New & Full moon - spring tides
1st & Last quarter - neap tides

The envelope of water around the Earth is always aimed towards sun or moon.

Tide Data Set, ideally 17-18 y.
There are multiple components that determine the height of a tide on any given day... astronomical, topographical, rotational
(distance Earth to moon, alignment Earth to moon, alignment Earth to sun, angle off the ecliptic, etc.)

Over a 17 year period, we measure the tide each day. There's a mathematical procedure developed by Fourier - the Fourier Transform Process - that breaks a wave into its components.
These components can be extracted and loaded into a math program to predict future tides. This sort of process is known as an Empirical process
(def.) Empirical process - when one looks at a system and then tries to describe how it operates based on their observations.

An Exercise in Tide Charts
Thurs, 14th
Disk of moon is 47% covered

Moon Set: 0117 Moon Rise:1025
• H 0055 3.2 ft
• L 0738 0.2 ft
• H 1327 2.5 ft
• L 1914 0.0 ft
• These are Neap Tides

Thurs, 21st
Disk of moon is 99% covered

Moon Set: 0643 Moon Rise: 1816
• L 0136 -0.3 ft
• H 0746 +3.5 ft
• L 1412 -0.2 ft
• H 2005 +3.6 ft
• These are Spring Tides

A number of different statistics can be derived from tide data:

• Mean High Tide
• Mean Sea Level
• Mean Low Water - the av. height of all the low waters
• Mean High Water - the av. height of all the high waters

Minus tides meant that the lowest tides that day will be lower than the usual low tide.
This occurs during spring tides. You don't get that during neap tides.
Low tides during neaps will be above the mean low water level.
High tides during Neap tides are also higher than average.