JO 7900.5E, Surface Weather Observing

1 Distribution: Electronic Initiated By: AJT-2 DEPARTMENT OF TRANSPORTATION FEDERAL AVIATION ADMINISTRATION Air Traffic Organization Policy SUBJ: Surface Weather Observing Effective Date: 01/15/2020 The Federal Aviation Administration (FAA) Surface Weather Observer Program is a component of the National Airspace System (NAS). It combines with other elements of the NAS to ensure the overall safety of air transportation services. The FAA is committed to providing the resources necessary to ensure the vibrancy of this critical aviation service. This order provides the practices and procedures for Weather observation services that support the important role it plays in the mission of the FAA.

2 The practices and procedures set forth in this order apply to all FAA personnel, FAA-contract personnel, and non-Federal Observer personnel who provide aviation Weather observation services. Weather observer personnel are required to apply the provision of this order as it pertains to their observational responsibilities. Observers are expected to exercise experienced judgment when encountering situations not covered by this order. Jeffrey U. Vincent Vice President Air Traffic Services ORDER JO ii 01/15/2020 JO Table of Contents Chapter 1. Introduction .. 1 Purpose of This Order .. 1 Audience.. 1 Where to Find This Order .. 1 Cancellation .. 1 Explanation of Changes.

3 1 Abbreviations and Acronyms .. 2 Relationship to FMH-1 and Other Documents .. 2 Applicability of Procedures and Practices .. 3 User Responsibilities .. 3 Distribution .. 4 Changing the Order .. 4 Maintaining the Order .. 4 Chapter 2. Guidelines .. 5 Introduction.. 5 Types of Stations .. 5 Non-Federal Weather Observation (NF-OBS) Station .. 5 General Types of Observations .. 5 Augmentation Requirements .. 6 Backup Requirements .. 7 Evaluating Weather Sensor Accuracy .. 8 Chapter 3. General Procedures .. 10 Introduction .. 10 Certification of Personnel and Currency 10 Definitions .. 10 Aviation Weather Observing Locations .. 12 General Observing Practices.

4 12 Dissemination .. 13 Corrections to Transmitted Data .. 14 Delayed Reports (Manual Stations Only) .. 14 Rounding Off Numbers .. 15 Record Keeping and Forms .. 15 Criteria for SPECI Observations .. 15 Content of METAR/SPECI Observations .. 17 Chapter 4. General Procedures at Automated Weather Stations .. 28 Purpose .. 28 Types of Automated Stations .. 28 Procedures for Handling Aircraft Mishaps at Automated Sites .. 29 Chapter 5. Augmentation Requirements at Automated Weather Stations .. 30 Introduction.. 30 Validity of Data .. 30 Sign On/Sign Off the Automated Weather Observing Systems .. 30 iii 01/15/2020 JO Augmentation Observing Procedures .. 31 General Reporting Procedures.

5 32 Chapter 6. Backup/Editing Requirements at Automated Weather Stations .. 35 Introduction.. 35 Validity of Data .. 35 Equipment Requirements .. 35 Procedures for Providing Backup Information.. 37 Coding of Missing Data .. 38 Procedures for Wind Speed and Wind Direction .. 38 Procedures for Visibility .. 38 Procedures for Present Weather and Obscurations .. 39 Procedures for Sky Condition.. 40 Procedures for Temperature and Dew Point (See Chapter 11) .. 40 Procedures for Altimeter Setting (See Chapter 12) .. 41 Malfunctions/Outages .. 42 Chapter 7. Wind .. 43 Introduction.. 43 Definitions .. 43 Observing , Determining, and Reporting Procedures .. 43 Wind Direction.

6 43 Estimating Wind Direction .. 44 Variable Wind Direction .. 44 Wind Shifts .. 44 Wind Speed.. 45 Estimating Wind Speed.. 45 Wind Character (Gusts) .. 45 Peak Wind Speed.. 45 Calm Wind .. 45 Conversion of True and Magnetic Winds .. 45 Chapter 8. Visibility .. 47 Introduction.. 47 Definitions .. 47 Visibility Standards .. 48 Unit of Measure .. 48 Observing Aids for Visibility .. 48 Selection of Visibility Markers .. 48 Dark Adaptation.. 49 Evaluating Visibility .. 49 Evaluating Prevailing Visibility .. 49 Evaluating Sector Visibility .. 49 Evaluating Variable Visibility .. 49 Reporting Visibility Values .. 49 Control Tower Visibility Observations and Actions at Collocated Sites.

7 49 Surface Observer Action at Stations with Control Tower .. 50 iv 01/15/2020 JO Chapter 9. Weather Phenomena .. 51 Introduction.. 51 Precipitation .. 51 Obscurations .. 52 Other Phenomena .. 54 54 Order for Reporting Multiple Types of Weather and Obscurations .. 55 Rules for Phenomena Not Occurring at the Point of Observation .. 56 Observing and Reporting Precipitation.. 56 Beginning and/or Ending Precipitation (NA LAWRS) .. 56 Determining and Reporting the Type of Precipitation.. 57 Determining the Character of Precipitation .. 57 Precipitation Intensity .. 57 Intensity of Snow, Snow Pellets, Snow Grains, Drizzle, and Freezing Drizzle .. 58 Reporting Freezing Precipitation.

8 59 Beginning and/or Ending of Freezing Precipitation.. 59 Intensity of Freezing Precipitation .. 59 Reporting Ice Pellets .. 59 Beginning and/or Ending of Ice Pellets (NA LAWRS) .. 59 Intensity of Ice Pellets .. 59 Reporting Precipitation Amounts (Automated) .. 59 Snowfall within Specified Periods (See Appendix F) .. 60 Observing and Reporting Tornado, Waterspout, or Funnel Cloud.. 60 Observing and Reporting Thunderstorms .. 61 Beginning and/or Ending of a Thunderstorm .. 62 Reporting Hail.. 62 Beginning and/or Ending of Hail .. 62 Reporting Lightning .. 62 Reporting Squalls .. 63 Observing and Reporting Procedures for Obscurations .. 63 Observing Obscurations.

9 63 Reporting Obscurations .. 63 Special Procedures for Volcanic Ash .. 63 Operationally Significant Remarks for Obscurations .. 63 Chapter 10. Sky Condition .. 64 Introduction.. 64 Sky Condition Evaluation.. 64 Cloud Forms and Obscuring Phenomena .. 64 64 Observing Sites .. 66 Layer Amounts .. 67 Summation Layer Amount .. 68 Layer Heights .. 68 Evaluation of Multiple Layers .. 69 Amount of Obscuration.. 69 Determining Amount of Sky Cover .. 69 v 01/15/2020 JO Evaluation of Sky Cover Amounts .. 69 Sky Cover Classification.. 69 Variable Sky Cover .. 70 Non-Uniform Sky Cover .. 70 Estimated Ceiling Heights .. 70 Variable Ceiling Height.. 71 Significant Clouds.

10 71 Chapter 11. Temperature and Dew Point .. 72 Introduction.. 72 Definitions .. 72 Temperature and Dew Point Observing and Reporting Practices .. 72 Obtaining Readings from a Sling Psychrometer .. 72 Maximum and Minimum Temperature .. 73 Maximum/Minimum Extremes .. 73 Chapter 12. Pressure .. 74 Introduction.. 74 Definitions .. 74 Observing , Determining, and Reporting Procedures .. 75 Determining Altimeter Setting .. 76 Pressure Related Remarks .. 76 Chapter 13. Coding .. 77 Introduction.. 77 Aviation Weather Reports Code .. 77 Format and Content of the METAR/SPECI Report .. 77 Coding Missing Data in METAR and SPECI Reports .. 78 Coding the Body of the METAR or SPECI Report.