Bill Read's Blog: How long will Isaac last
Today is the beginning of the end game for Isaac. The effects of Isaac are already being felt this morning as this large storm progresses steadily onshore on the northern Gulf coast. Because of the nature of the coastline and the large wind field of Isaac, tides have already become a problem for low lying areas from southeast Louisiana eastward through Alabama. Heavy rain bands and stronger winds will soon be impacting the immediate coastal communities. As these conditions will get progressively worse through the remainder of the day, the time for preparation has basically ended and people will have to ride out the approaching storm.
The exact center of Isaac has wobbled westward so the point on the coast where the center crosses will likely be between Grand Isle and Vermillion Bay in Louisiana. However, the strongest winds with this storm continue to be displaced well away from the center. Overnight tonight, the strongest portion of Isaac is expected to move across southeast Louisiana and coastal Mississippi with peak winds of 80 to 100 mph. Most people in the path of the large storm will experience less wind, however prolonged winds of at least tropical storm force will bring trees down and knockout power across a wide area.
The storm surge will be the initial big impact coming from Isaac.
On the storm’s current path, size and intensity, we expect upwards of 12 feet of surge along the Mississippi and the southeast Louisiana coast lines. While nothing like Katrina’s surge, there will be significant flooding outside the protection of the levees. Storm surge from Alabama to along the beaches of the Florida Panhandle could reach 5 feet, as will be the case on the south central coast of Louisiana. Also, the slow northwest movement after landfall will keep tide levels elevated much of Wednesday and Wednesday night.
Because Isaac is large and is forecast to move very slowly northwestward Tuesday night and all day Wednesday, extremely heavy rainfall is forecast with some areas expected to receive upwards of 20 inches of rain, which should cause severe flooding. Depending on where this heavy rain falls, this could be the big disaster story coming out of Isaac…and we all know what that is like here in Houston.
For us in southeast Texas…dry and hot will be the main impacts from north winds and subsiding air on the west side of Isaac. There may be some 2 to 4 foot swells reaching the beaches, but the tide elevations are expected to insignificantly different from normal.
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