SEVERE WEATHER PREPAREDNESS WEEK IN SOUTHERN NEW ENGLAND
APRIL 29 - MAY 3, 2013
Images of 1953 Worcester, MA and 2011 Munson, MA Tornado
The National Weather Service in Taunton would like everyone to review their
safety rules this week,in preparation for the upcoming severe weather season.
Here are all five informational statements that will be issued this week:
     
MONDAY - DEFINITION OF A SEVERE THUNDERSTORM

THE NATIONAL WEATHER SERVICE IN TAUNTON HAS DECLARED THE WEEK OF
APRIL 29 - MAY 3 AS SEVERE WEATHER PREPAREDNESS WEEK IN SOUTHERN NEW
ENGLAND. THE FOLLOWING IS THE FIRST IN A SERIES OF FIVE PUBLIC
INFORMATION STATEMENTS THAT WILL BE ISSUED THIS WEEK.

A 'SEVERE THUNDERSTORM' IS DEFINED AS A THUNDERSTORM THAT PRODUCES
WIND GUSTS OF AT LEAST 58 MPH AND/OR HAIL 1.00 INCHES IN DIAMETER OR
LARGER...THE SIZE OF A QUARTER. SEVERE THUNDERSTORMS CAN AND
OCCASIONALLY DO SPAWN TORNADOES.

A SEVERE THUNDERSTORM WATCH IS ISSUED BY THE STORM PREDICTION CENTER
IN NORMAN OKLAHOMA FOR LARGE PORTIONS OF THE REGION WHEN THE
POTENTIAL EXISTS FOR SEVERE THUNDERSTORMS. A SEVERE THUNDERSTORM
WARNING IS ISSUED BY THE LOCAL NATIONAL WEATHER SERVICE FORECAST
OFFICE...SUCH AS IN TAUNTON...WHEN SEVERE THUNDERSTORMS ARE IMMINENT
BASED ON RADAR OR ALREADY OCCURRING BASED ON SPOTTER OBSERVATIONS.

NOTE THAT TORRENTIAL DOWNPOURS OF RAIN THAT CAUSE FLOODING ARE NOT
PART OF THE DEFINITION OF 'SEVERE.' THEY WOULD PROMPT THE ISSUANCE
OF FLOOD OR FLASH FLOOD WARNINGS...BUT NOT SEVERE THUNDERSTORM
WARNINGS. IT IS IMPORTANT TO NOTE THAT FREQUENT LIGHTNING ALSO IS
NOT A CRITERIA FOR WHAT IS TERMED 'SEVERE.' OF COURSE LIGHTNING CAN
BE EXTREMELY DANGEROUS...BUT EVERY THUNDERSTORM HAS LIGHTNING --
THAT IS WHAT CAUSES THE THUNDER. IT IS NOT PRACTICAL TO ISSUE A
WARNING FOR EVERY THUNDERSTORM...THUS WE ISSUE SEVERE THUNDERSTORM
WARNINGS FOR THOSE STORMS THAT COULD PRODUCE LARGE HAIL AND DAMAGING
WINDS.

NOAA WEATHER RADIOS...WITH WARNING ALARM TONES...WILL ALERT YOU WHEN
A SEVERE THUNDERSTORM WARNING IS ISSUED. HOWEVER...THEY WILL NOT
SOUND AN ALARM FOR NON-SEVERE THUNDERSTORMS...WHICH STILL CAN
PRODUCE DEADLY LIGHTNING. WE RECOMMEND THAT LIFEGUARDS AT BEACHES
AND POOLS HAVE HAND-HELD LIGHTNING DETECTORS. THE SAME IS TRUE FOR
ATHLETIC COACHES...CAMP DIRECTORS...AND PARKS AND RECREATION
WORKERS. EVEN WITHOUT EQUIPMENT...YOU CAN PROTECT YOURSELF BY MOVING
INDOORS TO A PLACE OF SAFETY AT THE FIRST RUMBLE OF THUNDER. IF YOU
CAN HEAR THE THUNDER...THE STORM IS USUALLY CLOSE ENOUGH FOR YOU TO
HAVE THE POTENTIAL TO BE STRUCK BY LIGHTNING.
TUESDAY - THUNDERSTORMS AND LIGHTNING

THE NATIONAL WEATHER SERVICE HAS DECLARED THE WEEK OF APRIL 29 TO
MAY 3 AS SEVERE WEATHER AWARENESS WEEK IN SOUTHERN NEW ENGLAND. THIS
IS THE SECOND IN A SERIES OF FIVE PUBLIC INFORMATION STATEMENTS ON
VARIOUS TOPICS RELATED TO SEVERE WEATHER AWARENESS.

SUMMERTIME IS A GOOD TIME FOR OUTDOOR RECREATIONAL ACTIVITIES IN NEW
ENGLAND. IT IS ALSO THE TIME OF THE YEAR WHEN THUNDERSTORMS ARE MOST
LIKELY. THUNDERSTORMS CAN BE BEAUTIFUL, BUT THEY ALSO CAN BE DEADLY.
WHILE MANY PEOPLE THINK THEY ARE AWARE OF THE DANGERS OF
THUNDERSTORMS AND LIGHTNING, THE VAST MAJORITY ARE NOT.

THERE ARE THREE BASIC INGREDIENTS NEEDED FOR THE FORMATION OF A
THUNDERSTORM. THEY INCLUDE LOW-LEVEL MOISTURE, AN UNSTABLE
ATMOSPHERE, AND A TRIGGER (A SOURCE OF LIFT).

LOW-LEVEL MOISTURE:
     THIS MOISTURE IS NEEDED FOR CLOUD FORMATION, GROWTH, AND THE
     DEVELOPMENT OF PRECIPITATION WITHIN THE CLOUD.

UNSTABLE ATMOSPHERE:
     AN UNSTABLE ATMOSPHERE ALLOWS WARM, MOIST AIR NEAR THE GROUND TO
     RISE RAPIDLY TO HIGHER LEVELS IN THE ATMOSPHERE WHERE
     TEMPERATURES ARE BELOW FREEZING. AN UNSTABLE ATMOSPHERE ALSO
     ALLOWS AIR AT HIGHER LEVELS IN THE ATMOSPHERE TO SINK TO THE
     GROUND LEVEL RAPIDLY, BRINGING STRONGER WINDS FROM THE HIGHER
     LEVELS TO THE GROUND.

A TRIGGER:
     SOMETHING TO SET THE ATMOSPHERE IN MOTION.

ALL THREE INGREDIENTS CONTRIBUTE TO THE FORMATION OF A THUNDERSTORM.
IN FACT, AS THE MAGNITUDES OF THESE INGREDIENTS INCREASE, SO DO THE
CHANCES THAT A THUNDERSTORM COULD BECOME SEVERE.

IN THE SUMMERTIME, LISTEN TO THE LATEST FORECAST AND LEARN TO
RECOGNIZE THE SIGNS WHICH OFTEN PRECEDE THUNDERSTORM DEVELOPMENT.
WARM MUGGY AIR IS A SIGN THAT AMPLE LOW-LEVEL MOISTURE IS AVAILABLE
FOR THUNDERSTORM DEVELOPMENT. TOWERING CUMULUS CLOUDS INDICATE AN
ATMOSPHERE THAT IS, OR IS BECOMING, UNSTABLE. AND, THE TRIGGER COULD
BE CONTINUED HEATING FROM THE SUN; AN APPROACHING FRONT OR SEA
BREEZE FRONT; OR A COOLING OF THE UPPER ATMOSPHERE.

ALL THUNDERSTORMS GO THROUGH VARIOUS STAGES OF GROWTH AND
DEVELOPMENT. AS A THUNDERSTORM CLOUD CONTINUES TO GROW, SNOW AND ICE
BEGIN TO FORM IN THE HIGHER LEVELS OF THE CLOUD WHERE TEMPERATURES
ARE BELOW FREEZING, AND ELECTRICAL CHARGES START TO BUILD UP WITHIN
THE CLOUD. NEGATIVE ELECTRICAL CHARGES NEAR THE MIDDLE AND BASE OF
THE CLOUD CAUSE A POSITIVE CHARGE TO BUILD UP ON THE GROUND UNDER
AND NEAR THE THUNDERSTORM.  FINALLY, WHEN THE DIFFERENCE BETWEEN
THESE CHARGES BECOMES TO GREAT, A GIANT ATMOSPHERIC SPARK THAT WE
CALL LIGHTNING OCCURS.

LIGHTNING IS AN UNDERRATED KILLER, USUALLY CLAIMING ITS VICTIMS ONE
AT A TIME. LIGHTNING ALSO LEAVES MANY VICTIMS WITH LIFE-LONG SERIOUS
INJURIES. LIGHTNING CAN STRIKE AS FAR AS 10 MILES FROM THE SIDE OF
THE THUNDERSTORM CLOUD. IN FACT, MANY LIGHTNING VICTIMS ARE STRUCK
BEFORE THE RAIN ARRIVES OR AFTER THE RAIN HAS ENDED AND THE STORM IS
MOVING AWAY. MOST VICTIMS ALSO REPORT THAT AT LEAST A PORTION OF THE
SKY WAS BLUE WHEN THEY WERE STRUCK.

WHILE INSIDE A HOME OR BUILDING
  1. AVOID ANY CONTACT WITH CORDED PHONES.
  2. AVOID ANY CONTACT WITH ELECTRICAL OR ELECTRONIC EQUIPMENT OR
     CORDS THAT ARE PLUGGED INTO THE ELECTRICAL SYSTEM.
  3. AVOID ANY CONTACT WITH THE PLUMBING SYSTEM.  DO NOT WASH
     YOUR HANDS, DO NOT WASH THE DISHES, DO NOT TAKE A SHOWER, OR
     DO NOT DO LAUNDRY.
  4. DO NOT STAND NEXT TO A CONCRETE WALL AND DO NOT LIE ON A
     CONCRETE FLOOR.
  5. STAY AWAY FROM WINDOWS, OUTSIDE DOORWAYS, AND PORCHES.

TIPS WHILE OUTDOORS
  1. PLAN OUTSIDE ACTIVITIES SO THAT YOU MINIMIZE THE RISK OF BEING
     CAUGHT OUTSIDE IN A THUNDERSTORM.
  2. IF YOU HEAR THUNDER, MOVE INSIDE A SAFE SHELTER IMMEDIATELY.
     GENERALLY, IF YOU CAN HEAR THE THUNDER, YOU'RE WITHIN STRIKING
     DISTANCE OF THE STORM.
  3. IF THE SKY LOOKS THREATENING, MOVE INSIDE IMMEDIATELY.  DON'T
     WAIT FOR THE FIRST STROKE OF LIGHTNING. IT COULD OCCUR ANYWHERE
     UNDER OR NEAR THE STORM.
  4. STAY INSIDE A SAFE SHELTER FOR AT LEAST 30 MINUTES AFTER THE
     LAST RUMBLE OF THUNDER WAS HEARD.  MANY LIGHTNING VICTIMS ARE
     STRUCK AFTER THE WORST PART OF THE STORM HAS PASSED.
  5. IF YOU ARE CAUGHT OUTSIDE IN A THUNDERSTORM AND CAN'T REACH A
     SAFE SHELTER, YOU CAN ONLY MINIMIZE THE YOUR RISK OF BEING
     STRUCK BY LIGHTNING.  IF LIGHTNING STRIKES NEAR YOU, IT WILL
     MOST LIKELY STRIKE THE TALLEST OBJECT IN YOUR IMMEDIATE
     VICINITY.  FIRST, DON'T BE THE TALLEST OBJECT IN THE IMMEDIATE
     VICINITY AND DON'T BE NEAR THE TALLEST OBJECT. SECOND, GET AS
     LOW AS POSSIBLE TO THE GROUND, BUT MINIMIZE YOUR CONTACT WITH
     THE GROUND. DO NOT LIE ON THE GROUND.

REMEMBER, WHEN IT COMES TO THUNDERSTORM SAFETY, IT'S YOUR OWN ACTIONS
THAT WILL DETERMINE YOUR PERSONAL RISK OF BEING KILLED OR SERIOUSLY
INJURED BY THE HAZARDS OF A THUNDERSTORM.
WEDNESDAY - TORNADO SAFETY IN SCHOOLS

THE NATIONAL WEATHER SERVICE HAS DECLARED THE WEEK OF APRIL 29 TO
MAY 3 2013 AS SEVERE WEATHER PREPAREDNESS WEEK. THE FOLLOWING IS THE
THIRD IN A SERIES OF FIVE INFORMATIONAL STATEMENTS.

EVERY SCHOOL SHOULD HAVE A TORNADO SAFETY PLAN. THE PLAN SHOULD
ENSURE THAT EVERYONE WILL TAKE COVER WITHIN 60 SECONDS. FREQUENT
TORNADO DRILLS SHOULD BE CONDUCTED. THERE SHOULD BE PROVISIONS FOR
ALL AFTER-HOURS SCHOOL-RELATED ACTIVITIES.

EVERY SCHOOL SHOULD BE INSPECTED AND TORNADO SHELTER AREAS
DESIGNATED BY A REGISTERED ENGINEER OR ARCHITECT. ROOMS WITH
EXTERIOR WALLS SHOULD NEVER BE USED AS TORNADO SHELTERS. BASEMENTS
OFFER THE BEST PROTECTION. SCHOOLS WITHOUT BASEMENTS SHOULD USE
INTERIOR ROOMS AND HALLWAYS ON THE LOWEST FLOOR AWAY FROM WINDOWS.

SCHOOLS SHOULD DELAY ASSEMBLIES OR LUNCH IN LARGE ROOMS WITH WIDE
ROOF SPANS...SUCH AS GYMNASIUMS...AUDITORIUMS...AND CAFETERIAS.
THESE ROOMS OFFER LITTLE OR NO PROTECTION FOR TORNADO-STRENGTH WINDS
AND THE WIDE SPAN ROOFS CAN COLLAPSE.

STUDENTS AND STAFF SHOULD KNOW THE PROTECTIVE POSITION...SITTING AND
FACING AN INTERIOR WALL...ELBOWS TO KNEES...AND WITH HANDS OVER THE
BACK OF THEIR HEADS.

EACH SCHOOL SHOULD HAVE A NOAA WEATHER RADIO WITH BATTERY BACKUP.
REMEMBER THAT THE NATIONAL WEATHER SERVICE ISSUES A TORNADO WATCH
WHEN CONDITIONS ARE FAVORABLE FOR TORNADO DEVELOPMENT AND A TORNADO
WARNING WHEN A TORNADO HAS BEEN SPOTTED OR INDICATED BY RADAR.

IF THE ALARM SYSTEM OF A SCHOOL RELIES ON ELECTRICITY...THERE SHOULD
BE AN ALTERNATIVE METHOD TO NOTIFY TEACHERS AND STUDENTS IN CASE OF
POWER FAILURE.

PLEASE REMEMBER TO MAKE SPECIAL PROVISIONS FOR FACULTY AND STUDENTS
WITH DISABILITIES...THOSE WITH PORTABLE CLASSROOMS...AND THOSE
OUTDOORS.

KEEP CHILDREN AT SCHOOL BEYOND REGULAR HOURS DURING A TORNADO
WARNING. FOR THAT MATTER...IT WOULD BE GOOD PRACTICE TO DELAY
DEPARTURE OF SCHOOL BUSES WITH SEVERE THUNDERSTORM WARNINGS TOO...
SINCE THEY CAN PRODUCE LARGE HAIL AND DAMAGING WINDS WITHOUT A TORNADO.

WHEN PLANNING ADDITIONS OR NEW SCHOOL BUILDINGS...BE SURE TO INCLUDE
PROPERLY DESIGNED TORNADO SHELTERS.
THURSDAY - DOWNBURST WINDS FROM SEVERE THUNDERSTORMS CAN BE POWERFUL

THE NATIONAL WEATHER SERVICE HAS DECLARED THE WEEK OF APRIL 29 TO
MAY 3 AS SEVERE WEATHER PREPAREDNESS WEEK FOR SOUTHERN NEW ENGLAND.
THE FOLLOWING IS THE FOURTH IN A SERIES OF FIVE INFORMATIONAL
STATEMENTS ABOUT SEVERE WEATHER.

WHILE NOT AS NOTORIOUS...OR PERHAPS AS SPECTACULAR TO WITNESS AS A
TORNADO...STRAIGHT-LINE WINDS ARE RESPONSIBLE FOR MOST THUNDERSTORM
WIND DAMAGE...ESPECIALLY ACROSS SOUTHERN NEW ENGLAND.

A DOWNBURST IS A STRONG AND RELATIVELY SMALL AREA OF RAPIDLY
DESCENDING AIR BENEATH A THUNDERSTORM. IT CAN RESULT FROM STRONGER
JET STREAM WINDS BEING TRANSPORTED DOWNWARD TO THE SURFACE... OR IT
CAN RESULT AS AIR WITHIN THE DOWNBURST IS COOLED SIGNIFICANTLY AS
RAIN EVAPORATES INTO INITIALLY DRIER AIR. THIS COOL...THUS
DENSE...AIR SINKS RAPIDLY TO THE SURFACE. A DOWNBURST IS
DIFFERENTIATED FROM A COMMON THUNDERSTORM DOWNDRAFT BECAUSE THE
WINDS IT PRODUCES HAVE THE POTENTIAL TO CAUSE DAMAGE ON OR NEAR THE
GROUND.  SURFACE DAMAGE PATTERNS HAVE SHOWN THAT WHETHER THE WINDS
ARE STRAIGHT OR A LITTLE BIT CURVED...THEY TEND TO SPREAD OUT...OR
DIVERGE...CONSIDERABLY AS THEY REACH THE SURFACE. CONVERSELY...DAMAGE
PATTERNS RESULTING FROM A TORNADO GENERALLY CONVERGE TOWARD A NARROW
CENTRAL TRACK.

INTENSE DOWNBURSTS CAN BE PHENOMENAL.  SPEEDS HAVE BEEN CLOCKED AS
HIGH AS 175 MPH NEAR MOREHEAD CITY NORTH CAROLINA AND AT 158 MPH AT
ANDREWS AIR FORCE BASE IN MARYLAND. CLOSER TO HOME...104 MPH
DOWNBURST WINDS WERE MEASURED AT BOTH WORCESTER MASSACHUSETTS ON MAY
31 1998 AND WHITMAN MASSACHUSETTS ON MAY 21 1996.  STRONG DOWNBURSTS
WILL DEFINITELY CAUSE ROARING SOUNDS AND PEOPLE MAY OFTEN REFER TO A
SOUND LIKE A FREIGHT TRAIN...TERMS TYPICALLY ASSOCIATED WITH
TORNADOES.  ALTHOUGH DOWNBURSTS ARE NOT TORNADOES...THEY CAN CAUSE
DAMAGE EQUIVALENT TO THAT OF A SMALL TO MEDIUM TORNADO. AFTER ALL...
WIND IS WIND.

DOWNBURSTS ARE CLASSIFIED AS EITHER MACROBURSTS OR MICROBURSTS...
DEPENDING ON THE AREAL EXTENT OF THE DAMAGING WIND SWATH.
A MACROBURST/S DAMAGE EXTENDS HORIZONTALLY FOR MORE THAN 2.5 MILES.
A MICROBURST IS A SMALL DOWNBURST WITH ITS DAMAGING WINDS EXTENDING
2.5 MILES OR LESS.  THE SMALL HORIZONTAL SCALE AND SHORT TIME SPAN
OF A MICROBURST MAKES IT PARTICULARLY HAZARDOUS TO AVIATION.

THE NATIONAL WEATHER SERVICE ISSUES SEVERE THUNDERSTORM WARNINGS FOR
THUNDERSTORMS THAT ARE EXPECTED TO PRODUCE DAMAGING WIND GUSTS OF
58 MPH OR GREATER...OR HAIL THAT IS ONE INCH OR GREATER IN
DIAMETER.
FRIDAY - LOW-TOPPED THUNDERSTORMS

THE NATIONAL WEATHER SERVICE IN TAUNTON HAS DECLARED THE WEEK OF
APRIL 29 TO MAY 3 AS SEVERE WEATHER PREPAREDNESS WEEK IN SOUTHERN
NEW ENGLAND. THE FOLLOWING IS THE FIFTH IN A SERIES OF FIVE
INFORMATIONAL STATEMENTS.

WHICH WOULD PRODUCE MORE SEVERE WEATHER...A THUNDERSTORM WITH A
TOP OF 30,000 FEET OR ONE WITH A TOP OF 50,000 FEET? THE ANSWER IS
THAT IT DEPENDS ON HOW HIGH THE TROPOPAUSE LEVEL IS FOR THAT DAY.

MOST WEATHER OCCURS IN THE TROPOSPHERE...THE LOWEST LAYER OF THE
ATMOSPHERE. WHEN A THUNDERSTORM DEVELOPS...IT GROWS TALLER AND
EVENTUALLY REACHES THE TROPOPAUSE...THE INTERFACE BETWEEN THE
TROPOSPHERE AND THE VERY STABLE STRATOSPHERE. BECAUSE THE
STRATOSPHERE IS STABLE...IT CAUSES THE TOP OF THE THUNDERSTORM TO
FLATTEN OUT INTO WHAT IS TERMED AN ANVIL...WHICH IS ROUGHLY AT THE
TROPOPAUSE LEVEL.

IN THE HEART OF SUMMER...THE WARMER CONDITIONS LEAD TO A HIGHER
TROPOPAUSE LEVEL. IN THE SPRING...THE TROPOPAUSE CAN BE MUCH LOWER.
IF THE TROPOPAUSE LEVEL IS 30,000 FEET ON A PARTICULAR DAY...IT MAY
ONLY TAKE A 33,000 FOOT STORM TO BECOME SEVERE. ON A DAY WHEN THE
TROPOPAUSE IS 50,000 FEET...A 52,000 FOOT STORM COULD BECOME SEVERE.

THUS...WHAT DETERMINES THE SEVERITY OF A STORM IS HOW HIGH ITS CLOUD
TOP IS...RELATIVE TO THE TROPOPAUSE LEVEL FOR THAT DAY. A 30,000
FOOT LOW-TOPPED THUNDERSTORM IN NEW ENGLAND CAN PACK JUST AS MUCH
PUNCH AS A 50,000 FOOT STORM...IF THE TROPOPAUSE LEVEL IS LOW.

WEATHER BALLOONS ARE SENT UP AT 93 SITES ACROSS NORTH AMERICA...
TWICE PER DAY...AND THESE REPORT BACK TO THE WEATHER OFFICE WHAT THE
TROPOPAUSE LEVEL IS. BUT A SIMPLE VISUAL CLUE AS TO WHETHER A STORM
MAY BE SEVERE IS TO LOOK FOR A CLOUD TOP THAT MUSHROOMS UP ABOVE THE
REST OF THE ANVIL LEVEL...ACTUALLY OVERSHOOTING INTO THE
STRATOSPHERE FOR SEVERAL MINUTES.  THIS OVERSHOOTING TOP IS
INDICATIVE OF A VERY STRONG UPDRAFT AND IT IS YOUR VISUAL CLUE THAT
A STORM MAY BE SEVERE...PRODUCING LARGE HAIL AND DAMAGING WINDS.