Storm with lightnings and no thunder
"No, it is not possible to have thunder without lightning. Thunder is a direct result of lightning. However, it IS possible that you might see lightning and not hear the thunder because it was too far away. Sometimes this is called “heat lightning” because it occurs most often in the summer. "

here is more information regarding lightning:
http://www.nssl.noaa.gov/education/svrwx101/lightning/faq/