In reply to my own question this is what I use:
Mobile internet running GR Level 3, Spotter Network and APRS.
GR Level X is the cat's meow in mobile radar but when coupled with GPS, Spotter Network and amateur radio's Automatic Position Reporting System (APRS) you can see the storm relative to YOU and not to the RADAR site. With all the other overlays you can see where everyone else is as well. You would be surprised to see who is out there on the chase!
Radios: dual band HAM radio Yaesu FT-8800, Alinco DR-135 with TNC, Motorola HT-1250, and PSR-600 Scanner.
8800 to stay in touch with severe weather nets, DR-135 relays my position and information via APRS. Motorola for EMS / EMA and the scanner to monitor other public safety agencies. Most of this is turned off during a chase but needed when spotting.
Garmin GPS to run the APRS and help get me lost!
Curious about APRS? Click link to see where I am:
Advanced Life Support medical kit and cardiac monitor - defibrillator. Emergency lights and siren.