Isaac: Not a Katrina, Tracking Farther West
While Isaac is on a doomsday track for some areas of the Gulf Coast, it is not a doomsday storm. From a core meteorological standpoint Isaac will not be another Katrina in terms of intensity, but it is still a dangerous storm and will cause damage.
Isaac is forecast by AccuWeather.com to make landfall as a hurricane in Louisiana Tuesday night and will bring the risk of storm surge flooding, inland flooding, damaging wind, tornadoes and beach erosion to part of the central Gulf Coast area.
According to AccuWeather.com Hurricane Expert Dan Kottlowski, "The angle at which Isaac could come ashore could still drive a substantial amount of water inland over southeastern Louisiana and southern Mississippi."
As a result a relatively weaker storm (Category 1), when compared to Katrina (Category 3 at landfall in La./Miss.), could still pack a considerable punch.
Isaac will test the upgraded New Orleans levees.
While we have a doomsday track from a New Orleans standpoint, we do not have a doomsday storm intensity. In Mississippi, Katrina's storm surge was a record 27.8 feet at Pass Christian. During Isaac, a surge of up to 9 feet is forecast by AccuWeather.com for the area.
Katrina moved up from the south over the Mississippi Delta on a curved path. Isaac is likely to be rolling in straight from the southeast, so the counterclockwise flow around the storm will drive a significant surge toward Chanderleur Sound, Lake Borgne and Lake Pontchartrain early on and for a number of hours. A storm surge of 3 to 6 feet is forecast for Lake Pontchartrain with the highest levels on the western end of the lake initially.
Isaac is a large storm in terms of surface area with its circulation extending out hundreds of miles from the center, especially on its eastern and northern side.
Other cities at risk for coastal flooding include Biloxi and Gulfport, Miss., Mobile, Ala. and Houma, La.
Nasty conditions and water rises are likely to occur quickly, as the center approaches the coast Tuesday makes landfall overnight.
People are urged to speed necessary preventative measures on their property and evacuate if told to do so by officials. Some low-lying roads and communities soon could be cut off by rising surf and storm surge.
Isaac will bring flooding rainfall, downed trees and power outages at the very least in portions of Louisiana, Mississippi and Alabama. Outer bands from the storm, essentially severe thunderstorms can still cause damage and disruptions over portions of Florida and the interior South.
According to Severe Weather Expert Henry Margusity, "There is always a potential for a swarm of tornadoes being spawned by a hurricane making landfall."
With a storm moving in from this direction, winds in the wake of the storm over the Lake Pontchartrain area would shift to the south and southwest. While this will keep water levels high on the lake, wind-driven wave action would shift away from the New Orleans shores of the lake.
Recall that during Katrina, strong southeast winds drove water into Lake Pontchartrain initially. And, that is likely to happen again with Isaac to some extent. However, due to the south to north path of the Katrina, north to northwest winds on the back end of the hurricane drove the elevated lake water toward the city, contributing to levee failure.
"Isaac is large, but not an exceptionally healthy tropical storm at this time," Kottlowski stated. "Isaac continued to struggle with dry air entrainment and wind shear Monday into early Tuesday of this week and throughout last week."
Despite Isaac's struggles, the combination of warm Gulf waters and lowering wind shear Tuesday could lead to strengthening prior to landfall.
"People along the Louisiana, Mississippi and Alabama coasts need to take the threat from Isaac seriously," Kottlowski said. "It is better to be safe than sorry."
As a precaution petroleum rigs in the central and northeastern Gulf of Mexico were shut down and evacuated.