PUBLIC INFORMATION STATEMENT NATIONAL WEATHER SERVICE GRAY ME 1030 AM EDT MON MAY 24 1999 The National Weather Service in Gray, Maine has declared the week of May 23 through May 29, 1999, LIGHTNING SAFETY AWARENESS WEEK in Maine and New Hampshire. This is the second in a series of seven public information statements to be issued by the National Weather Service Office in Gray this week containing information on lightning and lightning safety. ...THUNDERSTORM BASICS... By definition, all thunderstorms contain lightning. Lightning is a giant spark of electricity that occurs within the atmosphere or between the atmosphere and the ground. As lightning passes through the air, it heats the air rapidly to a temperature of about 50,000 degrees Fahrenheit, considerably hotter than the surface of the sun. During a lightning discharge, the sudden heating of the air causes it to expand rapidly. After the discharge, the air contracts quickly as it cools back to a normal temperature. This rapid expansion and contraction of the air causes a shock wave that we hear as thunder (this shock wave can damage walls and break glass). All thunderstorms go through various stages of growth, development, and dissipation. On a warm summer day, as the sun heats the air, pockets of warmer air start to rise in the atmosphere. When these pockets reach a certain level in the atmosphere, cumulus clouds start to form. Continued heating can cause these clouds to grow vertically upward into the atmosphere. These "towering cumulus" clouds may be the one of the first indications of a developing thunderstorm. As the towering cumulus cloud continues to develop and grow, precipitation begins to form within the cloud, with snow in the upper levels of the cloud and rain in the lower levels of the cloud. The rapidly rising air in the cloud, combined with the movement of the precipitation within the cloud, cause electrical charges to build up within the cloud. Generally, positive charges build up near the top of the cloud, while negative charges build up near the bottom of the cloud. The negative charges that build up near the base of the cloud cause positive charges to build up on the ground beneath the cloud and in the area surrounding the cloud. As the cloud moves, these induced positive charges on the ground follow the cloud around like a shadow. Even though you may not be standing directly under the cloud, positive charges may be building up on you, or on nearby objects. If so, lightning could strike at any moment. With the onset of lightning, the thunderstorm has officially begun. Surface heating by the sun is only one of the ways in which thunderstorms are produced. Thunderstorms also can be triggered by colder air moving in at higher levels of the atmosphere or can be caused as air is forced upward into the atmosphere by frontal systems. Often, several of these factors contribute to the development of a thunderstorm. We are fortunate in northern New England to have less lightning than most other areas of the country. On the average, much of Maine and New Hampshire have less than 2 cloudİtoİground lightning strokes per square mile per year. Only several states in the western U.S. have lightning flash density rates as low. In comparison, many states in the midwest and south have flash density rates of 10 flashes or more per square mile per year, and in parts of central Florida, flash rates of 30 flashes per square mile per year are observed. Despite the relatively low incidence rate of lightning in Maine and New Hampshire, the two states have relatively high casualty rates (combined injury/death rate) due to lightning. Unfortunately, Maine's casualty rate due to lightning ranks 8th highest in the nation, while New Hampshire's rate is 16th highest in the nation. While there are several factors contributing to this high rate, residents and visitors to northern New England are likely more vulnerable to being struck by lightning because of the activities with which they are involved. Particularly on those warm summer days when lightning is most likely to occur, many people are outside enjoying the variety of recreational activities which attract people to northern New England during the summer. LIGHTNING FACT FOR THE DAY: Every thunderstorm has a first stroke of lightning, don't be a part of it. Even though you may not have heard thunder, if the sky looks threatening, you should find a safe shelter immediately. The first stroke of lightning is just as dangerous as any other stroke of lightning during the storm. LIGHTNING QUESTION OF THE DAY: How can you tell how far a stroke of lightning was away from you? ANSWER: While you see a stroke of lightning almost instantaneously, the sound of the thunder travels at a speed of about 1100 feet per second or about 1 mile in 5 seconds. For every 5 seconds between the time you observe the lightning and the time you hear the thunder, the lightning stroke is 1 mile away. If it takes 10 seconds between the lightning stroke and the thunder, the lightning stroke was 2 miles away. For 15 seconds, the stroke would be three miles away. Unfortunately, this method only works for the previous stroke and does not tell you how close the next lightning strike will be. Generally, if you hear thunder, you are within striking distance for the next stroke of lightning. If you are not in a safe place at the time, move to a safe place immediately. Here's a list of topics to be covered later this week. Tuesday İ Thunderstorm electricity. Wednesday İ Lightning safety while outdoors. Thursday İ Lightning safety inside the home. Friday İ Planning summer activities to minimize the lightning threat. Saturday İ Are you a potential lightning victim? In addition to the Public Information Statements, here are other activities available to the public. As part of LIGHTNING AWARENESS WEEK, the National Weather Service will be sponsoring public seminars to help educate the public on the dangers posed by lightning. Mr. Ronald Holle, one of the nation's top experts on lightning and lightning safety will be the featured speaker at these seminars. Mr. Holle is a Research Meteorologist at the National Severe Storms Laboratory in Norman Oklahoma and has published numerous articles on lightning and lightning safety. He has also given numerous lectures and talks on lightning and lightning safety in this and other countries. Public seminars are planned for the following places and times. Wednesday, May 26 9:30 am Bangor Kominsky Auditorium (in the main classroom building) Husson College Take Exit 48, Interstate 95 Take Route 15 north (Broadway) Left onto Husson Ave to Main Entrance (follow signs) 1:00 pm Augusta 1st Floor Lecture Hall City Hall 16 Cony Street Augusta, Maine Please park across the street at the old City Hall parking lot. 7:00 pm Portland Berstein Room Barron Center 1145 Brighton Avenue Portland, Maine Thursday, May 27 9:30 am South Berwick South Berwick Community Center 70 Norton Street South Berwick, Maine These seminars are FREE AND OPEN TO THE PUBLIC. Everyone is welcome to attend. In particular, those that supervise or manage outdoor recreational activities during the summer months are strongly encouraged to attend. Also, Mr. Ron Holle, along with John Jensenius, Warning Coordination Meteorologist at the National Weather Service Office in Gray, Maine will be the featured guests on "The Exchange" program on New Hampshire Public Radio on Friday morning, May 28 beginning at 9 am. The Exchange is a oneİhour callİin radio program produced and aired by New Hampshire Public Radio that allows listeners to call in and ask questions of the featured guests. In addition, both Ron Holle and John Jensenius will be the featured guests on a "Maine Watch" television show on lightning safety which will be taped during the week and is expected to be aired in early June. Maine Watch is a halfİhour television show produced and aired by Maine Public Television and broadcast Thursday and Sunday evenings. JENSENIUS NATIONAL WEATHER SERVICE GRAY, MAINE