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NOUS41 KGYX 281645
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MEZ007>009-012>014-018>022-023>028-NHZ001>010-013-014-291200

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE GRAY ME
1245 PM EST THU MAR 28 2013

THE NATIONAL WEATHER SERVICE AND THE NATIONAL OCEANIC AND 
ATMOSPHERIC ADMINISTRATION HAVE DECLARED THE WEEK OF MARCH 
24TH THROUGH 30TH TSUNAMI PREPAREDNESS WEEK IN THE UNITED 
STATES. 

...THE GULF OF MAINE TSUNAMI THREAT...

TSUNAMIS AND TSUNAMI-LIKE WAVES CAN EITHER ENTER THE GULF OF 
MAINE 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 VERY LOCALIZED PORTION OF 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 IN OCTOBER 
2008.   

$$

JENSENIUS
NATIONAL WEATHER SERVICE
GRAY, MAINE

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