Page:CAB Accident Report, American Airlines Flight 20.pdf/9

 showed a low pressure system centered over Illinois with a warm front extending southeastward from the center and a cold front extending southward from the center. To the north of the intersection of the warm and cold fronts an occluded front extended for a distance of 200 miles. There was a marked wind shift across the occlusion with easterly winds on the north and east side and northwesterly winds on the western side. This whole system was moving northeastward about 20 to 25 miles per hour. A forecast based on the last six-hour movement of the system placed the point of occlusion of the warm and cold fronts between Louisville and Cincinnati at 7:30 p.m.

Although neither the trip forecast nor the terminal forecast, furnished Captain Bryant prior to departure, indicated any probability of Trip 20 encountering the front en route, the 5:30 p.m. (EST) Weather Bureau airway forecast contained information as to the existence of this storm area and the direction of its movement. This information was called to Captain Bryant's attention by the company meteorologist in a conversation prior to departure from Chicago. All the forecasts predicted the arrival of the storm in the vicinity of Cincinnati some time after midnight and on that assumption the assistant flight superintendent on duty at Chicago issued authority for Trip 20 to proceed non-stop on instruments from Chicago, Illinois, to Cincinnati, Ohio. Captain Bryant's flight plan, which he prepared after conference with the company