Public Information Statement
Issued by NWS Charleston, SC

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NOUS42 KCHS 010724

Public Information Statement
National Weather Service Charleston SC
324 AM EDT Thu Aug 1 2019


The National Weather Service in Charleston is responsible for the
dissemination of coastal flood watches, warnings and advisories
as well as high surf advisories for all of south coastal South
Carolina and north coastal Georgia. Forecasters use a variety of
data sources to help monitor and forecast tidal levels along the
coast. These sources include but are not limited to tide gages
operated by NOAA`s National Ocean Service (NOS) at Charleston
Harbor SC and Fort Pulaski Georgia.

Unique topography and large tidal ranges make south coastal South
Carolina and north coastal Georgia highly susceptible to
astronomical high tides associated with the lunar cycle.
Forecasters will issue a coastal flood advisory whenever tide
levels are expected to meet or exceed established thresholds for
shallow coastal flooding. Shallow coastal flooding typically
begins along the lower South Carolina coast when water levels
reach 7.0 ft mean lower low water (MLLW) in the Charleston Harbor
and across north coastal Georgia when levels reach 9.2 ft MLLW at
Fort Pulaski.

Impacts: only minor impacts can be expected during shallow
coastal flooding events. Some minor inconveniences from standing
sea water may occur particularly if rain falls during the high
tide cycle. This is because storm drains that usually empty into
marshes, rivers or harbors may become backed up with sea water.
If heavy rains develop during this time, a more substantial
flood threat could develop since storm drains will be full.
Downtown Charleston is particularly vulnerable to flash flooding
when heavy rains occur during an astronomical high tide.

Forecasters will issue a Coastal Flood Watch when significant
damage from moderate to severe coastal flooding is possible within
12 to 36 hours, but the severity and timing of the highest tides
are still somewhat uncertain. Significant flooding and damage
typically begins across south coastal South Carolina when tide
levels reach 8.0 ft MLLW in the Charleston Harbor and 10.0 ft MLLW
at Fort Pulaski. These tides typically pose a significant risk to
both life and property for those living along beach fronts as
well as the adjacent marshes, rivers, sounds and harbors.

Forecasters will issue a Coastal Flood Warning when there is a
high probability that damage from moderate to severe coastal
flooding will occur, usually within 12 hours. A risk to both life
and property exists.

Impacts: Significant impacts can be expected. These include but
are not limited to severe beach erosion, strong rip currents and
significant ocean overwash which may result in damage to nearby
structures and roads. Access roads to the beaches and barrier
islands may become cut off for several hours prior to and after
high tide. Highway 80 heading to Tybee Island from Savannah is
particularly vulnerable to becoming inundated and impassable
during coastal flood situations.

A High Surf Advisory is issued by forecasters whenever seas of 8
ft or higher are expected to occur across the coastal waters or if
breakers of 5 ft or greater are expected to occur within the surf

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