content.html

<p>
	<strong>Winds</strong>&nbsp;can be gentle, hardly felt, like zephyrs flitting about in a local area, or they can be vast movements of air moving swiftly across oceans and continents at low and high altitudes.</p>
<p>
	A local area scale example of the effect of differential heating on air is well known to experienced sailors.</p>
<p>
	A parcel of air over land in summer at noon will be warmed by the land more than a parcel over water.&nbsp; Both are receiving the same amount of solar heat, but it takes more heat to raise water one degree than it does for land.&nbsp; Hence&nbsp;the parcel over the warmer land will warm more and rise, and the heavier cooler air over the water will flow in under it to take its place.&nbsp; This phenomenon gives birth to the so-called daytime &ldquo;sea breeze,&rdquo; the breeze from&nbsp;sea to land well known to coastal sailors.&nbsp; Air will sink over the water to replace the sea air going from&nbsp;there&nbsp;inland, leaving an area aloft over the sea into which the rising air from the land will flow.&nbsp; This completes the cycle: up over&nbsp;land, out to sea, down over the sea, in toward land, shown below.&nbsp; Sailors feel the bottom part of this loop.</p>
<p>
	<img alt="Winds" src="/course/img/ed6e9f70eb8613ca466e391fdb3d4360/b0441bbab94e70d4705157f91ffbd762/" style="width: 396px; height: 273px;" /></p>
<p>
	<br />
	<span style="font-size: 12px;">The reverse occurs at night, particularly clear nights when the earth can radiate a lot of heat out to space.&nbsp; As before, for a given amount of heat loss, the land will cool more than the water.&nbsp; This drives the air flow in the reverse direction, creating a &ldquo;land breeze&rdquo; as the warmer air over the water rises and cool dense heavy land air flows out to replace it.&nbsp; This can surprise an unwary sailor, when as the night wears on and he sleeps at anchor, the land breeze alters the wind and his boat swings to a new direction.&nbsp; Did he consider this effect when he anchored?</span></p>
<p>
	During daytime hours sea breezes can yield useful sailing conditions just next to a coast, when there might be no wind further offshore and none otherwise shown in weather forecasts.</p>
<p>
	Sea and land breezes demonstrate the importance of surface temperature in influencing air temperature and its motions.&nbsp;</p>
<p>
	We all know about the high altitude jet streams that are basically rivers of air moving from one part of the world to another, creating all kinds of weather with opportunities and challenges for airlines. Being caught in head winds extends the flight, while with tail winds time is saved. Sailing in winds is not unlike flying in&nbsp;wind, just more challenging.</p>
<p>
	Light surface winds produce &ldquo;cat paw&rdquo; looking waves, whereas stronger winds produce sharper and higher waves. As winds increase, energy is transferred to the water, waves become higher, and spray begins blowing off the crests of waves. Experienced sailors can often accurately determine wind speed by watching the wave.</p>
<p>
	When reading a weather map or wind map you need to know the symbols used. Make sure you understand this table especially the direction. The barbs are the tail of the arrows.</p>
<p>
	<img alt="Wind symbols" src="/course/img/20db546504c66a27533ab2faf633693b/b0441bbab94e70d4705157f91ffbd762/" style="width: 500px; height: 458px;" /></p>
<p>
	In compass named directions, the wind directions in the&nbsp;table above are:</p>
<ul>
	<li>
		5 knots northeasterly</li>
	<li>
		10 knots northwesterly</li>
	<li>
		25 knots easterly</li>
	<li>
		50 knots&nbsp;southsoutheasterly</li>
</ul>
<p>
	The following table is a rough summary of wind speed and effects. The column on reefing is of course a matter of choice and boat type. For example, in the large catamarans, you&#39;ll reef the mainsail first because of it&#39;s larger size over the genoa. Roller furling systems allow the crew to reef the sails to any position, however the sails will typically have marks on them for the recommended first reef and second reef points. Expected boat speed is stated for an average cruising type boat. Race boats can go much faster.</p>
<p>
	&nbsp;</p>
<table border="0" cellpadding="5" width="100%">
	<tbody>
		<tr>
			<td bgcolor="#999999">
				<p align="center">
					<strong>Wind Speed<br />
					(knots)</strong></p>
			</td>
			<td bgcolor="#999999">
				<div align="center">
					<strong>Wave Action</strong></div>
			</td>
			<td bgcolor="#999999">
				<div align="center">
					<strong>Expected Boat Speed<br />
					(knots)</strong></div>
			</td>
			<td bgcolor="#999999">
				<div align="center">
					<strong>Effect on Boat and Reefing Recommendation</strong></div>
			</td>
			<td>
				&nbsp;</td>
		</tr>
		<tr>
			<td bgcolor="#CCCCFF">
				0-5</td>
			<td bgcolor="#CCCCFF">
				calm - ripples</td>
			<td bgcolor="#CCCCFF">
				0-2 knots</td>
			<td bgcolor="#CCCCFF">
				No heeling</td>
			<td>
				&nbsp;</td>
		</tr>
		<tr>
			<td bgcolor="#CCFFCC">
				6-10</td>
			<td bgcolor="#CCFFCC">
				1-2ft (0.3 - 0.6 m)</td>
			<td bgcolor="#CCFFCC">
				2-6 knots</td>
			<td bgcolor="#CCFFCC">
				Slight heeling</td>
			<td>
				&nbsp;</td>
		</tr>
		<tr>
			<td bgcolor="#CCCCFF">
				11-15</td>
			<td bgcolor="#CCCCFF">
				2-4ft &nbsp;(0.6 - 1.3 m) white caps</td>
			<td bgcolor="#CCCCFF">
				6-10 knots</td>
			<td bgcolor="#CCCCFF">
				Moderate to heavy heeling</td>
			<td>
				&nbsp;</td>
		</tr>
		<tr>
			<td bgcolor="#CCFFCC">
				16-25</td>
			<td bgcolor="#CCFFCC">
				4-8ft (1.3 - 2.6 m)</td>
			<td bgcolor="#CCFFCC">
				6-12 knots</td>
			<td bgcolor="#CCFFCC">
				Reefing required heavy heeling</td>
			<td>
				&nbsp;</td>
		</tr>
		<tr>
			<td bgcolor="#CCCCFF">
				25-35</td>
			<td bgcolor="#CCCCFF">
				6-15 ft (2 - 4.6 m) spray</td>
			<td bgcolor="#CCCCFF">
				6-12 knots</td>
			<td bgcolor="#CCCCFF">
				2nd reef required &ndash; danger return to base ASAP &ndash; seek shelter</td>
			<td>
				&nbsp;</td>
		</tr>
		<tr>
			<td bgcolor="#CCFFCC">
				35+</td>
			<td bgcolor="#CCFFCC">
				8-20 ft (2.6 - 6.3 m)&nbsp;</td>
			<td bgcolor="#CCFFCC">
				6-12 knots</td>
			<td bgcolor="#CCFFCC">
				Max reefing- extreme danger seek immediate shelter. Employ storm tactics.</td>
			<td>
				&nbsp;</td>
		</tr>
	</tbody>
</table>
<p>
	&nbsp;</p>
<p>
	<strong>Another scale</strong>&nbsp;- The Beaufort Wind Scale is both historically and visually very interesting. It was designed by a British Admiral (Admiral Beaufort) to help large fully rigged vessels determine their sail requirements. It is a classic and still useful for today&#39;s sailors as a guide and component of your dreams to be a frigate captain.</p>
<p align="center">
	<strong><font color="#000099" face="Verdana, Arial, Helvetica, sans-serif" size="3">THE BEAUFORT WIND SCALE</font></strong></p>
<table border="0" cellpadding="2" width="100%">
	<tbody>
		<tr>
			<th align="center" bgcolor="#aaaacC" valign="bottom">
				Force</th>
			<th align="center" bgcolor="#aaaacC" valign="bottom">
				<div align="center">
					Wind<br />
					(Knots)</div>
			</th>
			<th align="center" bgcolor="#aaaacC" valign="bottom">
				WMO<br />
				Classification</th>
			<th align="center" bgcolor="#aaaacC" colspan="1" valign="bottom">
				Appearance of Wind Effects On the Water</th>
		</tr>
		<tr bgcolor="#ccccff">
			<td align="center" bgcolor="#ccccff">
				<strong>0</strong></td>
			<td>
				<div align="center">
					Less than 1</div>
			</td>
			<td>
				Calm</td>
			<td>
				Sea surface smooth and mirror-like</td>
		</tr>
		<tr bgcolor="ccffcc">
			<td align="center">
				<b>1</b></td>
			<td>
				<div align="center">
					1-3</div>
			</td>
			<td>
				Light Air</td>
			<td>
				Scaly ripples, no foam crests</td>
		</tr>
		<tr bgcolor="ccccff">
			<td align="center">
				<b>2</b></td>
			<td>
				<div align="center">
					4-6</div>
			</td>
			<td>
				Light Breeze</td>
			<td>
				Small wavelets, crests glassy, no breaking</td>
		</tr>
		<tr bgcolor="ccffcc">
			<td align="center">
				<b>3</b></td>
			<td>
				<div align="center">
					7-10</div>
			</td>
			<td>
				Gentle Breeze</td>
			<td>
				Large wavelets, crests begin to break, scattered whitecaps</td>
		</tr>
		<tr bgcolor="ccccff">
			<td align="center">
				<b>4</b></td>
			<td>
				<div align="center">
					11-16</div>
			</td>
			<td>
				Moderate Breeze</td>
			<td>
				Small waves 1-4 ft. becoming longer, numerous whitecaps</td>
		</tr>
		<tr bgcolor="ccffcc">
			<td align="center">
				<b>5</b></td>
			<td>
				<div align="center">
					17-21</div>
			</td>
			<td>
				Fresh Breeze</td>
			<td>
				Moderate waves 4-8 ft taking longer form, many whitecaps, some spray</td>
		</tr>
		<tr bgcolor="ccccff">
			<td align="center">
				<b>6</b></td>
			<td>
				<div align="center">
					22-27</div>
			</td>
			<td>
				Strong Wind Warning</td>
			<td>
				Larger waves 8-13 ft, whitecaps common, more spray</td>
		</tr>
		<tr bgcolor="ccffcc">
			<td align="center">
				<b>7</b></td>
			<td>
				<div align="center">
					28-33</div>
			</td>
			<td>
				Near Gale</td>
			<td>
				Sea heaps up, waves 13-20 ft, white foam streaks off breakers</td>
		</tr>
		<tr bgcolor="ccccff">
			<td align="center">
				<b>8</b></td>
			<td>
				<div align="center">
					34-40</div>
			</td>
			<td>
				Gale</td>
			<td>
				Moderately high (13-20 ft) waves of greater length, edges of crests begin to break into spindrift, foam blown in streaks</td>
		</tr>
		<tr bgcolor="ccffcc">
			<td align="center">
				<b>9</b></td>
			<td>
				<div align="center">
					41-47</div>
			</td>
			<td>
				Strong Gale</td>
			<td>
				High waves (20 ft), sea begins to roll, dense streaks of foam, spray may reduce visibility</td>
		</tr>
		<tr bgcolor="ccccff">
			<td align="center">
				<b>10</b></td>
			<td>
				<div align="center">
					48-55</div>
			</td>
			<td>
				Storm</td>
			<td>
				Very high waves (20-30 ft) with overhanging crests, sea white with densely blown foam, heavy rolling, lowered visibility</td>
		</tr>
		<tr bgcolor="ccffcc">
			<td align="center">
				<b>11</b></td>
			<td>
				<div align="center">
					56-63</div>
			</td>
			<td>
				Violent Storm</td>
			<td>
				Exceptionally high (30-45 ft) waves, foam patches cover sea, visibility more reduced</td>
		</tr>
		<tr bgcolor="ccccff">
			<td align="center">
				<b>12</b></td>
			<td>
				<div align="center">
					64+</div>
			</td>
			<td>
				Hurricane</td>
			<td>
				Air filled with foam, waves over 45 ft, sea completely white with driving spray, visibility greatly reduced</td>
		</tr>
	</tbody>
</table>
<p>
	This is pretty hard to remember. Thus, look at the table above and remember the wind conditions force number that you are comfortable sailing in. If force conditions are reported worse then you know not to go out or prepare if you are already out. e.g. force 4 is 11 - 16 knots. This is comfortable for most.</p>
<p>
	Yacht clubs and some harbor masters may fly flags to indicate any wind warnings. These are not internationally standardized so it is best you check for your country and State (yes even States are different in the USA). Don&#39;t go sailing in anything above Small Craft Advisory and note that a Small Craft Advisory is a warning to those in small craft that conditions are dangerous. If you are inexperienced, you should not go out under small craft advisory conditions.</p>
<p>
	Here is a table of the most common wind warning flags and in general works for the USA.</p>
<p>
	<img alt="Wind Flags" src="http://www.nauticed.org/course/img/5097ed3657985ea25b8b1d79de53f5a9/b0441bbab94e70d4705157f91ffbd762/" style="width: 500px; height: 311px;" /></p>
<h3>
	Gusts</h3>
<p>
	Gusts&nbsp;can occur at virtually&nbsp;anytime&nbsp;and can be extremely dangerous for several reasons.</p>
<ul>
	<li>
		If not properly handled, a gust can overpower the rig and cause the mast to come down (demasting)</li>
	<li>
		A gust heels the boat over and throws the crew and gear around</li>
	<li>
		A gust heels the boat making the&nbsp;rudder less&nbsp;effective and thus rounds the boat up into&nbsp;wind&nbsp;and into crossing traffic causing a collision</li>
	<li>
		A gust can broach the boat when sailing with a spinnaker. A broach is like a round up into&nbsp;wind&nbsp;except the boat is held down and on its size because of the spinnaker. It can cause&nbsp;sinking.</li>
	<li>
		A gust can cause the boom to gybe over unexpectedly killing crew members with their heads up.</li>
</ul>
<p>
	Gusts&nbsp;can be seen coming by a moving discoloration of the water. Good crew members point out approaching&nbsp;gusts&nbsp;to the helmsperson and prepare for action such as letting out the mainsail traveler or mainsheet. Helmspersons can prepare to adjust course.</p>
<p>
	Here is a series of&nbsp;gusts&nbsp;in &quot;The Bight&quot; in Norman Island, British Virgin Islands.</p>
<p>
	<iframe allowfullscreen="" frameborder="0" height="360" src="https://www.youtube.com/embed/tjk5ISEOdoA?rel=0" width="640"></iframe></p>
<p>
	Here is a series of gusts created by Katabatic winds in the Marlborough Sounds, New Zealand.</p>
<p>
	<iframe allowfullscreen="" frameborder="0" height="360" src="https://www.youtube.com/embed/GluAM2tNRKo?rel=0" width="640"></iframe></p>
<h3>
	In General</h3>
<p>
	Always keep in mind that you never want to overpower your vessel as this can lead to catastrophic results. As wind velocities increase, the force on a sailboat&rsquo;s rigging and sails is dramatically increased by the squared power. As an example if the wind&nbsp;speed&nbsp;doubles from 5 knots to 10 knots, the force on the rigging quadruples. From 5 knots to 20 knots, the force becomes 16 times greater.</p>
<p>
	Upper atmosphere level winds, jet streams, are not unlike the large water currents that flow through the oceans, they are just in a different media, but both affect safe and fun sailing.</p>
<p>
	As your sailing skills increase, you will learn to observe how the winds seem to affect your main sail, from the top of the mast to the boom. Also, winds that rebound off hills and large buildings will have an impact on your progress.</p>
<p>
	As wind moves across land&nbsp;and/or&nbsp;bodies of water it gains or loses heat from the surface that then produces an infinite array of weather conditions. Masses of winds circulating around either low or high-pressure areas are cyclones. More tightly circulating winds are hurricanes, tornadoes or, at sea - water spouts.</p>