Narrative:

We were on a 110 degree vectored heading approximately 10-15 NM northwest of sjc level at 4000 ft MSL. WX was IMC with scattered light rain showers in the vicinity. We were using WX mode on the radar for the showers. We received a terrain warning; 'terrain; terrain; pull up.' I glanced down at the radar but it was still painting WX. The egpws sounded the terrain warning again and I immediately disengaged the autoplt; applied maximum thrust; and rotated to 15 degrees nose up; maintaining 210 KIAS. The first officer notified approach control we were responding to a terrain alert and climbing out of 4000 ft. I stopped the climb at 5200 ft MSL. Approach gave us a vector to 030 degrees and a descent to 4000 ft after which we were handed off to another approach controller. We were established on a right downwind leg for runway 12R and continued the approach and landing without further incident. We are unsure why we received the terrain warning; level at 4000 ft. There is a mountain peak at 3231 ft which the controller stated was approximately 2.5 NM off our right. A tower at 3496 ft and one at 4081 ft 7-10 NM ahead may have triggered the alert.

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Original NASA ASRS Text

Title: B737-300 FLT CREW WHILE ON VECTORS TO APCH RECEIVE A GPWS 'TERRAIN WARNING.' FLT CREW EXECUTES AVOIDANCE MANEUVER AND CONTINUES APCH WITHOUT FURTHER INCIDENT.

Narrative: WE WERE ON A 110 DEG VECTORED HDG APPROX 10-15 NM NW OF SJC LEVEL AT 4000 FT MSL. WX WAS IMC WITH SCATTERED LIGHT RAIN SHOWERS IN THE VICINITY. WE WERE USING WX MODE ON THE RADAR FOR THE SHOWERS. WE RECEIVED A TERRAIN WARNING; 'TERRAIN; TERRAIN; PULL UP.' I GLANCED DOWN AT THE RADAR BUT IT WAS STILL PAINTING WX. THE EGPWS SOUNDED THE TERRAIN WARNING AGAIN AND I IMMEDIATELY DISENGAGED THE AUTOPLT; APPLIED MAX THRUST; AND ROTATED TO 15 DEGS NOSE UP; MAINTAINING 210 KIAS. THE FO NOTIFIED APCH CTL WE WERE RESPONDING TO A TERRAIN ALERT AND CLBING OUT OF 4000 FT. I STOPPED THE CLB AT 5200 FT MSL. APCH GAVE US A VECTOR TO 030 DEGS AND A DSCNT TO 4000 FT AFTER WHICH WE WERE HANDED OFF TO ANOTHER APCH CTLR. WE WERE ESTABLISHED ON A R DOWNWIND LEG FOR RWY 12R AND CONTINUED THE APCH AND LNDG WITHOUT FURTHER INCIDENT. WE ARE UNSURE WHY WE RECEIVED THE TERRAIN WARNING; LEVEL AT 4000 FT. THERE IS A MOUNTAIN PEAK AT 3231 FT WHICH THE CTLR STATED WAS APPROX 2.5 NM OFF OUR R. A TWR AT 3496 FT AND ONE AT 4081 FT 7-10 NM AHEAD MAY HAVE TRIGGERED THE ALERT.

Data retrieved from NASA's ASRS site as of January 2009 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.