weather

Only five days until I leave for the Laser Masters Worlds in Terrigal. Meanwhile Andrew Campbell has this inspiring weather update on his blog…

With four days of rain and onshore breezes and swells, New South Wales and the Central Coast is trying to wring itself out and get settled before the Laser World Championships starts here on Wednesday. While most of the counties have been in months long drought, the top stories are about flash floods swallowing objects such as Rescue Fire Trucks and small villages. The entire month of February’s expected rain has arrived in it’s first four days.

All the while the swell has rolled in bigger and bigger each day onto our little beach under the faint protection of a natural jetty beside ‘The Haven.’ I know of at least four boats in the last week that have been gobbled up by rogue breaking sets of waves and come ashore with broken masts, torn sails and thoroughly embarrassed sailors amongst cheering crowds of onlookers.

Last night apparently the race committee boat, which was peacefully anchored alongside the local fishing fleet, broke loose from it’s ground tackle and rode ashore to be found this morning full of a mix between buckets of rain water and sea water from the waves breaking into it.

All that and our forecast is calling for the swell to potentially increase over the next few days as the low pressure system intensifies. That could make it difficult getting through the already meter-high beach break, but we’ll see what happens.

Here is the race committee boat, high and not-so-dry.

According to the Laser Worlds Championship website…

Local police, the NSW Fire Brigade, inclusive of a Hazardous Materials Response Unit arrived at The Haven shortly after 10.00am this morning and are working away to lift the waterlogged and sand drenched boat out and onto land, where it will be inspected. It is yet to be determined whether the boat can be salvaged or not.

Yikes. What have I let myself in for? If the weather has wrecked the committee boat, what chance do we poor Laser sailors have? Now where is that advice on how to deal with fear?

Original post by Tillerman and software by Elliott Back

Forecast for tomorrow where I am now
High 40 degrees F
RealFeel 29 degrees F
Cloudy, breezy with a mix of snow and rain in the afternoon

Forecast for tomorrow where I’m going to be later this week
High 79 degrees F
Wind speed 11 knots
Waves 1.7m

Before the middle of January, I’m planning on ticking off at least the first seven of my one hundred days of Lasering in 2008. But can I sail more days than Edward next year?

Original post by Tillerman and software by Elliott Back

SUN
NE WINDS 25 TO 30 KT WITH GUSTS UP TO 40 KT. WAVES 2 TO
4 FT…EXCEPT UP TO 8 FT AT THE BAY ENTRANCE. RAIN…SNOW AND
SLEET IN THE MORNING…THEN RAIN IN THE AFTERNOON. VSBY 1 NM OR
LESS…INCREASING TO 1 TO 3 NM IN THE AFTERNOON.

SUN NIGHT
W WINDS 25 TO 30 KT WITH GUSTS UP TO 50 KT. WAVES
2 TO 4 FT…EXCEPT UP TO 10 FT AT THE BAY ENTRANCE. A CHANCE OF
SHOWERS IN THE EVENING…THEN A CHANCE OF SNOW SHOWERS AFTER
MIDNIGHT. VSBY 1 TO 3 NM.

Hmmm. Rain, snow, sleet. 40 knot gusts. Doesn’t look like ideal weather for my first day of Laser racing in two months.

Original post by Tillerman and software by Elliott Back

The second in a series of articles discussing Stuart Walker’s article in Sailing World on Unlocking the Mysterious Lake Winds with help from a “translation” of part of the article provided by Tom Donlan.

In Part 1 of this series, we set the scene by talking about “gradient” and “thermal winds” and why local thermal winds are often the dominant factor in lake sailing.

In the second part of the second paragraph of his article, Dr Walker discusses the kinds of wind to expect on a lake on a clear day when the sun is shining. This is classic Walker…. one sentence running on for nearly 70 words… technical words explained in phrases in parentheses… text galloping madly on and and on.

So let’s take it slowly and find out about each kind of wind one by one. I’ve split Walker’s words of wisdom into numbered bullet points, one for each type of wind, to make it somewhat easier to follow.

Cold lakes can only expect a sailing wind on clear days in the presence of insolation (surface heating by the sun), and the winds that are then most likely are

1. a morning offshore downslope wind,

2. an afternoon onshore lake breeze,
3. or an afternoon offshore expansion differential wind (created when the pressure levels above an elevated lake fail to rise as much as those above the surrounding heated lowlands).
4. Then thermal turbulence (heated air rising and expanding and cooler air sinking above the near-shore heated land) brings the cool air on the upper mountain slopes down to the lake
5. or brings the cool marine air onshore in a lake breeze
6. and brings upper, higher velocity airflow in an overflowing gradient or expansion differential wind offshore onto the lake surface.

The first two winds seem fairly straightforward. Expect air flowing over the land on to the lake in the morning. And then as the land warms up in the sun, expect a thermal breeze blowing towards the land in the afternoon.

Or as Donlan puts it (with my bullet points added again)…

On a clear, sunny day, a lake sailor may experience

1. a morning offshore wind coming down the slope from surrounding hills and then

2. an afternoon thermal lake breeze blowing toward the warm shore.

So far so good. If only life were so simple.

Another option according to Walker is an offshore breeze in the afternoon, or as he puts it, “an afternoon offshore expansion differential wind (created when the pressure levels above an elevated lake fail to rise as much as those above the surrounding heated lowlands.)”

You see, this is why I find Walker hard to read. I trust his information is correct because of his reputation but I don’t find that last idea very helpful. I sort of understand the physics of why the situation he describes would cause an offshore wind. But I want to know when that condition would occur. And why. And how I can predict when it will happen. It’s not much use to be told in effect, “in the afternoon the wind may blow offshore; then again it may not.”

Let’s see if Donlan conveys that thought any more clearly…

A lake high in the mountains, however, may generate an afternoon wind blowing off the shore if there is a great deal of temperature difference between the water and the surrounding land.

Aha. I think I get it now. If the water is warm and the land is cold, then the land may not warm enough to generate a thermal onshore breeze, so you get an offshore breeze in the afternoon instead. At least I think that’s what he means. And at least there’s some information in the Donlan version that I can use to predict what will happen in the afternoon.

And if the thermal onshore breeze doesn’t kick in, Walker says you can get any or all of winds 4, 5 and 6 which basically means

• it could be offshore
• it could be onshore
• it could be the gradient wind.

Thanks Doctor. I feel like one of your patients and you have just described that I have some awful medical condition and when I ask you what it means you tell me, “Well you could go blind, or impotent, or you might die tomorrow.” Thanks Doctor.

Let’s see how Donlan delivers the prognosis…

Heated air rising and expanding above the warm land near shore and cooler air sinking above the water near shore can create turbulence. This disruption can do almost anything.

It can bring the cool air on upper mountain slopes down to the lake, like the morning breeze. It can bring the cool moist air over the lake onshore in a lake breeze. It can even bring strong breezes from the overhead gradient wind onto the lake surface, in whatever direction the gradient wind happens to be blowing. Sometimes it can do all of these things simultaneously within short distances.

lol as they say on the forums. lmao even. I love that phrase, “This disruption can do almost anything.” And then having described the three kinds of winds you might see, he delivers the coup de grace, “Sometimes it can do all of these things simultaneously within short distances.”

Ah. That’s the lake sailing I know. Anything can happen anywhere. Some wind. No wind. Wind from almost any direction. I’m sailing a beat and that boat on the same leg 50 yards away is on a run. Yes, that’s lake sailing.

So, to sum up, what have we learned today? On a sunny day on a lake, expect an offshore breeze in the morning that might be replaced by a thermal onshore breeze in the afternoon if the land warms up enough in the sun. If not, anything can happen and probably will.

Comments welcomed. Especially if I have misinterpreted what the experts say. Does this explanation so far align with your experience of lake sailing?

Original post by Tillerman and software by Elliott Back

I accepted the challenge from TK. I promised I would explain in more simple language what Stuart Walker was trying to communicate in his Sailing World article Unlocking the Mysterious Lake Winds.

Since accepting the challenge last Wednesday I’ve studied the article. I’ve puzzled over the meaning of many of the statements in it. I’ve tried to make sense of them by referring to Stuart Walker’s book Sailor’s Wind. But that left me even more confused.

And then, out of the blue, came an email from Tom Donlan, a J-22 sailor from Annapolis, who is also a professional writer and a great fan of Dr. Walker’s thinking and writing. To my huge relief Tom had taken it upon himself to “translate” the first few paragraphs of Walker’s article. Magic!

So here we go. Walker as translated by Donlan. With a few random jottings from Tillerman along the way…

Walker wrote…

Lake sailing is more complex than sailing on the open sea, but more predictable. A lake, like any body of water enclosed by land, is subject to gradient winds, always offshore, and by thermal winds — the lake breeze itself as well as winds generated by the surrounding terrain.

Believe it or not, even this introductory paragraph left my feeble mind confused. I got stuck on that phrase, “gradient winds, always offshore”. Whaaaat? Last Wednesday I took my almost-two-years-old granddaughter down to the local lake to indulge in one of her favorite games, throwing rocks into what she calls the “ocean”. There was a big low pressure area over Hudson Bay creating a strong southerly “gradient wind” over southern New England. (Don’t worry if you don’t know that term “gradient wind”. Tom will explain it soon.)

Emily and I stood on the northern shore of Lake Whippersnapper with that wind blasting into our faces. And I kept thinking about Walker’s words. Gradient wind always offshore? Sure feels like it’s blowing onshore to me.

So here is Tom Donlan’s opening sentence…

Lake sailing is more complex than sailing on the open sea because the wind is always coming from the land and is therefore more shifty and puffy.

Oh, now I get it. Of course the wind over a lake has been blowing over land before it reaches the lake, even though in different parts of the lake it will be blowing offshore, onshore and even parallel. to the shore. That’s all the good doctor was trying to say. My bad.

But wait. Walker used two technical terms in that first paragraph. “Gradient” and “thermal” winds. I think I know what they mean, but other readers might not. If you don’t, then the rest of the article might not make much sense to you. So Donlan explains these terms …

No matter where you sail, there are two kinds of winds: “Gradient” winds are the winds from a weather system; “thermal” winds are those generated by local temperature differences between land and water.

Fair enough.

In the first sentence of his second paragraph Walker says…

A lake is an oasis of calm in the surrounding land; a pool of cool marine air trapped above its surface protects it from the gradient winds and facilitates the development of thermal winds confined to the lake surface and its surroundings.

Donlan’s version is…

A lake, surrounded by higher land, is less likely to be affected by gradient winds, which blow across the lake higher up than our masts. The smaller the lake, the more true this is. On the lake surface, the dominant winds are likely to be local thermal winds. There may be several different thermal winds in the course of a day.

(Tom confesses that he added the sentence “The smaller the lake, the more true this is”. And the last sentence about several different thermal winds is really a lead-in to the next thought where Walker gets into discussing those different winds.)

But wait. I’ve sailed on some pretty small lakes, probably the smallest lakes that anyone in their right mind would even consider organizing sailboat racing. And I agree that such lakes are shielded to some extent from gradient winds by the higher land around them. And though it’s less intuitively obvious I could even accept Walker’s point that the lake is protected from gradient winds by a pool of cool marine air trapped above its surface. But I’m not sure I accept the implication that small lake sailing is dominated by thermal winds rather than gradient winds.

I remember many summer Sunday mornings on a small lake in New Jersey waiting for the wind to come in. And if there was a gradient wind of any strength at all it almost always reached the lake surface at some point during the day and was the dominant wind for sailing that day.

What’s your experience on this question? Perhaps my New Jersey lake had some geographical factors that made it unusual?

Anyway, thanks to Ton Donlan for helping us out in understanding the insights of Dr Walker. There is lots more to come from both of them next Wednesday in our series on Walker’s Words of Wisdom.

Original post by Tillerman and software by Elliott Back

This week I received an email from TK that challenged me to explain one of Stuart Walker’s articles in Sailing World: Unlocking the Mysterious Lake Winds.

After reading your Wednesday additions of deciphering Dr. Walker, I stumbled into this one. I do a lot of lake sailing and figured I could make it through without scratching my head. Wrong! The itch in the scalp started at about paragraph 2. Phew! I didn’t absorb much of anything and now I need to lie down. Perhaps you can translate!

Wow. I see your point TK. As with much of the good doctor’s writing it seems that there’s a lot of good advice in there, but it’s certainly tough to understand. I may need several posts in the Walker’s Words of Wisdom series to unlock the mysteries embedded in this article.

I’d love to get straight into sailing advice but in order to untangle the messages in this mess, if only for my own benefit, I’m going to have to identify the reasons that Walker’s text is so perplexing…

1. He uses words like “insolation”, “entrained”, “lift-off” and “divergence” that are not part of the everyday vocabulary of normal racing sailors like myself, or that may have specific technical meanings different from their everyday meanings.

2. He writes complex sentences with clauses within clauses, parentheses within parentheses that are very hard to follow. Take this for example.
   

   The likelihood of development and the strength of lake breezes and upslope winds are proportional to the ease of liftoff from the near-lake land (which is proportional to the lapse rate [the disparity between the temperature of the insolated land surface and the overlying air]) and to the coldness of the lake water and are greatly influenced by the direction and temperature of the gradient wind.

3. He uses sentences that are ambiguous to the uninitiated. Take this for example…
   

   Cold lakes can only expect a sailing wind on clear days in the presence of insolation (surface heating by the sun)…

   Does this mean cold lakes will have winds only on those days that are clear and have surface heating by the sun, but never have wind on dull days or on clear days with no surface heating; or does it mean that if it’s a clear day and the land surface is heated by the sun the lake will have wind, but on days that aren’t clear there might be wind for other reasons?

4. He is trying to explain three things. What the wind on lakes does. Why it does it. And what to do about it in a race. Personally I need to understand and grasp the first two before I can learn the third. But these three kinds of information are all mixed up together in the text.
5. There are no pictures.
6. There is paragraph after paragraph of complex, abstruse text with no sub-headings or bullet points to help understand the structure of the article at a glance. How are those 17 paragraphs grouped into larger chunks of message? Or do they all stand alone?
7. He never makes clear what kind of lakes he is talking about. The tiny little puddle I used to sail on in New Jersey, surrounded by trees, only a couple of hundred yards across at its widest point? Larger reservoirs a mile or two across? Much larger lakes like Lake Ontario but sailing within a mile or two of the shore such as at CORK? Long distance racing on major lakes such as Lake Michigan? All of the above?

Did I miss anything?

Maybe it’s my fault. Maybe I don’t read enough books with complex arguments and technical explanations these days. But I don’t think so. I’d wager that I read more non-fiction on heavy and complicated issues than much of the population, and still I find Walker’s writings tough.

But now I’ve identified the major causes of the obscurity I may be able to tease the messages from the code.

Watch this space.

Original post by Tillerman and software by Elliott Back

I wrote a couple of weeks ago in Blind Squirrel about how, through superior powers of observation, deep meteorological understanding and outstanding reasoning abilities, I chose the right side of the race course on the first beat and was first sailor to the windward mark against tough competition in a race in our district championship.

This weekend at the Buzzards Bay Regatta I paid the price for that success.

Let’s think about this logically. On any given beat, there are three possibilities…

1. it doesn’t matter which side of the course you choose
2. it does matter and it’s pretty obvious which is the correct side
3. it does matter but it’s not clear which side is better.

OK. Now ignore the first category and concentrate on just the second and third categories. If they are all category 3 then just by chance you should make the right guess 50% of the time. Factor in some category 2 races, then isn’t it obvious that, statistically speaking, the chance of any reasonably competent sailor choosing the favored side of the course must be more than 50%?

Right?

Wrong!

This weekend I demonstrated to my own satisfaction that the normal laws of logic and statistics don’t apply to this issue. There is some hidden law of the universe that roughly speaking says, “For every beat where Tillerman chooses the correct side of the beat, he must pay for it by choosing the wrong side N times, where N=(1 + George Bush’s age - Tillerman’s age + number of years since Tillerman read a book by Stuart Walker + number of glasses of wine consumed by Tillerman on previous evening). N cannot be less than 3 and could be well over 10.

For example…

On Day 1 of BBR, the wind was swinging around at the start of the day. The race committee tried a start while the wind was in the west and it swung way to the south so they had to postpone the start. It stayed southish for a while, and we got one light air race in.

Then it went west again. Oh no, now it’s south-west. No wait. There’s a north-westerly coming in. Eventually we got a start off with the wind sorta kinda westerly. I didn’t have a great first beat and run so at the start of the second and final beat I had a choice. Right or left. Most of the fleet went left. I figured that, given the earlier push by the north-westerly the wind was just as likely to swing right. And I figured I wouldn’t pass many boats by going left so I went right.

Right was wrong. Left was right. Duh. N=1 and counting.

On Day 3 the pattern was similar. Wind swinging all over the place. Two postponed starts. Eventually we got away in a westerly. I had a decent start in clear air about a third of the way down the line from committee boat.

Ahah, I thought. At least I can learn from my own mistakes. This is like race 2 of day 1. The secret of success is to bang the left corner in expectation of the shift to the south-west. Halfway up the beat I look over my shoulder and see that two boats who tacked on to port out of a start at the committee boat are now about half a mile to windward of me. And everyone who started right of me is way ahead of me too. Huge righty. N=2 and counting.

(Actually that race was abandoned but the hidden law of the universe didn’t know that was going to happen.)

In race 2 on Day 3, a similar thing happened. The wind had settled in to a consistent direction and a few smart souls like me, blessed with superior wind intuition, hit the left side of the beat. Man, that was a good choice. We were gaining bigtime on the dumb shits that went right and by the top third of the beat it looked like we had gained several hundred yards on them. But then a huge righty came in and the lucky fools on the starboard tack layline were reaching in to the mark. Some of them were actually planing to the windward mark! While we brave band of sailors on the left were struggling to the mark on a massive header in spite of our higher intelligence and advanced decision-making abilities.

N=3 and counting.

See what I mean? I am cursed by the hidden law of the universe. How many more races must go wrong before I get it right again?

Original post by Tillerman and software by Elliott Back