28-Aug-12
Isaac intensified to hurricane status this morning (11:20 AM CDT), with maximum sustained winds at 75 mph. The storm is in the central Gulf of Mexico approximately 75 miles south of the mouth of the Mississippi River and is moving northwest at approximately 10 mph. Isaac is expected to make landfall tonight or early tomorrow morning (August 29) as a weak Category 1 hurricane. A strong prolonged onshore flow of winds and expected rainfall totals from 7 to 14 inches are increasing concerns for storm surge and flooding in the area.
The projected hurricane track has drifted westward over the last few days and is expected to remain to the west of New Orleans. The National Hurricane Center is projecting a 22% probability of hurricane force winds within the city of New Orleans. The windward side of Isaac is producing a heightened risk of coastal flooding (storm surge) along the coast between Gulf Port and New Orleans (see figure). Areas of the coast with low probabilities of 6 foot surge heights (west of Gulfport) are expected to have isolated pockets of damage to properties (extending out to Mobile, AL). Areas with larger probabilities of exceeding 6 foot surge heights are expected to be at risk to damage from storm surge. The Greater New Orleans Area Hurricane & Storm Damage Risk Reduction System (HSDRRS) represents a significant improvement in flood defenses since Hurricane Katrina (2005) and is expected to restrain storm surge and reduce damage in the New Orleans region. The report on the Hurricane and Storm Damage Risk Reduction System (HSDRRS) complied by ABS group is available on eqecat.com.
Storm Surge Probabilities - August 28, 2012
Source: National Hurricane Center (NHC) accessed August 28, 2012 12:45 EDT
Losses from Isaac will be strongly influenced by key uncertainties in the storm that will present themselves over the next 24 hours. Breaches in flood protections usually present themselves after the storm has occurred, with the delay due to the scouring of the backside of over-topped levees. The National Weather Service is warning of elevated convective storm activity (tornadoes and hail) and localized flooding will come from concentrations of rainfall.
In the northern Gulf of Mexico, maximum wave heights are predicted to be from 24 to 27 feet presenting a risk to some of the fixed and floating assets in the Gulf. Oil production has already been impacted as companies are evacuating workers from platforms and rigs and temporarily suspending operations due to the Isaac. Surface waves create underwater currents that can damage underwater pipelines and facilities. The modest wave heights expected from Isaac (Hurricane Ivan produced measured wave heights at up to 90 feet) lead to an expectation of damage concentrated on platforms and collection facilities at or above the water surface.
Tropical Storm Isaac Potential Storm Track - August 28, 2012
Source: National Hurricane Center (NHC)
At 11:20 am CDT, Tuesday, August 28, the center of Isaac was located at latitude 28.1N, longitude 88.6W, and was 75 miles southeast of the mouth of the Mississippi River. Maximum sustained winds were 75 mph. Isaac is moving to the northwest at 10 mph, and this motion is expected to continue over the next day or two. On the current forecast track, the center of Isaac should reach the southeastern coast of Louisiana this evening, Tuesday, August 28. On Wednesday morning, the storm center should pass just to the west of New Orleans.
A hurricane warning is in effect for the northern Gulf Coast from east of Morgan City, Louisiana, eastward to the Alabama-Florida border, including metropolitan New Orleans.
With Isaac's slow forward motion as it approaches the northern Gulf Coast, rainfall amounts are predicted to be high, with 7 to 14 inches, and maximum amounts of 20 inches possible in southeastern Louisiana, Mississippi, southern Alabama, and the western Florida panhandle. These rains may cause significant lowland flooding.
Because of its broad size, Isaac poses a significant storm surge threat to the northern Gulf Coast. Should it occur during the time of high tide, a surge of 6 to 12 feet is possible in southeastern Louisiana and Mississippi. The highest surge levels are expected in areas of strong onshore winds, generally near and to the east of where the center crosses the coast. Tornadoes are possible along the northern Gulf coast as rain bands from Isaac move ashore.
Users of EQECAT's North Atlantic Hurricane Model are advised to use the following event IDs to ascertain the impacts on their portfolio from this event:
Onshore Losses - August 28, 2012
Source: EQECAT
Offshore Losses - August 28, 2012
Source: EQECAT
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