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Cover Photo - Alan Moller 1 I. INTRODUCTION The Spotter’s Role The National Wea

Cover Photo - Alan Moller 1 I. INTRODUCTION The Spotter’s Role The National Weather Service (NWS) has a number of devices for detecting severe thunderstorms. Included in these are radar, satel- lite, and lightning detection networks. However, the most important tool for observing thunderstorms is the trained eye of the storm spotter. While radar is used quite often in severe storm warnings, conventional weather radar will only indicate areas and intensities of precipitation. It does not give any indication of cloud formations or wind fields associated with a storm. Doppler radar, which is being introduced across the country, will give some indication of air motions inside a storm. Doppler radar, though, will not give these indications down to ground level. It is impossible for any radar to detect every severe weather event in its coverage area, and radar occasionally suggests severe weather when, in fact, none is present. Satellite and lightning detection networks provide general thunderstorm locations and are extremely valuable in data-sparse regions (such as over mountainous terrain or over bodies of water). They help to identify persistent thunderstorm areas and can be of aid in flash flood forecasting. These systems provide little in the way of quantitative real-time information, though, and are not especially helpful during times of fast-breaking severe weather. As a trained spotter, you perform an invaluable service for the NWS. Your real-time observations of tornadoes, hail, wind, and significant cloud formations provide a truly reliable information base for severe weather detection and verification. By providing observations, you are assisting NWS staff members in their warning decisions and enabling the NWS to fulfill its mission of protecting life and property. You are helping to provide the citizens of your community with potentially life-saving information. Objectives of this Handbook During the past several years, researchers have uncovered a tremendous amount of information regarding severe thunderstorm structure and behavior. New theories regarding thunderstorm formation and tornado development have been presented. Storm- intercept teams have correlated these theories with observed visual features. Our current understanding of the thunderstorm is markedly more complete than it was just ten years ago. With this handbook and the Advanced Spotter Training Slide Set which was released a few years ago, the time has come to pass this new understanding on to you, the spotter. Only by providing fresh training material can the NWS expect to maintain what has become a very important group of observers. Prerequisites for Using this Guide The information contained in this guide is not for the novice spotter. It is recommended that spotters go through two or more basic spotter training sessions and have some experience at actual storm spotting before attempting the intermediate/advanced train- ing material. Spotters should be comfortable with the basic concepts of storm structure and storm spotting. Obviously, spotters should have a desire to learn the latest concepts of tornado and severe thunderstorm behavior. II. REPORTING PROCEDURES Primary and Secondary Contacts It is essential that any spotter network have a clear set of procedures for reporting severe weather and other observations. All networks should have a designated methodology for relaying reports from the field to the local NWS office. There should be a primary contact for activation and operation of the spotter network. It is also suggested that a secondary contact be established for those occasions when widespread severe weather is occurring or when the primary contact is not available. 2 Amateur radio operators comprise the backbone of many spotter networks. Most amateur radio networks include an operator at the NWS office for quick relay of reports and direction of spotters in the field to “hot spots.” This has proven to be an effective, efficient method of relaying severe weather observations. Other operators may be deployed at television or radio stations in the NWS office’s county warning area. Law enforcement and fire department personnel also serve as spotter networks in many areas. Many of these groups report to a dispatcher who, in turn, relays reports to the NWS. These spotter networks should establish a secondary contact (such as the dis- patcher of another city/county agency) for those times when pri- mary communications are impeded. The dispatchers should also receive at least basic spotter training. Although they are not actually observing the storms in the field, dispatchers serve as a critical link in the severe weather information chain. If they are familiar with thunderstorm and spotting terminol- ogy, dispatchers are able to screen out less important observations and quickly relay significant reports to the local NWS office. In remote or sparsely populated areas, private citizens may have to serve as spotters. While these individuals may not be as well organized as the amateur radio or law enforcement-based groups, there should still be established reporting procedures. Local law enforcement or emergency management offices are candidates for contacts in these situations. Spotter Coordination Spotting is not a one-person job. It is difficult, if not impossible, for one spotter to accurately observe all aspects of a thunderstorm. Rather, it is necessary for spotters and spotter groups to coordinate and share information (with the NWS and with each other) to obtain the best possible assessment of the storm. Spotters with two-way radio communications should talk not only with their dispatch/control personnel but with other spotters in the area. Positioning spotter teams at several strategic locations around a storm, with active communication between the spotters, should enable a great deal of information concerning the thunderstorm to be relayed to the local NWS office. If two or more spotter groups are working in the same area (i.e., an amateur radio group and a law enforcement group), then these groups should share information regarding their observations. The NWS should also attempt to coordinate between spotter groups. As a storm moves from one spotter group’s area to another, the downstream spotter group should be notified well in advance to allow time for their activation and deployment. Reporting Criteria There are certain criteria for reporting severe weather. Recall that a thunderstorm is defined as severe if it produces a tornado, hail 3/4 inch in diameter or larger, and/or wind gusts 58 miles an hour or higher. It would be desirable to report events associated with a thunderstorm before they reach these severe levels. Use the follow- ing guidelines for reporting weather events. Report hail occurrences when the hailstones have a diameter of 1/ 2 inch, and report wind gusts when their speed reaches 50 miles an hour. See tables 1 and 2 for estimations of hail size and wind speed. Obviously, tornadoes and funnel clouds should be reported. A funnel cloud is defined as a violently rotating column of air which is not in contact with the ground. It is usually marked by a funnel- shaped cloud extending downward from the cloud base (hence its name). If the violently rotating air column reaches the ground, it is called a tornado. An important point to note is that the visible funnel DOES NOT have to extend to the ground for a tornado to be present. Instead, look for a rotating cloud of dust and debris under- neath a funnel cloud as evidence that the tornado’s circulation has reached the ground. 3 Hail Size Estimates Pea .................................. 25 Penny ...................... 0.75 Quarter ............................ 1.00 Half Dollar .............. 1.25 Golf ball........................... 1.75 Tennis Ball............... 2.50 Baseball .......................... 2.75 Grapefruit ............... 4.00 Table 1: Hail Size Estimations. Wind Speed Estimates Speed (MPH) Effects 25-31 Large branches in motion; whistling in telephone wires 32-38 Whole trees in motion 39-54 Twigs break off of trees; wind impedes walking 55-72 Damage to chimneys and TV antennas; pushes over shallow rooted trees 73-112 Peels surface off roofs; windows broken; trailer houses overturned 113+ Roofs torn off houses; weak buildings and trailer houses destroyed; large trees uprooted Table 2: Wind Speed Estimations. Flash flooding should be reported, but the reporting criteria are not as well defined as with severe weather events. A flash flood is defined as a rapid rise in water usually during or after a period of heavy rain. Variations in soil type, terrain, and urbanization result in a wide variation in the amount of runoff which will occur during and after a given amount of rain. Consult your local NWS office regarding flash flood reporting procedures in your area. When making a report, you (or your dispatcher/control person) should include the following information: (1) WHO you are, and the name of your spotter group. (2) WHERE the event is occurring. Use reports from other nearby spotters to triangulate and pinpoint the event’s location. (3) WHAT you have seen (the severe weather event). (4) MOVEMENT of the event. When estimating movement, don’t use the motion of small cloud elements for estimation. Instead, observe the storms a whole for estimates of motion. III. SAFETY TIPS Safety should be first and foremost on the mind of a spotter. Remember, the NWS values your safety more than we do your observations. It is essential that spotters proceed into the field armed not only with knowledge uploads/Management/ advanced-spotter-guide.pdf