Aviation::Report - Perl extension for translating U.S. METAR, TAF and PIREP textual reports into plain English.

  use strict;
  use Aviation::Report;

  print decode_METAR_TAF(report, style);
  print decode_PIREP(report, style);

package Aviation::Report;

use strict;

use vars qw($VERSION @ISA @EXPORT @EXPORT_OK);

require Exporter;

@ISA = qw(Exporter AutoLoader);
# Items to export into callers namespace by default. Note: do not export
# names by default without a very good reason. Use EXPORT_OK instead.
# Do not simply export all your public functions/methods/constants.
@EXPORT = qw(
	decode_METAR_TAF decode_PIREP
);
$VERSION = '1.02';

   my %abb = ();

   while (<DATA>) {
      chomp;
      next if /^#?$/;
      my ($abbrev, $desc) = split /:/;
      $abb{$abbrev} = $desc;
   }

   my @low = ('None', 'Cumulus  (fair wx)', ' Cumulus (towering)', 'Cumulonimbus (no anvil)', 'Stratocumulus', 'Stratocumulus', 'Stratus', 'Fractocumulus/Fractostratus', 'Cumulus and Stratocumulus', 'Cumulonimbus');

   my @middle = ('None', 'Altostratus (thin)', 'Altostratus (thick)', 'Altocumulus (thin)', 'Altocumulus (patchy)', 'Altocumulus (thickening)', 'Altocumulus (from Cumulonimbus)', 'Altocumulus (w/Ac,As,Ns)', 'Altocumulus (w/turrets)', 'Altocumulus (chaotic)');

   my @high = ('None', 'Cirrus (filaments)', 'Cirrus (dense)', 'Cirrus (often w/Cb)', 'Cirrus (thickening)', 'Cirrus/Cirrostratus (low in sky)', 'Cirrus/Cirrostratus (high in sky)', 'Cirrostratus (entire sky)', 'Cirrostratus (partial)', 'Cirrocumulus or Cirrocumulus/Cirrus/Cirrostratus');

   my %abb_pirep = ( UA => 'routine pilot report',
                     UUA => 'urgent pilot report',
                     OV => 'location',
                     TM => 'time',
                     FL => 'altitude',
                     TP => 'type of aircraft',
                     SK => 'sky cover',
                     WX => 'weather',
                     TA => 'temperature',
                     WV => 'wind',
                     TB => 'turbulence',
                     IC => 'icing',
                     RM => 'remarks',
                     CLR => 'clear',
                     LGT => 'light',
                     MDT => 'moderate',
                     HVY => 'heavy',
   );
1;

sub decode_PIREP {
   my ($s, $style) = @_;
   my $s = uc $s;
   my ($out) = $s . "\n" if $style;

   my $token;

   my @tokens = split m:/:, $s;

   while ($token = shift @tokens) {
         my ($element, $value) = ('', '');
         if (($element, $value) = split / /, $token, 2) {
            if (exists $abb_pirep{$element}) {
               $out .= $abb_pirep{$element} . ' ';
            }
            else {
               if ($element =~ /^(\d{3})$/) {
                  $out .= int($1)."00 feet ";
                  foreach (split / /, $value) {
                     if (/^(\d{3})$/) {
                        $out .= int($1)."00 feet ";
                     }
                     elsif (/^([A-Z]+)$/) {
                        if (exists $abb{$1}) {
                           $out .= $abb{$1} . ' ';
                        }
                        else {
                           $out .= $1 . ' ';
                        }
                     }
                     else {
                        $out .= $_;
                     }
                  }
               }
               else {
                  $out .= $element;
               }
               $out .= "\n";
               next;
            }
            if ($element eq 'IC' or $element eq 'TB') {
               if (exists $abb_pirep{$value}) {
                  $out .= $abb_pirep{$value};
               }
               else {
                  $out .= $value;
               }
            }
            elsif ($element eq 'OV' and $value =~ /^(.*?) (\d{3})(\d{3})$/) {
               $out .= int($2) ." nautical miles on the $3 degree radial from $1";
            }
            elsif ($element eq 'SK') {
               foreach (split / /, $value) {
                  if (/^(\d{3})$/) {
                     $out .= int($1)."00 feet msl ";
                  }
                  elsif (/^([A-Z]+)$/) {
                    if (exists $abb{$1}) {
                       $out .= $abb{$1};
                    }
                    else {
                       $out .= $1;
                    }
                  }
                  else {
                     $out .= $_;
                  }
               }
            }
            elsif ($value =~ /^(\d{3})(\d{3})$/) {
               $out .= "from $1 degrees magnetic at @{[int $2]} knots";
            }
            elsif ($value =~ /^(\d{2})(\d{2})$/) {
               $out .= "$1:$2 zulu";
            }
            elsif ($value =~ /^(\d{3})$/) {
               $out .= int($1)."00 feet msl ";
            }
            else {
               $out .= $value;
            }
            $out .= " degrees Celsius" if $element eq 'TA';
            $out .= " (MSL)" if $element eq 'SK';
         }

         $out .= "\n";
   }

   $out;
}
 
sub decode_METAR_TAF {
   my ($s, $style) = @_;
   $s = uc $s if $style;

   $s =~ s/=//g;

   my ($out) = '';

   $out = $s . "\n";

   my $id = '';
   my $token;

   my @tokens = split /\s+/, $s;

   while ($token = shift @tokens) {
         $out .= $token . "\t" if $style;

         my $intensity = substr($token, 0, 1);
         if ($intensity eq '-') {
            $intensity = 'light';
         }
         elsif ($intensity eq '+') {
            $intensity = 'heavy';
         }

         if ($intensity eq 'light' or $intensity eq 'heavy') {
            $out .= $intensity . ' ';# off for -TSRA
            $token = substr($token,1);
         }

# Part 1: Identification Section
         if ($id eq '' and $token =~ /^[A-Z]{4}$/) {
            $id = $token;
            $out .= "for airport " . $token;
         }
         elsif ($token =~ /^(\d{2})(\d{2})(\d{2})Z$/) {
            $out .= "issued day $1 at $2:$3 zulu";
         }
         elsif ($token =~ /^(\d{2})(\d{2})(\d{2})$/) {
            $out .= "valid from day $1 at $2:00 to $3:00 zulu";
         }
# Part 2: Observations Section
         elsif ($token =~ /^00000KT$/) {
            $out .= "wind light and variable";
         }
         elsif ($token =~ /^VRB(\d{2})KT$/) {
            $out .= "variable wind direction at @{[int $1]} knots";
         }
         elsif ($token =~ /^(\d{3})V(\d{3})$/) {
            $out .= "wind varies from $1 to $2";
         }
         elsif ($token =~ /^(\d{3})(\d{2})(G?)(\d+)?KT$/) {
            $out .= "wind from $1 true at @{[int $2]} knots";
            $out .= " gusts to $4" if $3 eq 'G';
         }
         elsif ($token =~ /^(\d{1,2})$/) {
            $out .= "ground visibility $1";
            if ($token = shift @tokens) {
               if ($token =~ /^(\d+\/\d+)$/) {
                  $out .= " and $1 statute miles";
               }
            }
         }
         elsif ($token =~ /^(P?)(\d+)SM$/) {
            $out .= "ground visibility @{[$1 eq 'P'?'more than ':'']}$2 statute miles";
         }
         elsif ($token =~ /^(\d+)\/(\d+)SM$/) {
            $out .= "ground visibility $1/$2 statute miles	";
         }
         elsif ($token =~ /^R(\d{2})(L|C|R)\/(M|P)?(\d+)FT$/) {
            $out .= "runway visibility for Rwy $1$2 is @{[$3 eq 'M'?'less than minimum of ':'']}@{[$3 eq 'M'?'more than maximum of ':'']}$4 feet";
         }
         elsif ($token =~ /^HZ$/) {
            $out .= "weather hazard (or maybe just haze)";
         }
# Part 3: Gauge Readings
         elsif ($token =~ /^(M?)(\d{2,3})\/(M?)(\d{2,3})$/) {
            $out .= "temperature @{[$1?'-':'']}@{[int($2)]} Celsius, dew point @{[$3?'-':'']}@{[int($4)]} Celsius.";
         }
         elsif ($token =~ /^A(\d{2})(\d{2})$/) {
            $out .= "altimeter setting $1.$2 inches mercury";
         }
         elsif ($token =~ /^Q(\d{3})(\d)$/) {
            $out .= "altimeter setting $1.$2 hectopascals";
         }
# Part 4: Remarks and Coded Data
         elsif ($token =~ /^AO(1|2)$/) {
            $out .= "automated station type $1: @{[$1 eq '01'?'cannot detect precipitation':'has precipitation discriminator']}";
         }
         elsif ($token =~ /^P(\d{4})$/) {
            $out .= "precipitation @{[$1/100]} inches in last hour";
         }
         elsif ($token =~ /^(\d{3})(\d{2})\/(\d{2})$/) {
            $out .= "wind from $1 at $2 knots starting at $3 after the hour";
         }
         elsif ($token =~ /^1(0|1)(\d{3})$/) {
            $out .= "max temp in last 6 hours @{[$1?'-':'']}@{[$2/10]} Celsius";
         }
         elsif ($token =~ /^2(0|1)(\d{3})$/) {
            $out .= "min temp in last 6 hours @{[$1?'-':'']}@{[$2/10]} Celsius";
         }
         elsif ($token =~ /^4\/(\d{3})$/) {
            $out .= "snow depth on ground is @{[$1]} inches";
         }
         elsif ($token =~ /^5(\d)(\d{3})$/) {
            $out .= "3 hour pressure tendency ";
            if ($1 eq '4') {
               $out .= "stationary ";
            }
            elsif ($1 gt '4') {
               $out .= "decreased ";
            }
            else {
               $out .= "increased ";
            }
            $out .= $2/10 . " millibars";
         }
         elsif ($token =~ /^6(\d{4})$/) {
            $out .= "3 and 6 hour precipitation @{[$1/100]} inches";
         }
         elsif ($token =~ /^7(\d{4})$/) {
            $out .= "24 hour total precipitation @{[$1/100]} inches";
         }
         elsif ($token =~ /^8\/(\d)(\d)(\d)$/) {
            $out .= "WMO cloud types $low[$1], $middle[$2], $high[$3]";
         }
         elsif ($token =~ /^98(\d{3})$/) {
            $out .= "$1 minutes of sunshine during day";
         }
         elsif ($token =~ /^933(\d{3})$/) {
            $out .= "standing water equivalent of @{[$1/10]} inches";
         }
         elsif ($token =~ /^SLP(\d{3})$/) {
            $out .= "sea level Pressure @{[($1/10) + (($1<700)?1000:900)]} millibars";
         }
         elsif ($token =~ /^FM(\d{2})(\d{2})$/) {
            $out .= "from $1:$2 zulu";
         }
         elsif ($token =~ /^PROB(\d{2})$/) {
            $out .= "probability $1%";
         }
         elsif ($token =~ /^WS(\d{3})\/(\d{3})(\d{2,3})KT$/) { # TAF WS
            $out .= "wind shear at $1 feet from $2 degrees at $3 knots";
         }
         elsif ($token =~ /^4(\d)(\d{3})(\d)(\d{3})$/) {
            $out .= "max 6 hour temperature @{[$1?'-':'']}@{[$2/10]} Celsius, min 6 hour temp @{[$3?'-':'']}@{[$4/10]} Celsius";
         }
         elsif ($token =~ /^T(\d)(\d{3})(\d)(\d{3})$/) {
            $out .= "temperature @{[$1?'-':'']}@{[$2/10]} Celsius, dew point @{[$3?'-':'']}@{[$4/10]} Celsius";
         }
         elsif ($token =~ /^([A-Z]{2})B(\d{2})$/) {
            if (exists $abb{$1}) {
               $out .= $abb{$1} . " began at $2 minutes after the hour";
            }
            else {
               $out .= $token . "?";
            }
         }
         elsif ($token =~ /^(\d{2})(\d{2})$/) {
            $out .= "from $1:00 to $2:00";
         }
# Miscellaneous Tokens
         elsif (exists $abb{$token}) {
            $out .= $abb{$token};
         }
         elsif ($token =~ /^([A-Z]{3})([0-9]+)(CB|TCU)?(VV)?(\d{3})?$/) {
            if ($1 eq 'FEW' or $1 eq 'SCT' or $1 eq 'BKN' or $1 eq 'OVC') {
               $out .= $abb{$1} . " clouds start at @{[$2 * 100]} feet AGL";
            }
            elsif (exists $abb{$1}) {
               $out .= $abb{$1} . $2;
            }
            else {
               $out .= $token . "?";
            }

            if ($3 eq 'CB') {
               $out .= " with cumulonimbus (rain)";
            }
            elsif ($3 eq 'TCU') {
               $out .= " with towering cumulus";
            }

            if ($4 eq 'VV') {
               $out .= " vertical visibility (indefinite ceiling) $5 feet";
            }
         }
# supposed to be max 3 groups, BR should always be by itself
         elsif ($token =~ /^([A-Z]{2,})$/) {
            my $i = 0;
            my $x = '';

            foreach (split //, $1) {
                  $i++;
                  $x .= $_;

                  if ($i == 2) {
                     if (exists $abb{$x}) {
                        $out .= $abb{$x} . ' ';
                     }
                     else {
                        $out .= $x . "?";
                     }

                     $i = 0;
                     $x = '';
                  }
            }
         }
         else {
            $out .= $token . "?";
         }

         $out .= "\n";
   } 

   $out;
}

__END__
Copyright 1998, AvWeb.com
$:maintenance needed
A:Altimeter
ACC:altocumulus castellanus
ACFT MSHP:aircraft mishap
ACSL:altocumulus standing lenticular cloud
ALP:airport location point
AMD:amended
AO1:automated station without precipitation discriminator
AO2:automated station with precipitation discriminator
APRNT:apparent
APRX:approximately
ATCT:airport traffic control tower
AUTO:automated report
B:began
BC:patches
BECMG:becoming
BKN:broken (5/8 - 7/8 coverage)
BL:blowing
BR:mist (visibility > 1/2 mile)
C:center (with reference to runway designation)
CA:cloud-air lightning
CAVOK:ceiling and visibility OK (viz >10 km, ceiling > 5000 feet, no precip)
CB:cumulonimbus cloud
CBMAM:cumulonimbus mammatus cloud
CC:cloud-cloud lightning
CCSL:cirrocumulus standing lenticular cloud
CG:cloud-ground lightning
CHI:cloud-height indicator
CHINO:sky condition at secondary location not available
CIG:ceiling
CLR:clear below 12,000 feet (automated)
CONS:continuous
COR:correction to a previously disseminated report
DOC:Department of Commerce
DOD:Department of Defense
DOT:Department of Transportation
DR:low drifting
DS:duststorm
DSNT:distant
DU:widespread dust
DZ:drizzle
E:east, ended
FAA:Federal Aviation Administration
FC:funnel cloud
FEW:few clouds (0/8 - 2/8 coverage)
FG:fog
FIBI:filed but impracticable to transmit
FIRST:first observation after a break in coverage at manual station
FROPA:frontal passage
FRQ:frequent
FT:feet
FU:smoke
FZ:freezing
FZRANO:freezing rain sensor not available
G:gust
GR:hail
GS:small hail and/or snow pellets
HZ:haze
IC:ice crystals, in-cloud lightning
ICAO:International Civil Aviation Organization
LTGIC:lightning in cloud
LTGICCG:lightning in cloud and cloud to ground
KT:knots
L:left (with reference to runway designation)
LAST:last observation before a break in coverage at a manual station
LST:Local Standard Time
LTG:lightning
LWR:lower
M:minus, less than
METAR:aviation routine weather report (observation)
MI:shallow
MOV:moved/moving/movement
MT:mountains
N:north
N/A:not applicable
NCDC:National Climatic Data Center
NE:northeast
NOS:National Ocean Service
NOSPECI:no SPECI reports are taken at the station
NSW:no significant weather
NW:northwest
NWS:National Weather Service
OCNL:occasional
OFCM:Office of the Federal Coordinator for Meteorology
OVC:overcast (8/8 coverage)
OHD:overhead
P:greater than 
PE:ice pellets
PK:peak
PK WND:peak wind
PNO:precipitation amount not available
PO:well-developed dust/sand whirls (dust devils)
PR:partial
PRESFR:pressure falling rapidly
PRESRR:pressure rising rapidly
PWINO:precipitation identifier sensor not available
PY:spray
R:right (with reference to runway designation)
RA:rain
RMK:Remarks
RVR:Runway Visual Range
RVRNO:RVR system not available
RWY:runway
S:south
SA:sand
SCSL:stratocumulus standing lenticular cloud
SCT:scattered (3/8 - 4/8 coverage)
SE:southeast
SFC:surface
SG:snow grains
SH:shower(s)
SKC:sky clear
SLP:sea-level pressure
SLPNO:sea-level pressure not available
SM:statute miles
SN:snow
SNINCR:snow increasing rapidly
SPECI:an unscheduled report taken when certain criteria have been met
SQ:squalls
SS:sandstorm
SW:southwest
TAF:routine terminal aerodrome forecast
TCU:towering cumulus
TEMPO:temporary
TESTM:AWOS METAR Test Report
TRSA:thunderstorm and rain shower
TS:thunderstorm
TSNO:thunderstorm information not available
TWR:tower
UP:unknown precipitation
UTC:Coordinated Universal Time
V:variable
VA:volcanic ash
VC:in the vicinity (5 - 10 miles from airport)
VIRGA:rain that doesn't reach ground
VIS:visibility
VISNO:visibility at secondary location not available
VRB:variable
VV:vertical visibility
W:west
WG/SO:Working Group for Surface Observations
WMO:World Meteorological Organization
WND:wind
WSHFT:wind shift
Z:zulu, i.e., Coordinated Universal Time