U.
S. Department of Transportation Federal Aviation Administration Advisory Circular Subject: Aviation Weather Services Date: 3/6/19 AC No: 00-45H Initiated by: AFS-400 Change: 2 1 PURPOSE OF THIS ADVISORY CIRCULAR (AC). This AC explains U.S. aviation weather products and services. It provides details when necessary for interpretation and to aid usage. This publication supplements its companion manual, AC 00-6, Aviation Weather, which documents weather theory and its application to aviation. The objective of this AC is to bring the pilot and operator up-to-date on new and evolving weather information and capabilities to help plan a safe and efficient flight, while also describing the traditional weather products that remain.
2 PRINCIPAL CHANGES. This change adds guidance and information on new Flight Information Service-Broadcast (FIS-B) weather products/tables and updates the GS/GR coding elements, the Convective significant meteorological information (SIGMET) description, and changes Helicopter Emergency Management Service (HEMS) to helicopter air ambulance (HAA).
PAGE CONTROL CHART Remove Pages Dated Insert Pages Dated Pages iii thru vi 1/8/18 Pages iii thru vi 3/6/19 Pages viii thru ix 1/8/18 Pages viii thru ix 3/6/19 Page xii 1/8/18 Page xii 3/6/19 Page 1-8 1/8/18 Pages 1-9 thru 1-12 11/14/16 Pages 1-8 thru 1-13 3/6/19 Page 2-2 11/14/16 Page 2-2 3/6/19 Page 3-3 11/14/16 Page 3-3 3/6/19 Pages 3-10 thru 3-12 11/14/16 Pages 3-10 thru 3-12 3/6/19 Page 3-61 1/8/18 Page 3-61 3/6/19 Page 5-7 11/14/16 Page 5-7 3/6/19 Page 5-63 1/8/18 Page 5-63 3/6/19 Page 5-172 11/14/16 Page 5-173 3/6/19 Page 6-1 11/14/16 Page 6-1 3/6/19 Page 6-13 11/14/16 Page 6-13 3/6/19 Page D-1 1/8/18 Page D-1 3/6/19 ORIGINAL SIGNED by /s/ Robert C. Carty Deputy Executive Director, Flight Standards Service
U.S . Department of Transportation Federal Aviation Administration Advisory Circular Subject: Aviation Weather Services Date: 11/14/16 AC No: 00-45H Initiated by: AFS-400 Change:
The Federal Aviation Administration (FAA) publishes Advisory Circular (AC) 00-45, Aviation Weather Services. This publication supplements its companion manual, AC 00-6, Aviation Weather, which documents weather theory and its application to aviation.
Revision H of AC 00-45 (AC 00-45H) provides an improved organization of aviation weather information. The document is organized using the FAA’s three distinct types of weather information: observations, analyses, and forecasts. Within this construct, AC 00-45H explains U.S. aviation weather products and services. It provides details when necessary for interpretation and to aid usage.
In the past decade, access to aviation weather products has greatly improved with the increase of flight planning services and weather websites. The experience of listening to a weather briefing over a phone while trying to write down pertinent weather information becomes less tolerable when the reports are easily obtainable on a home computer, tablet computer, or even a smart phone. To see weather along your route using a graphic of plotted weather reports combined with radar and satellite is preferable to trying to mentally visualize a picture from verbalized reports.
Although most of the traditional weather products, which rolled off the teletype and facsimile machines decades ago, are still available, some are being phased out by the National Weather Service (NWS) in favor of new, Web-based weather information.
It is the objective of AC 00-45H to bring the pilot and operator up to date on new and evolving weather information and capabilities to help plan a safe and efficient flight, while also describing the traditional weather products that remain.
On line aviation weather information is easy to access, and so are references explaining the information. That is why AC 00-45H contains fewer illustrations and less detail for products available online. This AC will give an overview and direct the pilot where to find more weather information and explanatory details. Product examples and explanations are taken primarily from the National Oceanic and Atmospheric Administration (NOAA) NWS Aviation Weather Center’s (AWC) website (https://www.aviationweather.gov) and other pertinent NWS websites.
Due to the fluid nature of Web addresses, this AC minimizes the inclusion of website links.
Ins tead, it provides the name of the website which can be easily found using Internet search tools.
ii An onli ne version of this document (including digital images) can be found at http://rgl.faa.gov/.
AC 00-45H cancels AC 00-45G, Change 2, published October 2014.
If you have suggestions for improving this AC, you may use the Advisory Circular Feedback Form at the end of this AC.
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CONTENTS Paragraph Page
Chapter 1. Aviation Weather Service Program1-1
1.1 National Oceanic and Atmospheric Administration (NOAA)1-1
1.1.1 National Environmental Satellite, Data, and Information Service
(NESDIS)1-1
1.1.2 National Weather Service (NWS)1-1
1.2 Federal Aviation Administration (FAA)1-4
1.2.1 Air Traffic Control Systems Command Center (ATCSCC)1-4
1.2.2 Air Route Traffic Control Center (ARTCC)1-4
1.2.3 Airport Traffic Control Tower (ATCT) and Terminal Radar Approach
Control (TRACON)1-5
1.2.4 Flight Service Station (FSS)1-5
1.3 Dissemination of Aviation Weather Products1-5
1.3.1 Weather Briefings1-6
1.3.2 Pilot Briefing via the Internet1-8
1.3.3 Hazardous In-Flight Weather Advisory Service (HIWAS)1-8
1.3.4 Flight Information Service-Broadcast (FIS-B)1-9
1.3.5 Operational Use of FIS-B Products1-13
Chapter 2. Aviation Weather Product Policy2-1
2.1 Use of Aviation Weather Products2-1
2.2 Types of Aviation Weather Information2-1
2.2.1 Observations2-1
2.2.2 Analyses2-1
2.2.3 Forecasts2-2
2.3 Categorizing Aviation Weather Sources2-2
2.3.1 Federal Government2-2
2.4 Commercial Weather Information Providers2-2
Chapter 3. Observations3-1
3.1 Aviation Routine Weather Reports (METAR) and Special Weather
Reports (SPECI)3-1
3.1.1 Aviation Routine Weather Report (METAR)3-1
iv
3.1.2 Special Weather Report (SPECI)3-1
3.1.3 General Types of Observations3-3
3.1.4 Recency of Observed Elements at Automated Stations3-3
3.1.5 Format3-4
3.2 Aircraft Observations and Reports3-26
3.2.1 Pilot Weather Report (PIREP)3-26
3.2.2 Air-Reports (AIREP)3-36
3.3 Radar Observations3-37
3.3.1 Description3-37
3.3.2 Issuance3-37
3.3.3 Modes of Operation3-39
3.3.4 Echo Intensities3-40
3.3.5 Radar Products3-41
3.3.6 Precipitation3-48
3.3.7 Limitations3-50
3.3.8 Use3-56
3.3.9 Future Products3-56
3.4 Terminal Doppler Weather Radar (TDWR)3-57
3.4.1 History3-57
3.4.2 Data Access3-58
3.4.3 Products3-58
3.4.4 How Does the Radar Collect Data?3-59
3.4.5 Volume Coverage Pattern (VCP) 903-59
3.4.6 Volume Coverage Pattern (VCP) 803-60
3.4.7 Where Can I Get Details on TDWR-SPG?3-60
3.4.8 TDWR Level-II (Base) Data3-60
3.4.9 TDWR Level-III Products3-60
3.5 Satellite3-65
3.5.1 Description3-65
3.5.2 Imagery Types3-65
3.5.3 Polar Orbiting Environment Satellites (POES)3-70
3.6 Upper-Air Observations3-70
3.6.1 Radiosonde Observations3-70
v
3.7 Graphical Depiction of Surface Observations3-72
3.7.1 AAWU Surface Observations3-72
3.7.2 METARs on Aviationweather.gov3-77
3.8 Aviation Weather Cameras3-82
3.8.1 FAA Aviation Weather Cameras3-82
3.8.2 Issuance3-82
3.8.3 Use3-84
Chapter 4. Analysis4-1
4.1 Surface Analysis Charts4-1
4.1.1 WPC Surface Analysis Charts4-2
4.1.2 Unified Surface Analysis Chart4-11
4.1.3 AAWU Surface Chart4-12
4.2 Ceiling and Visibility4-13
4.2.1 Ceiling and Visibility Analysis (CVA)4-13
4.2.2 Weather Depiction Chart4-19
4.3 Upper-Air Analyses4-20
4.3.1 Issuance4-20
4.3.2 Radiosonde Observation Analysis4-23
Chapter 5. Forecasts5-1
5.1 Significant Meteorological Information (SIGMET)5-1
5.1.1 SIGMET Issuance5-1
5.1.2 SIGMET Standardization5-4
5.1.3 SIGMET (Non-Convective)—CONUS5-4
5.1.4 Convective SIGMET5-7
5.1.5 SIGMET—Outside the CONUS5-11
5.2 Airmen’s Meteorological Information (AIRMET)5-16
5.2.1 AIRMET Issuance5-17
5.2.2 AIRMET Issuance Criteria5-19
5.2.3 AIRMET Standardization5-19
5.2.4 AIRMET Bulletins, Issuance Times, and Valid Period5-20
5.2.5 AIRMET Format and Example5-20
vi
5.3 Graphical Airman’s Meteorological Advisory (G-AIRMET)5-23
5.3.1 G-AIRMET Issuance5-24
5.3.2 G-AIRMET Content5-24
5.3.3 Use5-30
5.4 Center Weather Advisory (CWA)5-30
5.4.1 CWA Issuance5-30
5.4.2 CWA Criteria5-31
5.4.3 CWA Format and Example5-32
5.5 Meteorological Impact Statement (MIS)5-33
5.5.1 Valid Period5-34
5.5.2 Content5-34
5.5.3 Format5-34
5.6 Additional Products for Convection5-35
5.6.1 Convective Outlooks (AC)5-35
5.6.2 Watch Notification Messages5-38
5.6.3 Traffic Flow Management (TFM) Convective Forecast (TCF)5-46
5.6.4 Extended Convective Forecast Product (ECFP)5-50
5.6.5 National Convective Weather Forecast (NCWF)5-51
5.7 Products for Tropical Cyclones5-56
5.7.1 Tropical Cyclone Advisory (TCA)5-56
5.8 Volcanic Ash Forecasts5-58
5.8.1 Volcanic Ash Advisory Center (VAAC)5-58
5.8.2 Volcanic Ash Advisory (VAA)5-59
5.9 Graphical Forecast for Aviation (GFA)5-61
5.9.1 Time Selection and Slider5-62
5.9.2 GFA Static Images5-64
5.9.3 Strengths and Limitations (GFA)5-66
5.9.4 Recommended Action for Users5-67
5.10 Localized Aviation Model Output Statistics (MOS) Program (LAMP)5-67
5.10.1 Strengths and Limitations (LAMP)5-67
5.10.2 Recommended Action for Users5-67
5.11 Area Forecasts (FA)5-68
5.11.1 FA—Gulf of Mexico, Caribbean, Hawaii, and Alaska5-68
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5.12 Alaskan Graphical Area Forecasts (FA)5-78
5.12.1 Issuance5-79
5.12.2 Content5-80
5.12.3 Use5-84
5.13 Terminal Aerodrome Forecast (TAF)5-84
5.13.1 Responsibility5-84
5.13.2 Generic Format of the Forecast Text of an NWS-Prepared TAF5-85
5.13.3 Issuance5-105
5.14 Route Forecasts (ROFOR)5-107
5.14.1 Issuance5-107
5.14.2 ROFOR Amendments5-107
5.14.3 ROFOR Corrections5-107
5.14.4 ROFOR Content5-108
5.14.5 Example5-108
5.15 Wind and Temperature Aloft5-109
5.15.1 Wind and Temperature Aloft Forecast (FB)5-109
5.16 Freezing-Level Graphics5-113
5.16.1 Issuance5-114
5.16.2 Format5-114
5.16.3 Use5-114
5.17 Upper-Air Forecasts5-115
5.17.1 Constant Pressure Levels Forecasts5-116
5.18 Short-Range Surface Prognostic (Prog) Charts5-118
5.18.1 Content5-119
5.18.2 Issuance5-121
5.18.3 Use5-121
5.19 Significant Weather (SIGWX) Forecast5-121
5.19.1 Low-Level Significant Weather (SIGWX) Charts5-121
5.19.2 Mid-Level Significant Weather (SIGWX) Chart5-127
5.19.3 High-Level Significant Weather (SIGWX) Charts5-129
5.19.4 Alaska Significant Weather (SIGWX) Charts5-135
5.20 World Area Forecast System (WAFS)5-137
5.20.1 WAFS Forecasts5-137
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5.21 Additional Products for Icing and Turbulence5-146
5.21.1 Current and Forecast Icing Products (CIP/FIP)5-146
5.21.2 Graphical Turbulence Guidance (GTG)5-155
5.22 Additional Products for Clouds, Visibility, Weather, and Surface Wind
Forecasts5-160
5.22.1 NWS Aviation Forecast Discussion5-160
5.22.2 NWS National Digital Forecast Database Graphic Products5-162
5.22.3 Cloud Top Heights Product5-173
5.22.4 Cloud Layer Product5-175
5.23 Airport Weather Warning (AWW)5-175
5.23.1 Issuance5-175
5.23.2 Airport Weather Warning (AWW) Format and Example5-176
5.23.3 Use5-176
5.24 Space Weather5-176
5.24.1 NOAA Space Weather Scales5-176
5.24.2 Space Weather Products5-177
5.24.3 Use5-182
5.25 Soaring Forecast5-183
5.25.1 Issuance5-183
5.25.2 Content and Format5-183
5.25.3 Example5-183
Chapter 6. Aviation Weather Tools6-1
6.1 Helicopter Emergency Medical Services (HEMS) Tool6-1
6.1.1 Availability6-1
6.1.2 Content6-1
6.1.3 Strengths and Limitations6-13
6.1.4 Use6-14
6.2 Flight Path Tool6-14
6.2.1 Description6-14
Appendix A. Definition of Common Terms Used in En Route Forecasts and AdvisoriesA-1
Appendix B. Standard Conversion ChartB-1
Appendix C. Density Altitude CalculationC-1
ix
Appendix D. Internet LinksD-1
Appendix E. WSR-88D Weather Radar NetworkE-1
L ist of Figures
Figure 3-1. METAR/SPECI Coding Format3-4
Figure 3-2. ICAO Continental Codes3-5
Figure 3-3. Obscuration Effects on Slant Range Visibility .................................................................................... 3- 14 Figure 3-4. METAR/SPECI Sky Condition Coding ............................................................................................... 3- 16 Figure 3-5. Pilot Weather Report (PIREP) Coding Format .................................................................................... 3- 27 Figure 3-6. Location of WSR-88D Weather Radar in the CONUS and Their Respective Coverage at 4,000 Feet AGL, 6,000 Feet AGL, and 10,000 Feet AGL ................................................................... 3- 38 Figure 3-7. Location of WSR-88D Weather Radar Outside of the CONUS .......................................................... 3- 39 Figure 3-8. WSR-88D (NEXRAD) Weather Radar Echo Intensity Legend........................................................... 3- 40
Figure 3-9. NWS National Radar Mosaic Example, Which Utilizes NEXRAD Base Reflectivity3-42
Figure 3-10. NWS Regional Radar Mosaic Sector Example, Which Utilizes NEXRAD Base Reflectivity3-43
Figure 3-11. Alaska Radar Mosaic Example .......................................................................................................... 3- 43
Figure 3-12. WSR-88D Weather Radar Composite Reflectivity, Single-Site Product Example3-44
Figure 3-13. Creation of a Composite Reflectivity, Single-Site Product ................................................................ 3- 45
Figure 3-14. Weather Radar 0.5º Base Reflectivity (left) versus Composite Reflectivity (right) Comparison3-45
Figure 3-15. WSR-88D Weather Radar Short-Range (124 NM) Base Reflectivity, Single-Site Product Example ............................................................................................................................................. 3- 46 Figure 3-16. WSR-88D Weather Radar Long-Range (248 NM) Base Reflectivity, Single-Site Product Example ............................................................................................................................................. 3- 47 Figure 3-17. Radar Coded Message (RCM) Display .............................................................................................. 3- 48 Figure 3-18. WSR-88D Weather Radar Convective Precipitation on the 0.5º Base Reflectivity Product Example ............................................................................................................................................. 3- 49 Figure 3-19. WSR-88D Weather Radar Stratiform Precipitation on the 0.5º Base Reflectivity Product Example ............................................................................................................................................. 3- 50 Figure 3-20. Cone of Silence .................................................................................................................................. 3- 51
Figure 3-21. WSR-88D Weather Radar Beam Blockage on Base Reflectivity Product Example3-52
Figure 3-22. WSR-88D Weather Radar Ground Clutter Example .......................................................................... 3- 52 Figure 3-23. WSR-88D Weather Radar Ghost Example ........................................................................................ 3- 53 Figure 3-24. WSR-88D Weather Radar Angel Example ........................................................................................ 3- 54
Figure 3-25. WSR-88D Weather Radar Anomalous Propagation (AP) Example3-55
Figure 3-26. Wind Farms Have Been Known to Make Benign Echoes Appear as Small Storms3-56
Figure 3-27. WSR-88D vs. TDWR ......................................................................................................................... 3- 63 Figure 3-28. TDWR Site Locations ........................................................................................................................ 3- 64 Figure 3-29. Thunderstorm Producing a Microburst .............................................................................................. 3- 64 Figure 3-30. Visible Satellite Image—U.S. Example ............................................................................................. 3- 66 Figure 3-31. Visible Satellite Data Legend ............................................................................................................. 3- 66 Figure 3-32. Infrared (Color) Satellite Image—U.S. Example ............................................................................... 3- 67
Figure 3-33. Unenhanced Infrared (Black and White) Satellite Image—U.S. Example3-68
Figure 3-34. Infrared (Color) Satellite Image Data Legend .................................................................................... 3- 68
Figure 3-35. Unenhanced Infrared (Black and White) Satellite Image Data Legend3-68
Figure 3-36. W ater Vapor Satellite Image—U.S. Example .................................................................................... 3- 69 Figure 3-37. Water Vapor Satellite Image Data Legend ......................................................................................... 3- 70 Figure 3-38. U.S. Radiosonde Network .................................................................................................................. 3- 71 Figure 3-39. AAWU Surface Observations Example ............................................................................................. 3- 72 Figure 3-40. AAWU Surface Observation Plot Legend ......................................................................................... 3- 73
Figure 3-41. Surface Observations—Aviationweather.gov METAR Interactive Display Example3-77
Figure 3-42. Interactive Display Station Plot Example .......................................................................................... 3- 78 Figure 3-43. Station Plot Sky Symbols ................................................................................................................... 3- 80
Figure 3-44. Surface Observations—Aviationweather.gov METAR Static Display Example3-81
Figure 3-45. Static Display Station Plot Example .................................................................................................. 3- 81
x Figure 3-46. Map of FAA’s Aviation Weather Camera Network in Alaska........................................................... 3- 83
Figure 3-47. Sectional Chart Depicting Shungnak (SHG), Alaska Camera Orientations3-83
Figure 3-48. “Clear Day” Image from Aviation Weather Camera Image at Shungnak (SHG), Alaska3-84
Figure 3-49. Aviation Weather Camera Image at Shungnak (SHG), Alaska .......................................................... 3- 84
Figure 4-1. NWS Surface Analysis Chart Example4-1
Figure 4-2. NWS Surface Analysis and Radar Composite Example4-2
Figure 4-3. NWS Surface Analysis Chart Symbols4-3
Figure 4-4. NWS Surface Analysis Chart Station Plot Model4-4
Figure 4-5. NWS Surface Analysis Chart Ship/Buoy Plot Model4-4
Figure 4-6. NWS Surface Analysis Chart for Aviation Interests Station Plot Model4-5
Figure 4-7. NWS Surface Analysis Chart Common Weather Symbols4-6
Figure 4-8. NWS Surface Analysis Chart Wind Plotting Model4-7
Figure 4-9. NWS Surface Analysis Chart Pressure Trends4-8
Figure 4-10. NWS Surface Analysis Chart Sky Cover Symbols4-9
Figure 4-11. Unified Surface Analysis Chart Example .......................................................................................... 4- 11 Figure 4-12. Unified Surface Analysis Chart Example .......................................................................................... 4- 12
Figure 4-13. Unified Surface Analysis Chart Example With Fixed Area Coverage Over Alaska4-13
Figure 4-14. CONUS Display of CVA Ceiling Analysis........................................................................................ 4- 15 Figure 4-15. Regional Display of CVA Ceiling Analysis ....................................................................................... 4- 16 Figure 4-16. Regional Display of CVA Visibility Analysis ................................................................................... 4- 17 Figure 4-17. Regional Display of CVA Flight Category Analysis ......................................................................... 4- 18 Figure 4-18. Weather Depiction Chart—Example.................................................................................................. 4- 20
Figure 4-19. NWS NCEP Central Operations Model Analyses and Guidance Website4-21
Figure 4-20. 500 MB Analysis Chart—Example .................................................................................................... 4- 22 Figure 4-21. 500 MB Height, Temperature, and Wind, 00-hour Forecast (i.e., Model’s Analyses from the NWS’s North American Model (NAM) Example) ............................................................................ 4- 22 Figure 4-22. Skew-T Diagram—Example .............................................................................................................. 4- 24 Figure 4-23. Skew-T Diagram—Multiple Freezing Level Example ...................................................................... 4- 25 Figure 4-24. Skew-T Diagram—Cloud Top Example ............................................................................................ 4- 25
Figure 5-1. AWC SIGMET Areas of Responsibility—Continental U.S5-2
Figure 5-2. AWC SIGMET Areas of Responsibility—Atlantic Basin5-2
Figure 5-3. SIGMET Areas of Responsibility—Pacific Basin5-3
Figure 5-4. SIGMET for the Continental U.S.—Example5-5
Figure 5-5. AWC Convective SIGMET Areas of Responsibility5-8
Figure 5-6. Convective SIGMET Decoding—Example5-9
Figure 5-7. SIGMET Outside the Continental U.S. Decoding Example ................................................................ 5- 13 Figure 5-8. AWC AIRMET Areas of Responsibility—Continental U.S. ............................................................... 5- 17
Figure 5-9. AAWU Flight Advisory and Area Forecast (FA) Zones—Alaska5-17
Figure 5-10. WFO Honolulu AIRMET Areas of Responsibility—Hawaii5-18
Figure 5-11. AIRMET Bulletin Decoding—Example ............................................................................................ 5- 21
Figure 5-12. G- AIRMET—Ceiling and Visibility (IFR) Snapshot Example5-25
Figure 5-13. G- AIRMET—Mountain Obscuration Snapshot Example .................................................................. 5- 25 Figure 5-14. G- AIRMET—Icing Snapshot Example ............................................................................................. 5- 26 Figure 5-15. G- AIRMET—Freezing Level Snapshot Example .............................................................................. 5- 27 Figure 5-16. G- AIRMET—Turbulence-High Snapshot Example .......................................................................... 5- 28 Figure 5-17. G- AIRMET—Turbulence-Low Snapshot Example ........................................................................... 5- 28
Figure 5-18. G- AIRMET—Low-Level Wind Shear (LLWS) Snapshot Example5-29
Figure 5-19. G- AIRMET—Strong Surface Winds Snapshot Example .................................................................. 5- 30
Figure 5-20. Center Weather Service Unit (CWSU) Areas of Responsibility5-31
Figure 5-21. Center Weather Advisory (CWA) Decoding Example ...................................................................... 5- 32 Figure 5-22. Day 1 Categorical Convective Outlook Graphic Example ................................................................. 5- 36
Figure 5-23. Categorical Outlook Legend for Days 1-3 Convective Outlook Graphic Example5-36
Figure 5-24. Aviation Watch (polygon) Compared to Public Watch (shaded) Example5-39
Figure 5-25. TFM Convective Forecast (TCF)—Example ..................................................................................... 5- 47 Figure 5-26. TFM Convective Forecast (TCF)—Example ..................................................................................... 5- 48 Figure 5-27. TCF Product Legend .......................................................................................................................... 5- 48