On 4 October 1995, tornado-producing (TP) mesocyclones developed along and ahead of an Hurricane Opal outer rainband. Eight tornadoes occurred over northwest Florida, classifying the event as a major tornado outbreak. Within the pre-landfall environment, maximum hourly 0-3 km storm-relative helicity (SRH) and convective available potential energy (CAPE) values were observed as 362 m² s^-2 and 1881 J/kg , respectively.

Single Doppler radar, upper-air and surface data were used to investigate the pre-storm environmental conditions and the evolution of twenty-six mesocyclones prior to, during and after coastal landfall. Evolutionary differences in rainband and non-rainband mesocyclones, and their behavior during landfall were also investigated. Particular attention was paid to those mesocyclones that produced tornadoes versus those that did not.

The observation of deep (> 2.5-5 km), persistent (1-2 h), large diameter (5.6-9.6 km) and intensely rotating mesocyclones (15.2-28.2 m/s) over the Gulf of Mexico demonstrates that such mesocyclones can evolve well beyond the coast (ie.. where the boundary layer friction force enhances vertical wind shear) and further suggests that tropical cyclone (TC) rainbands must play a significant role in providing the necessary and sufficient vertical wind shear conditions to aid their support. A statistical analyses reveals two separate classes of mesocyclones in this event. Rainband mesocyclones exhibited mean values of duration, rotation depth, diameter and rotational velocity that exceeded their non-rainband counterparts by 220%, 128%, 146% and 158%, respectively. In the case of TP mesocyclones, persistence discriminated reliably between tornado and non-tornado producing mesocyclones. A (z-t) radial velocity analysis of four TP tornadic vortex signatures (TVSs) showed that both ascending and descending modes of tornadogenesis occurred in this event and were consistent with observed ambient vertical horizontal divergence profiles.