B757-200
Flight Crew Air Transport Pilot (ATP)
Deviation - Speed All Types; Inflight Event / Encounter Weather / Turbulence
Flight Crew Took Evasive Action
Weather
Departing Runway 02 with winds 030 at 19 gusting 24 and moderate rain. ATIS; tower; and [Company] weather briefing made no mention of windshear; however we briefed and performed the 757 windshear takeoff profile just to be safe. Takeoff was normal until just above 1000 AGL. After the Captain called 'VNAV' and I selected it; we experienced an almost instantaneous drop in airspeed of 40 knots; from 169 to 129 knots. We did not receive a windshear warning; however; I called out 'windshear' because the airspeed was not recovering. The Captain executed the windshear profile and after approximately 5 seconds the airspeed jumped back into a normal range. No engine limitations were exceeded; so the Captain elected to continue to [destination].Environmental conditions caused the event. However; the Captain and I talked about and briefed windshear takeoff profile and escape maneuver before flight because of the weather conditions. It definitely came in handy tonight.
B757 First Officer reported encountering windshear shortly after takeoff that resulted in an 'almost instantaneous' 40 knot drop in airspeed.