Severe Weather Awareness
Today we will define exactly what is a severe thunderstorm?
2006 was a record setting year for severe thunderstorms in North Carolina. Statewide there
were over 3000 reports of large hail and damaging winds resulting in over three million
dollars in damage. Powerful thunderstorms are also responsible for injuries and sometimes
deaths in the state as a result of lightning and high winds. The severe thunderstorm season
in central North Carolina typically starts in mid to late March and does not end until the middle
of summer.
Severe Thunderstorms...
The National Weather Service considers a thunderstorm severe if it produces a tornado, hail
at least the size of a penny and or wind in excess of 58 mph. These minimum wind and hail
parameters are the National Weather Service's warning criteria for severe thunderstorms.
Note the national Weather Service does not issue warnings for lightning and given the deadly
nature of lightning you should always be aware of the lightning danger anytime a
thunderstorm is nearby. In 2006 warnings issued by the Raleigh NWS office provided an
average of fifteen minutes lead time for severe thunderstorms with a detection rate of nearly
ninety percent.
Large Hail...
In the past several years severe thunderstorms in North Carolina have produced hail as
large as tennis balls and even baseballs. Just last year baseball size hail struck Eastern
North Carolina resulting in over one hundreds thousand dollars in damage. Just two years
ago hail of nearly 4 inches caused damage across the triangle. In the last 10 years there
have been over 1000 reports of hail of at least one inch in diameter. While hail is not usually
life threatening, these large chucks of ice when driven by strong winds cause serious
damage to roofs, automobiles, and crops. Hail season in central North Carolina typically
runs from mid March through early July, typically maxing in May.
Hailstones grow in thunderstorms with strong updrafts. These strong upward moving
currents of air keep the ice suspended inside the thunderstorm...allowing the chunk of ice or
hailstones to grow larger and larger. Once ice stones become too heavy for the updrafts to
keep suspended...they fall to earth as hail. Thunderstorm updrafts which show signs of
rotation on radar are very effective at suspending hail since the internal velocities in rotating
updrafts are higher than those of non rotating updrafts.
Damaging Winds…
Strong gusts of wind from a thunderstorm called downbursts or straight line wind, are
another serious danger. These gusts of wind rush down from the sky sometimes reaching
speeds in excess of 100 mph. Thunderstorm wind of this magnitude can impact large areas
creating widespread damage. Damaging straight line winds can even cause damage
equivalent to that of a tornado.
Lines of well organized thunderstorms...called squall lines...also occasionally move across
central North Carolina in the spring and early summer. These dangerous storm systems
can be very explosive and race across the state at over 50 mph creating widespread wind
damage over entire counties.
Damaging wind events in central North Carolina typically start as early as mid March and run
into August. Damaging thunderstorm wind events usually occur from May through early
August which is much longer than the typical severe hail season.
Safety...
You can protect yourself during thunderstorms by remembering this phrase…hide from the
wind and lightning. Stay away from windows when storms approach and seek shelter in an
interior bathroom or closet when the wind really starts to blow.
Your best line of defense against severe thunderstorms...is to stay informed. There are so
many great outdoor activities across the state of North Carolina and severe weather can
bring a quick end to a days pleasure. Listen to NOAA weather radio, television or local radio
for the latest forecasts and possible threat of thunderstorms and severe weather. If warnings
are issued...take action and protect your family and property. Remember being safe is a lot
better than being sorry.
2006 was a record setting year for severe thunderstorms in North Carolina. Statewide there
were over 3000 reports of large hail and damaging winds resulting in over three million
dollars in damage. Powerful thunderstorms are also responsible for injuries and sometimes
deaths in the state as a result of lightning and high winds. The severe thunderstorm season
in central North Carolina typically starts in mid to late March and does not end until the middle
of summer.
Severe Thunderstorms...
The National Weather Service considers a thunderstorm severe if it produces a tornado, hail
at least the size of a penny and or wind in excess of 58 mph. These minimum wind and hail
parameters are the National Weather Service's warning criteria for severe thunderstorms.
Note the national Weather Service does not issue warnings for lightning and given the deadly
nature of lightning you should always be aware of the lightning danger anytime a
thunderstorm is nearby. In 2006 warnings issued by the Raleigh NWS office provided an
average of fifteen minutes lead time for severe thunderstorms with a detection rate of nearly
ninety percent.
Large Hail...
In the past several years severe thunderstorms in North Carolina have produced hail as
large as tennis balls and even baseballs. Just last year baseball size hail struck Eastern
North Carolina resulting in over one hundreds thousand dollars in damage. Just two years
ago hail of nearly 4 inches caused damage across the triangle. In the last 10 years there
have been over 1000 reports of hail of at least one inch in diameter. While hail is not usually
life threatening, these large chucks of ice when driven by strong winds cause serious
damage to roofs, automobiles, and crops. Hail season in central North Carolina typically
runs from mid March through early July, typically maxing in May.
Hailstones grow in thunderstorms with strong updrafts. These strong upward moving
currents of air keep the ice suspended inside the thunderstorm...allowing the chunk of ice or
hailstones to grow larger and larger. Once ice stones become too heavy for the updrafts to
keep suspended...they fall to earth as hail. Thunderstorm updrafts which show signs of
rotation on radar are very effective at suspending hail since the internal velocities in rotating
updrafts are higher than those of non rotating updrafts.
Damaging Winds…
Strong gusts of wind from a thunderstorm called downbursts or straight line wind, are
another serious danger. These gusts of wind rush down from the sky sometimes reaching
speeds in excess of 100 mph. Thunderstorm wind of this magnitude can impact large areas
creating widespread damage. Damaging straight line winds can even cause damage
equivalent to that of a tornado.
Lines of well organized thunderstorms...called squall lines...also occasionally move across
central North Carolina in the spring and early summer. These dangerous storm systems
can be very explosive and race across the state at over 50 mph creating widespread wind
damage over entire counties.
Damaging wind events in central North Carolina typically start as early as mid March and run
into August. Damaging thunderstorm wind events usually occur from May through early
August which is much longer than the typical severe hail season.
Safety...
You can protect yourself during thunderstorms by remembering this phrase…hide from the
wind and lightning. Stay away from windows when storms approach and seek shelter in an
interior bathroom or closet when the wind really starts to blow.
Your best line of defense against severe thunderstorms...is to stay informed. There are so
many great outdoor activities across the state of North Carolina and severe weather can
bring a quick end to a days pleasure. Listen to NOAA weather radio, television or local radio
for the latest forecasts and possible threat of thunderstorms and severe weather. If warnings
are issued...take action and protect your family and property. Remember being safe is a lot
better than being sorry.
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