Launch Weather:
On the afternoon of February 27, NASA mission managers decided to delay the launch for 24 hours due to concerns that low temperatures would violate Launch Commit Criteria (LCC). Temperatures did reach the LCC limit on the early morning of February 28, but did not exceed limits. On the evening of February 28, High Pressure was centered over VA/NC with easterly low-level flow over Florida. Warm air overrunning cold air at the surface was causing a solid deck of low clouds over south Florida to spread northward up the peninsula. Forecasters at the Spaceflight Meteorology Group (SMG) were relying on infrared satellite imagery but were deterred somewhat by the temporary loss of GOES-8 imagery due to the Spring eclipse. Limited nighttime surface observations were also a hindrance. However, the astronaut pilot flying weather reconnaissance in the Shuttle Training Aircraft (STA) using night vision goggles was helpful in identifying cloud bases and tops. By L-9 hours, ceilings below 5 thousand ft were being reported as far north as MLB, but were beginning to show breaks as the northern edge of the clouds reached central Florida. From launch-6 hours until launch-1 hour, the cloud condition at the Shuttle Landing Facility (SLF) varied from BKN to FEW clouds below 5 thousand ft. NASA flight rule limit for a Return to Launch Site (RTLS) abort landing is 5 thousand ft ceiling. From launch-1 hour through launch, the sky condition improved to scattered or few. This enabled Columbia to launch on time at 1122 UTC. At RTLS (1147 UTC), the SLF observer reported a broken ceiling at 6 thousand ft. Weather at Ben Guerir, the lone TAL site for STS-109, remained acceptable throughout the launch count and at TAL (1157 UTC).

Landing Weather:
On the evening of March 12, low-level easterly flow over Florida was producing scattered low clouds offshore, but clouds were dissipating as they approached the central Florida coast. Occasionally one or two of these would develop into a light rainshower. By 0800 UTC, winds at the SLF went calm and temperature/dewpoint spreads at the 6 ft sensor dropped to 2 degrees F. This raised the concern of fog forming at the SLF. One hour later the TT/Td spread fell to 0. Fortunately the winds above 50 ft gradually increased, creating enough turbulent mixing aloft to inhibit fog formation. Visibility at the SLF never fell below 8 miles even though shallow ground fog was being reported by the observer. Columbia executed a perfect landing at 0932 UTC on the first landing opportunity. SMG Lead Meteorologist was Wayne Baggett working his 11th mission as Lead. Karl Silverman was the Assistant Lead and Tim Oram was the Lead Techniques Development Unit Meteorologist.

Submitted by: G. Wayne Baggett, STS 109 Lead Meteorologist