Public Information Statement
Issued by NWS Portland, ME

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NOUS41 KGYX 021126

725 AM EDT TUE MAY 2 2017

The National Weather Service has declared the week of May 1st
through 5th, SEVERE WEATHER AWARENESS WEEK in New England.
This is the second in a series of five Public Information
Statements on various topics related to severe weather


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 thunder-
storm. In fact, as the magnitudes of these ingredients increase,
so do the chances that a thunderstorms could become severe.

In the summertime, listen to the latest forecast and learn to
recognize the signs that 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

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 middle and 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 of the thunderstorm cloud cause positive charges
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 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.  Many victims also report that at least a
portion of the sky was blue when they were struck.  During the
past 10 years, Maine has had 3 lightning fatalities while New
Hampshire has not had any.  Although Maine has less lightning
than most states east of the Rocky Mountains, Maine ranks 10th
in terms of lightning deaths per capita.

This summer, the National Weather Service will participate in a
nationwide awareness campaign to reduce the number of deaths and
injuries from lightning.  Although more information on lightning
and lightning safety will be provided during Lightning Safety
Awareness Week, the last full week in June, here are some basic
tips to help keep you and your family safe this summer.


  1. Avoid any contact with electrical or electronic equipment
     or cords that are plugged into the electrical system.
  2. Avoid any contact with corded phones.
  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.


  1. There is no safe place outside in a thunderstorm.  To be
     safe, you must get inside a substantial building or hard-
     topped metal vehicle.
  2. Plan outside activities so that you minimize the risk of
     being caught outside in a thunderstorm.
  3. If you hear thunder, move inside a safe shelter immedi-
     ately.  Generally, if you can hear the thunder, you`re
     within striking distance of the storm.
  4. If the sky looks threatening, move inside immediately.
     Don`t wait for the first flash of lightning.  It could
     occur anywhere under or near the storm.
  5. 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

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 that accompany

Here is a list of the other topics that have been or will be
covered in Public Information Statements issued by the National
Weather Service this week.

Monday......Some Basic Definitions
Wednesday...Severe Thunderstorms - Downbursts, Microbursts,
            and Hail
Friday......Flash Floods


National Weather Service
Gray, Maine

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