Narrative:

We were just inside a two mile final for runway 24R at lax and had been cleared to land; when the local controller reported a windshear alert of a 35 knot loss on a two mile final; which again; was right where we were or slightly behind us. Nothing in the cockpit indicated any windshear (no airspeed; glide slope or pitch variations or unusual power settings and the wind indications were within a few knots of the reported wind on the ground and similar direction). The co-pilot; who was PF; added 10 knots to approach speed and we discussed going around and as I was about to ask the controller to confirm the wind speed loss he issued a second windshear alert of 35 knots this time also right behind us at 500 feet. We were now at about 300 feet and had experienced nothing other than the usual 5 knot variations due to thermal and orographic shifting on short final to 24R. There was no precip in the area; no virga and we had watched the aircraft in front of us land and he reported no windshear. We went ahead and landed based on our cockpit indications and the lack of report from the aircraft in front of us. After we landed; the windshear alerts stopped and the 737 which landed behind us also reported no windshear. I reviewed the windshear section of the afm later in the day and saw that we should have gone around; based on the amount of windshear reported by the tdwr (terminal doppler weather radar); even though the reports did not reflect the actual conditions we experienced at those points and our cockpit indications did not suggest windshear. This is not the first time I've received tdwr windshear reports right at our location or slightly behind us 'out of the blue' when flying a 757; but it was the first time I'd ever received at 35 knot report. Based on my previous experiences and this one; I believe that tdwr may be detecting 757 wake turbulence under certain conditions and reporting it as windshear. And next time; regardless of cockpit indications; suspected spurious report or not; I'll go around.

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Original NASA ASRS Text

Title: B757 Captain reported he failed to follow company SOPs when he received a windshear warning on final at LAX and did not execute a go-around.

Narrative: We were just inside a two mile final for RWY 24R at LAX and had been cleared to land; when the local controller reported a windshear alert of a 35 knot loss on a two mile final; which again; was right where we were or slightly behind us. Nothing in the cockpit indicated any windshear (no airspeed; glide slope or pitch variations or unusual power settings and the wind indications were within a few knots of the reported wind on the ground and similar direction). The co-pilot; who was PF; added 10 knots to approach speed and we discussed going around and as I was about to ask the controller to confirm the wind speed loss he issued a second windshear alert of 35 knots this time also right behind us at 500 feet. We were now at about 300 feet and had experienced nothing other than the usual 5 knot variations due to thermal and orographic shifting on short final to 24R. There was no precip in the area; no virga and we had watched the aircraft in front of us land and he reported no windshear. We went ahead and landed based on our cockpit indications and the lack of report from the aircraft in front of us. After we landed; the windshear alerts stopped and the 737 which landed behind us also reported no windshear. I reviewed the Windshear section of the AFM later in the day and saw that we should have gone around; based on the amount of windshear reported by the TDWR (Terminal Doppler Weather Radar); even though the reports did not reflect the actual conditions we experienced at those points and our cockpit indications did not suggest windshear. This is not the first time I've received TDWR windshear reports right at our location or slightly behind us 'out of the blue' when flying a 757; but it was the first time I'd ever received at 35 knot report. Based on my previous experiences and this one; I believe that TDWR may be detecting 757 wake turbulence under certain conditions and reporting it as windshear. And next time; regardless of cockpit indications; suspected spurious report or not; I'll go around.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.