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Tide Bulletin Predicts San Francisco King Tide

14 Dec 2016, 7:29 am

Coastal areas of San Francisco are experiencing abnormally high tidal surges this week, known to many as the King Tide. Events like this happen a few times of the year to all coastal communities in the US and are predictable based on the orientation of the moon and the sun. Heavy rainfall this week could amplify the problem and pose infrastructure problems.

Tides are the regular rise and fall of the sea surface caused by the gravitational pull of the moon and sun and their position relative to the earth. About three or four times a year (in the spring and the fall), the new or full moon coincides closely in time with the perigee of the moon—the point when the moon is closest to the Earth. These occurrences are often called ‘perigean spring tides.’ There are some factors we can predict that cause the tides to be higher or lower than what is “normally” seen from day to day.

Here is a look at the Winter 2016 Tide Bulletin for when these high tide events could happen again across the country:

West Coast Outlook
(Includes California, Oregon, Washington State)

When will the tides be higher than normal?
December 11-16; January 10-13

Why will they be higher than normal?
A perigean spring tide will be occurring. This is when the moon is either new or full and closest to earth, higher than normal high tides and lower than normal low tides will occur.
The increased angle of the sun relative to the Earth, which reaches a maximum during the Winter Solstice (December 21).

What kind of impact might I expect along the coast?
Minor tidal flooding along the coast, especially in low-lying areas. If a local storm or large swell are present at this time, increased levels of tidal flooding and coastal erosion may occur.
Lower than normal low tides will also occur.

Northeast Outlook
(Includes Maine, New Hampshire, Massachussets, Connecticut, New York)

When will the tides be higher than normal?
December 13 – 15

Why will they be higher than normal?
A perigean spring tide will be occurring. This is when the moon is either new or full and closest to earth. Higher than normal high tides and lower than normal low tides will occur.

What kind of impact might I expect along the coast?
Due to the topography of the northeast (less low lying areas), tidal flooding will generally not have a significant impact on the coast unless there is a severe storm.

Mid-Atlantic Outlook
(Includes New Jersey, Delaware, Pennsylvania, Maryland, District of Columbia, Virginia)

When will the tides be higher than normal?
During this time of the year, tides will not be significantly higher than normal.

Why not?
Mean sea level is generally lower in the winter months in the mid Atlantic due to colder, ocean water and changes in weather patterns.

Southeast Outlook
(Includes North Carolina, South Carolina, Georgia, Eastern Florida coast)

When will the tides be higher than normal?
December 13 – 15

Why will they be higher than normal?
A perigean spring tide will be occurring. This is when the moon is either new or full and closest to earth. Higher than normal high tides and lower than normal low tides will occur.

What kind of impact might I expect along the coast?
Minor tidal flooding along the coast, especially in low-lying areas. If a storm occurs at this time, increased levels of tidal flooding and coastal erosion may occur. Lower than normal low tides will also occur.

Gulf Coast Outlook
(Includes Texas, Louisiana, Mississippi, Alabama, Western Florida coast)

When will the tides be higher than normal?
The Gulf Coast will not be significantly impacted.

Why not?
In many locations of the Gulf Coast, the tidal range is relatively small compared to other regions of the U.S, so they will not be as significantly impacted by a perigean spring tide.

Cover Photo Credit: Dave R. Image cropped.

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