AN ECLIPSE 500 USED EMER AUTHORITY TO DEVIATE AROUND WX.

Narrative

DURING THE PREFLIGHT PLANNING STAGE IT WAS FOUND THAT SOME VERY LIGHT WX MIGHT BE AROUND THE ARPT AT THE TIME OF DEP. THE ECLIPSE 500 DOES NOT HAVE WX RADAR; THE AIRPLANE HAS BEEN DELIVERED BY ECLIPSE WITH A PORTABLE XM WEATHER WHICH HAS BEEN APPROVED FOR USE BY THE FAA FOR WX AVOIDANCE FOR OUR OP. AFTER WE BECAME AIRBORNE; THE WX AS DEPICTED ON XM WEATHER INDICATED MODERATE TO INTENSE PRECIPITATION AT ZZZ. DEP ALSO INDICATED THAT THEY SHOWED MODERATE TO INTENSE PRECIPITATION AT OUR TWELVE O'CLOCK POSITION. ZZZ DEP SUGGESTED A NINETY DEG L TURN AND TOLD US TO SWITCH TO ZZZ CENTER. WHEN I CONTACTED CENTER; I ADVISED THEM OF OUR NEW HDG 'TO AVOID WX' AND WAS IMMEDIATELY QUESTIONED IF WE WERE USING OUR 'EMER AUTHORITY' TO DEVIATE AROUND WX. I WAS SURPRISED BY THE QUESTION; DID NOT RESPOND IMMEDIATELY; AND WHEN ZZZ CENTER ASKED AGAIN IF WE WERE USING OUR 'EMER AUTHORITY;' THE PIC TOOK OVER THE RADIO COM AND RESPONDED THAT 'I GUESS WE ARE USING OUR EMER AUTHORITY.' WE WERE EVENTUALLY SWITCHED BACK TO ZZZ DEP AND WERE VECTORED AROUND WX WITHOUT INCIDENT. XM WEATHER HAS A DELAY IN THE DISPLAY OF WX/THUNDERSTORMS; MAKING THE USE OF XM WEATHER IN WX AVOIDANCE WITH RAPIDLY DEVELOPING STORMS USELESS. IT APPEARS THERE WAS A MISCOM BETWEEN DEP CTL AND CENTER ABOUT OUR NEW HDG; CENTER APPEARED OVERLY EAGER TO GET US TO USE OUR 'EMER AUTHORITY' RATHER THAN HELP US AVOID WX. THE ECLIPSE 500 IS NOT SUITABLY EQUIPPED TO BE FLOWN IN ANY TYPE OF WX ENVIRONMENT THAT MIGHT POTENTIALLY DEVELOP THUNDERSTORM ACTIVITY.