the Arabian Sea and Bay of Bengal. In the Arabian Sea the concentration is highest in May/June then again in September. The intensity of the southwest monsoon can inhibit the development of cyclones in the Arabian Sea during the summer months. This region of the world is not the most active area for tropical cyclones but when they do form the impact can be catastrophic. Many coastal areas have extended low elevation plains extending far inland. This topography allows destructive storm surges to flood enormous areas when they come ashore.

BVS is under a continuous state of improvement to bring the latest science to our users. From India to Alaska and all across the globe we aim to provide quality information that mariners can use to make effective decisions. We are proud to support Abhilash Tomy on this circumnavigation of the world and look forward to his success.


Click here for the video

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