Page:CAB Aircraft Accident Report, Northwest Airlines Flight 705.pdf/3

 Statements were received from the crews of four other flights operating in the Miami area at the approximate time of the accident. The first, in a large jet which approached Miami from the west at 7,000 feet, reported the weather as "... in and out of broken clouds and light rain showers with light turbulence. Darker heavy shower activity was observed to the (south) of course... We observed no small cells on our radar scope... only a broad rain area..." Another crew, in a four-engine aircraft, departed Miami at 1318, via a departure pattern similar to that which Flight 705 later followed. They described the worst turbulence as "... medium to moderate..." from west of the airport to north of the Miami VORTAC. They were maintaining 5,000 feet at the time. A third crew in a 720B was holding southeast of Miami at 13,000 feet. They observed numerous rain cells on radar in the Miami area and encountered light ice at this altitude. The fourth crew, also flying a large jet, taxied out shortly after Flight 705 but delayed takeoff for nearly an hour because of the weather.

The weather in Miami at the time of the accident was characterized by a pre-frontal squall line approximately 250 miles in length oriented on a northeast-southwest line immediately northwest of Miami (See Attachment A). The U. S. Weather Bureau (USWB) radar observation at Miami at 1344 indicated a broken area of thunderstorms associated with this line, with cells two to twenty miles in diameter, and tops of detectable moisture at 30,000 feet. The line was moving southeast at eight knots, and moderate rain showers were occurring at the station. The 0600 and 1800 Miami radiosonde ascents showed the freezing level to have been at 11,100 and 12,400 feet m.s.l., respectively.

SIGMET No. 3 prepared by the USWB at Miami, valid from 0900-1300, forecast moderate to severe turbulence in thunderstorms, with a chance of extreme