Welcome to the NavList Message Boards.

NavList:

A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Message:αβγ
Message:abc
Add Images & Files
    or...
       
    Reply
    Re: Big Full Moon and Perigee Spring Tides
    From: John Huth
    Date: 2011 Mar 17, 12:18 -0400
    I tried to hunt around a bit for the definition of high and low astronomical tide.  I couldn't get a really good answer, except an 'operational' definition, listed below.   US charts use MLLW for the bathymetric datum - "mean lowest low water" - i.e. over the course of a lunar month.

    LAT, "lowest astronomical tide" seems to be the lowest level based on measurements over the course of some length of time.   So, perhaps Frank's perigean moon near the equinox qualifies?

    Still, I can imagine far more rare circumstances that would contribute to a super-high or super low tide, but these might happen once every 19 years or so.


    HAT - Highest astronomical tide
    LAT - Lowest astronomical tide

    Highest astronomical tide (HAT) is the highest level, and Lowest astronomical tide (LAT) the lowest level that can be expected to occur under average meteorological conditions and under any combination of astronomical conditions. HAT and LAT are not extreme levels, as certai meteorological conditions can cause a higher or lower level, respectively. The level under these circumstances is known as a 'storm surge' ('negative surge' in the case of level lower than LAT). HAT and LAT are determined by inspecting predicted sea levels over a number of years.

    Note
    The value of HAT and LAT may not have the same value as other reference sources. The value given in any source is dependent on the years of inspection, the period which the inspection covered and the exact location and calibration of the tide gauge used. The values listed here have been produced from predictions over a 19 year period from 1996 to 2015 with the gauges being maintained and calibrated to a uniform standard by the Tide Gauge Inspectorate at Proudman Oceanographic Laboratory


    On Thu, Mar 17, 2011 at 8:36 AM, Apache Runner <apacherunner---.com> wrote:
     
       
    Reply
    Browse Files

    Drop Files

    NavList

    What is NavList?

    Join NavList

    Name:
    (please, no nicknames or handles)
    Email:
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.
    Email:

    Email Settings

    Posting Code:

    Custom Index

    Subject:
    Author:
    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site