AFWA TN-98/002 15 JULY 1998 Air Force Weather Agency/DNT Offutt Air Force Base, Nebraska 6811368113 MeteorologicalMeteorological TechniquesTechniques This technical note is a compilation of various techniques in forecasting - Surface Weather Elements, - Flight Weather Elements, and - Convective Weather APPROVED FOR PUBLIC RELEASE;i DISTRIBUTION IS UNLIMITED. REVIEW AND APPROVAL STATEMENT AFWA/TN—98/002, Meteorological Techniques, 15 July 1998, has been reviewed and is approved for public release. There is no objection to unlimited distribution of this document to the public at large, or by the Defense Technical Information Center (DTIC) to the National Technical Information Service (NTIS). ______________________________ LARRY E. FREEMAN, Colonel, USAF Director of Air and Space Sciences FOR THE COMMANDER _____________________________ JAMES S. PERKINS Scientific and Technical Information Program Manager 15 July 1998 ii REPORT DOCUMENTATION PAGE 2. Report Date: 15 July 1998 3. Report Type: Technical Note 4. Title: Meteorological Techniques 6. Authors: Capt Maria Reymann, Capt Joe Piasecki, MSgt Fizal Hosein, MSgt Salinda Larabee, TSgt Greg Williams, Mike Jimenez, Debbie Chapdelaine 7. Performing Organization Names and Address: Air Force Weather Agency (AFWA), Offutt AFB IL 8. Performing Organization Report Number: AFWA/TN—98/002 12. Distribution/Availability Statement: Approved for public release; distribution is unlimited. 13. Abstract: Contains weather forecasting techniques of interest to military meteorologists, in three sections: surface weather elements, flight weather elements, and severe weather. Includes both general and geographically specific rules of thumb, results of research, lessons learned from experience, etc, gathered from military and other sources. Update to earlier Air Weather Service Manual 105-56 “Forecasting Techniques.” 14. Subject Terms: ATMOSPHERIC PRESSURE, ATMOSPHERIC STABILITY, CLIMATOLOGY, CLOUDS, CONTRAILS, D-VALUES, ICING, PRECIPITATION, SEVERE WEATHER, TEMPERATURE, THUNDERSTORM, TORNADO, TURBULENCE, VISIBILITY, WIND 15: Number of Pages: 242 17. Security Classification of Report: UNCLASSIFIED 18. Security Classification of this Page: UNCLASSIFIED 19. Security Classification of Abstract: UNCLASSIFIED 20. Limitation of Abstract: UL Standard Form 298 iii TABLE OF CONTENTS Abstract ........................................................................................................................................................... iii List of Figures ................................................................................................................................................. vi List of Tables .................................................................................................................................................... x Preface ............................................................................................................................................................ xii Acknowledgement.......................................................................................................................... xiii Chapter 1. Surface Weather Elements ...................................................................................................... 1-1 I. Visibility............................................................................................................................................... 1-1 A. Dry Obstructions ........................................................................................................................... 1-1 B. Moist Obstructions ........................................................................................................................ 1-1 C. Visibility Forecasting Rules of Thumb ......................................................................................... 1-3 D. Forecasting Aids/Techniques ....................................................................................................... 1-17 II. Precipitation ..................................................................................................................................... 1-23 A. General Guidance ........................................................................................................................ 1-23 B. Model Guidance .......................................................................................................................... 1-27 C. Determining Precipitation Type .................................................................................................. 1-27 D. Forecasting Rainfall Amounts ..................................................................................................... 1-34 E. Snowfall ....................................................................................................................................... 1-38 III. Surface Winds ................................................................................................................................. 1-51 A. Wind Basics ................................................................................................................................. 1-51 B. General Tools for Forecasting Surface Winds ............................................................................. 1-52 C. Specialized Airfield Operations Topics ....................................................................................... 1-62 D. Forecasting Gusty Surface Winds in the United States ............................................................... 1-66 E. Additional Regional Wind Forecasting Guidance ....................................................................... 1-73 IV. Temperature ..................................................................................................................................... 1-84 A. General Temperature Forecasting Tools...................................................................................... 1-84 B. Maximum Temperature Forecasts ............................................................................................... 1-86 C. Minimum Temperature Forecasts................................................................................................ 1-88 D. Some Additional Rules of Thumb ............................................................................................... 1-88 E. Temperature Indices .................................................................................................................... 1-89 V. Pressure ............................................................................................................................................. 1-93 A. General Guidance ........................................................................................................................ 1-93 B. Pressure-Related Parameters ....................................................................................................... 1-94 Chapter 2. Flight Weather Elements ......................................................................................................... 2-1 I. Clouds .................................................................................................................................................. 2-1 A. Cloud Types/States of the Sky ....................................................................................................... 2-1 B. General Forecasting Tools ............................................................................................................. 2-3 iv C. Cloud Forecasting Techniques ...................................................................................................... 2-6 D. Regional Guidance ...................................................................................................................... 2-13 II. Turbulence ........................................................................................................................................ 2-20 A. Levels of Intensity ....................................................................................................................... 2-20 B. Aircraft Turbulence Sensitivities ................................................................................................. 2-21 C. Causes of Turbulence .................................................................................................................. 2-22 D. Clear Air Turbulence ................................................................................................................... 2-23 E. Mountain Wave Turbulence ......................................................................................................... 2-31 F Wake Turbulence ......................................................................................................................... 2-34 G. Forecasting Aids .......................................................................................................................... 2-35 III. Aircraft Icing ................................................................................................................................... 2-48 A. Icing Processes and Classification .............................................................................................. 2-48 B. Variables for Determining Icing Accumulation .......................................................................... 2-50 C. Meteorological Considerations ..................................................................................................