Maritime Meteorology

Maritime Meteorology

There is steady development going on in the ports, docks, berths, and terminals. An unavoidable difficulty with any port directory is its sheer size. This results in many months passing between the input of the data and the actual publication date. There is no replacement for local information so if any port dimension or restriction is so important, communicate with a trustworthy agent. Frequently, the charter party stipulates One Safe Berth (1SB) when referring to loading or discharging port which places the onus upon the charterer to secure that the nominated berth is safe for the ship concerned. Nevertheless, the ship managers must operate ships efficiently; not to win lawsuits. It should not be ignored that although the ship manager is freed of many duties when a ship is on time charter rather than voyage charter, observing the safety of where the ship is ordered still has to be done. There is no substitute for experience in knowing about berth and no practical alternatives.  


Some regions of the world are ill-famed for heavy weather such as the North Atlantic in winter or Cape Horn at almost any time. Mediocre bad weather may increase the voyage time enough to erode the voyage profit. There are seasonal times of extremes of weather that can be damaging or deadly. In various parts of the world, storms have different names but basically, storms occur in regions of extremely low atmospheric pressure. Storms occur anti-clockwise in the Northern Hemisphere. Storms occur clockwise Southern Hemisphere. Storms develop over the sea and generate wind speeds averaging around 75 knots and gusts approaching twice that speed at times. Besides powerful winds, storms produce particularly heavy rain, and seldom does the wind cause tidal waves. The most damaging storms occur along the tropics of Cancer and Capricorn. Storms can put port facilities out of action and can devastate crops that would otherwise be ready for shipping.

Storms are common in the Southern Indian Ocean where they are naturally known by the meteorological name of Cyclones. Cyclones may be encountered from November to May. Infrequently, these storms can reach as far north as the Indian sub-continent they should not be confused with Monsoons which draw heavy rains with random gales between June and August. The gales are not of the same severity as cyclones but are violent enough to prevent loading and discharging operations at the port.

In the Gulf of Mexico – West Indies region the storms are named Hurricanes. Usually, hurricanes devastate crops, properties, and may take human lives. Hurricanes’ path can take them along the line of the Caribbean Islands, then on to the mainland where hurricanes do additional damage before being moderated by their passage over the landmass. The Hurricane Season is between June and November with the maximum recurrence between August and October. The Chinese name for heavy wind is Tai Fung from which the Westerners have derived the word Typhoon. In the Far East, numerous islands often suffer harsh financial loss when whole crops of rice, wheat, sugar, palm oil, etc. are damaged. Typhoons may occur any time between May and December with a maximum recurrence from July to OctoberAustralia experiences comparable storms that are known as Willy-Willies from January to April. Therefore, the Shipowner or Ship Manager should understand the risks of seasonal storms when planning voyages.


The cold Labrador Current which is responsible for the Newfoundland fogs also carries down icebergs which are pieces that have broken off the Polar icecap. Modern electronic systems in the ships make it more manageable to avoid iceberg perils.


Tides may have an impact on the safety of a berth. There is nothing unsafe about a berth to which the access is restricted such as by a sand bar at certain stages of the tide, so long as the berth itself allows the ship to be afloat at all times. Some coaster charter parties stipulate for Not Always Afloat But Safe Aground (NAABSA) but unless the charter is negotiated in such a way to ensure time counts while waiting for the tide, then the shipowner experiences that delay. This might be several days because during Neap Tides when there is the tiniest change, the depth may not rise adequately to permit access, and the ship has to wait for Spring Tides which could be as much as a week or more. In the coaster market, understanding tides can be even more critical. There is no point in ordering overtime to discharge fast or speeding at full speed to the loading port if the ship has to wait many hours for the tide to make before the ship can enter the berth.


Some regions in the world which are essential to shipping can have navigation prevented or even made inaccessible during winter months. For example, it seems reasonable for the farmers in the Canadian plains to deliver their grain for export to Churchill in the Hudson Bay but navigation is only possible there for the four (4) months of July-October. The St. Lawrence Seaway linking the Atlantic Ocean to the Great Lakes allows ocean-going ships to reach deep into the heart of the North American region but ice blocks this route from December to April. Weather forecasting has been reasonably reliable and there have not been any cases of large numbers of ships being trapped in the Great Lakes by an unanticipated freeze-up. The Baltic Sea becomes ice-bound from November to March and notwithstanding the sophistication of the ice-breakers, some of the ports are closed during the depths of winter. In some circumstances, there are quite attractive freight rates to be collected for late-season cargoes in ice-blocked regions but the risks have to be precisely estimated.


Fog is always associated with calm circumstances whilst at sea considerably mild winds may be involved. Sea Fog is different from that experienced inland. The primary component for a sea fog is warm moist air blowing over a cold sea. Fog may occur anywhere, however, fogs are especially prevalent off Newfoundland, California, Bering Sea, Baltic Sea, and Hudson Bay.

Weather Routing Service

Weather Routing Service is a system to avoid not only catastrophic sea perils but also to utilize the information obtained from far more complicated weather forecasting to avoid any sort of heavy weather. When ships crossing the North Atlantic in winter, the first thought would be to take as southerly a route as possible. However, this might be quite wrong as the systems bringing harsh weather could just as simply be lurking along that southerly route while on the northern route favorable conditions prevail.

Weather Routing Services aim to inform the Ship Master what weather conditions are anticipated for the voyage including storms, ice, fog, swell, winds, etc. Furthermore, Weather Routing Services recommend a route that will avoid the worst weather conditions. The Ship Master frequently sends feedback about the conditions in the ship’s location. Such feedbacks from many ships gives the  Weather Routing Service meteorologists a tremendous of data linked with satellite observation enables them to keep their weather forecast thoroughly up to date. 

Today, Weather Routing Services have become so successful an aid to faster and weather-damage-free voyages that it is customary for Time Charterers to insist upon Weather Routing Service information being received for all voyages undertaken under the time charter. Furthermore, Weather Routing Services can give unbiased data for a ship’s speed and fuel consumption performance under a time charter.


A load-line is the greatest depth to which a ship may be loaded. A load-line differs depending upon:

  1. Density of the water
  2. Time of the year
  3. Region (Load-line Zones)

The density of water is simply that if the ship is loading in freshwater, the ship can load to a greater depth because when the ship enters the sea, the greater density of saltwater will lift the ship to her saltwater load-line.

The time of the year is concerned with the ship having a higher freeboard for safety in wintertime when more turbulent weather may be confronted. Therefore, the highest freeboard is required Winter North Atlantic (WNA). Load-line is also called Plimsoll-mark. Politician Samuel Plimsoll persuaded the British government to take measures for the safety of life at sea by adopting the statutory marking. Load-line Convention devised a system of classifying the world into zones to correspond to the lines on the Plimsoll-mark. On the load-line map, there is a wide band around the world extending several degrees on either side of the Equator, marked T (Tropical Zone) which allows the deepest draft. Logically, the additional depth means more cargo and so more freight income. Sailing between Europe and North America in winter means loading to the lowest load-line mark Winter North Atlantic (WNA) where winter limitations are commanded from October to April. Long voyages are expected to involve more than one zone. Therefore, Shipowners and Ship Managers need to have a picture of the load-line zones in their minds. The foremost influence of load-line zones is on bunker planning. Ship Manager makes bunker planning to take full advantage of the load-line zones. Ship Manager should be careful if a ship is to load right down to the Tropical Marks (T) at a port on the edge of the Tropical Zone and then steam to the Winter North Atlantic (WNA) zone without having burnt off enough bunkers to bring the ship up to the Winter North Atlantic Marks (WNA). Even arriving with the Winter North Atlantic Marks (WNA) clear may not be enough. Port State Control (PSC) Surveyors can easily estimate from the ship’s Deadweight Scale whether or not the ship has nevertheless been sailing through winter zones with the appropriate mark well submerged. Ship Master may face heavy fines and an overloaded ship is technically unseaworthy. Therefore, an overloaded ship’s insurance cover could be void.

International Navigating Limits (INL)

The International Navigating Limits (INL) define the geographical limits within which ships can operate without incurring additional insurance premiums from Hull and Machinery (H&M) and other relevant underwriters. International Navigating Limits (INL) are, as a result of general agreement amongst Marine underwriters, incorporated into Hull and Machinery (H&M) insurance policies. Clause 34 of the International Hull Clauses imposes an undertaking upon the ship not to trade into icy regions during cold weather. However, International Navigating Limits (INL) can be broken if an application is made to the underwriters and the relevant additional premium (extra premium) is paid.