RESOURCE GUIDE Federal Emergency Management Agency Emergency Management Institute U.S. Department of Commerce National Oceanic & Atmospheric Administration National Weather Service HAZARDOUS WEATHER RESOURCE GUIDE A Source Book For: Planning For Hazardous Weather And Flooding Developed By: Federal Emergency Management Agency Emergency Management Institute And: U.S. Department of Commerce National Oceanic & Atmospheric Administration National Weather Service August 1996 II. WEATHER AND CLIMATE REVIEW Hazardous Weather Resource Guide Page II-1 TABLE OF CONTENTS Page I. INTRODUCTION ...............................................................................................................I-1 Purpose.......................................................................................................................................I-1 How To Use This Guide ............................................................................................................I-1 II. WEATHER AND CLIMATE REVIEW....................................................................... II-1 Weather Review........................................................................................................................II-1 Table 1. Physical Elements Of Weather ..................................................................................II-2 Table 2. General Circulation Of The Atmosphere.................................................................II-18 Table 3. Global Effects On U.S. Weather..............................................................................II-24 III. HAZARDOUS WEATHER FACT SHEETS .............................................................III-1 Introduction............................................................................................................................. III-1 Thunderstorms ........................................................................................................................ III-2 Tornadoes.............................................................................................................................. III-22 Flash Floods .......................................................................................................................... III-28 Riverine Floods..................................................................................................................... III-39 Coastal Floods....................................................................................................................... III-46 Extratropical Cyclones.......................................................................................................... III-65 Tropical Cyclones ................................................................................................................. III-67 Tsunamis ............................................................................................................................... III-90 Winter Storms ..................................................................................................................... III-101 Excessive Cold .................................................................................................................... III-117 Fog ...................................................................................................................................... III-123 Excessive Heat .................................................................................................................... III-129 Duststorms .......................................................................................................................... III-136 Windstrorms........................................................................................................................ III-143 Fire Weather........................................................................................................................ III-150 Index of NWS Products ...................................................................................................... III-175 II. WEATHER AND CLIMATE REVIEW Hazardous Weather Resource Guide Page II-2 TABLE OF CONTENTS (Continued) Page APPENDIX A: SOURCES OF WEATHER INFORMATION.........................................A-1 State Climatologist................................................................................................................... A-1 National Weather Service Organization.................................................................................. A-1 National Weather Service Dissemination Systems .................................................................. A-6 National Weather Service Technology.................................................................................... A-8 Internet/World Wide Web Information.................................................................................... A-8 University Services .................................................................................................................. A-9 Private Sector Meteorologists ................................................................................................ A-12 APPENDIX B: NWS ABBREVIATIONS ...........................................................................B-1 List Of Node Offices.................................................................................................................B-2 Partial List Of Product Codes ...................................................................................................B-3 List Of Cities Of Issuing Office Codes.....................................................................................B-4 APPENDIX C: TEMPERATURE, RELATIVE HUMIDITY, AND DEW POINT CONVERSION........................................................................................C-1 APPENDIX D: BIBLIOGRAPY..........................................................................................E-1 APPENDIX E: GLOSSARY.................................................................................................F-1 II. WEATHER AND CLIMATE REVIEW Hazardous Weather Resource Guide Page II-3 I. INTRODUCTION II. WEATHER AND CLIMATE REVIEW Hazardous Weather Resource Guide Page II-4 Purpose How To Use This Guide INTRODUCTION PURPOSE This Resource Guide has been designed as a desk reference for you to use when you return to your job. HOW TO USE THIS GUIDE II. WEATHER AND CLIMATE REVIEW Hazardous Weather Resource Guide Page II-5 This guide is organized in three sections. Each section is indicated with a weather icon. Ì Section I: Introduction describes this guide, including its purpose and intended use. Ì Section II: Weather Review summarizes important climate and weather concepts from this course. Ì Section III: Hazardous Weather Fact Sheets presents characteristics (including hazards), historical examples, a table listing information products, and sample National Weather Service (NWS) products related to major U.S. weather events. These products are listed in an index at the end of Section III. Several appendixes follow this guide: Ì Appendix A includes sources of additional information about hazardous weather, including private vendors and universities. Where possible, Internet addresses are included. Ì Appendix B provides an explanation of NWS Product Identifier List (PIL) Codes that are included on all products. It also contains a list of abbreviations of cities, as used in the PIL codes. Ì Appendix C provides a conversion chart for temperature, relative humidity, and dew point. Ì Appendix D includes a bibliography of hazardous weather resources. Ì Appendix E includes a glossary of weather-related terms. Use this guide: Ì During your planning process as a guide to the types of damage you can expect for the hazards facing your community. II. WEATHER AND CLIMATE REVIEW Hazardous Weather Resource Guide Page II-6 HOW TO USE THIS GUIDE (Continued) Ì When you have a question about the physical elements that cause weather or the factors that influence weather in your area. Ì When you have a question about a specific hazard facing your community. Refer to specific fact sheets for information about the type of damage that the hazard can cause or products that the NWS issues for the hazard—or to review a sample product. II. WEATHER AND CLIMATE REVIEW Hazardous Weather Resource Guide Page II-7 II. WEATHER AND CLIMATE REVIEW II. WEATHER AND CLIMATE REVIEW Hazardous Weather Resource Guide Page II-8 Weather Review Physical Elements Of Weather General Circulation Of The Atmosphere Global Effects on U.S. Weather II. WEATHER AND CLIMATE REVIEW Hazardous Weather Resource Guide Page II-9 WEATHER AND CLIMATE REVIEW WEATHER REVIEW To understand and plan for hazardous weather events, you must have a basic understanding of the physical elements and hydrometeorological factors that work together to cause weather—and how, under certain conditions, these elements and factors can contribute to hazardous weather. This weather review provides a general review of those factors. Various physical elements, or building blocks, contribute to the differences in the atmosphere that create weather. These elements are the basic components of weather and are described in Table 1. Scientists have observed how the physical elements interact to form some general, systematic weather phenomena. Understanding how the physical elements interact helps us to understand how the atmosphere circulates and how weather events, such as storms, are formed. Major systematic factors are summarized in Table 2 and include water currents, air movement, temperature and air pressure differences, and geographic features. Table 3 describes several global effects of the interaction of the physical elements. As you review each of these tables, consider how: Ì The information relates to weather that affects your community. Ì You can use the information in your planning process. II. WEATHER AND CLIMATE REVIEW Hazardous Weather Resource Guide Page II-10 DESCRIPTION The sun heats the earth’s surface during the day. Incoming solar radiation to the earth’s surface is called insolation. Heat is radiated from the earth by outgoing radiation, called terrestrial radiation. Cooling results at night as terrestrial radiation continues and insolation ceases. The earth has two basic motions within the solar system. The first is the daily rotation of the earth about its axis. A complete rotation of the Earth takes about 24 hours. This rotation causes periods of daylight and darkness and, in turn, produces numerous weather effects and causes a predictable effect on the flow of wind over the surface of the Earth. This second motion of the Earth is the rotation around the sun, which takes 1 year. This causes the seasonal variation in temperature. The atmosphere is the gaseous envelope covering the Earth and is held in place by gravity. The atmosphere consists of a mixture of various gases. The atmosphere is divided into layers, or spheres, each having certain properties and characteristics. Ë The troposphere is the layer adjacent to the Earth. It varies in depth from an average of 60,000 feet over the equator to 28,000 feet over the poles, with greater depth in the summer than in the winter. The troposphere is characterized by a decrease in temperature with height. Ë At the top of the troposphere is the tropopause, which serves as the boundary between the troposphere and the next layer, the stratosphere. The location of the tropopause is characterized by a pronounced warming of temperature with altitude. The tropopause acts like a lid in that it resists exchange of air between the tropopause and the atmosphere above. This helps explain why almost all water vapor is found in the troposphere. Ë The atmospheric layer just above the tropopause is the stratosphere. The average altitude at the top of this layer is 22 miles. Characteristic of the stratosphere are a slight increase in temperature with height and the near absence of water vapor and clouds. Occasionally a strong thunderstorm will break through the tropopause. Except for a substantial increase in the amount of ozone, the composition of the stratosphere is the same as that of the troposphere. Ozone is important because it absorbs most of the deadly ultra-violet rays from the sun. PHYSICAL ELEMENT Solar Energy Earth’s Motions Atmosphere Table 1. Physical Elements Of Weather II. WEATHER AND CLIMATE REVIEW Hazardous Weather Resource Guide Page II-11 DESCRIPTION The remaining atmospheric layers include the mesosphere and thermosphere. Atmospheric Composition Ì Pure, dry air is composed of about 78 percent nitrogen, 21 percent oxygen, and a one-percent mixture of other gases, mostly argon. Ì Suspended in the air is water vapor, which varies in amounts from 0 to 5 percent by volume. The maximum amount of water vapor the air can hold depends primarily on the temperature of the air; the higher the temperature, the move vapor it can hold. The water vapor will remain suspended in the air until, through condensation, it grows to sufficient droplet or ice crystal size to fall to the earth as precipitation. A jet stream is a narrow, shallow band of winds 58 mph (50 knots) or more meandering vertically and horizontally around the hemisphere in wave-like patterns. Jet streams are characteristic of both hemispheres. Jet stream winds can be found at breaks in the troposphere. Wind speeds in the jet stream sometimes may reach 200 mph (185 knots). Since the jet stream is stronger at some places than at others, it rarely encircles the entire hemisphere as a continuous river of wind. More frequently it is found in segments from 1,000 to 3,000 miles in length, 100 to 400 miles in width, and 3,000 to 7,000 feet in depth. PHYSICAL ELEMENT Atmosphere (Continued) Jet Stream Table 1. Physical Elements Of Weather (Continued) II. WEATHER AND CLIMATE REVIEW Hazardous Weather Resource Guide Page II-12 DESCRIPTION Temperature is a measurement of heat energy and expresses the degree of molecular activity. Since different substances have different molecular structures, equal amounts of heat applied to different substances will cause one to get hotter than the other. Fahrenheit and Celsius are the names given to the two temperature scales most commonly used to measure heat energy. Diurnal variation is the change in temperature from day to night caused by the daily rotation of the earth. During the day solar radiation exceeds outgoing terrestrial radiation and the surface becomes warmer. At night, solar insolation ceases, but terrestrial radiation continues and cools the surface. Temperature distribution over the surface of the earth depends first on the seasons and secondly on the composition and distribution of land and sea surfaces over the earth. Key points: Ì Ocean areas between latitudes 40ºN and 40ºS show very little temperature change from summer to winter. Ì Land areas are warmer than the adjacent water areas at the same latitude during the summer. Ì Water areas are warmer than adjacent land areas at the same latitude during winter. Ì Both the warmest and coldest temperatures are found over land areas. Temperature normally decreases with increasing height throughout the troposphere. This decrease in temperature with altitude is called the lapse rate and is usually expressed in degrees per thousand feet. The average or standard lapse rate is 3ºC (5.4ºF) per 1,000 feet. Many times there are layers within the troposphere that are characterized by an increase of temperature with altitude rather than a decrease. Such increases are usually confined to a relatively shallow layer — called an inversion because the usual decrease in temperature with height is inverted. PHYSICAL ELEMENT Temperature Table 1. Physical Elements Of Weather (Continued) II. WEATHER AND CLIMATE REVIEW Hazardous Weather Resource Guide Page II-13 DESCRIPTION The most frequent type of inversion over land is that produced immediately above the ground on a clear, relatively still night. The ground loses heat rapidly through terrestrial radiation, cooling the layer of air in contact with it. The amount of cooling decreases rapidly with height, and the temperature of the air a few hundred feet above the surface is affected very little or not at all. Inversions are also found when colder air moves under warm air or when warm air moves over cold air. These inversions are call frontal inversions. Inversions sometimes form as a result of widespread sinking air within a relatively thick layer aloft, while the air below remains essentially unchanged. This sinking air is heated by compression and may become warmer than the air below. This type of inversion is called a subsidence inversion. Restrictions to vision, such as fog, haze, smoke, and low clouds, are often in or below inversions and in layers through which there is only a small change in temperature. Water in the atmosphere is found in three states: vapor, liquid, and solid. Water vapor is water in its gaseous state and is not visible. As a liquid, water is found as rain, as drizzle, and as the small visible water droplets that form clouds and fog. As a solid, water takes the form of snow, hail, ice pellets, ice-crystal clouds, and ice-crystal fog. More than two-thirds of the Earth’s surface is covered with water. This water is continually evaporating into the atmosphere, cooling by various processes, condensing, and falling to Earth again as precipitation. This never-ending process is referred to as the hydrologic cycle. This cycle keeps the atmosphere supplied with moisture and aids in producing temperature and pressure changes. The remaining one-third of the Earth’s surface is composed of land of various and vastly different terrains. Each type of terrain significantly influences local wind flow, moisture availability, and in turn, the resulting weather. PHYSICAL ELEMENT Temperature (Continued) Moisture Table 1. Physical Elements Of Weather (Continued)