chart for 18Z run of the GFS
	00 hour 12 hour 24 hour 36 hour 48 hour 60 hour 72 hour 84 hour 96 hour 108 hour 120 hour 132 hour 144 hour 156 hour 168 hour 180 hour 192 hour 204 hour 216 hour 228 hour 240 hour 252 hour 264 hour 276 hour 288 hour 300 hour 312 hour 324 hour 336 hour 348 hour 360 hour 372 hour 384 hour