Public Information Statement
Issued by NWS Caribou, ME

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PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE CARIBOU ME
619 AM EDT WED MAR 30 2016

...TSUNAMI PREPAREDNESS WEEK IN MAINE...

THE NATIONAL WEATHER SERVICE AND THE NATIONAL OCEANIC AND
ATMOSPHERIC ADMINISTRATION HAVE DECLARED THE WEEK OF MARCH 28TH
THROUGH APRIL 1ST TSUNAMI PREPAREDNESS WEEK IN MAINE, AS WELL AS IN
THE REMAINDER OF THE COASTAL UNITED STATES.

TODAY`S TOPIC...THE GULF OF MAINE TSUNAMI THREAT

TSUNAMIS AND TSUNAMI-LIKE WAVES CAN ENTER THE GULF OF MAINE EITHER
FROM THE OPEN WATERS OF THE ATLANTIC OR ORIGINATE IN THE GULF OF
MAINE.  THOSE ORIGINATING OUTSIDE THE GULF OF MAINE WOULD PRODUCE
SMALL BUT POTENTIALLY DANGEROUS AND DAMAGING IMPACTS ALONG THE
ENTIRE NORTHERN NEW ENGLAND COAST.  THOSE ORIGINATING IN THE GULF OF
MAINE WOULD ALSO PRODUCE SMALL BUT POTENTIALLY DANGEROUS AND
DAMAGING IMPACTS, BUT USUALLY ONLY TO A LOCALIZED AREA ALONG THE
COAST.

TSUNAMI WAVES ENTERING THE GULF OF MAINE

THE NORTHERN NEW ENGLAND COAST AND THE GULF OF MAINE ARE SOMEWHAT
PROTECTED FROM A MAJOR TSUNAMI THREAT BY THE SHALLOW WATERS OF
GEORGES BANK AND THE CONTINENTAL SHELF. WHEN TSUNAMIS GENERATED
OUTSIDE THE GULF OF MAINE ENCOUNTER THE SHALLOW WATERS OF GEORGES
BANK, A PORTION OF THE WAVE ENERGY IS REFLECTED BACK OUT TO SEA.
MOST OF THE WAVE ENERGY ENTERING THE GULF OF MAINE WOULD COME
THROUGH THE NORTHEAST CHANNEL AND THE GREAT SOUTH CHANNEL.  BECAUSE
OF THE DEEPER WATERS IN THESE CHANNELS, THE LEADING EDGE OF THE
TSUNAMI WAVES WOULD MOVE FASTER IN THE CHANNELS THAN IN THE
SHALLOWER WATERS ON EITHER SIDE.  THIS WOULD CAUSE MUCH OF THE
TSUNAMI WAVE ENERGY TO BE REFRACTED TO THE RIGHT AND LEFT OF THE
CHANNELS.  AS A RESULT, MUCH OF THE TSUNAMI WAVE ENERGY ENTERING THE
GULF OF MAINE INITIALLY WOULD BE DIRECTED TOWARD THE GEORGES BANK
AND NOVA SCOTIA.  HOWEVER, ADDITIONAL REFLECTIONS AND REFRACTIONS OF
THIS WAVE ENERGY WOULD LEAD TO VERY RAPID AND CHAOTIC FLUCTUATIONS
OF WATER LEVELS IN THE GULF OF MAINE THAT COULD LAST FOR MORE THAN 6
HOURS.  THESE FLUCTUATIONS COULD CAUSE STRONG, DANGEROUS, AND
DAMAGING CURRENTS ALONG THE COAST, AND COULD CAUSE SOME MINOR
INUNDATION AT THE TIME OF HIGH TIDE.

THE TWO MOST SIGNIFICANT TSUNAMI SOURCES OUTSIDE THE GULF OF MAINE
WOULD BE A MAJOR EARTHQUAKE ALONG THE SUBDUCTION ZONE OF THE PUERTO
RICAN TRENCH (JUST TO THE NORTH OF PUERTO RICO) OR A LARGE SEDIMENT
SLIDE ON THE CONTINENTAL SLOPE OF THE EAST COAST.   IN THE CASE OF
AN EARTHQUAKE ALONG THE PUERTO RICAN TRENCH, MUCH OF THE TSUNAMI
WAVE ENERGY WOULD BE DIRECTED NORTH TOWARD THE GULF OF MAINE. TRAVEL
TIME FROM THE INITIAL QUAKE UNTIL THE TSUNAMI WAVE REACHED THE COAST
WOULD BE ABOUT 5 TO 6 HOURS, ALLOWING PLENTY OF TIME FOR A WARNING
OR ADVISORY.  ALTHOUGH DANGEROUS AND DAMAGING, THE IMPACTS TO
NORTHERN NEW ENGLAND OF A TSUNAMI GENERATED ALONG THE PUERTO RICAN
TRENCH WOULD BE RELATIVELY SMALL COMPARED TO THE POTENTIALLY
DEVASTATING IMPACTS ON PUERTO RICO AND BERMUDA.  THE OTHER SOURCE
OUTSIDE THE GULF OF MAINE WOULD BE A LARGE SEDIMENT SLIDE OR SLUMP
ON THE CONTINENTAL SLOPE.  THE EXACT IMPACTS OF SLIDE OR SLUMP WOULD
DEPEND ON THE ORIENTATION OF THE SLIDE OR SLUMP WITH RESPECT TO THE
NORTHEAST AND GREAT SOUTH CHANNELS AND MAGNITUDE OF THE SLIDE OR
SLUMP.

TSUNAMI WAVES GENERATED IN THE GULF OF MAINE

SIMILAR TO TSUNAMIS INITIATED OUTSIDE THE GULF OF MAINE, SEDIMENT
SLIDES OR SLUMPS IN THE GULF OF MAINE COULD CAUSE LOCALIZED TSUNAMI
WAVES.  IN THE GULF OF MAINE, SLIDES OR SLUMPS MOST LIKELY WOULD BE
NEAR THE COAST OR ALONG THE NORTHERN EDGE OF ONE OF THE BANKS OR
LEDGES.  IN EITHER CASE, THE EXACT IMPACTS OF THE TSUNAMI WAVES
WOULD DEPEND ON THE ORIENTATION AND MAGNITUDE OR THE SLIDE OR SLUMP
AND WOULD AFFECT ONLY A LOCALIZED AREA.  THESE SLIDES AND SLUMPS AND
THE SUBSEQUENT TSUNAMI WAVES COULD OCCUR WITHOUT WARNING.

ALTHOUGH TECHNICALLY NOT A TSUNAMI, TSUNAMI-LIKE WAVES CAN DEVELOP
IN CERTAIN SPECIFIC WEATHER SITUATIONS.  THESE "METEO-TSUNAMIS"
DEVELOP WHEN AN ATMOSPHERIC PRESSURE WAVE MOVES ACROSS THE GULF OF
MAINE AT JUST THE RIGHT SPEED, CREATING A HARMONIC RESONANCE WITH A
DEVELOPING TSUNAMI-LIKE OCEAN WAVE BELOW.  THIS RESONANCE WOULD
ALLOW THE OCEAN WAVE TO GROW WITH TIME AS BOTH WAVES MOVE IN UNISON.
SINCE THE FORWARD SPEED OF THE TSUNAMI-LIKE WAVE IS DETERMINED BY
THE DEPTH OF THE OCEAN, THE ATMOSPHERIC FEATURE NEEDS TO MOVE AT THE
JUST THE RIGHT SPEED AS DETERMINED BY THE OCEAN DEPTH.  IN THE GULF
OF MAINE, VERY FAST MOVING WEATHER SYSTEMS COULD MEET THIS
REQUIREMENT.  IN ADDITION, THE MOVEMENT OF BOTH THE ATMOSPHERIC AND
THE TSUNAMI-LIKE WAVES WOULD NEED TO BE TOWARD THE COAST.  WHILE
RARE, METEO-TSUNAMIS DO OCCUR IN THE GULF OF MAINE.  IN FACT, A
METEO-TSUNAMI IS BELIEVED TO HAVE CAUSED THE UNUSUAL TIDAL
FLUCTUATIONS THAT WERE OBSERVED ALONG THE MID-COAST OF MAINE IN
OCTOBER 2008.

PLEASE STAYED TUNED-IN THIS WEEK AS WE PROVIDE ADDITIONAL
EDUCATIONAL MATERIAL ON THE TSUNAMI THREAT IN MAINE.

$$



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