Strange Weather System Passage
While working in the tower, I was witness to a fascinating weather pattern. While a trainee worked, I was pushed to the back of the tower cab to see this all without having to watch traffic.
The sky was divided 50/50 on a northeast/southwest line. The northwest portion was clear blue, and the rest was altostratus and solid. Winds at the field were 150@10-15. A line of cloud that paralleled the overhead line of cloud appeared low on the northwest horizon, and initially appeared to be moving pretty quickly. As it approached, it became apparent that it was comparatively low at the base, and nowhere near as high as the altostratus above as we could see blue sky and the horizon below it, and the clear blue sky above it, too. Traffic was lining up for runway 15 on approach. As the line approached, the aircraft on final started to descend into it, and then poke out the side of it. Each aircraft reported "strong moderate" turbulence within, smooth above and outside. The line appeared to be rolling as well, the base rolling toward the tower as the line progressed southeastward, and the front wall, as seen from the tower, rolling up and over the back of it. As each aircraft passed through the wall of cloud, I noted on the radar the distance at which he broke out. Each aircraft (spaced about 3-4NM apart), showed the line moving fairly quickly, gaining a half-mile with each one. Eventually, the cloud line moved overhead the airport. When it did, the winds dropped to zero fairly quickly, moderate to heavy rain fell, but only for a short time, and the blue sky was visible to the northwest with the original higher cloud still visible to the southeast. After the cloud line passed, the rain subsided, and the wind shifted -- same speed, but 180° away from where it had been all morning. Even with the cloud line overhead, we remained VMC. The wind remained 330@10-15 as the cloud line continued to roll away to the southeast, meaning a change in active runway and a screwed up traffic pattern. Eventually, the sky returned to its original condition, leaving the aforementioned 50/50 split of clear blue to the northwest with altostratus covering the rest. The cloud line was out of sight, as if it had never existed, and the winds remained from the northwest. Otherwise, it all appeared as it had before the line even came into sight.
One of the many things I miss about working in the tower was watching the weather. I saw many, many interesting phenomena there, and I am still fascinated by it all.
The sky was divided 50/50 on a northeast/southwest line. The northwest portion was clear blue, and the rest was altostratus and solid. Winds at the field were 150@10-15. A line of cloud that paralleled the overhead line of cloud appeared low on the northwest horizon, and initially appeared to be moving pretty quickly. As it approached, it became apparent that it was comparatively low at the base, and nowhere near as high as the altostratus above as we could see blue sky and the horizon below it, and the clear blue sky above it, too. Traffic was lining up for runway 15 on approach. As the line approached, the aircraft on final started to descend into it, and then poke out the side of it. Each aircraft reported "strong moderate" turbulence within, smooth above and outside. The line appeared to be rolling as well, the base rolling toward the tower as the line progressed southeastward, and the front wall, as seen from the tower, rolling up and over the back of it. As each aircraft passed through the wall of cloud, I noted on the radar the distance at which he broke out. Each aircraft (spaced about 3-4NM apart), showed the line moving fairly quickly, gaining a half-mile with each one. Eventually, the cloud line moved overhead the airport. When it did, the winds dropped to zero fairly quickly, moderate to heavy rain fell, but only for a short time, and the blue sky was visible to the northwest with the original higher cloud still visible to the southeast. After the cloud line passed, the rain subsided, and the wind shifted -- same speed, but 180° away from where it had been all morning. Even with the cloud line overhead, we remained VMC. The wind remained 330@10-15 as the cloud line continued to roll away to the southeast, meaning a change in active runway and a screwed up traffic pattern. Eventually, the sky returned to its original condition, leaving the aforementioned 50/50 split of clear blue to the northwest with altostratus covering the rest. The cloud line was out of sight, as if it had never existed, and the winds remained from the northwest. Otherwise, it all appeared as it had before the line even came into sight.
One of the many things I miss about working in the tower was watching the weather. I saw many, many interesting phenomena there, and I am still fascinated by it all.
posted by Michael at
08:14
