000
NOUS41 KGYX 021259
PNSGYX
MEZ007>009-012>014-018>022-023>028-NHZ001>010-013-014-
031200


PUBLIC INFORMATION STATEMENT 
NATIONAL WEATHER SERVICE GRAY ME
900 AM EDT THU MAY 2 2013

THE NATIONAL WEATHER SERVICE HAS DECLARED THE WEEK OF 
APRIL 29TH  THROUGH MAY 4TH, SEVERE WEATHER AWARENESS 
WEEK IN NEW ENGLAND.  THIS IS THE THIRD IN A SERIES OF 
FIVE PUBLIC INFORMATION STATEMENTS ON VARIOUS TOPICS 
RELATED TO SEVERE WEATHER AWARENESS.


...SEVERE WEATHER AWARENESS - SEVERE THUNDERSTORMS - 
DOWNBURSTS, MICROBURSTS, MESO-CYCLONES, AND HAIL...

BY DEFINITION, A SEVERE THUNDERSTORM IS ONE WHICH 
PRODUCES WIND GUSTS OF 58 MPH OR MORE, OR HAIL 1 INCH IN 
DIAMETER OR GREATER. SEVERE THUNDERSTORMS CAN ALSO 
PRODUCE TORNADOES.

IN NEW ENGLAND, SEVERE THUNDERSTORMS ARE NOT UNCOMMON 
DURING THE SUMMER.  EVERY YEAR, THE NATIONAL WEATHER 
SERVICE GETS NUMEROUS REPORTS OF WIND AND HAIL DAMAGE 
THROUGHOUT MAINE AND NEW HAMPSHIRE.  SEVERE THUNDERSTORM 
WINDS DOWN TREES AND BRANCHES ONTO HOMES, BUILDINGS, 
VEHICLES, AND POWER LINES.  SCATTERED POWER OUTAGES ARE 
OFTEN THE RESULT OF LIGHTNING OR WIND-FALLEN TREES AND 
BRANCHES.  ALSO, WIND-DRIVEN HAIL FROM THUNDERSTORMS 
FLATTENS AND/OR DAMAGES CROPS IN THE STATES.  ON RARE 
OCCASIONS, LARGE HAILSTONES DAMAGE HOMES, BUILDINGS, AND 
VEHICLES.  IN ADDITION TO THE LIGHTNING, FALLING TREES 
AND LARGE HAIL ALSO POSE A SIGNIFICANT THREAT TO PEOPLE, 
AS WELL.


THUNDERSTORM WINDS, DOWNDRAFTS, DOWNBURSTS, AND 
MICROBURSTS

DURING THE DEVELOPMENT OF A THUNDERSTORM, WARM AIR RISES 
UPWARD IN THE ATMOSPHERE (AN UPDRAFT) CAUSING THE 
FORMATION OF CLOUDS AND PRECIPITATION.  AS A THUNDERSTORM 
MATURES, COOL, PRECIPITATION-LADEN AIR SINKS DOWNWARD 
THROUGH THE ATMOSPHERE (A DOWNDRAFT).  WHEN A DOWNDRAFT 
REACHES THE GROUND IT SPREADS OUT CAUSING THE COOL, GUSTY 
WIND THAT OFTEN ACCOMPANIES A THUNDERSTORM.

IN SOME THUNDERSTORMS, INTENSE DOWNDRAFTS DEVELOP.  WHEN 
THESE DOWNDRAFTS REACH THE GROUND, THEY SPREAD OUT VERY 
QUICKLY CAUSING STRONG AND OFTEN DAMAGING WINDS AT THE 
GROUND.  THESE INTENSE DOWNDRAFTS ARE CALLED DOWNBURSTS 
AND CAN CAUSE SIGNIFICANT WIND DAMAGE OVER LARGE AREAS.  
IN THE CASE OF DOWNBURSTS, THE DAMAGE IS GENERALLY 
REFERRED TO AS STRAIGHT-LINE WIND DAMAGE SINCE FALLEN 
TREES GENERALLY LINE UP IN THE SAME DIRECTION.  IN MAINE 
AND NEW HAMPSHIRE, MOST THUNDERSTORM WIND DAMAGE IS 
CAUSED BY DOWNBURSTS. 

A SPECIAL TYPE OF DOWNBURST IS THE MICROBURST.  
MICROBURSTS GET THEIR NAME BECAUSE THEY GENERALLY AFFECT 
A MUCH SMALLER GEOGRAPHICAL AREA, BUT THE WINDS IN A 
MICROBURST CAN BE VERY INTENSE.  LIKE THE GENERAL 
DOWNBURST, MOST OF THE DAMAGE WITH MICROBURSTS LINES UP 
IN ONE DIRECTION, ALTHOUGH, THERE MAY BE A TENDENCY FOR 
THE DAMAGE TO RADIATE OUTWARD.  MICROBURSTS ARE USUALLY 
ACCOMPANIED BY HEAVY RAIN AND/OR HAIL AND CAN HAVE WINDS 
AS STRONG AS THOSE IN A SMALL TORNADO. 

UNDER CERTAIN ATMOSPHERIC CONDITIONS, THUNDERSTORMS CAN 
BEGIN TO DEVELOP A CIRCULATION WITHIN THE THUNDERSTORM 
CLOUD.  THESE STORMS ARE OFTEN CALLED MESO-CYCLONES 
BECAUSE OF THE COUNTER-CLOCKWISE CIRCULATION THAT 
DEVELOPS WITHIN THE STORM.  THE UPDRAFTS AND DOWNDRAFTS 
IN THESE STORMS CAN PERSIST FOR HOURS AS THE STORM MOVES 
ALONG ITS PATH.  SEVERE WINDS AND HAIL ARE ALSO MORE 
LIKELY WITH MESO-CYCLONES, AND IF THE ROTATION WITHIN THE 
STORM BECOMES MORE INTENSE, THERE IS AN INCREASING 
POSSIBILITY THAT THE STORM MIGHT PRODUCE A TORNADO.  
NATIONAL WEATHER SERVICE DOPPLER RADAR ALLOWS 
METEOROLOGISTS TO MONITOR AIR MOVEMENT WITHIN THESE 
STORMS AND TO SEE THE DEVELOPMENT AND STRENGTH OF ANY 
CIRCULATION WITHIN THE STORM.  

DURING THE SUMMER OF 2011, MAINE AND NEW HAMPSHIRE HAD 
NUMEROUS THUNDERSTORMS THAT PRODUCED DAMAGING STRAIGHT-
LINE WINDS.  FORTUNATELY, NO ONE WAS KILLED BY ANY OF THE 
FALLING TREES CAUSED BY THESE WINDS.  


HAIL

THE CIRCULATION THAT ACCOMPANIES A MESO-CYCLONE IS ALSO A 
FACTOR IN HAIL FORMATION.  HAIL INITIALLY FORMS WHEN 
LIQUID WATER DROPLETS ARE CARRIED UPWARD BY THE UPDRAFT 
TO A LEVEL WHERE THE DROPLETS FREEZE.  EVENTUALLY, THE 
SMALL HAIL STONE MAY BEGIN TO FALL DOWNWARD, ONLY TO BE 
CAUGHT ONCE AGAIN BY THE PERSISTENT UPDRAFT OF A MESO-
CYCLONE.  EACH TIME THE HAILSTONE GOES THROUGH THIS 
PROCESS, IT GETS LARGER AND HEAVIER.  EVENTUALLY, THE 
HAILSTONE WILL BE BLOWN AWAY FROM THE UPDRAFT OR WILL 
BECOME TOO HEAVY FOR THE UPDRAFT TO SUPPORT AND THE 
HAILSTONE WILL FALL TO THE GROUND.

IN MAINE AND NEW HAMPSHIRE, HAIL IS FAIRLY COMMON DURING 
WELL- DEVELOPED SUMMERTIME THUNDERSTORMS.  ALTHOUGH MOST 
HAIL THAT REACHES THE GROUND IN NORTHERN NEW ENGLAND IS 
AN INCH OR LESS IN DIAMETER, OCCASIONALLY HAILSTONES OVER 
2 INCHES IN DIAMETER WILL FALL.  LARGE HAILSTONES CAN 
FALL AT SPEEDS FASTER THAN 100 MPH AND CAN DO 
CONSIDERABLE DAMAGE TO CARS, HOMES, AND BUILDINGS, AND 
CAN BE A SIGNIFICANT THREAT TO PEOPLE, AS WELL.

DURING 2012 IN NEW HAMPSHIRE, THE MOST SIGNIFICANT HAIL 
REPORT WAS 2.00 INCHES IN WESTMORELAND IN CHESHIRE 
COUNTY. IN MAINE IN 2012, THERE WERE NO REPORTS OF HAIL 2 
INCHES OR GREATER.
 
HERE ARE SOME OF THE LARGER HAILSTONES REPORTED IN 
NORTHERN NEW ENGLAND SINCE 1995.

3.00 INCHES
     JUN 19 1995  SPRINGFIELD, MAINE
     JUN 22 2008  MT. CARDIGAN, NEW HAMPSHIRE

2.75 INCHES
     AUG 24 1998  TAMWORTH/FREEDOM, NEW HAMPSHIRE
     JUN  1 2011  KINGFIELD, MAINE

2.50 INCHES
     AUG  4 2007  FT. KENT, MAINE
     MAY 27 2011  BINGHAM, MAINE

2.00 INCHES
     AUG 18 1996  LINCOLNVILLE, MAINE
     JUL 11 2006  EXETER, NEW HAMPSHIRE
     JUL 11 2006  HAMPTON FALLS, NEW HAMPSHIRE
     JUL  9 2007  CONCORD, NEW HAMPSHIRE 
     AUG  4 2007  GRAND ISLE, MAINE
     AUG  4 2007  CARIBOU, MAINE
     AUG 30 2007  ROME, MAINE
     JUL 18 2008  STRAFFORD, NEW HAMPSHIRE
     JUN  5 2010  SOUTH PARIS, MAINE
     MAY 29 2012  WESTMORELAND, NEW HAMPSHIRE  

FOR BOTH SEVERE WINDS (58 MPH OR GREATER) AND LARGE HAIL 
(1 INCH OR GREATER IN DIAMETER), THE NATIONAL WEATHER 
SERVICE ISSUES SEVERE THUNDERSTORM WATCHES AND WARNINGS. 
 A WATCH INDICATES THAT THE ATMOSPHERIC CONDITIONS ARE 
FAVORABLE FOR SEVERE WEATHER TO DEVELOP.  A WARNING 
INDICATES THAT SEVERE WEATHER IS IMMINENT OR IS ALREADY 
OCCURRING.  IF YOU HEAR A WARNING FOR YOUR AREA, BE 
PREPARED TO SEEK A SAFE SHELTER IF YOU ARE IN THE PATH OF 
THE STORM.

HERE IS A LIST OF THE OTHER TOPICS THAT WILL BE COVERED 
IN PUBLIC INFORMATION STATEMENTS ISSUED BY THE NATIONAL 
WEATHER SERVICE THIS WEEK. 

THURSDAY....TORNADOES
FRIDAY......FLASH FLOODS

$$

JENSENIUS
NATIONAL WEATHER SERVICE
GRAY, MAINE

NNNN