On a freighter, or on any vessel for that matter, you will immediately find that once under way the exterior of the ship can be a very windy place, whether walking on deck or just trying to get some sun. If you want to settle down in a deck chair, in a comfortable spot, that's not too breezy, you need to understand the following:
There are two types of wind: true and apparent. Imagine two ships, one heading north at 10 miles per hour and one heading south, with the wind coming from the north at 10 miles per hour. The apparent wind on the north bound ship would 20 miles per hour. The apparent wind on the south bound ship would be zero miles per hour. Thus, the true wind plus the wind you are making while moving equals the apparent wind. Most ships will move at about 20-25 miles per hour. Thus, with a 20 mile per hour northerly wind and the ship moving at 20 miles per hour into that northerly wind, the apparent wind will be 40 miles per hour. (Strictly speaking, at sea, speed is measured in knots, not miles or kilometers per hour. One nautical mile per hour equals 1.15 statute miles).
If you are out to bag some rays, you will want to be on the lee side of the vessel, but you may still have to put up with some wind depending on its true direction. You will have to shift the location of your sun bathing activities not only from day to day, but even from hour to hour. After a couple of days at sea you will likely find a sheltered place where you can get maxim sun and minimum wind. Likewise, you will quickly learn to walk on the lee side of the ship rather than the windward, especially if the weather is cool. All those containers on deck make a great wind break.
All the way forward on the vessel (the bow to you 'lubbers), the quietest place aboard a ship, can be a windy spot indeed, epically if you plan to lean on the rail. However, you will find that by moving a couple of feet back from the rail there is a dead spot with no breeze at all. Please keep in mind that you should never try to throw a cigarette butt, or anything else for that matter, off the bow of the ship. In fact, you should not be smoking on the main deck, fo's'cle, or any place else, except perhaps abaft the superstructure.
As an aside, the bow is exactly where seaman, in the 17th and 18th century, went to perform their bodily functions: sitting or standing on an iron grate mounted on each side of the bowsprit. Thus the "head" was truly at the head of the ship. No doubt this is the origin of the expression "pissing into wind". Of course, the modern day freighter passenger will have a "head", adjacent to their sleeping quarters.
While aboard you can follow some simple rules if you wish to predict the weather. Of course, if you are lazy you can ask the captain or take a look at the weather forecast. The forecast is found on the bridge and is faxed to the bridge a couple of times a day. If you could care less about weather forecasting, stop here.
The Generic Forecast:
"Probable nor'east to sou'west winds, varying to the southward and westward and eastward and points between; high and low barometer, sweeping round from place to place; probable areas of rain, snow, hail, and drought, succeeded or preceded by earthquakes with thunder and lightning." (Mark Twain)
Their shape, size, height, color and sequence will fortell what's to come.
Stand with your back to the wind (true no apparent) and watch which way the clouds are moving. High altitude clouds moving from left to right indicate the weather will worsen; from right to left it will improve. If the clouds move toward or away from you the weather will stay about the same.
Your viability at sea, assuming you are on the bridge, or better still on the flying bridge, will be 12 to 15 miles on a clear day. This is a good place to watch changes in the weather. You will be able to see squall lines approaching and view them on the radar screen. While there, compare the appearance of the sea and correlate it with the wind direction and speed. When you think the waves look pretty small, but there is a little pitch and roll, take a walk down to the main deck and see what they really look like. You will find a "Force" Chart on the bridge. Look at the sea and then take a look at the force chart and you will be able to predict the height of the sea with a good degree of accuracy.
In Matthew 16:2 Christ said "When evening comes, you say it will be fair weather, for the sky is red." The old sailors saying "red sky at night sailor's delight..." is not pure fancy. For the most part, weather moves from west to east. When the setting sun is seen thru the dust of dry air it will appear red. Fair, dry weather is likely the next day.
A halo around the moon is a sign of rain. It is caused by the moon shining through ice crystals of moisture-laden clouds. If the halo is tight, rain is far off. If it forms a large ring, rain is near. If the clouds close and the moon looses its outline, look for rain in about ten hours. Ditto for the sun. Of course keep in mind that you are on a ship that will cover 350-450 miles in a 24 hour period. So there well might be rain where you are, not where you will be tomorrow.
The large diesel engines of freighters kick out a lot of smoke. When it curls down and hangs by the water's surface, it means approaching rain. This is due to the fact that lowering air pressure is not of sufficient density to support the heavy, unburned particulate material in the exhaust. Another sign of rain is when the ship's exhaust, bell, horn, or any other loud sound will have a hollow quality. This is attributable to the sound bouncing off a low cloud ceiling.
Many experienced seaman will tell you that they can "smell rain". There is a bases for this assertion: lowering air pressure helps odors emanate (so does an ebb tide).
Wind changes direction either by veering or backing. A wind that veers is changing its direction to your right as you face it. A wind that backs changes directions to your left. A veering wind suggests fair or improving weather (in the northern hemisphere due to clockwise rotation of high pressure areas). A backing wind comes from a low pressure area and suggest nasty weather. The rule: "A veering wind will clear the sky; a backing wind wind says storms are nigh."
Though not predictive of weather, you may experience swells while at sea. These have been generated by weather patterns hundreds or thousands of miles away. Swells may be moving in a direction different from the local wind patterns.
An experienced seaman, given a barometer and by knowing the direction of the wind, and by observing their relationship, has a pretty reliable way to predict the weather. However, in this day and age, shipping lines employ long range forecasters to predict the weather over a given area of the ocean. On my last Pacific crossing we took a straight line course from Oakland, California, to Taiwan, rather than a more northerly, polar route. The forecast for the North Pacific was for some rough weather. This would have meant a slower passage with the potential for damaged cargo. Of course the trade off was that the more direct route would use more fuel, being longer. However, using a few thousand tons, yes tons, more fuel was a cheap trade off as compared to potential cargo or ship damage.
the rules listed must be reversed when south of the equator".