But the storm could strengthen to a Category 3 hurricane with winds of at least 111 miles (179 kilometers) an hour just before it makes landfall.
Ike's worst impact on Texas will be from flooding, not from high winds, Sisco said.
Tides already are 3 to 5 feet (0.9 to 1.5 meters) above normal along the Texas coast, said Wendy Wong, a meteorologist with the Houston-Galveston office of the National Weather Service.
Ike's surge may be high enough to go over Galveston's 17-foot (5.2-meter) seawall, which was built after the catastrophic hurricane of 1900 killed at least 6,000 people in that city.
(Related: "In Texas, Rita Stirs Memories of U.S.'s Deadliest Storm" [September 23, 2005].)
The threat of long-lasting flooding from Ike prompted the National Weather Service to issue the sternly worded warning.
The storm surge combined with the hurricane's winds could also create "battering waves" near the coast, the advisory said.
"Such waves will exacerbate property damage with massive destruction of homes, including those of block construction."
A similar warning was issued in advance of Hurricane Katrina in August 2005.
Instead of striking Texas, that hurricane sent a huge storm surge into New Orleans and the coast of Mississippi, causing catastrophic damage.
Moving the Ocean
One reason for Ike's massive storm surge is that the storm has put much of the Gulf of Mexico into motion, according to Keith Blackwell, a meteorologist with the University of South Alabama's Coastal Weather Research Center in Mobile.
"This storm is moving a huge amount of ocean with it, because of its huge size," Blackwell said.
Ike's tropical storm-force winds of up to 73 miles (117.5 kilometers) an hour extend more than 225 miles (362 kilometers) from its center, Blackwell said.
The storm weakened to a minimal hurricane when it moved into the Gulf of Mexico Tuesday.
Ike was expected to quickly regain strength over the Gulf's warm waters, but Blackwell said the storm was hampered by wind shear—or high-level winds—which disrupted its organization and slowed its strengthening.
The wind shear could diminish as Ike gets closer to the Texas coast, and this might allow the storm to regain some of its intensity, Blackwell said.
The last time Texas faced a storm of such magnitude was Hurricane Alicia in 1983, Blackwell said. That storm was a Category 3 hurricane with winds of about 115 miles (185 kilometers) an hour.
Willie Drye is author of Storm of the Century: the Labor Day Hurricane of 1935, published by National Geographic Books.
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