Cold Front

Time: 2247 central time

Location: Over Corpus Christi VOR

Altitude: 25,000 feet

After a long night of turbulence and thunderstorms, we’re finally in clear air. Today is the first day of a four-day trip and we’re heading for the overnight in Harlingen, Texas. This evening we’ve traced a line ahead of a fast moving cold front that’s extending from the Dakotas down through Central Texas and into Mexico. Back on the first leg in Little Rock we were delayed for over an hour while we (the crew and the passengers) huddled in a stairwell in the terminal building waiting out a passing tornado. Being from Florida, I’ve never experienced anything like that, but I guess it’s not so uncommon in the Midwest.

The air is smooth now and I’m relaxing a bit before I start preparing for the arrival into Harlingen. The control tower has closed for the night, so the captain tunes in the AWOS (Automated Weather Observation Service) and reports back 9 miles of visibility, winds 11 knots out of the southeast, and clear skies. Looking forward to an easy approach and my bed at the Hilton I set up and brief a visual to runway 17R.

30 nautical miles northeast of Harlingen Airport descending through 10,000 feet. The approach controller breaks us off of our course direct to the airport and gives a heading to intercept the final approach for runway 17R. As we continue to descend I still can’t see any lights on the ground – strange, because the sky was reported as clear. At 4,000 feet 15 miles from the runway we descend into a layer of clouds and it’s bumpy, solid moderate turbulence. Why is it so rough? Being so close to the airport already there’s not a lot of time to figure out why the clouds have taken the place of the reported clear skies in the AWOS recording, and we tell ATC that we will need to shoot the instrument approach. They give us a vector further to the right, affording a little time to set up.

Turn left heading 210, maintain 3,000 feet until established on the final approach course, cleared ILS runway 17R approach. Turning onto the extended centerline of runway I call for landing gear down, flaps 22. There’s no precipitation, but the turbulence seems to be getting worse and it’s taking a lot of my attention just to maintain airspeed. I call for a final configuration change and before landing checklist as we intercept the glideslope and we start a final descent towards the runway. At 800 feet we break out of the bottoms of the clouds and I can see the runway. Before I can verbalize runway in sight, we hit an invisible wall of air and instantly planes airspeed is 25 knots higher. The plane’s computer shouts Windshear Windshear. It’s a scenario straight out of training – maximum thrust, go around. The thrust control computer commands reserve thrust, a higher power setting only used in emergencies or to get out of bad situations. I pitch the nose up as the engines roar behind us. The captain tells ATC we are aborting the approach and reports the windshear. It doesn’t take long to reach a safe altitude where we reconfigure and regroup. The captain runs the checklist and we discuss the abort. The turbulence, the low clouds, the windshear – we must have passed through the edge of the front. Approach control calls, reporting a wind shift at the airport, wind is now 330 degrees (northwest) at 15 knots. This confirms the suspected frontal passage. We talk about the best course of action and decide there is enough fuel for one more landing attempt, then we must divert to another airport. ATC gives us a vector to set up for an approach to the north facing runway 35L and we find that to the south of the airport the sky is mostly clear and smooth. I brief the likelihood of encountering the shear again and decide to fly a flaps 22 approach and landing. This will allow us to fly a slightly faster approach and better cope with a wind shift while not risking over speeding the flaps.

2,500 feet above runway 35L on a 10 mile final. Still in clear air, fully configured and nose pointed straight towards the runway I see something I have never seen before. The very line where the two air masses converge is actually visible. We’ve crossed over to the warm-air side of the front, and I can see a color and consistency difference where the cold air abuts the warm, similar to a thermocline in the ocean. As we hit the wall of cold air the airspeed indicator jumps again. This time I’m ready for it. I keep the nose pointed toward the runway, managing the airspeed the best I can as we blast into the dense air. Ten seconds later it’s over and I’m back on speed and a stable glidepath towards runway 35L.

I touch down and we make the high-speed turn off towards the terminal building. I have to give ATC a call to close our flight plan and when I do I hear that an American MD88 that was arriving behind us executed a go around for wind shear as well.

Finishing the last checklist the first day of our trip is over and it’s time for some well-deserved rest.

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