Grantville Gazette 35

Untying the Wind

In Macbeth (1606), the Second Witch tells the First, "I'll give thee a wind." (I, iii), and later Macbeth acknowledges their power to "untie the winds." Gustavus Adolphus "was said to have been aided by wind magic practiced by the Lapps and Finns in his armies." (Deblieu 34) Izaak Walton, in The Compleat Angler (1653), declared, "I wish I were in Lapland, to buy a good wind of one of the honest witches, that sell so many winds there and so cheap." (Watson 119).

Winds were important-windmills required winds that were neither too light nor too strong, and for sailors, the wind had to be from the right directions, too. In the new universe created by the Ring of Fire, the wind will aid or hinder aircraft and airships.

In this article, I will try to answer the following questions: (1) what did the down-timers know about the prevailing winds on the eve of the RoF? (2) what can they readily determine about the winds from the books of Grantville and from observation during the first few years after the RoF? (3) if an author needs to determine what winds prevail for a particular season and locale, what's the most efficient way of finding that information?

Pre-Rof Knowledge of Surface Winds

Before the RoF, mariners were already exploiting some of the world's major prevailing wind patterns.

At least since classical times, sailors have journeyed from East Africa to India on the southwest monsoon, and returned on the northeast monsoon (Deblieu 50). The monsoon alternation was even mentioned by Aristotle (Watson 41). The round trip from Rome to India took a year (101). When the Roman power ebbed, the Arabs took over. And once the Europeans circumnavigated Africa, they elbowed their way into this trade, too.

The pre-RoF trade route between Europe and North America likewise evolved to take advantage of favorable winds and avoid unfavorable ones. From Europe, the ships hurry as quickly as possible south through the variables, a region characterized by calms or light winds of no particular preferred direction. The down-timers called them the Horse Latitudes.

The sailors are pleased to reach the northeast trade wind zone, a region in which the winds blow steadily and strongly from the northeast. With this wind (more or less) at their back, they head westward, making landfall in the eastern Caribbean. They go about their business and then head northward along the American coast, passing through the Horse Latitudes a second time, and then arrive in the region of the westerlies. These are not as steady as the trade winds, but are still on average, favorable for the return to Europe.

The trade between Europe and South America is still mostly in Portuguese hands, although Recife in Brazil is occupied by the Dutch. The Portuguese ships head further south than those going to New Spain; if their destination is Rio or Bahia, they must cross the Doldrums (the Inter-Tropical Convergence Zone) near the equator and enter the southeast trade winds for the westward haul. However, they have to work their way far enough south in the process so that, by the time they reach Brazil, they are in the southern hemisphere's variable zones, and can work their way along the coast to their destination.

Returning, they zigzag a bit. They descend to the westerlies (which, in the South Atlantic, are stronger and more reliable than their North Atlantic counterparts) and, cross back over the Atlantic. Nearing the Cape of Good Hope, they head north and pick up the southeast trades, which take them back northwest, above the triangular wedge of eastern Brazil. They make the difficult but fortunately short crossing of the Doldrums and then follow the North Atlantic return route to Europe. Note that they can't just round North Africa northward because they'd be fighting the northeast trades.

It is interesting to note that the Cory's Shearwater migrates from the northern to the southern hemisphere along this very route, and times its migration for when the African monsoon westerlies associated with the intertropical convergence zone are weakest (November). (Felicismo).

Those southeast trades also hindered the early Portuguese attempts at circumnavigation of Africa. The easiest (albeit not shortest) sea route to the Cape of Good Hope was by way of Brazil. However, once they developed that route, they were able to enter the Indian Ocean, and join the monsoon trade with India.

There is also a monsoon in the South China Sea, which dominates trade among China and the Philippines, and also affects trade with Japan, southeast Asia, and the Spice Islands of Indonesia.

In 1611, Hendrik Brouwer discovered that he could journey from the Cape of Good Hope to Java (the gateway to the Spice Islands) much more quickly by avoiding the monsoon belt of the Indian Ocean and instead taking advantage of its westerlies (the Roaring Forties). This route was made compulsory for the Dutch traders in 1616. Because you had to turn northeast eventually, to avoid Australia, it led to some inadvertent encounters (shipwrecks) with the Australian west coast when longitude was miscalculated.

Since the 1560s, Spanish ships have taken advantage of the North Pacific westerlies and northeast trade winds (Deblieu 51). The Acapulco Galleon leaves Acapulco with Spanish silver and gold, and takes the trade wind route to the Philippines. Then the Manila Galleon leaves Manila with Chinese silk, heads north along the coast of Japan (taking advantage of the northward Kuroshio current) and turns east as soon as it encounters the westerlies, making landfall off the coast of Upper or Lower California, and returns to Acapulco on the southward California current.

The southeast trades of the South Pacific were used, much earlier, by the ancient Polynesians. Their ships sailed best on a "reaching" course-one with the wind off the beam, and they expanded northeast from southeast Asia and Australia. (Watson 91).

Finally, Norse exploration of Iceland and Greenland was made possible by their exploitation of the polar easterlies. (Deblieu 50).

The desired routes are described in sailing directions composed by governments and trading companies. While these are nominally kept secret, the precautions are ineffectual. For example, the Dutch learned the Portuguese monsoon routes because the Portuguese allowed Dutchmen to serve as sailors on their ships.

Wind Meteorology in Grantville Literature

The Grantville encyclopedias and school earth science textbooks will put this information into perspective. That is, they will explain the physical mechanisms that create the westerlies, the trade winds, etc. However, they aren't likely to provide detailed information about the spatial extent of these prevailing wind regions, the average wind speed, or the steadiness of the wind direction.

Monsoon systems are characterized by prevailing wind patterns that reverse twice a year. There are monsoon systems in both the Indian and Pacific Oceans. EB2002CD/"Indian Ocean" explains that the monsoon zone extends north from 10° S, and that in May-October it experiences the wet southwest monsoon with wind speeds up to 24 knots (28 miles per hour), and in November-April the dry northeast monsoon. The term southwest monsoon is something of a misnomer as there's a west wind over the Arabian Sea and a south wind over the Bay of Bengal. The monsoon season begins over the Arabian Sea first. Also note that during the changeovers (October and March-May), there may be "desultory breezes with no strong prevailing patterns" (EB2002CD/"India," "Climate").

EB2002CD/"Monsoon" warns that "At the poleward limit of a monsoon system, the winds shift sharply. In India, for example, the monsoon blows from the southwest in July-August, while north of India the winds are from the east. Over northern Australia the monsoon comes from the northwest in January-February, and at the southern limit the winds again become easterly."

Another monsoon system affects both southeast Asia and northern Australia. Its northern limit is about 25° N. In South China and the Philippines, the trade winds prevail in October-April and southwest monsoon winds in May-September. The summer monsoon is stronger over Vietnam and Thailand, but monsoon winds are weak over Indonesia. Northern Australia experiences northwest summer (November-April) monsoons and winter (May-September) southeast monsoons, but even in summer there are periods of southeast trade winds. (EB2002CD/"Climate").

Another essay notes that monsoon winds of the East China Sea blow from the southeast in summer and from the north in winter (EB2002CD/"China Sea"), but says nothing about their strength. Even less information is given about the monsoons of the South China Sea; essentially just that they exist.

In the Sea of Japan, further north, we are informed that the northwest monsoon prevails December (or September) to March, and the south(east) monsoon in summer (or, more broadly, mid-April to early September). (EB2002CD/"Japan, Sea of"; "Japan").

There are also small monsoonal systems in West Africa and Central America. (EB2002CD/"Climate").

EB11/"Trade Winds" says, "The area of their greatest influence may be taken to extend from about 3° to 35° N., and from the equator to 28° S., though these belts are actually somewhat narrower at any given season, as the whole system of surface winds over the globe moves north and south following the sun."

EB2002CD/"Wind" (my surrogate for the EB2000) says that the trade wind is a "very steady wind that blows westward and toward the equator from the subtropical high-pressure belts at latitudes near 30° N and 30° S toward the intertropical convergence zone. It is stronger and more consistent over the oceans than over land and produces fairly clear skies that make trade-wind islands popular tourist resorts. Its average speed is about 5 to 6 m per second (11 to 13 miles per hour). "

Some further information is provided in EB2002CD/"Pacific Ocean: Climate": "The obliquity of the ecliptic . . . limits the seasonal shifting of the Pacific trade-wind belts to about 5° of latitude. The easterly winds . . . tend to be strongest in the eastern Pacific. . . . The average wind speed of the Pacific trade winds is about 13 knots (15 miles per hour). The weather in the trade-wind belts is normally fine, with relatively little cloud cover. . . ."

There is also a southeast trade wind zone in the Indian Ocean, between 10° and 30° S; the winds are strongest June-September. EB2002CD/"Indian Ocean."

EB11/"Climate and Climatology" comments that the westerlies "are much less regular than the trades. They vary greatly in velocity in different regions and in different seasons, and are stronger in winter than in summer." Note that the southern hemisphere westerlies are more reliable: " Between latitudes 40° and 60° S the " brave west winds " blow with a constancy and velocity found in the northern hemisphere only on the oceans, and then in a modified form."

To this, EB2002CD/"Atlantic Ocean" adds, "the prevailing westerlies of mid-latitudes, . . . are found to be half as strong and about 10° farther north in latitude over the North Atlantic in summer than in winter. "

It continues, "In latitudes 15° to 30° N the North Atlantic is characterized by prevailing high pressure with an attendant lack of intense storms and severe weather." This, of course, is a reference to the Variables (Horse Latitudes).

The essay continues, "Over the South Atlantic the belt of prevailing westerlies extends from about 40° S almost to Antarctica, and the South Atlantic high-pressure area is centered around 30° S. . . ."

With regard to wind conditions in the polar regions, EB2002CD/"Atmospheric Circulation" informs us that "Poleward of 60° N and 60° S, the winds generally blow westward and equatorward as the polar easterlies. In the northern polar regions, where water and land are interspersed, the polar easterlies give way in summer to variable winds."

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The North Marion High School in Mannington has the McGraw-Hill Encyclopedia of Science and Technology (1977)(McGHEST); I checked the 2002 edition and hopefully the relevant points are the same. McGHEST/"Atmosphere" provides a formula for the geostrophic wind (the wind resulting from the balancing of pressure gradient force and Coriolis force; this is dominant above about one kilometer, except near the equator. It also explains how the north-south temperature difference can cause winds aloft to be more westerly than those at the surface ("thermal wind"). McGHEST/"Wind" states that the trade winds run from 30° equatorward, and the westerlies from 30-35° to 55-60°. In winter, it says that these have mean speeds of 15 knots, and in summer, half that. And it says that these systems move poleward in summer and equatorward in winter. McGHEST/"Wind Power" provides a formula for the power of the wind.

McGHEST/"Monsoon Meteorology" states that the average onset date for the summer monsoon rains is June 1 at Kerala (8° N), June 10 at Bombay (19° N), and June 15 at Delhi (28.5° N), affecting the entire Indian subcontinent by mid-July. The monsoon rains withdraw southward beginning in September.

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More detailed data is available in books and magazines geared for sailors and pilots. Since West Virginia is quite a distance from the sea, I am not very sanguine about finding a treasure trove of relevant nautical literature. Still, there are people in Grantville with nautical or aeronautical experience, and some basic books on navigation and meteorology could be in their private libraries.

For example, there is a reasonable chance that one of the many editions of Bowditch's American Practical Navigator came through the RoF. Chapter 35 of the 1995 edition provides the "generalized pattern of actual surface winds" in January-February and July-August over the ocean, worldwide. It also notes that the North Atlantic westerlies average 25 knots in winter and 14 knots in summer, but are unsteady (blowing between south and northwest 74% of the time). The Southern Hemisphere westerlies are steadier, and 17-27 knots, with the greatest strength at 50° S. http://www.irbs.com/bowditch/pdf/chapt35.pdf

Bowditch isn't very informative about the trade winds. However, a book in my personal library-which has not been proven to be in Grantville-says that the NE trade winds have an average strength of Beaufort force 3-4 (7-16 knots), but can reach force 6-7 in Jan-Mar. Their direction and speed is very steady. The trade wind zone is 2-25° N in winter and 10-30° N in summer, but they are less reliable at the northern margin. See Cornell, World Cruising Routes 34.

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If there are books on "wind power" in Grantville, they may have a world map showing wind speed distribution. Continental maps prepared in the early 1980s are duplicated in Gipe, Wind Power 406ff (2004), and I believe also in his pre-RoF Wind Power for Home and Business (1993). Of course, these maps do not show wind direction, but the up-timers would figure that the prevailing zonal winds (polar easterlies, mid-latitude westerlies, tropical easterly trades) would extend, in modified form, over the continents.

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The Ring of Fire itself will perturb the post-RoF weather-the Great Colonial Hurricane of 1635 will not strike the same places on the same day that it did in the old timeline-but prevailing winds are an aspect of climate, not weather, and shouldn't change much.

The Hidden Treasure-Trove of Wind Knowledge: Ships' Logbooks

Even if we didn't have this info in available Grantville literature, it can be reconstructed to some degree by the down-timers, from ships' logbooks. "Even from the beginning of the great voyages in the 16th century, the positions and weather observations were taken every day. From the 17th century onwards, the observations were in tabular form." (Garcia-Herrera 3). "A Royal Order issued in 1575 required masters and pilots from the Spanish ships who navigated in the Carrera de Indias (the route from the mainland to the colonies in America) to keep a record of each trans-Atlantic journey, including a detailed description of the voyage and of any geographical discoveries, winds, currents, and hurricanes. The completed logbooks had to be delivered to the Professor of Cosmology in the Casa de Contratacion." (Prieto 38).

Naturally, the older the logbook, the less likely it is to have escaped loss or destruction, and I have relatively little information on the nature of logbooks compiled prior to 1750. However, sailors are a conservative lot, and there is reason to believe that the logbooks of the 1630s and before present similar information, albeit in more archaic terms.

The earliest logbook I have been able to read was from HMS Experiment (1697), it was tabular, and recorded the date, the day of the week, the wind direction (on the 32 point compass), the course, the distance sailed that day, the latitude and longitude, bearings to landmarks, and a description that begins with a remark about the weather, including the force of the wind (e.g., "small winds with much thunder, lightning and raine"). (Wheeler 135ff). The description might also mention what sails were set. Records were made at least daily.

Thus, there are three different indications of the wind force: the verbal descriptor, the amount of sail carried, and the distance traveled (the last being a function of the wind speed and direction relative to course). (Wheeler 68). This allows some degree of quantitative analysis of the logbooks right off the bat; wind force terms may be arranged by average distance sailed (Fig. 4). Once anemometers are placed on ships, it will be possible to correlate these traditional indications with wind speed.

At least in the British Navy, logbooks were kept by the captain, the lieutenants, and the master. Diligence was assured by the fact that the officer didn't get his pay until he handed in his logbook. In the East India Company, the journals were kept by the captain, the first mate, and occasionally the second mate. Enough British logbooks have survived to the present so that it was possible to reconstruct the probability of wind from each of the cardinal directions for each month of the year, in the English Channel, during 1685-1700. (Wheeler).

I can't speak about period Portuguese logbooks, because they were pretty much all destroyed by the Lisbon earthquake and fire. Spanish logbooks recorded all astronomical observations, and the distance traveled, course, and wind direction every two hours. (Garcia 16).

In Dutch logbooks, including information about wind force was routine by around 1600. (Koek 82). Dutch eighteenth-century logbooks anticipated the Beaufort scale descriptions by use of wind terms that specified the sail set, e.g., "double reefed topsail wind." (83). But bear in mind that the terminology in the early-seventeenth century must have been different, as reefing wasn't practiced then.

The French captains did keep logbooks, but in the seventeenth century it apparently was not commonplace for them to record meteorological observations in them. One exception was Georges Fournier (1593-1652), who in his 1643 treatise urged his fellows to record wind direction and quality. (Prieto 41).

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The utility of this wind data is of course dependent on the accuracy of the computation of the place of observation, expressed as latitude and longitude. At the time of the Ring of Fire, you had perhaps half a degree accuracy for shipboard observations of latitude (with occasional several degree flubs). As for longitude, this was determined by dead reckoning, and became less and less reliable the longer you were at sea (so, on a major voyage, you could be off by tens of degrees). This will change as a result of Grantville knowledge, but it will change slowly. The raw logbook data will have to be corrected for the differences between compass (magnetic) and true directions, and for changes in reference meridian. (Wheeler 97ff).

In the nineteenth century, Maury studied American and British logbooks. By then, of course, navigation was more accurate, and addition the wind speeds were quantified at least as Beaufort force and possibly by anemometer (haven't checked this). Maury created track charts which showed what winds were encountered where and when by particular ships. From these, he then prepared "pilot charts" that showed, for a particular "grid box," the frequency of winds from different 16 compass points, for each month. From his charts, he created sailing directions. His directions and charts reduced the average New York-San Francisco passage time from 180 to 133 days. (Lewis; Maury), and New York to Rio from 41 to 21 days. (De Villiers 68).

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Sailors, of course, aren't going to know anything about overland winds. In 1582-97, the landlubber Tycho Brahe kept a meteorological daybook on the Island of Ven, with an eleven level wind scale, but this was exceptional. (De Villiers 61; Huler 82). There are undoubtedly documents that make reference to winds so strong that they destroyed property, but it's doubtful that there are many systematic records of wind direction and force over land.

Observation of the Wind

At the time of the Ring of Fire, the characters will not know the average speed of the wind, as no devices for that purpose had yet been invented. The wind will be described in qualitative terms. Smith's Sea Grammar (1627) classified the wind level as stark calm, calm, fresh gale, loome gale, stiff gale, storm, tempest, and "hericano"; note that "gale" was then a generic term for a wind, and "breeze" was used only along the coast, in the context of a "land breeze" or "sea breeze." (Huler 85).

In 1806, Beaufort proposed standardization of the British Navy's wind descriptions in log entries, characterizing the wind force in terms of how much sail a sailing ship may safely carry, and his scale was mandated by the Admiralty in 1838. In 1906, the scale was recast, for the benefit of steamships, in terms of sea state.

The first anemometer was one in which the wind caused a hinged, hanging plate to be deflected from the vertical; this was described by Leon Battista Alberti in 1450 (Huler 189). Unfortunately, swinging plate anemometers aren't accurate at sea, because of the motion of the ship. Still, one was carried on a Swedish warship in 1779 (89). The more practical cup anemometer was invented in 1846 (191). There is probably an exemplar at the high school science department in Grantville.

A variety of anemometers are described in the Grantville encyclopedias, and possibly in other Grantville literature (Popular Science back issues, Amateur Scientist column in Scientific American, science fair project books) and it's reasonably likely that at least the Science Department at the school has basic weather equipment such as a barometer, a thermometer and a anemometer mounted on the rooftop. Indeed, it probably has a combination barograph-thermograph for recording pressure and temperature.

So, within a year or two after the RoF, it's possible that anemometers have been built, and governments could require their use on shipboard to record wind information for the ship's log.

Each year, as the logbooks were turned in and analyzed, you would refine the body of wind climatology data for the standard sailing routes. Ideally, you would collect wind data for at least thirty years, the standard period for computation of climatological norms.

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While the broader development of meteorology is outside the focus of this article, this author thinks it likely that crude but serviceable thermometers, barometers and anemometers will be manufactured within a few years after RoF, and purchased by governments, nobles, professionals, merchants and the military throughout Europe.

Inevitably, meteorological records will be kept, and this will lead in turn to meteorological reports and even forecasts in the newspapers and on the radio and telegraph. In eighteenth-century Europe, informal networks of towns shared weather observations (De Villiers 133), and by the 1840s, weather events were telegraphed across regions of the United States and Britain. (Monmonier, 40).

In Flint, 1633, Chapter 14, Jesse tells Jim, "We need someone to organize a weather service. . . ." In October 1633, the Voice of America, broadcasting from Grantville, features a "local weather forecast." Hughes, "Turn Your Radio on, Episode Two" (Grantville Gazette 20).

I imagine that the weather was mentioned on the weekly Farm-to-Market report mentioned in Huff and Goodlett, "Waves of Change" (Grantville Gazette 9).

Merton Smith of TransEuropean Airlines calls up the weather service in Huff and Goodlett, "High Road to Venice," and he has weather information from as far away as Rome. (Grantville Gazette 19). By fall, 1635, there are weather stations in Russia, at least one of which is equipped with an up-time thermometer and barometer, although their data is transmitted by messenger rather than by radio. Huff and Goodlett, "Butterflies in the Kremlin, Part Seven, The Bureaucrats are Revolting" (Grantville Gazette 9).

Thus, we anticipate that the characters will combine their qualitative knowledge of the winds that prevailed before the Ring of Fire, with the limited quantitative information that the Grantville literature furnishes on late-twentieth century wind climatology, and use it to predict the prevailing winds that will be experienced in the decades following the Ring of Fire.

Winds Aloft

As you go higher, air temperature and pressure drop, at least until you reach 11 km. Upper air weather maps often are identified in terms of the standard pressure at the height the measurements were made, rather than the height (above sea level) directly. Note that one millibar (mb) equals 100 pascals. The weather maps most often available are for the "pressure altitudes" shown below:

Winds increase in speed with altitude, because they aren't slowed down as much by friction with the earth's surface. I assume an exponential increase in wind speed with height, with the reference height being 10 meters (standard meteorological practice) and the exponent being 0.2. The exponent in fact depends on the terrain below, and the stability of the air, and you can find a list of suitable values for different circumstances at

http://en.wikipedia.org/wiki/Wind_gradient

Winds also change direction with altitude, either veering (turning clockwise with height) or backing (turning counter-clockwise). Generally speaking, they veer in the northern hemisphere and back in the southern, because the upper air levels experience less "frictional" drag than the lower ones and thus the wind is faster, and this means that the Coriolis force, which is perpendicular to the wind and proportional to the wind speed, is greater. Here's an applet to play with:

http://itg1.meteor.wisc.edu/wxwise/kinematics/testwind2.html

However, veering and backing can also occur as a result of horizontal temperature gradients ("thermal wind") so it's a complex matter. The matter is alluded to by McGHEST/"Wind."

Over the ocean, the average veering is 10.5° at 1,000 meters height (relative to the surface wind), and rising another 1,000 meters adds another 2.5°. (Gray 49). The effects of latitude (0-60°), wind speed and season are minor, with, at 1,000 meters height, perhaps a 4° range (Gray 49, 51, 54). Over land, the veer at 1,000 meters is much larger, perhaps 25-35°. (Gray 75-6).

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There's a weather proverb, "If clouds move against the wind, rain will follow." It's evidence of wind shear, wind direction aloft being different than wind direction at the surface. (So, too, is the movement of different cloud layers in different directions at the same time.) I am not sure how old the saying is, but I found it in Loudon's 1824 Encyclopaedia of Gardening. The down-timers are much more familiar with the outdoors than we are, and may have noticed this phenomenon. Certainly, ships' officers may be asked to note any evidence of wind shear in the future.

There is limited information in Grantville Literature about winds aloft. The EB2002CD essays on monsoons set forth the vertical thickness of the monsoon zone. EB2002CD also mentions the "antitrade wind," a "steady wind that blows poleward and eastward between latitudes 30° N and 30° S, at altitudes of 2 to 12 kilometres (about 1 to 7 miles). Such winds overlie the westward-blowing trade winds." So, if a transatlantic airship could cruise at an altitude of 2 kilometers or higher, it could take advantage of the antitrades to retrace its steps, if that would be more convenient than jogging northward to the westerlies.

If you are wondering about the jet stream, this lies at 10-50 km, well out of airship reach. (EB2002CD/"Jet Stream").

In the old time line, upper air meteorological data was collected by miniaturized "meteorographs," carried by kites and balloons, beginning at least by the 1890s (Monmonier 69). This surely will happen much sooner in the new universe-if we can't build a meteorological balloon, we certainly aren't ready to launch airships!

"Author's Only" Information on Surface and Upper Air Winds

A prospective author may (indeed, better) know more than his or her characters about the conditions awaiting them. That may mean consulting modern, scholarly sources of wind climatology.

For overland flights over the United States, go here for "wind roses" (graphical representations of the probability of various wind speeds and directions):

http://www.wcc.nrcs.usda.gov/climate/windrose.html

and for wind speed only:

http://www.ncdc.noaa.gov/societal-impacts/wind

There is wind data for other parts of the world here:

http://www.windfinder.com/windstats/

Ocean data comes from voluntary shipboard observers, buoys, and, most recently, satellites. You may obtain monthly norms of wind speed and direction for the entire world (sea only) at http://cioss.coas.oregonstate.edu/scow/opendap.html

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Here is a sample of the combined overland and ocean wind speed data that's available from the wind atlases prepared for the wind energy industry:

http://www.ceoe.udel.edu/windpower/ResourceMap/sse_figure28a_rev.gif

In general, the surface wind speed over land is half the surface wind speed over water, and one-third the speed aloft above the "friction layer." (Watts 117).

This site has separate January and July maps of (separately) wind speed and wind direction for January and July.

http://www.climate-charts.com/World-Climate-Maps.html

This site has flash animations showing changes in sea level pressure and wind vector, and 500 mb height and wind vector, for the entire world on a monthly basis:

http://geography.uoregon.edu/envchange/clim_animations/index.html

Here you can find the monthly mean 850 hPa winds for the entire world:

http://www.cpc.ncep.noaa.gov/products/precip/realtime/clim/annual/monthly/monthly.12.w850.html

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/climatology/Wind-850.shtml

and for the 200 hPa pressure altitude:

http://www.cpc.ncep.noaa.gov/products/precip/realtime/clim/annual/monthly/monthly.12.w200.html

http://www.cpc.ncep.noaa.gov/products/precip/CWlink/climatology/Wind-200.shtml

The following website allows you to create maps of vector wind, scalar wind speed, zonal wind or meridional wind, for any of a great variety of pressure altitudes from the surface up, based on the average over a specified year range (chosen from 1948-2011) for any specified month or range of months or the entire year, for the entire world or specified regions. The data is from the NCEP/NCAR reanalysis, and is gridded at 2.5 degree intervals.

http://www.esrl.noaa.gov/psd/cgi-bin/data/composites/printpage.pl

After you generate the map, you can also get a copy of the u-wind and v-wind text data file used to generate the vector wind-u-wind is the east-west component and v-wind the north-south component.

If you are dealing with a trip at the time of monsoon changeover, you may need weekly rather than monthly data. You can create a weekly report by use of a daily composite:

http://www.esrl.noaa.gov/psd/data/composites/day/

You may also access daily data here,

http://www.esrl.noaa.gov/psd/data/gridded/data.ncep.html

(click on create plot/subset for the wind data of interest).

If that's not enough information for you, you'll need to launch your own weather satellite. . . .

Conclusion

It's a pity that our characters can't carry the winds in a knotted cord, and release the wind they need by untying it. But they can do the next best thing, which is to learn to predict which winds will prevail at a particular place during a particular time of the year.

Bibliography

Meteorology

"Pressure Altitude"

http://www.wrh.noaa.gov/slc/projects/wxcalc/formulas/pressureAltitude.pdf

(formula used to convert pressure altitude (mb) to geometric altitude (ft, m) on spreadsheet)

Cavcar, "The International Standard Atmosphere (ISA)",

http://home.anadolu.edu.tr/~mcavcar/common/ISAweb.pdf

Deblieu, Wind: How the Flow of Air has Shaped Life, Myth and the Land (1998)

De Villiers, Windswept (2006).

Huler, Defining the Wind: The Beaufort Scale, and how a 19th-Century Admiral Turned Science into Poetry (2004).

Monmonier, Air Apparent: How Meteorologists Learned to Map, Predict, and Dramatize Weather (2000).

Watson, Heaven's Breath: A Natural History of the Wind (1984).

Gray, "Diagnostic Study of the Planetary Boundary Layer over the Oceans," Atmospheric Science Paper No. 179, Dept. Atmospheric Science, Colorado State U. (Feb. 1972)

http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2 amp;doc=GetTRDoc.pdf amp;AD=AD0741717

Lewis, "Winds over the World Sea: Maury and Koppen, Bull. Am. Meteorol. Soc'y, 77:935 (May 1996). http://journals.ametsoc.org/doi/pdf/10.1175/1520-0477%281996%29077%3C0935%3AWOTWSM%3E2.0.CO%3B2

NASA,

http://earthobservatory.nasa.gov/Features/AmazonLAI/amazon_lai3.php

Voeikov, Discussion and Analysis of Professor Coffin's Tables and Charts of the Winds of the Globe (1876)

http://www.archive.org/stream/discussionandan00voegoog#page/n90/mode/2up

Watts, The Weather Handbook (1994).

Cushman-Roisin, Chapter 8, "The Ekman Layer," in Introduction to Geophysical Fluid Dynamics: Physical and Numerical Aspects (2011)

http://engineering.dartmouth.edu/~cushman/books/GFD/chap8.pdf

(for possible use in trying to quantify frictional veering)

Wikipedia "Density of air"

http://en.wikipedia.org/wiki/Air_density

Ship's Logbooks

Garcia-Herrera, CLIWOC: A Climatological Database for the World's Oceans 1750-1854, Climate Change, 73: 1-12 (2005).

Garcia-Herrera, Description and General Background to Ships' Logbooks as a Source of Climactic Data, Climatic Change, 73: 13-36 (2005).

Prieto, Deriving Wind Force Terms from Nautical Reports through Content Analysis: The Spanish and French Cases, Climatic Change 73: 37-55 (2005).

Wheeler amp; Wilkinson, The Determination of Logbook Wind Force and Weather Terms: The English Case, Climatic Change, 73: 57-77 (2005).

Koek, Determination of Wind Force and Present Weather Terms: The Dutch Case, Climatic Change, 73: 79-95 (2005).

Wheeler, An Examination of the Accuracy and Consistency of Ships' Logbook Weather Observations and Records, Climatic Change 73: 97-116 (2005).

Wheeler, British Naval Logbooks from the Late Seventeenth Century: New Climatic Information from Old Sources, History of Meteorology 2:133-145 (2005).

Wheeler, Using Ships' Logbooks to Understand the Little Ice Age (1685 to 1750): developing a new source of climatic data

Wheeler, The weather during the voyage of the Royal Spanish mail Ship Grimaldi, February-March 1795

Garcia, Sailing Ship Records as Proxies of Climate Variability over the World's Oceans

Garcia-Herrera, The Use of Spanish and British Documentary Sources in the Investigation of Atlantic Hurricane Incidence in Historical Times

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