Federal Meteorological Handbook No. 1






1.1	 Purpose
1.2	 Applicability of Standards
1.3	 Relation to Other Handbooks and Manuals
1.4	 Format of This Handbook
1.5	 Changes to The Handbook
1.6	 Agency Procedures and Procedural Changes
1.7	 Reference Library
1.8	 Unforeseen Requirements
1.9	 Other Questions and Suggestions Regarding FMH-1


2.1	 General
2.2	 Scope
2.3	 Surface Weather Observation Program
2.4	 Aviation Weather Observing Locations
2.5	 Types of Reports
2.5.1	 Aviation Routine Weather Report (METAR)
2.5.2	 Aviation Selected Special Weather Report (SPECI)
2.6	 Observing Standards Applicable to All Stations
2.6.1	 Use of Certified Observers
2.6.2	 Backup
2.6.3	 Rounding Figures
2.6.4	 Time Used in Reports
2.6.5	 Sensor Siting Standards
2.6.6	 Algorithms Used by Automated Stations
2.7	 Recency of Observed Elements
2.7.1	 Recency of Observed Elements at Automated Stations
2.7.2	 Recency of Observed Elements at Manual Stations
2.8	 Dissemination
2.8.1	 Types of Dissemination
2.8.2	 Dissemination Requirements
2.8.3	 Dissemination Priority
2.8.4	 Corrections to Transmitted Data
2.9	 Report Filing Time
2.10	 Delayed Reports


3.1	 General
3.2	 Scope
3.3	 Certification Requirements
3.3.1	 Certification of Observers
3.3.2	 Certification of Stations
3.4	 Quality Control
3.4.1	 Quality Control of Observing Programs
3.4.2	 Quality Control of Instruments and Sensors
3.4.3	 Quality Control of Weather Reports
3.5	 Quality Control Performed at Central Locations
3.6	 Customer Feedback


4.1	 General
4.2	 Scope
4.3	 Types of Records
4.3.1	 Station Information File
4.3.2	 Retention of Station Observational Records
4.3.3	 Station System/Sensor/Configuration Records


5.1	 General
5.2	 Scope
5.3	 Wind Parameters
5.4	 Wind Observing Standards
5.4.1	 Wind Direction
5.4.2	 Variable Wind Direction
5.4.3	 Wind Speed
5.4.4	 Wind Gust
5.4.5	 Peak Wind Speed
5.4.6	 Wind Shifts
5.4.7	 Wind Sensor Range, Accuracy, and Resolution
5.5	 Wind Reporting Standards
5.5.1	 Units of Measure and Resolution for Wind
5.5.2	 Calm Winds
5.5.3	 Variable Wind Direction
5.5.4	 Wind Gust
5.5.5	 Peak Wind Data
5.5.6	 Wind Shifts
5.6	 Summary of Wind Observing and Reporting Standards


6.1	 General
6.2	 Scope
6.3	 Visibility Parameters
6.4	 Visibility Observing Standards
6.4.1	 Observing Sites
6.4.2	 Manual Observing Aids
6.4.3	 Observer Adaptation to Ambient Light Conditions
6.4.4	 Visibility
6.4.5	 Variable Prevailing Visibility
6.4.6	 Sector Visibility
6.5	 Visibility Reporting Standards
6.5.1	 Unit of Measure
6.5.2	 Prevailing Visibility
6.5.3	 Variable Prevailing Visibility
6.5.4	 Tower Visibility
6.5.5	 Surface Visibility
6.5.6	 Visibility At Second Location
6.5.7	 Sector Visibility
6.6	 Summary of Visibility Observing and Reporting Standards


7.1	 General
7.2	 Scope
7.3	 Visual Range Parameters
7.4	 Runway Visual Range Observing Standards
7.4.1	 Observing Positions
7.4.2	 Day-Night Observations for Transmissometers
7.5	 Runway Visual Range Reporting Standards
7.5.1	 Multiple Runway Visual Range Sensors
7.5.2	 Units of Measure
7.5.3	 Runway Visual Range Based on a Transmissometer
7.6	 Summary of Runway Visual Range Observing and Reporting


8.1	 General
8.2	 Scope
8.3	 Present Weather Parameters
8.3.1	 Precipitation
8.3.2	 Obscurations
8.3.3	 Other Weather Phenomena
8.4	 Present Weather Observing Standards
8.4.1	 Qualifiers
8.4.2	 Weather Phenomena
8.5	 Present Weather Reporting Standards
8.5.1	 Precipitation
8.5.2	 Obscuration
8.5.3	 Other Weather Phenomena
8.5.4	 Thunderstorm
8.5.5	 Beginning/Ending Times of Precipitation, Tornadic
	 Activity, and Thunderstorms
8.5.6	 Other Significant Weather Phenomena
8.6	 Summary of Weather


9.1	 General
9.2	 Scope
9.3	 Sky Condition Parameters
9.4	 Sky Condition Standards
9.4.1	 Sky Condition Observing Standards
9.4.2	 Sky Cover
9.4.3	 Obscuration
9.4.4	 Vertical Visibility
9.4.5	 Ceiling
9.4.6	 Significant Clouds and Cloud Types
9.4.7	 Height of Sky Cover
9.5	 Sky Cover Reporting Standards
9.5.1	 Frequency for Sky Cover
9.5.2	 Layer Amount
9.5.3	 Units of Measure for Heights
9.5.4	 Reportable Values for Sky Cover Height
9.5.5	 Layer Heights
9.5.6	 Obscuration
9.5.7	 Variable Ceiling
9.5.8	 Ceiling Height at a Second Location
9.5.9	 Variable Sky Condition
9.5.10	 Significant Cloud Types
9.6	 Summary of Sky Condition Observing and Reporting


10.1	 General
10.2	 Scope
10.3	 Temperature and Dew Point Parameters
10.4	 Temperature and Dew Point Observing Standards
10.4.1	 Temperature and Dew Point Sensor Range
10.4.2	 Temperature10-1
10.4.3	 Dew Point
10.4.4	 Maximum and Minimum Temperature
10.5	 Temperature and Dew Point Reporting Standards
10.5.1	 Resolution for Temperature and Dew Point
10.5.2	 Maximum and Minimum Temperatures
10.5.3	 Reporting Procedures
10.6	 Summary of Temperature and Dew Point Observing and
	 Reporting Standards


11.1	 General
11.2	 Scope
11.3	 Pressure Parameters
11.4	 Pressure Observing Standards
11.4.1	 Barometer Comparisons
11.4.2	 Atmospheric Pressure
11.4.3	 Station Pressure
11.4.4	 Sea-level Pressure
11.4.5	 Altimeter Setting
11.4.6	 Pressure Change (Rising/Falling)
11.4.7	 Pressure Tendency
11.5	 Reporting Standards
11.5.1	 Rounding Pressure Values
11.5.2	 Units of Measure
11.5.3	 Altimeter Setting
11.5.4	 Sea-Level Pressure
11.5.5	 Remarks
11.6	 Summary of Pressure Observing and Reporting Standards


12.1	 General
12.2	 Scope
12.3	 METAR/SPECI Code
12.4	 Format and Content of the METAR/SPECI
12.5	 Coding Missing Data in METAR/SPECI
12.6	 Coding the Body of the METAR/SPECI
12.6.1	 Type of Report (METAR and SPECI)
12.6.2	 Station Identifier (CCCC)
12.6.3	 Date and Time of Report (YYGGggZ)
12.6.4	 Report Modifier (AUTO or COR)
12.6.5	 Wind Group (dddff(f)Gfmfm(fm)KT_dndndnVdxdxdx)
12.6.6	 Visibility Group (VVVVVSM)
12.6.7	 Runway Visual Range Group (RDRDR/VRVRVRVRFT or
12.6.8	 Present Weather Group (w'w')
12.6.9	 Sky Condition Group (NsNsNshshshs or VVhshshs or SKC/CLR)
12.6.10	 Temperature/Dew Point Group (T'T'/T'dT'd)
12.6.11	 Altimeter (APHPHPHPH)
12.7	 Remarks (RMK)
12.7.1	 Automated, Manual, and Plain Language Remarks
	 a.  Volcanic Eruptions [Plain Language]
	 b.  Funnel Cloud (Tornadic activity_B/E(hh)mm_LOC/DIR_(MOV))
	 c.  Type of Automated Station (AO1 or AO2)
	 d.  Peak Wind (PK_WND_dddff(f)/(hh)mm)
	 e.  Wind Shift (WSHFT_(hh)mm)
	 f.  Tower or Surface Visibility (TWR_VIS_vvvvv or SFC_VIS_vvvvv)
	 g.  Variable Prevailing Visibility (VIS_vnvnvnvnvnVvxvxvxvxvx)
	 h.  Sector Visibility (VIS_[DIR]_vvvvv) [Plain Language]
	 i.  Visibility At Second Location (VIS_vvvvv_[LOC])
	 j.  Lightning (Frequency_LTG(type)_[LOC])
	 k.  Beginning and Ending of Precipitation (w'w'B(hh)mmE(hh)mm)
	 l.  Beginning and Ending of Thunderstorms (TSB(hh)mmE(hh)mm)
	 m.  Thunderstorm Location (TS_LOC_(MOV_DIR)) [Plain Language]
	 n.  Hailstone Size (GR_[size]) [Plain Language]
	 o.  Virga (VIRGA_(DIR)) [Plain Language]
	 p.  Variable Ceiling Height (CIG_hnhnhnVhxhxhx)
	 q.  Obscuration (w'w'_[NsNsNs]hshshs) [Plain Language]
	 r.  Variable Sky Condition (NsNsNs(hshshs)_V_NsNsNs) [Plain Language]
	 s.  Significant Cloud Types [Plain Language]
	 t.  Ceiling Height at Second Location (CIG_hhh_[LOC])
	 u.  Pressure Rising or Falling Rapidly (PRESRR/PRESFR)
	 v.  Sea-Level Pressure (SLPppp)
	 w.  Aircraft Mishap (ACFT_MSHP) [Plain Language]
	 x.  No SPECI Reports Taken (NOSPECI) [Plain Language]
	 y.  Snow Increasing Rapidly (SNINCR_[inches-hour/inches on ground])
	 z.  Other Significant Information [Plain Language]
12.7.2	 Additive and Automated Maintenance Data
	 a.  Precipitation
	 b.  Cloud Types (8/CLCMCH)
	 c.  Duration of Sunshine (98mmm)
	 d.  Hourly Temperature and Dew Point (TsnT'T'T'snT'dT'dT'd)
	 e.  6-Hourly Maximum Temperature (1snTxTxTx)
	 f.  6-Hourly Minimum Temperature (2snTnTnTn)
	 g.  24-Hour Maximum and Minimum Temperature (4snTxTxTxsnTnTnTn)
	 h.  3-Hourly Pressure Tendency (5appp)
	 i.  Sensor Status Indicators
	 j.  Maintenance Indicator

Appendix A

Appendix B

Appendix C

Appendix D