NASA/TM—2014–218385 Complete Decoding and Reporting of Aviation Routine Weather Reports (METARs) Max Lui Intrinsyx Technologies Corporation Ames Research Center, Moffett Field, California Click here: Press F1 key (Windows) or Help key (Mac) for help October 2014 This page is required and contains approved text that cannot be changed. NASA STI Program ... in Profile Since its founding, NASA has been dedicated • CONFERENCE PUBLICATION. to the advancement of aeronautics and space Collected papers from scientific and science. The NASA scientific and technical technical conferences, symposia, seminars, information (STI) program plays a key part in or other meetings sponsored or helping NASA maintain this important role. co-sponsored by NASA. The NASA STI program operates under the • SPECIAL PUBLICATION. 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NASA/TM—2014–218385 Complete Decoding and Reporting of Aviation Routine Weather Reports (METARs) Max Lui Intrinsyx Technologies Corporation Ames Research Center, Moffett Field, California Insert conference information, if applicable; otherwise delete Click here: Press F1 key (Windows) or Help key (Mac) for help National Aeronautics and Space Administration Ames Research Center Moffett Field, CA 94035-1000 October 2014 Acknowledgments A special acknowledgement to William Chan, Branch Chief of Code AFO at NASA Ames Research Center, for his input in identifying important weather observations that needed to be decoded at the early part of this project. Click here: Press F1 key (Windows) or Help key (Mac) for help Available from: NASA Center for AeroSpace Information National Technical Information Service 7115 Standard Drive 5301 Shawnee Road Hanover, MD 21076-1320 Alexandria, VA 22312 443-757-5802 703-605-6000 Click here: Press F1 key (Windows) or Help key (Mac) for help This report is also available in electronic form at http://www.sti.nasa.gov/ Table of Contents Summary ....................................................................................................................................... 1 1 Introduction ............................................................................................................................ 2 2 Current METAR Decoding Tools ........................................................................................... 3 3 Collecting METAR Data ......................................................................................................... 3 4 Coding Format Overview ....................................................................................................... 4 4.1 Observations Described Only in Remarks Section ......................................................... 4 4.2 Blank Space as a Delimiter ............................................................................................ 6 4.3 Coding Missing Data ...................................................................................................... 6 5 Undocumented Groups .......................................................................................................... 7 5.1 Depth of New Snow (931nnn) ........................................................................................ 7 5.2 Ice Accretion (IHnnn) ...................................................................................................... 7 5.3 Significant Cloud Type Cumulus (CU_LOC) .................................................................. 7 5.4 Low-Level Wind Shear (LLWS) [Plain Language] .......................................................... 7 5.5 Pilot Report (PIREP) [Plain Language] ........................................................................... 7 6 Deviations From Group Coding Format ................................................................................. 8 6.1 Groups Not Reported in Suggested Order ..................................................................... 8 6.2 Standard Coding Format Not Followed .......................................................................... 9 6.3 Combining Multiple Groups Into One Group ................................................................ 10 6.4 Single Group is Split Into Multiple Groups .................................................................... 10 6.5 Missing Separator RMK ................................................................................................ 11 6.6 Wrong Order Within Group Coding Format .................................................................. 12 6.7 Unexpected Descriptors in Groups ............................................................................... 12 6.8 Use of FEW as Descriptor and Cloud Cover Layer ...................................................... 13 6.9 Using Nonstandard Contractions .................................................................................. 14 6.10 Use of NO in Remarks .................................................................................................. 14 6.11 Typographical Errors in Use of 0 (Zero) and O ("Oh") .................................................. 16 6.12 Misspelling of Contractions ........................................................................................... 16 6.13 Inserting Extra Blank Spaces ....................................................................................... 17 6.14 Missing Blank Space .................................................................................................... 17 6.15 Missing or Wrong Units of Measure ............................................................................. 18 6.16 Missing Leading or Trailing Zeroes .............................................................................. 19 iii Table of Contents (cont.) 7 Algorithm for Decoding Body and Remarks Sections .......................................................... 21 7.1 Using Regular Expressions for Text Pattern Matching ................................................. 21 7.2 Groups Containing Plain Text ....................................................................................... 23 7.3 Metadata Structure to Identify Group ........................................................................... 24 7.4 Steps in Decoding METAR ........................................................................................... 25 7.4.1 Identify All Candidate Tokens ................................................................................ 25 7.4.2 Body Groups Are Not Supposed to Be in the Remarks Section of a Report ......... 26 7.4.3 Copy Qualified Tokens From candidateGroups to qualifiedGroups .......... 26 7.4.4 Fill in Any Unmatched Text ................................................................................... 26 7.4.5 Copy Unique Tokens From qualifiedGroups to uniqueGroups .................. 26 7.4.6 Set Output Fields ................................................................................................... 27 8 Software Implementation ..................................................................................................... 28 9 Storing Decoded METARs Into a Relational Database ....................................................... 30 10 Aggregating Daily Decoded METARs .................................................................................. 31 11 Reporting on Decoded METARs ......................................................................................... 32 12 Case Study of Dust Storm