The storm clearly is becoming better organized as indicated both on satellite and radar. The satellite from 4:32pm CDT looks like a classic hurricane except for a cloud-free eye.
The radar in the last 30 minutes seems to show an eye forming. The image below is from 4:53pm CDT.
The National Hurricane Center rates Isaac's sustained winds at 80 mph at 4pm. I'm getting concerned that significant strengthening may be occurring because the radar is measuring winds as high as 107 mph about 8,000 ft. above the ground at 5pm. At 4:35pm, a wind measuring device 280' above sea level on an oil platform off the coast measured a gust of 105 mph. I'm concerned these stronger winds will make their way down toward ground and sea level as the evening and night progress.
Currently, at New Orleans' Lakefront Airport, winds are gusting to 58 mph. The winds will gradually increase during the evening. Late addition: 30,000 homes and businesses without power in New Orleans.
A tornado watch is in effect for the entire area outlined in red until 7pm CDT. The watch will likely be extended.
Additional rainfall from 7pm this evening through 7pm Friday includes a forecast of more than 17" in New Orleans. Widespread flooding from both rainfall and storm surge are likely.