16 Points North

The Compass Rose …


20 thoughts on “16 Points North

  1. I tried to getthe compass rose from the Wikipedia with the names of the Mediterranean winds on it but it wouldn't save.You can easily construct the above by scoring a sheet of paper by folding it judiciously.You end up with a 90 degree calibration that is accurate enough to build houses with.The trick is not to think in terms of 11.5 degrees and imagine the whole as an whole and the subdivisions as niceties.The ancients had pretty muxh most of the world summed up in charts an army could march to. A stadium was a fraction of the earth's circumfrence, a fact still "metered" out in the British Mile.To the nearest 12th (not a Roman maths term, they preferred tenths with subdivisions that were logarithmic.) …to the nearest 12th, the above "rose" is made of 16th's of a circle. The modern day 360 degrees gives just under 12 degrees for each "compass point".Quite accurate enough to map the Med for shipping even today.Any vessel going out past the bar in the good old days was either a small family owned boat just big enough to go fishing offshore, or it was a business enterprise financed by shareholders taking a sufficiently large enough crew to see off bandits and hold their own at any port in which they were to do business or take shelter in a storm.With the birth of large empires such as Babylon and Greece, the shipping lanes in the Med were considered safe enough to do business over a large distance.Taking silk and Damask from Syria to Gaul could be a seriously profitable venture. Some ships were taking luxuries as far as Briton. Which meant considerable danger from pirates and the weather.Getting through the narrows at Gibraltar was a lucky dip, and the chances of a storm at Biscay was a deadly risk.And all the pilot had going for him was bronze swords, iron spears and copper shields overlaid on rawhide.None of which floated exceptionally well.They must have been very brave men.After a generation or so of exploration (by the time of the Assyrians I should imagine, though the Lebanese were doing good business before then) the ship's captains must have had a pretty good idea of the winds to be found in the various shipping lanes.And these would have been marked out on his "compass".

  2. World winds:http://ggweather.com/winds.htmlThey should be considered as "Singularities" they require a certain seasonal "set-up" before they appear.Mediterranean windsFrom the north by the right:Tramontane.Gregale.Levante.Sirocco.Ostro.LibeccioOnente and Mistral.8 winds you can navigate by.After that, once offshore and especially at night, you would use the sun to navigate by.Yes. At night.With the sun and some idea where you were whatever division of the week ago, you could sail fairly safely by the local wind and get your bearings from the stars to keep you off-shore, then the next day you would be safe to get your heading corrections from the sun.Of course the stars aren't all that much use to you for steering. They tend to disappear when you need them most. Any fool can sail safely in weather you can see stars by.You would be far better off learning the local winds and seasonal variations. Besides, if you were paying a mariner for his expertise, you wouldn't ant him pulling into shore looking for local non-pirates to give him directions.You'd want someone worth his silver, capable of turning the ship around double quick time and bringing home the golden fleeces.That's the whole point of having a ship, isn't it?Rather than walking to market every sabbath?

  3. http://www.1yachtua.com/medit-marinas/Mediterranean_Sailing/mediterranean_winds.shtmI've nabbed this image without copyright so I might have to delete it i f they don't give me per.Originally posted by Jefferson White:

    Apostle Paul's ShipwreckAn Historical Examination of Acts 27 and 28Following the Apostle Paul's missionary journeys, he was arrested in Judea, tried, and then transported as a prisoner to Rome.From the standpoint of historical evidence, the account found in the book of Acts recording Saint Paul's voyage and shipwreck is supported by a wealth of detail. History provides us with a striking meteorological and nautical confirmation of the biblical record.

    http://www.parsagard.com/shipwreck.htmThis is very readable and interesting if you are interested in history or navigation. Since I am interested in both and in the scriptures I found it fascinating.Doubly so since I am interested in geophysics.

  4. It's worth looking at the account for though it tells a lot about conditions in those days it doesn't specify exactly which days they were:Originally posted by Luke:

    Paul defended himself before King Agrippa but Festus said with a loud voice:"Paul, much learning has made you mad."But he said:"I am not mad but speaking the sober truth. The king knows this for I have been led to believe that none of these things are hidden from him; with nothing sneaky being said.Do you believe the prophets King Agrippa?I know you do."Agrippa said to Paul"You'd persuade me to be a Christian.""I would to God, not only that but also all that hear me this day, were such as me."The king rose with the governor, Bernice, and their advisors, deciding:"This man has done nothing worthy of death or of bonds. He might have been set at liberty, if he had not appealed to Caesar."Acts 27It was determined we'd sail to Italy, delivering Paul and certain other prisoners to Julius, a centurion of Augustus' band. Boarding an Adramittan ship, we set off, meaning to sail by the coasts of Asia. Aristarchus, a Macedonian of Thessalonica came with us.The next day we touched at Sidon. And Julius gave Paul liberty to go to his friends to refresh himself. From there we sailed under Cyprus, because the winds were contrary; sailing over the sea of Cilicia and Pamphylia, we came to Myra, a city of Lycia.There the centurion found an Alexandrian ship sailing to Italy and put us aboard. We sailed slowly, for many days, barely making Cnidus because of the winds, we sailed under Crete, over against Salmone and just past there, came to The Fair Havens; near the city of Lasea.When much time was spent, and sailing was now dangerous, because the fast was now already past, (It got late in the season?) And Paul admonished them:Sirs, I perceive that this voyage will be with hurt and much damage, not only of the lading and ship, but also of our lives.Nevertheless the centurion believed the master and the owner of the ship, rather than Paul. And because the haven was not good to winter in, he was persuaded to try for Phenice an haven of Crete, to winter between the south and north west (points?)The south wind blew softly, so thinking they were safe, they sailed close by Crete. But not long after there arose against it a tempest called the Euroclydon. (North easter.) This drove the ship and, running under an island called Clauda, we struggled to haul in the ship's boat with which they undergirded the ship and, fearing quicksand, struck the sails.Thus driven, tossed in the storm, the next day they lightened the ship. And the third day we cast out with our own hands the tackling of the ship. (Either all hands made the ship safe -throwing broken tackle over the side or dropping sea anchors.)When neither sun nor stars in many days appeared and no small tempest lay on us, all hope that we should be saved diminished. (What little reliance there was in navigation was lost by three days dead reckoning in such a storm and the ship was suffering, probably leaking badly.)After long abstinence, Paul stood in the midst of them, and said:"Sirs, you should have listened to me and not sailed from Crete and come to this harm and loss. Be of good cheer: for there shall be no loss of any man's life among you, though the ship will be lost."For there stood by me this night the messenger of the God I serve, saying:"Fear not, Paul; you will be brought before Caesar: and see, God has given you the lives of all that sail with you.However, we must be cast upon a certain island.""When the fourteenth night came, as we were driven up and down the Adriatic, about midnight the crew deemed that were near some country;Sounding the depth they found it twenty fathoms (a shore.) When they had gone a little further, they sounded again, and found it fifteen fathoms. Fearing rocks, they cast four anchors out of the stern, hoping for daylight.The shipmen were about to flee, letting down the boat disguised as casting anchors out of the foreship, Paul said to the centurion and to the soldiers:"Except these abide in the ship, ye cannot be saved." (All who leave the ship will die.)So the soldiers cut off the ropes of the boat, and let her fall off. At first light, Paul encouraged them to take meat, saying:"This day is the fourteenth day that ye have starved yourselves and continued fasting, having taken nothing till now.Please to take some meat for your health: for there shall not an hair fall from the head of any of you."After speaking, he took bread, and gave thanks to God in presence of them all: and when he had broken it, he began to eat. Then they cheered up and ate. There were in the ship two hundred and seventy six souls. When they had eaten enough, they lightened the ship, casting the wheat into the sea.At daylight, they did not recognise the land: but they found a creek with a shore they hoped it was possible to get the ship in. So they took up the anchors, committed themselves to the sea, loosed the rudders and hoisted the mainsail and made toward shore.Falling into a place where two seas met (crossing the bar?) they ran the ship aground. The forepart stuck fast, unmoveable, but the stern was broken with the violence of the waves.(Under the mainsail they would have prevented the ship banking and twisting and being dashed to pieces, without a good crew to see to this in a difficult sea they would have broken to pieces, side on to the waves.)The soldiers determined to kill the prisoners, lest any escaped. But the centurion, willing to save Paul, stopped them, commanding those who could swim to dive in and get to land. The rest, on boards and wreckage escaped all safe to land.

    Acts 26 – 27 http://www.biblegateway.com/passage/?search=Acts+27&version=KJV

  5. I've been assuming it was a Levant wind:The wind rises in the central Mediterranean or around the Balearic Islands and blows westwards reaching its greatest intensity through the Strait of Gibraltar.The winds are moist carrying fog and precipitation in the eastern side of the Strait, but dry in the western side, as the moisture rains on the mountains between Algeciras and Tarifa. The winds are well known for creating a particular cloud formation above the Rock of Gibraltar;In Almería, the winds are well known for making the temperatures rise as the wind blows from the desert interior of the province. The Levanter winds can occur at any time in the year, but are most common from May to October.So it isn't that one either!I'll get there sooner or later.Bloody weather.

  6. Originally posted by Weatherlawyer:


    It's a lloopp that won't pass muster. Lok up the eather conditions in the western Mediterranean for this date 8 November 2011 if you care to find out more.Here is what the Wikipedia says about the cause of the mistral:The mistral takes place each time there is an anticyclone, or area of high pressure, in the Atlantic between Spain and the southeast of France, and an area of low pressure around the Gulf of Genoa. When this happens, the flow of air between the high and low pressure areas draws in a current of cold air from the north which accelerates through the lower elevations between the foothills of the Alps and the Cevennes.The conditions for a mistral are even more favorable when a cold rainy front has crossed France from the northwest to the southeast as far as the Mediterranean. This cold, dry wind usually causes a period of cloudless skies and luminous sunshine, which gives the mistral its reputation for making the sky especially clear. There is also, however, the mistral noir, which brings clouds and rain. The mistral noir occurs when the Azores High is extended and draws in unusually moist air from the northeast.So I doubt it is that one.

  7. It takes a few weeks to build up a system large enough to develop an hurricane.The above description sees them at see for 14 stressful days and several more they should have waited in.14 days is 2 spells. OK in November you can get a couple running to 8 days and some. But having, more or less a sustained system at full pelt for two lunar phases means there is a condition to the times of the phases and the declinations and probably the apsides (perigees and apogees) involved all adding to the mix. It should be almost straightforward to gauge the actual date for this event.All we have to know is what the Phoenecians, Tyrhennians, Macedonians, Egyptians, Lybians, Moroccans, Spanish, French, Italians, Greeks and all the others knew about the winds in the Med.For though modern reasonings give the causes as geostrophic, it seems clear tyo me that the wnds only develop in strong positive cycles where a blocking High and relatively deep Lows can cause them.

  8. The Mistral mistery?The mistral is a strong, cold north-westerly wind system that blows from Southern France into the Gulf of Lions (See locater map below). Although strongest in the Gulf of Lions, with sustained winds often exceeding 40 kt, and gusts sometimes to 100 kt, its effects are often felt past Sicily into the eastern portion of the Mediterranean basin. Wave heights associated with the mistral are commonly 15-20 ft (4.5-6.0 m) and have sometimes reached a maximum height about 30 ft (9 m).The mistral is most common in winter and in spring with the strongest episodes tending to occur in the transition between those two seasons. Duration of effects with winds exceeding 30 kt for over 65 hours have been reported at some locations.A favored sequence for mistral development is passage of a cold front into the Gulf in advance of a short wave trough at upper levels. The upper- level trough produces south-westerly flow aloft and positive vorticity advection over the position of the cold front in the Gulf.This pattern leads to cyclogenesis in the Gulf of Genoa. As the upper level trough advances so that northerly winds aloft are in phase with the northerly surface flow over Southern France, strong mistral winds occur (Fett, et al, 1981).Mistral winds have been well documented in literature, as in the previous reference, with satellite visible and infrared data, and conventional weather reports.With the advent of Special Sensor Microwave Imager (SSM/I) data in the late 1980's it was possible to directly measure wind speed effects and changes in total integrated water vapor associated with a mistral. This study shows examples of infrared and SSM/I imagery obtained during such an event. Damn.Lost the link.

  9. ,Hmm,interesting. I have never read anything like this before.But i am sure gonna try to fold some paper to make the compass rose,

  10. Originally posted by Zulia:

    Tot MomotZulia # Wednesday, November 9, 2011 7:17:45 PM,Hmm,interesting. I have never read anything like this before.But i am sure gonna try to fold some paper to make the compass rose,

    It's pretty obvious stuff really.People say the daftest things about our ancestors but what you use is wha t you have when you have to have it.You don't steer a boat along a chart. And when you have to climb rigging to adjust sails you aren't going to bother if you don't have to, not if you are doing it for a living.And if you are just out for a joy ride on a small boat you don't have much need anyway.Off the coast of CoramandelWhere the sailors ride the swellThere, boats are naught but tree lumpsTheir charts are where they dwell.But for stately Spanish galleonsOars are what you need In the places they dump their horsesIn the black sargasso weed.

  11. Originally posted by Weatherlawyer:

    It should be almost straightforward to gauge the actual date for this event. All we have to know is what the Phoenecians, Tyrhennians, Macedonians, Egyptians, Lybians, Moroccans, Spanish, French, Italians, Greeks and all the others knew about the winds in the Med. For though modern reasoning gives the causes as geostrophic, it seems clear to me that the winds only develop in strong positive cycles where a blocking High and relatively deep Lows can cause them.

    That was badly written but I had already been blown off course while surfing for information.I had started out intending to find links to the names of the winds, as I was attempting to work out the causes. Then I found that book about Paul's journey.A "spell" of weather is what happens everywhere between one lunar phase and the next. The moon is the original cause of the weather but not directly.For an hurricane to run for 14 days (which is about 2 lunar phases) the lunar phases have to have more or less the same effect:Two stormy spells.It should be relatively easy to locate two such runs in a catalogue of lunar phases, once you know what to look for.If you can find them, then the next time they occur or if such a run of phases has occurred in recent history then weather details from them will be available.The other way of doing it is to find reports of such an hurricane in the Med that lasted about 2 weeks and ran along the same course, then look up the times of the lunar phases for those dates.Then you will know what year St Paul was almost lost at sea. And you will also have established a "certain" historical date. There are only about 2 or 3 of them for Jesus' time.(His birth and his death. Coincidence or what?)Let me rewrite the above quote:From the quote:It should be almost straightforward to gauge the actual date for this event. (The journey to Malta.) All we have to know is what all the locals knew back then) the Phoenecians, Tyrhennians, Macedonians, Egyptians, Lybians, Moroccans, Spanish, French, Italians, Greeks and all the others.)Surely modern navigation and meteorology can do that? Modern reasoning about the causes of winds makes believe that the shape of the land forces air into geostrophic winds.(Air flows along the lie of the land and gets compressed in valleys.)It seems clear to me that the winds only develop in strong positive North Atlantic cycles where a Blocking High and relatively deep Lows can cause them. For if air gets compressed in valleys, it will stop flowing, won't it?Think about it.If a leaking balloon lets air flow into a large room, the air is lost and the balloon deflates. But if it flows into a thimble the air pressures balance. The air isn't forced to move anywhere.Even if that were not so; why would a gently expanding flow of air continue over the sea as an hurricane?Forceslike that needs to be applied continually.Virtually nothing written or taught about how stuff happens in meteorology stands up to logic and the three basic laws of motion.For instance:Think about what you know about the causes of thunderstorms.I bet you know the basics, even if you might have difficulty explaining them.Something about calm air being heated by warm earth and rising so fast it sets up a wild current?So how does that work at night?OOH! Never thought of… errrmmm…How do hurricanes start?Something about the sea temperature being abnormally high?In cloudy weather; at sea; at night?Really?Not sure now are you?Well"they" must know!OK.Go and ask them.

  12. Originally posted by Weatherlawyer:

    It seems to me, winds only develop in strong positive North Atlantic cycles where a Blocking High and relatively deep Lows can cause them. For if air gets compressed in valleys, it will stop flowing, won't it?

    High pressure rotates one wayLow pressure rotates another.(The cutting off point is about 1016 millibars.)When the North Atlantic has a strong series of pressure systems set up, that is known as a positive North Atlantic cycle.A situation like that, when it gets out of hand is called a "Singularity". The anticyclones become blocking Highs.They dominate wherever they form for the complete run of spells. Low pressure systems have to change course and go around them. Different regions get rain. Other regions that rely on seasonal rains may get none. Some regions will get fires and some will get floods.Some will get super cyclones.Normally these blocks sit over the Azores and the Poles. People who live there deal with them the way we deal with our stuff.When a stron Low sits next to a strong High the wind that flows bewteen them is a composite of anticyclonic and cyclonic. For when they are side by side the two such sides are flowing in the same direction.This is the cause of Snow in Britain in winter and of Lake Effect in North America.SO it stands to reason that it is also the cause of strong winds elsewhere when the same situation develops.The directions of these winds merely depends on where the Highs and the Lows meet.Get two bits of paper and place them side by side.Rotate one in an anticlockwise direction and rotate the other in a clockwise direction.Notice that the sides where the papers meet are both going the same way.Well air can do that as well.The real trick is not in understanding such a simple explanation but in guessing why the two systems don't just mix and cancel each other out in the first place.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s