B757-200 CREW HAD SEVERE WINDSHEAR ON TKOF AT SFO.

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SURFACE WINDS STRONG AND GUSTY. ATIS RPTING LLWS ADVISORIES. NO PIREPS. INBOUND CREW RPTED 'ROUGH RIDE DOWN FINAL.' TRIM SETTING 3.7 ANU. NORMAL ACCELERATION TO VR. AT ROTATION (149 KIAS); THE NOSE WAS EXTREMELY HVY. A SLOW; BUT DELIBERATE ROTATION WAS ACCOMPLISHED. MAX PWR WAS USED FOR THIS DEP. AT APPROX 100 FT; THE AIRSPD INCREASED DRAMATICALLY (IN EXCESS OF 258 KTS). FURTHER ROTATION TOWARDS THE PITCH LIMIT INDICATOR WAS ACCOMPLISHED. AT ABOUT 3-5 DEGS BEFORE THE PITCH LIMIT INDICATOR; THE AIRSPD BEGAN TO STABILIZE. JUST AFTER LIFTOFF; WE RECEIVED A PREDICTED WINDSHEAR EICAS MESSAGE AND STATUS MESSAGE (LOGBOOK ENTRY MADE IN ZZZ). IT IS MY OPINION THAT WE ENCOUNTERED WINDSHEAR ON DEP. THE FO DID NOT NOTICE ANY OVERSPD SITS DURING FLAP RETRACTION. THE PITCH AND TURB HAD MY FULL ATTN; THEREFORE; I CANNOT COMMENT WITH CERTAINTY AS TO THE ABOVE. WE DID RETRACT ON SCHEDULE ONCE WE WERE CLR OF THE WINDSHEAR. IT SHOULD BE NOTED THAT THE AIRSPD INCREASE WAS SO RAPID THAT THE FO COMMENTED AFTER THE EVENT HE WAS CHKING FOR ERRONEOUS AIRSPD INDICATIONS THROUGHOUT THE COCKPIT. (A POINT I FELT WAS QUICK THINKING ON HIS PART.)