US. DEPARTMENT OF COMMERCE ° National Oceanic and Atmospheric Administration - National Weather Service for Identifying and Reporting Severe Local Storms t 4 ~ I‘ wtrr‘ , Wichita Falls, Tex., tornado of April 10, 1979. Spotters played an essential role in the advance warning. There were more than 18,000 people in the tornado‘s damage path and yet only 44 persons died. Loss of life would have been much higher without warnings and knowledge of safety rules. (Photo: Len Hooten, Wichita Falls, Tex.) 463‘ l 1033“ TO THE SEVERE LOCAL STORM SPOTTER: .9, 1," t c. 'fw The National Weather Service of the US. Commerce Department’s National Oceanic and Atmospheric Administration, and cooperating organizations have established Severe Local Storm Spotter Networks in order to secure critical information on severe local storms. During the past 10 years tornadoes, severe thunderstorms, and flash floods have killed about 3,000 people and injured thousands of others. While this figure may appear staggering, we believe that thousands and possibly tens of thousands of lives have been saved by reports from storm spotters, such as yourself. Your information, coupled with radar, satellite, and other data has enabled the National Weather Service, to issue more timely and accurate warnings for tornadoes, severe thunderstorms, and flash floods. This guide has been designed to assist you in this important job. lam pleased to welcome you to the ranks of the tens of thousands of your counterparts who form the Nation’s first line of defense against tornadoes, flash floods, and other severe local storm hazards. There can be no finer individual reward than to-know that your efforts have given a community the gift of time—seconds and minutes that save lives. Sincerely, Vfflagw Richard E. Hallgren Director, National Weather Service A1 MD \c ““0 Sam/C «7 “ON 9° “" “00% .50 94% 3° C F Normals“ a, ”New or 9° . I Use of this Guide: fiThe information which is contained in this guide is not sufficient to qualify you as a SKYWARN spotter. Rather, it is provided as a refer- ence source to supplement the National Weather Service’s spotter training film and slide series. It has been compiled for use by trained spotters in the field and communi- cations specialists who receive and relay the reports. It is not a ' general handout forthe public. As a result of its specialized subject matter, a number of technical terms are used. Their meanings " are explained in the text or in the glossary. #3 NOAA Spotters Guide (36955 1. Severe Thunderstorms g é, 7 All thunderstorms are capable of producing tornadoes. ln coastal areas, waterspouts and weak funnels frequently form in areas of weak shower activity. While these are dangerous and should be reported,'they usually are not preceded by the cloud structures described in this guide. Strong to violent tornadoes are usually associated with what we shall call the Tornadic Thunderstorm. Other significant tornadoes do occa- sionally occur with Squall Line Thunderstorms. In the following sections, we will review the ex- tremely important cloud features which commonly precede tornado and severe weather events. A. The Tornadic Thunderstorm: These thunderstorms are usually separated from other thunder- storms or may even be isolated. This separation allows them to feed upon warm moist air from miles around. Figure 1 is a repre- sentation of a tornadic thunder- storm as a spotter might see it when located east of the storm, EART looking west. The storm is gener- ally moving from the left to the right. The main updraft of warm moist air is entering the storm at cloud base below the Main Storm Tower. Strong winds aloft are blowing from the southwest to northeast. Air in the upper portion of the updraft eventually becomes colder than the surrounding air. At this level, the cloud spreads out rapidly, forming an Anvil Cloud. As precipitation begins to occur, downdrafts are created. Figure 2 is a view of the same storm and its associated weather from above, looking down. The intense updraft, which is rising out of the drawing, is located within the main storm tower as shown by the scalIOped lines in a semi-circle surrounding the dark blue area. The downdraft air sinks to the ground in the area where precipi- tation is falling, mainly to the north FIGURE 1 V and northeast of the updraft. A second downdraft forms just‘ southwest of the updraft. This is the area, near the intersection of the updraft and this “rear-flank” downdraft, where the tornado is most likely to occur. Large hail is likely to fall just outside the up- draft core, mainly northeast of the updraft. Tornadoes may also form along the Gust Front and Flanking Line, these are usually weak and short-lived. Looking back at Figure 1, we can see the primary features to look for at the cloud base. The Flanking Line Towers, Collar Cloud, and Tail Cloud are ex- plained in the glossary. The three features of primary importance are the Rain Free Base, Wall Cloud, and Precipitation Area. In Figure 3, we are west of the storm looking east-southeast, and the storm is moving to the left. The heavy rain area to the left tells us where a main downdraft is located. The Rain Free Base extends from under the Main Storm Tower (which is tilted slightly to the left by the upper level winds) to the Flanking Line Towers. The lower- ing of the cloud base near the center is a Wall Cloud. The Wall Cloud is usually in the southwest portion of the storm within several miles of the rain area. Not all Wall Clouds rotate. Nevertheless, a rotating Wall Cloud usual/y pre- cedes significant tornado develop- ment from minutes to over an hour. Be alert to the fact that some tor- nadoes may develop from the Rain Free Base itself. FIGURE 2 A FIGURE 3 V SllVWMlll B. The Tornado: Tornadoes vary greatly in ap- pearance and intensity, ranging from the violent type (pictured on the cover) to the very weak and short-lived ones that last only a few seconds. In addition, a torna- do’s appearance frequently changes during its life cycle. Figure 4 shows a multiple vortex tornado which is composed of sev- eral small but intense vortices which revolve around a common center. These small vortices may develop and dissipate very quickly. Attimes, rainfall is drawn into the tornado’s circulation, making it very difficult to see. While this is common in the Southeast United States, it is not limited to that area as illustrated by the Kansas tor- nado in Figure 5. in Figure 6, we see a tornadic dust whirl. It should not be confused with a dust devil which usually occurs on nearly cloudless and warm days having light winds. The first stage of tor- nado development is often a dust whirl at the ground with or without a funnel aloft. The tornadic dust whirl in Figure 6 did not develop beyond this initial stage. It is ' common forflanking line dust ”6”“ 5 V whirls to form along the gust front; these generally remain weak and short-lived. FIGURE 4 A FIGURE 5 V NOAA Spotters Guide C. The Life Cycle of a Tornado: In Figure 7, we are looking west and can see the typical pattern: Rain Free Base, Wall Cloud, and Precipitation Area. The Wall Cloud is located in the southwest quad- rant ot the storm, and formed 30 minutes prior to the tornado. In Figure 8, what appears to be a funnel cloud is visible under the left portion of the Wall Cloud. In fact, this is a tornado because damage was occurring at the ground even though it is too far away to see the surface debris. In such a situation, you should prop~ erly report this as a funnel cloud, along with the fact that it is too far away for you to determine if it is on the ground. Report what you see, along with any additional remarks which would make the report more useful. In Figure 9, the circulation becomes visible all the way to the ground. The thin, “needle-tipped” shape is common for a tornado in this early stage. The tornado reaches its mature stage in Figure 10, with its width at the surface expanding to 1/4 mile. Note the Tail Cloud forming to the right. We have changed position in Figure 11 and are looking south- east as the tornado moves away from the town of Union City, Okla- homa. The tornado is shrinking rapidly into the “rope stage,” but is still very destructive. During the latter portion of a tornado’s life, it is common for it to decrease in size (not necessarily In intensity) and become increasingly tilted. FIGURE ‘7 A FIGURE 8 A FIGURE 9 A FIGURE 11 A I A w a A" U nlu F Guide ‘ Spofl‘grs NOAA 56316 0 ‘0 20 M 00 50 Kilomnlul % Developing Cumulus Towers 0 5 ‘0 15 20 25 Nlulicllflllu FIGURE 12 A Height, Feel — 50,000 - 40,000 —' 30,000 — 20,000 — 10,000 r..— z / FIGURE 13 A \\\ 4 \\\ ii \\ i ‘ ii \\\\\\\ i A F—aakm(20nml)——| Shell Cloud Height, Kilometers D. The Squall Line Thunderstorms: Figure 12 is a view of a squall line as seen from above. Precipi- tation is shown in black and greys, the gust front is the white line with teeth, and the anvil edge is in blue. While any hail which may occur is usually smaller than that occurring in the tornadic thunderstorm and considerably fewer tornadoes result, strong straight-line winds are common with squall lines. The strongest winds usually occur a few minutes after the gust front passage, just before or just after rain and hail begin. If tornadoes occur, they are generally weak, short—lived, and are found along the gust front. Occasionally, a tornadic thunderstorm will develop in association with a squall line. These storms are most often on the south end or ahead of the squall line. The most distinctive cloud associated with the squall line is the Shelf Cloud, shown in black in Figure 12. It is usually located above the squall line gust front. An individual tornadic thunder- storm or even an isolated non- severe thunderstorm may at times develop a shelf cloud associated with its gust front. Before we look closer at the shelf cloud, let’s take a look at a vertical cross section of the squall line from point A to B in Figure 12. This is shown in Figure 13. Note that the squall line thunderstorm has a significantly different struc- ture than the tornadic thunder- storm. In Figure 13, the squall line is moving from left to right. Up- drafts form a nearly continuous curtain along the leading edge above the gust front. Downdrafts are located in the precipitation area to the rear. Thus, the updraft- rainy downdraft orientation is reversed from that of the tornadic thunderstorm. In Figure 14, we are looking west at 3 layers of cloud near the south end of a gust front. The lowest band of cloud is a shelf cloud. This cloud is wedge-shaped and smooth and sometimes ap- pears layered. As the squall line passes overhead, shown in Figure 15, gusty winds and a sharp drop in temperature can be expected. Upward motion is along the lead- ing edge and downward motion along the trailing edge of the shelf cloud. Cloud base behind the gust front is often very turbulent, as shown here. Less common than the shelf cloud is a Roll Cloud. In Figure 16 it is seen as the de- tached tube shaped cloud. It can often be seen to rotate slowly about a horizontal axis. Like the shelf cloud, it may indicate the leading edge of a zone of strong straight-line winds. Because of its horizontal rotation, it may be mis- taken for a tornado. Let’s look at some other structures that are frequently falsely reported as FIGURE 16 V tornadoes. FIGURE 14 A FIGURE 15 V s ; y: NOAA Spotters Guide 9 E. Tornado Look-Alikes: Virga or rain shafts are often reported as tornadoes. In Figure 17, we see a developing rain shaft, which is fuzzy in appearance. An intense rain column, as in Figure 18, can be more difficult. Although it looks similar to the violent tor- nado on the cover of this guide, its edges are much less distinct. Mammatus clouds, as seen in Figure 19, are often mistaken for tornadoes. While mammatus often accompany severe thunderstorms (see Figure 1), they are not severe in themselves and may also ac— company non-severe thunder- storms. The feature most often mistaken for a tornado is a scud cloud. These are ragged, low cloud fragments which usually are not attached to the cloud base. When the scud is attached to the cloud base, as in Figure 20, it is very difficult to distinguish it from a wall cloud or tornado. In this example, and for all tornado look-alikes, the key is to: LOOK FOR ORGANIZED AND SUSTAINED ROTATION ABOUT A NEARLY VERTICAL AXIS. FIGURE 17 A FIGURE 18 V SKVWAIIII 10 m , ~25 FIGURE 20 A { FIGURE 19 11 NCAA Spotters Guide Spotter Reporting Procedures 0 From radio-equipped vehicles, report severe weather observations to a central collection point and request them to relay the report to the National Weather Service. 0 Law enforcement and Civil Defense spotters—report to the National Weather Service via NAWAS, radio, or other direct communications links as pre- scribed by your Emergency Operations Plan. 0 When the telephone is your only communications method, call your primary or alternate contact and ask them to relay your report to the National Weather Service. If you are unable to reach the pri- mary or alternate contact, place an emergency call through the tele- phone operator to the National Weather Service. If the call is long distance, it can be made collect. Report promptly as the storm may interrupt communications. REPORT BRIEFLY: What you have seen: wall cloud, tornado, funnel cloud, waterspout, heavy rain, etc. Where you saw it: the direction and distance from a known loca- tion, e.g., 3 miles south of Belts- ville. When you saw it: make sure you . note the time of your observation. What it was doing: describe the storm’s direction and speed of travel, size and intensity, and de- structiveness. Include any amount of uncertainty as needed, i.e., “funnel cloud; no debris visible at the surface but too far away to be certain it is not on the ground.” Identify yourself and your location. Give spotter code number if one has been assigned. Report: 1. Tornado, Funnel Cloud, Waterspout, or Wall Cloud 2. Hail, 1/4 inch or larger 3. Damaging Winds (usually 50 mph or greater) 4. Flash Flooding 5. Rain, (rate of 1 inch per hour or more) Additional Tips for Skywarn Spotters 0 The first sign of a tornado may not be a funnel at the cloud base. Your first clue may be debris or dust at the surface, so be alert to events at ground level, as well as in the clouds. 0 At night, lightning flashes can aid in identifying the Rain Free Base, Wall Cloud, and Precipita- tion Area. Although aloud roar is frequently associated with a tor- nado, strong straight-line winds can also produce such a sound. 0 If you spot from a fixed loca- tion, use a map to determine dis- tances and directions to known landmarks such as water towers, TV towers, etc. This will help you estimate distance and direction in your reports. Mobile spotters should always have up-to-date maps and be familiar with the area in which they are operating. 0 When available, use binocu- lars to look for rotation and other cloud features. Once you spot a funnel, tornado, or wall cloud, be alert for the formation of others in the area. 0 If you find yourself in large hail, remember you are in or near the area where tornado formation is most likely in a tornadic thunderstorm. 0 Always follow the basic safety rules. In open country, a spotter may be able to use his knowledge of the tornado’s motion and avail- able escape routes to drive away from the tornado safely. In urban areas this is usually not possible because of traffic congestion. Make certain your family knows what to do in tornado emergencies as you may not be available to assist or direct them. Spotter Aids ESTIMATING HAIL SIZE: pea size 1%: inch; marble size 1/2 inch; dime size % inch; quarter size 1 inch; golfball size 1.75 inch; baseball size 2.75 inch. ESTIMATING WIND SPEEDS“ (miles per hour) 25-31 ..... Large branches in motion; whistling heard in telephone wires 12 32-38 ..... Whole trees in motion; inconvenience felt walking against wind 39-54 ..... Twigs break off trees; wind generally impedes progress 55-72 ..... Damage to chimneys and TV antenna; pushes over shallow rooted trees 73-112. . . .Peels surface off roofs; windows broken; light trailer houses pushed or overturned; moving automobiles pushed off roads 113-157. . .Roofs torn off houses; weak buildings and trailer houses de- stroyed; large trees snapped and uprooted 158 & up. .Severe damage; cars lifted off ground " Adapted from the Beaufort and Fujila Wind Scales. National Weather Service Storm Spotters Glossary and Supplemental Guide Accessory Clouds Clouds that are dependent on a larger cloud system for development and continuance. Accessory clouds associated with the thunderstorm include roll, shelf, mammatus, and wall clouds. Anvil The spreading of the upper portion of a cumulonimbus cloud into an anvil- shaped plume usually of fibrous or smooth appearance. Strong or severe thunderstorms often have thicker anvils with the side and bottom having a cumuliform or slowly boiling appear- ance in the immediate vicinity of the parent cumulonimbus. Collar Cloud Frequently used as a synonym for a wall cloud although it actually is a generally circular ring of cloud sur- rounding the upper portion of a wall cloud. Cumulonimbus Cloud The parent cloud of a thunderstorm. The cumulonimbus cloud towers above ordinary cumulus clouds, with stronger or severe storms often having a more sharply outlined ”hard" appearance with relatively rapid rising motions visible. The cloud’s upper portion includes the anvil. Accompanying precipitation is often heavy and the usual occurrence of lightning and thunder with these clouds leads to the popular names of thunderhead or thundercloud. See also Thunderstorm. Cumulus Cloud A column of rising air that has con- densed into a dense, nonfibrous cloud with distinct outlines, appearing much like a rising mound, a dome, or cauliflower. The base of the cloud is relatively flat and dark, while the tower is usually white and sunlit. The cumulus cloud is the first stage of a developing thunderstorm, although most cumulus do not form thunder- storms. Downdraft A column of generally cool air that rapidly sinks to the ground, most often accompanied by precipitation in a shower or thunderstorm. Areas of downdraft usually contain little cloud, and what clouds that may be present are typically dissipating. Flanking Line Aline of cumulus connected to and extending outward from the most active portion of a parent cumulonim- bus, usually found on the southwest side of the storm. The cloud line has roughly a stair step appearance with the taller clouds adjacent to the parent cumulonimbus. It is most frequently associated with strong or severe thunderstorms. Flash Flooding Flooding that develops very quickly on streams and river tributaries usually as a result of thunderstorms. Some- times the onset of flash flooding comes before the end of heavy rains. There is little time between the detection of flood conditions and the arrival of the flood crest. Swift action is essential to the protection of life and property. Front A transition zone between two differ- ing air masses. Basic frontal types are (1) COLD FRONT where cooler air advances replacing warmer air; (2) WARM FRONT—warmer air advances replacing cooler air; (3) STATIONARY FRONT—warmer air meeting cooler air with neither air mass moving appre- ciably. Thunderstorms can form in association with any of these fronts. However, fronts are not necessary for thunderstorm development. Funnel Cloud A funnel-shaped cloud extending from a towering cumulus or cumulo- nimbus base. It is associated with a rotating air column that is not in contact with the ground. The cloud is a tornado if a ground-based debris or dust whirl is visible below the funnel aloft. Gust Front The leading edge of the thunder- storm downdraft air. The gust front is most prominent beneath the rain-free base and on the leading edge of an approaching thunderstorm. It is usually marked by gusty, cool winds, and sometimes blowing dust. The gust front often precedes the thunderstorm pre- cipitation by several minutes. The shelf or roll cloud sometimes accompanies the gust front, especially when the gust front precedes a line of thunderstorms. Hall Precipitation in the form of balls or clumps of ice, produced by thunder- storms. Severe storms with intense updrafts are the most likely large hail producers. Hook Echo A radar pattern sometimes observed in the southwest quadrant of a tornadic thunderstorm. Appearing like the number six or a fishhook turned in toward the east, the hook echo is precipitation aloft around the periphery of a rotating column of air 2-10 miles in diameter. The hook echo is often found in a local area favorable for tornado development. However, many tornadoes occur without a hook echo and not all hook echoes produce tornadoes. Lightning Any and all of the various forms of visible electrical discharge caused by thunderstorms. Severe thunderstorms usually have very frequent and some- times nearly continuous lightning. However, some non-severe thunder- storms also contain frequent and vivid electrical displays, while some severe storms are accompanied by little lightning. Mamma Clouds Also called mammatus, these clouds appear as hanging, rounded protuber- ances or pouches on the under surface of a cloud. With thunderstorms, mam- matus are seen on the underside of the anvil. These clouds do not produce tornadoes, funnels, hall, or any other type of severe weather, although they often accompany severe thunderstorms. Precipitation Shaft A visible column of rain and/or hail falling from a cloud base. When viewed against a light background, heavy precipitation appears very dark gray, sometimes with a turquoise tinge. This turquoise tinge has been commonly attributed to hail but its actual cause is unknown. 13 Rain-Free Base A horizontal, dark cumulonimbus base that has no visible precipitation beneath it. This structure usually marks the location of the thunderstorm updraft. Tornadoes most commonly develop (1) from wall clouds that are attached to the rain-free base, or (2) from the rain-free base itself. This is particularly true when the rain-free base is observed to the south or southwest of the precipitation shaft. River Flood Usually occurs on rivers, after flash flooding has occurred on streams and tributaries. River floods develop and reach their peak more slowly than flash floods. In many cases, the river flood peak occurs after the rain has ended. Roll Cloud A relatively rare, low-level, horizon- tal, tube-shaped accessory cloud com- pletely detached from the cumulonim- bus base. When present, it is located along the gust front and most fre- quently observed on the leading edge of a line of thunderstorms. The roll cloud will appear to be slowly “rolling” about its horizontal axis. Roll clouds are not and do not produce tornadoes. Scud Clouds Low cloud fragments often seen in association with and behind thunder- storm gust fronts. These clouds are ragged and wind torn and are not usually attached to the thunderstorm base. Scud clouds do not produce severe weather. In some cases, when scud clouds are attached to the thunderstorm base they can be mis- taken for wall clouds or tornadoes. Severe Thunderstorm A thunderstorm that goes from the mature stage to the severe stage before dissipating. Severe thunder- storms are most efficient “machines" because the updraft remains strong for a long time. They also occasionally contain rotation on a broad scale. Because of its structure. the severe storm may iast for hours beyond the lifetime of a normal thunderstorm while producing large hail, high winds, torrential rain, and possible tornadoes. Officially, a thunderstorm is classified as severe if 50 knot (58 mph) winds are measured, 3/: inch or larger hail occurs, or funnel clouds or tornadoes develop. Straight Winds Winds associated with a thunder- storm, most frequently found with the gust front. These winds originate as 14 downdraft air reaches the ground and rapidly spreads out, becoming strong horizontal flow. Damaging straight winds, although relatively rare them- selves, are much more common than are tornadoes. Shelf Cloud A low-level horizontal accessory cloud that frequently appears to be wedge-shaped as it approaches. It is usually attached to the thunderstorm base and forms along the gust front. The leading edge of the shelf is often smooth and at times layered or ter— raced. It is most often seen along the leading edge of an approaching line of thunderstorms, accompanied by gusty straight winds as it passes overhead and followed by precipitation. The underside is concave upward, turbu- lent, boiling, or wind~torn. Tornadoes rarely occur with the shelf cloud. Squall Line Any line or narrow band of active thunderstorms. The term is usually used to describe solid or broken lines of strong or severe thunderstorms. Tail Cloud A low tail-shaped cloud extending outward from the northern quadrant of a wall cloud. Motions in the tail cloud are toward the wall cloud with rapid updraft at the junction of tail and wall cloud. This horizontal cloud is not a funnel or tornado. Thunderstorm A local storm (accompanied by lightning and thunder) produced by a cumulonimbus cloud, usually with gusty winds, heavy rain, and some- times hail. Non-severe thunderstorms rarely have lifetimes over two hours. A typical, non—severe thunderstorm life cycle consists of three stages: (1) CUMULUS STAGE—warm, moist air rises (updraft) and condenses into tiny water droplets which make up the visible cloud. (2) MATURE STAGE— th-e cloud grows above the freezing level; precipitation forms and becomes heavy enough to fall back to earth. This precipitation generates cool air which also sinks back to earth with the precipitation. (3) DISSIPAT/ON STAGE —Cool rain and downdraft spread throughout the storm replacing the updraft which is the lifeblood of the thunderstorm. The visible cumulonim- bus cloud becomes softer in appear- ance, less distinctly outlined or ”fuzzy and dissipates, sometimes leaving only the high anvil cloud, as the storm rains itself out. Tornado A violently rotating narrow column of air in contact with the ground and extending from a thunderstorm base. The tornado is most often found in the southwest quadrant of the storm, near the trailing edge of the cumulonimbus cloud. Tornadoes and funnel clouds are usually pendant from (1) wall clouds or (2) directly from the thunder- storm base, within a few miles to the southwest of the precipitation shaft. The spinning moton of a tornado is most often left to right on the front side and right to left on the backside (counterclockwise). Tornadoes have been called twisters and cyclones, but these words are all synonyms for the most violent storm on earth, with esti- mated wind speeds up to 300 mph. Updraft Warm moist air which rises and condenses into a visible cumulus or cumulonimbus cloud. Once the cloud forms, it depends on the updraft for continuance and further development. Virga Wisps or streaks of rain falling out of a cloud but not reaching the earth's surface. When seen from a distance, these streaks can be mistaken for funnels or tornadoes. Wall Clouds A local and often abrupt lowering of a rain-free cumulonimbus base into a low-hanging accessory cloud, from 1 to 4 miles in diameter. The wall cloud is usually situated in the southwest portion of the storm below an intense updraft, marked by the main cumulo- nimbus cloud and associated with a very strong or severe thunderstorm. When seen from within several miles, many wall clouds exhibit rapid upward motion and rotation in the same sense as a tornado, except with considerably slower speed. A rotating wall cloud - usually develops before tornadoes or funnel clouds by a time which can range from a few minutes up to possi- bly an hour. Spotters should key on any lowering of the cumulonimbus base as suspect wall cloud. particu- larly when it is located southwest of the precipitation shaft. Wall clouds should be reported. NOTE: Sometimes other low-hanging accessory clouds are mistakenly identified as wall clouds. Warning (Issued for tornadoes, severe thun- derstorm, flash flood, river flood.) A warning is issued when severe weather has already developed and has been reported by spotters or indicated by radar. Warnings are statements of imminent danger and are issued for relatively small areas near and down- stream from the severe storm or flood. Watch - (issued for tornado, severe thunder- storm, flash flood.) A watch identifies a relatively large area in which flash floods or severe storms might occur. Watches are quite often issued before any severe weather has developed. Severe thunderstorm and tornado watches usually include an area 140 miles wide by about 200 miles long. The watch is only an indication of where and when the severe weather probabilities are highest, and should not be confused with a warning. . NOAA Spotters Guide 1‘! U3. GOVERNMENT PRINTING OFFICE: SKVWMIN 15 1982 - 360-009 - 227/2046 U.S. DEPARTMENT OF COMMERCE National Oceanic and Atmospheric Administration Rockvllle, Maryland 20852 POSTAGE AND FEES PAID U.S. DEPARTg/IOE'uTQEE COMMERCE OFFICIAL BUSINESS Penalty for Private Use. $300 When in doubt, make your report anyway! at (telephone) Alternate at (your name) (your address) (telephone) (your Spotter Code number) For further information, call or write to the National Weather Service office indicated NOAA/PA 81011 (Rev. April 1982)