Skip Vaccarello

Weather and winds clearly have a significant effect on ship performance. “How often does good weather exist?” and “How accurate are satellite wind observations?” are questions AWT is often asked. As you will see in this month's articles, the answers to these important questions are not always simple.

Our experts, George Schlinkert, AWT's VP of Operations and John Caito, AWT's Study and Claims expert provide valuable insight on these issues.

Enjoy reading this month's articles. We welcome your feedback.

Thank you,
Skip Vaccarello

George Schlinkert

How often does good weather exist?
by George Schlinkert

Under the NYPE 1946, the description of a vessel states: “…capable of steaming, fully laden, under good weather conditions about … knots…” The criteria for ascertaining good weather was left open and various assignments were made based on particulars of a vessel or voyage, although Force 4 was the favored standard.

Under the updated NYPE 1993, the description of vessel states: “Speed about… knots, fully laden, in good weather conditions up to and including maximum Force… on the Beaufort wind scale, …” The criteria for good weather was tied to the Beaufort Scale.

More and more clauses and restrictions have subsequently been added such that the speed description of a vessel may sometimes reflect a sea trial result rather than what a vessel can accomplish in realistic and measurable conditions. The following clause depicts this trend:

ABT 19.0 KNOTS ON ABT 36.5 MTS IFO PLUS ABOUT 2.5 MTS MGO AT DESIGN DRAFT OF 7.6 M BASIS CLEAN AND SMOOTH BOTTOM, EVEN KEEL, DEEP AND CURRENTLESS WATER/SEA WITH A TEMPERATURE OF MAX 28 DEGREES CELSIUS, WIND MAX BAUFORT 2 AND SEA NOT EXCEEDING DOUGLAS SEA STATE 2… read more >

John Caito

Satellite Observed Winds Vs.
Ship Observed Winds
by John Caito

We are frequently queried regarding the accuracy of satellite wind observations. Satellite observed wind speeds have been found to be very accurate, especially in the range of Beaufort Force 4 to 5. But how does this compare to that of shipboard wind observations?

Measuring wind velocity from a ship is not a straight forward process. There are two methods of wind observations from a vessel. Observations made by anemometer would appear to be the most accurate possible. However, factors such as the height of the anemometer above the deck and the shape of the vessel’s superstructure affect the accuracy of these observations. Wind speeds vary with height, and the shape of the vessel’s superstructure distorts the flow of air reaching the anemometer, affecting the observed wind speed. Both factors can be corrected, but not easily, and not before these observations appear on synoptic weather charts frequently used for weather verification.

The other method of observing winds from a vessel estimates wind speed by matching sea state photographs to the Beaufort scale. This is a subjective process and therefore subject to human bias.

We often see shipboard weather observations referred to as having been made by the ‘man on the spot,’ implying that such observations are the most accurate possible. This is an assumption not supported by research, which has found that ship wind observations are frequently inconsistent, even when the reporting vessels are in close proximity. … read more >

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AWT (www.awtworldwide.com) is the leading provider of fleet optimization services, ship routing services and onboard voyage management software to ship owners, operators and charterers seeking the safest and most efficient routes for their fleets. Unlike companies that provide weather services for multiple industries, or companies which only offer onboard weather software, AWT is staffed by world-renown experts in ship routing, meteorology, IT, maritime science and former mariners who are focused solely on the maritime industry. Using the most sophisticated technology available, AWT routes more ships per month than any other company. Its superior customer service and integrity have made AWT the most trusted fleet optimization provider in the maritime industry. Founded in 1996, AWT is privately held and headquartered in Sunnyvale, California with worldwide offices located in the UK, Hong Kong, Shanghai, Korea, Germany, New York, and New Jersey. More information is available at www.awtworldwide.com or by calling 1-408-731-8600.