feat: Decode special METAR remarks and directional patterns

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>

metar.html

@@ -246,6 +246,15 @@
                 'CU': 'Cumulus',
                 'CB': 'Cumulonimbus'
             };
+            const specialRemarks = {
+                'FROIN': 'Frontal passage in vicinity',
+                'CONTRAILS': 'Contrails observed',
+                'VIRGA': 'Virga (precipitation not reaching the ground)'
+            };
+            const directions = {
+                'N': 'North', 'NE': 'Northeast', 'E': 'East', 'SE': 'Southeast',
+                'S': 'South', 'SW': 'Southwest', 'W': 'West', 'NW': 'Northwest'
+            };
 
             for (let i = 0; i < parts.length; i++) {
                 const part = parts[i];
@@ -255,6 +264,16 @@
                     decoded.push(`  - ${decodeObscurationRemark(part)}`);
                 } else if (part.match(/^([A-Z]{2}\d)+$/)) {
                     decoded.push(`  - ${decodeCloudTypesRemark(part)}`);
+                } else if (part === 'VIRGA' && i + 1 < parts.length && directions[parts[i+1]]) {
+                    const direction = directions[parts[i+1]];
+                    decoded.push(`  - VIRGA ${parts[i+1]}: Virga to the ${direction.toLowerCase()}`);
+                    i++; // Consume direction part
+                } else if (part === 'TCU' && i + 2 < parts.length && parts[i+1] === 'DSNT' && directions[parts[i+2]]) {
+                    const direction = directions[parts[i+2]];
+                    decoded.push(`  - TCU DSNT ${parts[i+2]}: Towering cumulus distant ${direction.toLowerCase()}`);
+                    i += 2; // Consume DSNT and direction
+                } else if (specialRemarks[part]) {
+                    decoded.push(`  - ${part}: ${specialRemarks[part]}`);
                 } else if (cloudTypes[part] && i + 1 < parts.length && parts[i + 1] === 'TR') {
                     const cloudName = cloudTypes[part];
                     decoded.push(`  - ${part} ${parts[i+1]}: ${cloudName} clouds are translucent (thin)`);