I would think the low pressure would increase the surge. It has in other storms.

Using deltaP of 1013 minus mcp (current) 950 mb = 63/ 4= a possible surge height of 15.75 feet

(Formula has not been peer reviewed. But has been checked against many hurricanes from Category 1 up.
Formula was within a +/- 1 foot margin for Katina's high Water Marks~danielw)

This doesn't mean Irene will produce a 15.75 foot surge. It suggest Irene is capable of generating a surge to that limit.

Note: I have attached a jpeg of a spreadsheet that I developed a few years ago for calculating or estimating Storm Parameters, called HurriSheet. Some of the formulas are used by Meterologists the others are simple variations of their formulas. A+B=C/ D type formulas.~danielw