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

 moderate to heavy rain and considerable turbulence existed at all levels below 3000 feet. Coincident with the arrival of this frontal system, such turbulence, at times almost down to the surface, was to be expected as well as locally heavy rain squalls and a sharply defined transition from west-southwesterly winds in the upper levels to south and southeast winds in a shallow layer near the ground. Although the frontal system reached Cincinnati earlier than was predicted and prior to the arrival of Trip 20, it must be understood that in the preparation of the forecasts the movement of the frontal system was computed upon the basis of the known movement of the air masses during a number of hours preceding the making of the forecasts. This was in accordance with the normal practice. The accuracy of forecasts depends as much upon the observational facilities available as it does upon experience in the science of meteorology. Additional facilities as well as further development of the science of meteorology are necessary in order that more accurate forecasts can be made in predicting the acceleration in movements of air masses.

The significance of the failure of the forecasts to predict accurately the movement of the storm fronts is mitigated by the fact that the company meteorologist at Chicago called the Captain Bryant's attention before departure the information contained in the Weather Bureau airway forecast and that contained in the 1:30 p.m. weather map. With this information in mind Captain Bryant testified that he was not surprised by the conditions which he encountered upon arrival at Cincinnati and that he understood what was happening. Even if the forecasts had accurately predicted the frontal movement, Trip 20, according to the normal practice, would have been dispatched if the ceilings and visibility had been expected to remain equal to or above approved minimums. In such a situation Captain Bryant,