PARALLEL RWY OPERATOIN. LGT ENCOUNTERS JET WASH AT ROTATION FROM ACFT HOLDING TO CROSS OTHER RWY.

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FLT WAS CLRED FOR TKOF. RWY 25L AT LAX. AT THE FAR END OF THE RWY THERE WAS AN MLG AND MLG Y HOLD BTWN RWY 25R AND 25L. THEY WERE AT EITHER 47H OR 45H. IT LOOKED AS THOUGH THE TAIL OF THE MLG Y WAS JUST AT THE END OF RWY EDGE LINE. WE STARTED THE TKOF ROLL; GOT TO V1 VR. STARTED OUR ROTATION AS WE CAME ABEAM THE MLG AND MLG Y. AT THAT TIME OUR ACFT WAS HIT WITH THE FULL JET BLAST OF THE MLG AND MLG Y THAT HAD JUST STARTED TO TAXI ACROSS RWY 25R. FIRST; I FEEL THAT THE TXWY THAT THEY WERE ON (BOTH) WAS TOO SMALL FOR BOTH AIRPLANES. SECOND; THE TWR SHOULD BE AWARE OF WHERE THE JET BLAST IS GOING WHEN THE TAIL IS POINTED ON THE RWY BEING USED FOR TKOF OR LNDGS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: NEITHER RPTR NOR THE CAPT TALKED WITH LAX TWR REFERENCE THE INCIDENT. CLAIMS THIS IS HAPPENING FREQUENTLY ESPECIALLY FOR ACI WITH GATE POSITIONS ON THE WEST PART OF THE ARPT. FEELS HAD IT BEEN A WDB IT WOULD HAVE REALLY GOTTEN INTERESTING. DID NOT FOLLOW UP BECAUSE IT WAS BEGINNING OF A FOUR DAY SEQUENCE.