Understanding Weather and Tides

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folky
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Understanding Weather and Tides

Post by folky » Thu Oct 07, 2010 11:38 pm

I noticed a post on the Thames Forums about Wind directions Help and Stuff like that So i tought i would cobble something together that might help you guys understand things alittle more.
If im wrong about any of this stuff lemme know as i Got most of it from the net anyways so its even been alittle bit of a learning experence for me to.

Having an awareness and basic understanding of the tides will determine when you travel to a beach or estuary to fish and hopefully Catch something. The Problem with most fishing marks is that not all the marks fish at the same state of the tide. Like my local areas of seabrook and nearby hythe beaches, the area fishes best from high water down. You are generally wasting your time during the flood unless it is really rough, or its night.

If you are local to the coast, get hold of a tide table for your area, if not tide times can be found on the internet, like http://www.tidetimes.org.uk/ or http://www.bbc.co.uk/weather/coast/tides/ and http://www.bbc.co.uk/weather/coast/

The tide tables are usually for the nearest commercial port so be sure to look on the back for local time adjustments. E.g for Folkestone add 11 minutes to Dover tide times.

This is what you might see on one day in a tide table

0600 6.2m
1200 1.1m
1800 6.3m
0000 1.2m

In the UK it takes 6 hours to go from high to low tide and 6 hours to go from low to high tide resulting in 2 high tides and 2 low tides over a 24 hour period. In Pembrokeshire the tidal range can be up to 7 metres so it is quite a significant force to be reckoned with. Not like other parts of thew world where you have 2 tides a day taking 12 hours to rise and fall a metre and therefore it is pretty negligible. Each day the tide moves on from between 45-mins to 1 hour.
Below is a diagram of the Rule of Twelfths which helps explain that the tide does not flow at a constant rate. This is useful to determine how much beach space you are likely to have or how strong the tidal flows will be at any point during the tide.

Image

Imagine that this diagram represents the rise and fall of the tide on a harbour wall. In the first hour of the rising tide 1/12th of the total volume of water floods the harbour. In the third hour 3/12th of the total volume of water floods the harbour; this is as much water in one hour as there was in the first 2 hours combined. This means that the tidal flow is at its strongest and the beach is going to disappear very quickly in the 3rd and 4th hours.
The left hand side of the diagram illustrates the difference in tidal range between Spring tides and Neap tides. Spring or Neap tides can be recognised by looking at the tidal heights given in a tide table. Spring tides are high high tides and low low tides. Neap tides are Low high tides and high low tides. The reason for this variation is related to the orientation of the moon and the sun in relation to the earth as illustrated below. The tides are caused by the gravitational pull of the moon but the sun has an affect as well.

When the sun and moon are in line with each other, we experience a combined gravitational pull resulting in Spring tides. When they are offset from each other there is less of a Gravitational force resulting in Neap tides. They occur alternatively so One week of spring, one week of neaps, one week of springs and one week of neaps. This gives us a month Which is the Duration of a lunar cycle.

Image

Wind Speed and Directions can also affect how a mark is going to fish, Be sure to note Units of wind speed (mph, Knots etc) 1 Knot = 1 nautical mile per hour 1 nautical mile = 1.1 of land mile Roughly 12 Knots = 15 mph. Wind Direction is determined by where the wind if coming from.

Weather systems ie: Low and High pressure systems can also affect how fish feed. It has been known for a long time that the barometric pressure has an effect on fishing. How the pressure directly effects the fish is still not fully understood, but knowing how to use the barometric pressure readings can greatly increase your chances of catching fish, especially in shallow waters.

Low Pressure System

Image

Anti-Clockwise winds, bending inwards
Tightly Packed Isobars
Changeable Winds
Strong Winds
Fast Moving- easier to predict weather and system's movement


High Pressure system

Image

Clockwise winds, Bending outwards
Wider spaced isobars
Static Weather
lighter Winds
Slow moving harder or predict Weather and system's movement
Last edited by folky on Fri Oct 08, 2010 9:27 am, edited 1 time in total.



rabbi2
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Post by rabbi2 » Fri Oct 08, 2010 6:14 am

A good post so I have made it a sticky. Well done
Cheers
keith

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Judgegeoff
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Post by Judgegeoff » Fri Oct 15, 2010 2:12 pm

Hi Folky,
Thanks for your post, it was most educational. I was particularly interested by the 'Rule of Twelfths' - it has answered questions thart I have had for some time.
Cheers, Geoff

geordiesandman
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Post by geordiesandman » Sat Oct 16, 2010 9:03 am

very informative. well done mate

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