METEOROLOGICAL INFORMATION
National Weather Service (NWS) surface analysis station models showed, about 0600, a low pressure area centered over northern Mexico and two frontal boundaries extended through
13 The MFD displays a number for each approach waypoint, which indicates the waypoint‘s chronological orderin the waypoint list.
14 Federal regulations required that all turbine engine-powered airplanes with six or more passenger seats be equipped with an enhanced ground proximity warning system (EGPWS) by March 29, 2005. The EGPWS provides pilots with a pictorial view of terrain in addition to the aural alerts provided by the GPWS.
central and southern Texas. Station models in southeastern Texas showed that surface winds were generally less than 5 knots and that mist and light rain existed in the area.
A Terminal Aerodrome Forecast prepared by the NWS for HOU, which was valid at the time of the accident, stated, in part, the following: Wind at 100° at 5 knots, visibility 1/4 sm in fog, vertical visibility15 100 feet. The NWS issued a dense fog advisory at 0159 local time on November 22, which was valid at the time of the accident and warned of a large area of fog over the surrounding area and of visibility of less than 1/4 sm.
About 0245 local time, the NWS issued Airman‘s Meteorological Information (AIRMET) —Sierra,“ which covered the area surrounding the airplane‘s flightpath and was valid at the time of the accident. AIRMET —Sierra“ warned of occasional ceilings below 1,000 feet and/or visibility below 3 sm in precipitation, mist, and/or fog. About 0455 local time, the NWS issued a convective significant meteorological information (SIGMET),16 which covered the area near the accident site and was valid at the time of the accident. The SIGMET warned of embedded thunderstorms moving from 250° at 20 knots, with cloud tops above 45,000 feet.
Weather observations at HOU are made by an automated surface observing system (ASOS), which is located about 4 miles northeast of the accident site at an elevation of about 45 feet. ASOS transmits official meteorological aerodrome reports (METAR) 53 minutes past each hour and special weather observations (SPECI) as conditions warrant, including wind shift, visibility change, and cloud cover or height ceiling change. The 0553 METAR reported that winds were 110° at 3 knots; the tower visibility was 1/8 sm in fog; the sky condition was clouds scattered at 100 feet, broken at 600 feet, and overcast at 5,500 feet; and the surface visibility was 1/2 sm. The HOU ASOS issued SPECIs at 0605 and 0627 because the cloud ceiling had changed from scattered to broken at 100 feet and from broken to overcast at 600 feet, respectively. The HOU ASOS provides unofficial weather observations that are recorded every 5 minutes. At 0615, the HOU ASOS reported that winds were 90° at 3 knots, the tower visibility was 1/8 sm in fog, the sky condition was clouds broken at 100 feet and overcast at 600 feet, and the surface visibility was 1/2 sm.

AIRPORT INFORMATION
HOU is located about 8 miles southeast of Houston at an elevation of 46 feet. Runway 4 is equipped with a medium intensity approach lighting system with runway alignment indicator lights, high intensity runway edge lights, touchdown lights, and centerline lights. The approach end of runway 4 at HOU is equipped with a suite of sensors that measure the RVR.
Minimum Safe Altitude Warning Information
Houston TRACON provides approach control services to the HOU ATCT. Houston TRACON is equipped with an automated radar terminal system IIIA radar data processing unit
15 Vertical visibility is defined as the vertical distance a person can see from the surface of the earth to the obscuring phenomenon.
16 Convective SIGMETs are issued when severe thunderstorms and embedded thunderstorms occur for more than 30 minutes of the valid period, regardless of the size of the area; when a line of thunderstorms exists; or when an area of active thunderstorms affecting at least 3,000 square miles exists.
　
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