Public Information Statement
Issued by NWS Boston, MA

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NOUS41 KBOX 021315

Public Information Statement
National Weather Service Taunton MA
915 AM EDT Tue May 2 2017


The National Weather Service has declared the week of May 1 to
May 5 as Severe Weather Preparedness 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

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

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. 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 too 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,
     and 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.

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
     are within striking distance of the storm.
  3. If the sky looks threatening, move inside immediately. Do
     not 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 cannot reach
     a safe shelter, you can only minimize 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, do not be the tallest object in the
     immediate vicinity and do not be near the tallest object.
     Second, get as low as possible to the ground, but minimize
     your contact with the ground. Do not fully lie on the

Remember, when it comes to thunderstorm safety, it is your own
actions that will determine your personal risk of being killed or
seriously injured by the hazards of a thunderstorm.


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