Weather wind

1
Weather (wind) Tides Anchoring
I cant predict the wind so I use all the
resources available to me to give as much advance
notice as possible. There are lots of reasons
for wind all of them make sense, but in the end
you will use the on-line resources know that
they are based on good science.
2
The sun is the driving force behind weather. As
solar energy reaches the Earth, equatorial
regions heat up more than the poles. tropics.
As land or ocean water warms, it heats the air
next to it and this air begins rising. As the
heated air rises, air from elsewhere flows in to
replace it. If the Earth were not rotating on its
axis, the air flowing in to replace the rising
air would be coming from the polar regions. At
the same time, the air that rises near the
equator would be flowing high above the ground,
to descend and replace the air that's flowing
along the surface toward the
In simple terms, as air begins flowing from high
to low pressure, the Earth rotates under it,
making the wind follow a curved path. In the
Northern Hemisphere, the wind turns to the right
of its direction of motion. In the Southern
Hemisphere, it turns to the left. The Coriolis
force is zero at the equator.
3
One must distinguish between the direction of
deviation caused by the Coriolis force (operating
on its own) and the direction of rotation (when
other forces are present). Both directions of
rotation are evident in both hemispheres
depending upon the whether the flow is around a
high pressure area (the pressure gradient force
points radially outward) or around a low (the
pressure gradient force points radially
inward).In a geophysical flow, such as motion in
the atmosphere or oceans, there is always some
other force operating (such as the pressure
gradient force) or how else would the material
have started to move. The illustration shows a
situation for a northern hemisphere low. The
Coriolis force (Cf) does indeed point to the
right of the flow. But it is slightly over
balanced by the pressure gradient force (pgf)
which points toward the center of the low (the
imbalance is what causes the fluid to move along
a curved path). A good way to convince yourself
of this behavior is to watch the direction of
rotation seen in radar and satellite loops of
storms. It is very easy to see the
counterclockwise rotation around the low pressure
areas in the (northern) hemisphere storms.
4
http//apollo.lsc.vsc.edu/classes/met130/notes/cha
pter9/scales.html
5

• Thermal circulations
• many mesoscale phenomena are the result of a
  thermal circulation
• thermal circulation - a circulation generated by
  pressure gradients produced by differential
  heating
• thermal circulations tend to be shallow - do not
  extend up through the depth of the troposphere
• examples of thermal circulations
• sea breeze
• land breeze
• monsoons
• mountain and valley breezes

6
(No Transcript)
7
(No Transcript)
8
(No Transcript)
9
http//apollo.lsc.vsc.edu/classes/met130/notes/cha
pter9/lakebreeze.html
10
(No Transcript)
11
(No Transcript)
12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
Note - borrowed from
http//apollo.lsc.vsc.edu/classes/met130/notes/cha
pter9/index.html
18
As a cold front passes, the wind veers clockwise
(look from above) If you face the wind, it will
move to your right Watch the barometer it really
works.
When the wind before the rain, Let your topsails
draw again When the rain before the
wind, Topsail sheets and halyards mind
Red sky in the morning, Sailor take warning. Red
sky at night, Sailor delight
When the dew is on the grass Rain will never come
to pass. When the grass is dry at morning
light Look for rain before the night.
19
Weather Last night
PDT UTC-8
20
http//bis_portal.apl.washington.edu/
21
(No Transcript)
22
(No Transcript)
23
(No Transcript)
24
(No Transcript)
25
(No Transcript)
26
(No Transcript)
27
(No Transcript)
28
(No Transcript)
29
(No Transcript)
30
(No Transcript)
31
(No Transcript)
32
(No Transcript)
33
Waves Not usually an issue in the Sound as it is
relatively short Of course wind increases the
waves. The Sound (and lake) are very
deep. Watch out in the Straits. There are
plenty of instances of rogue waves documented
34

• Tides
• Current for sailing
• Depth for anchoring, ground
• Bridge clearance

• Sprint tide, range between high and low tides
  when the moon Is full and new
• Neap tide, range at the moons 1st and 3rd
  quarters
• Average depth and range
• Average low tide excluding spring and neap tides
• Mean lower low water is the average of the lower
  of low tides

35
Tides NOAA charts datum MLLW Tide tables
datum MLLW Bridges datum MHW Difference
between MLLW and MHW varies. There are
charts. At Shilshoe, the difference is 10.4
feet. BN bridge is 44 feet Rule of
12ths Calculate tidal difference (High
Low) Tide will change 1/12 in the first
hour 2/12 in the second hour 3/12 in the third
hour Thus ½ of the water is moved in 3
hours. 3/12 in the fourth hour 2/12 in the
fifth hour 1/12 in the last hour Most of the
water moves (current) between the third and
fourth hours.
36
(No Transcript)
37
(No Transcript)
38
Rule of 60
39
Or look at your GPS and find the bearing to where
you want go Follow that bearing on the GPS For
interest check the boat compass against the GPS
bearing Difference between the boat compass and
the GPS Tides Windage Compass inaccuracy
40
Anchoring Anchors Danforth Plow Mushroom Sandy
Mud Bottom, only Flat, only Protected area Lots
of company The anchoring process Find the
spot Calculate the scope Set up clean rode
cleat Stop boat over anchor point Set anchor
out Back down on it Pay attention to exact
location
Anchoring Never anchor without good
soundings Careful of the depth sounders check
with the lead Use the tide chart to check the
variance
41
You should anchor so that the maximum force will
be taken in the direction the anchor flukes are
pointing. In all our anchorages, you can expect
to swing about the anchor as the tide changes.
We back down hard on the anchor to dig it as
deeply as possible into the mud/sand. If the
anchor is properly set, it will stay that way.
If it is not, it might roll over and (hopefully)
reset.
42
(No Transcript)
43
After tide changed
Anchor practice
Where we started
Rafted to Platypus