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000
NOUS41 KGYX 191044
PNSGYX

Public Information Statement
National Weather Service Gray ME
0645 AM EDT Wed Jul 19 2017

The National Weather Service has declared the week of July 17th
through 21st, HURRICANE AWARENESS WEEK in New England.  This is the
third in a series of five public information statements to be issued
by the National Weather Service Office in Gray, containing
information on hurricanes and hurricane safety.

STORM SURGE, WAVES, AND MARINE SAFETY

The storm surge is a large dome of water that is pushed toward
the shore by the force of the winds circulating around the storm.
This advancing surge combines with the normal tides to create the
hurricane storm tide, which can increase the mean water level
15 feet or more.  The greatest storm surge generally occurs just
to the right of the storm track, where the strongest winds of the
storm are blowing onshore, perpendicular to the coast.  In
addition to the surge, wind driven waves in that area can also
cause considerable damage to structures.  This rise in water
level due to the surge can result in severe flooding in coastal
areas, particularly when the storm surge coincides with the
normal high tides. For areas of the coast less than 10 feet above
mean sea level, the danger from storm surge can be tremendous.

Along the New Hampshire and Maine coast, the greatest threat of
damage from storm surge lies in the beach areas south of Portland
and in the Penobscot Bay.

In addition to the speed and intensity of the hurricane, the level
of surge in a particular area is also determined by the slope of
the underwater topography and the shape of the coast line.   A
shallow slope and the funneling effects of a bay will contribute
to a greater surge.  Areas with a steeper continental shelf will
not see as much surge, although large breaking waves can still
present major problems.  Storm tides, waves, and currents in
confined harbors can severely damage ships, marinas, and pleasure
boats.

In northern New England, the greatest factor in determining the
effects of a storm surge is the timing of the surge with respect
to the astronomical tides.  If the storm surge hits at the time
of low tide, little if any coastal flooding will occur.  If,
however, the surge hits at high tide, considerable coastal
flooding, beach erosion, and other damage is possible.
Unfortunately, the exact timing of landfall in northern New
England is often difficult to predict very far in advance, so
plans should be made based on the possibility the surge could
strike at high tide.

Wave and current action associated with the tide also causes
extensive damage.  Water weighs approximately 1700 pounds per
cubic yard, and extended pounding by frequent waves can demolish
any structure not specifically designed to withstand such forces.
Waves generated from distant or approaching storms can also
present a hazard to those who are near the ocean.  Strong rip
currents can carry even strong swimmers out to sea, and unexpected
large waves can wash people from rocks.

Hurricanes have been the cause of many maritime disasters and,
unfortunately, there is no single rule of thumb that can be used
by mariners to ensure safe separation from a hurricane at sea.
In order to minimize risk, mariners should allow for a large
margin of error in the hurricane track and intensity forecasts.
Today, even as our understanding of and ability to forecast
hurricanes increases, there is still considerable error in
forecasting the movement and intensity of these systems.

Average errors in the hurricane track forecast increase
considerably as the forecast projection increases.  The
following list gives average errors of hurricane forecasts for
the 5-year period from 2012 to 2016.  Note that errors for storms
in northern New England are likely greater than these "average"
values due to the acceleration that often occurs south of New
England and due to the comparatively fast movement of the storms
in New England waters.

       Forecast projection       Average Error
            12 hours                25 n mi
            24 hours                40 n mi
            48 hours                71 n mi
            72 hours               103 n mi
            96 hours               149 n mi
           120 hours               196 n mi


For those with boats, it`s important to plan ahead.  Know exactly
what you need to do and how long it will take you to accomplish
the necessary tasks.  Keep in mind that others will also be taking
preparatory actions too, so you should leave yourself additional
time.

If you plan to leave your boat in the water, consider the possible
effects of the storm tide and waves.  Make sure your anchor is
sufficient to hold the boat, and have enough anchor line to
account for the storm tide.  Secure or remove all non-permanent
equipment from the deck.  Never try to ride out the storm on your
boat.  You will endanger your life and possibly the lives of
rescuers.

If you are able to put your boat on a trailer, get it out of the
water early.  If you wait too long, you may be in a long line.
If possible, store your boat inside a garage.  However, if you
leave your boat outside, put it in a sheltered location, and
secure it to sturdy objects such as large trees.


QUESTION OF THE DAY:  What was the greatest loss of life
associated with any storm surge in the United States?

While not all the details are known, the category 4, Galveston,
Texas hurricane of September 8, 1900, caused the greatest loss
of life from a storm surge.  Not only was it the greatest loss
of life from a storm surge, it was also the greatest loss of life
in the United States associated with any weather-related
disaster.  The hurricane created an 8 to 15 foot surge that
inundated all of Galveston Island, as well as other portions of
the nearby Texas coast. This surge was largely responsible for
the estimated 6,000 to 12,000 deaths attributed to the storm. The
damage to property was estimated at $30 million.

Fortunately, satellites, computers, advanced sensing and
prediction techniques, and better communication systems allow
meteorologists to better predict and warn the public of impending
hurricanes.

Other notable surges occurred with Hurricane Andrew (17 feet),
Hurricane Hugo (20 ft), and Hurricane Camille (24.6 feet).  The
1938 hurricane that affected New England caused a 10 to 12 ft surge
in Narragansett and Buzzards Bays.


FACT FOR THE DAY:  The location with the greatest potential for
storm surge along the northern New England coast is the Penobscot
River near Bangor, Maine.  Computer model estimates indicate
that the funneling effect of the Penobscot Bay and River could
lead to a 23 foot tide for a Category 3 hurricane moving north
at 40 mph.


Here`s a list of the other topics covered in statements issued
this week:

Monday - Tropical Cyclones, Tropical Storms, and
         Hurricanes--The Basics
Tuesday - Hurricane Winds and Tornadoes
Thursday - Inland Flooding
Friday - The Forecast Process--Statements, Watches, and Warnings

For additional information about hurricanes and hurricane
safety, visit the National Hurricane Center`s web site at:

http://www.nhc.noaa.gov/

$$

Jensenius
National Weather Service
Gray...Maine

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