Looking at the data from Hurricane Research Division.
Ivan may have been in an ERC.
I do remember about three hours prior to landfall. Ivan ingested some drier air on the SW Quadrant. This could possibly be due to the ERC trapping a pocket of dry air during it's evolution and rotation around the center.
This was visible on both the Mobile and Slidell NWS radar sites.
http://coastal.er.usgs.gov/hurricanes/ivan/images/ivan-radarLG.gif
http://www.srh.noaa.gov/mob/cgi-bin/imag...an-animated.gif

http://www.srh.noaa.gov/mob/ivan_page/Ivan-main.htm

...Despite the unfavorable environmental conditions, the presence of cooler shelf water just offshore and eyewall replacement cycles, Ivan weakened only slowly and made landfall as a 105 kt hurricane (category 3 on the SSHS; see Figure 2c and Figure 3b.) at approximately 0650 UTC 16 September, just west of Gulf Shores, Alabama...(from paragraph 7~danielw)
http://www.nhc.noaa.gov/2004ivan.shtml?text