GA pilot reported a near midair collision that required an evasive maneuver while operating between ...

Narrative:

Heading eastbound at 4;800 [feet] MSL; above the lgb delta airspace; and below the 5;000 bravo shelf. Ceiling was unlimited at my position; clear below me; with visibility 10+ miles; except for low clouds extending eastward from the northwest to southeast approximately 3;000 feet laterally from my position; with tops about 4;800 MSL. As I was beginning to turn southeastward to keep cloud clearance and head for a higher bravo floor; I received a TCAS traffic alert; 100 feet below; less than 1 mile; at my 11:00 [position]. I took immediate evasive measures including climbing and turning faster to the south. I curtailed my climb abruptly at the floor of bravo. While I did not ever see the actual traffic conflict (in a turning climb away from target); the TCAS target appeared to cross almost directly under me; with only 300 feet separation. Knowledge of the bravo shelf kept me from aggressively climbing to avoid the conflict. Had bravo shelf not been there; I would have climbed much more aggressively higher.

Original NASA ASRS Text

Title: GA pilot reported a NMAC that required an evasive maneuver while operating between the ceiling of Delta airspace and the floor of Bravo airspace.

Narrative: Heading Eastbound at 4;800 [feet] MSL; above the LGB Delta airspace; and below the 5;000 Bravo shelf. Ceiling was unlimited at my position; clear below me; with visibility 10+ miles; except for low clouds extending eastward from the NW to SE approximately 3;000 feet laterally from my position; with tops about 4;800 MSL. As I was beginning to turn southeastward to keep cloud clearance and head for a higher Bravo floor; I received a TCAS traffic alert; 100 feet below; less than 1 mile; at my 11:00 [position]. I took immediate evasive measures including climbing and turning faster to the south. I curtailed my climb abruptly at the floor of Bravo. While I did not ever see the actual traffic conflict (in a turning climb away from target); the TCAS target appeared to cross almost directly under me; with only 300 feet separation. Knowledge of the Bravo shelf kept me from aggressively climbing to avoid the conflict. Had Bravo shelf not been there; I would have climbed much more aggressively higher.

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.

Attributes
ACN	1597208
Time
Date	201811
Local Time Of Day	1201-1800
Place
Locale Reference	LGB.Airport
State Reference	CA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Small Aircraft Low Wing 1 Eng Fixed Gear
Operating Under FAR Part	Part 91
Flight Phase	Climb
Flight Plan	None
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Person 1
Function	Single Pilot
Qualification	Flight Crew Private Flight Crew Instrument
Experience	Flight Crew Last 90 Days 31 Flight Crew Total 955 Flight Crew Type 955
Events
Anomaly	Conflict NMAC
Miss Distance	Horizontal 300 Vertical 300

GA pilot reported a near midair collision that required an evasive maneuver while operating between the ceiling of delta airspace and the floor of bravo airspace.