Date: 201207
Local time of day: 1201-1800
Location: PHL.TRACON, PA
Flight conditions: Mixed
Weather elements / visibility: Fog; Rain; Turbulence; Thunderstorm
Light: Daylight
Aircraft: Rockwell Aero Commander Single-Engine Undifferentiated or Other Model
Operator: Personal
Flight plan: IFR
Mission: Personal
Flight phase: Cruise
Airspace: Class E PHL
ATC / advisory: TRACON PHL
Reporter organization: Personal
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Instrument; Flight Crew Private
Human factors: Other / Unknown
Anomaly: Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
Result: Flight Crew Took Evasive Action
Contributing factors: ATC Equipment / Nav Facility / Buildings; Weather
Primary problem: ATC Equipment / Nav Facility / Buildings

Narrative: I had obtained a complete weather briefing from the FSS within the hour prior to departing 58M and was advised in that briefing that there was a possibility of severe weather (thunderstorms/convective activity) moving into my destination at my estimated time of arrival. I decided to depart 58M and try to make it into POU either well ahead of the forecast storms or possibly well behind the storms after they had gone through POU and quickly continued on their Eastward track. While in flight began noticing the skies ahead changing in color to those unmistakable hues with summertime embedded thunderstorm activity. I was still at least 40 minutes or so away from my destination. I called ATC and asked if they knew of any weather ahead of me and on my route of flight and especially at my planned destination. ATC responded that they were only aware of some 'Level 1' precipitation; mostly 'just some light rain shower activity;' and that there was no other weather ahead. Satisfied with their reply; I continued on to my intended destination. The skies continued to intensify in deep dark color; strongly indicating to me that there was a very likely dangerous weather-related condition in the not-too-distant area ahead. I was aware; and am aware; that ATC doesn't always have weather equipment which can paint accurate weather all the time; and that they often rely on pilot reports. New York EFAS pulled up the weather for my location and for my destination and confirmed what I had already suspected; that the area I was flying in was on the border of severe thunderstorm/convective activity; that there definitely was severe thunderstorm/convective activity I would be entering very shortly if I remained on course and that my destination airport was just minutes from severe thunderstorm/convective activity hitting it. Returning to ATC's frequency; my call was preceded by another aircraft calling ATC and also asking for weather in the same vicinity I was flying in and for a destination very close to my originally planed destination. I waited for ATC to respond to the other pilot; for one; to hear if ATC had changed its report on weather conditions from the erroneous one they had just recently given me. Much to my surprise and alarm; I heard ATC give the other aircraft the same advisement they had just given me minutes before. I knew this was not true because of my own personal in-air weather observations and because my observations matched EFAS' warning of severe thunderstorm/convective activity immediately ahead. Despite my telling ATC of the known weather ahead; they continued stating that there were only Level 1 rain showers as though to refute or negate what I was seeing and what EFAS had reported to me. I told ATC that I was executing an immediate 180 degree turn to avoid the dangerous weather area ahead. It continues to upset and depress me that America's aviation system has excellent weather tools available to some parts of it; like FSS and EFAS; while in flight controllers (ATC) do not have access to this information. This state of affairs creates unnecessarily dangerous environments for all aircraft. Resources should be expended immediately so as to provide all ATC facilities with accurate weather reporting tools and information.




Synopsis: General Aviation pilot initiated an emergency unauthorized turn to avoid significant weather. The reporter noted ATC's weather detection equipment is very limited and needs to be improved.