New wave off Africa ; New Orleans levees on hold

A new area of concern has developed today off of the coast of Africa, 300 miles south-southwest of the Cape Verde Islands, at about 12N 25W. This large and well-organized tropical wave has developed a surface circulation, and is beginning to show some intense thunderstorms developing near its center. Wind shear is a marginal 10-20 knots over the wave, but is forecast to remain at this level or decrease some over the next two days. Sea surface temperatures are marginal for development, about 26-27 degrees C. There is some African dust to the wave's north, but not as much as we've been seeing in previous weeks. This wave could slowly organize into a tropical depression in the next day or two as it moves west-northwest at 15-20 mph. It's too early to speculate what the long-term track of this system might be. NHC is not impressed with this wave; they have not mentioned it in their 5:30 pm tropical outlook. No doubt the marginal SSTs and moderate wind shear--plus the fact that systems in this vicinity generally do not start developing until early August--are giving them a wait-and-see attitude.


Figure 1. Visible image of the Cape Verdes tropical wave. image credit: Navy Research Lab. Try animating this image from their web site to watch the wave spin up, and see the interesting eddies downwind of the islands off the coast of Africa.

Gulf of Mexico
Thunderstorms in the Gulf of Mexico near Key West, associated with a westward moving tropical wave, have decreased since this morning. Surface pressures are not falling, and no computer models are predicting that this area will be a future threat. However, wind shear is low enough to permit some slow development of this disturbance over the next day or two, so we'll have to keep an eye on it.


Figure 2. Latest satellite image of the Gulf of Mexico.

An upper level low pressure system is spinning over the western Gulf of Mexico. This low is expected to move ashore over Mexico by Friday without any tropical development occurring.

A tropical wave that moved through the Lesser Antilles Wednesday is in the eastern Caribbean. The wave has limited thunderstorm activty, and there is high wind shear and plenty of dry air in the eastern Caribbean. Development of this wave is unlikely.

Update on New Orleans flood protection
The Army Corps of Engineers has missed a July 9 deadline to complete new floodgates at the Lake Pontchartrain entrance to one of the drainage canals that flooded New Orleans during Katrina. No revised date has been set for the completion of the project. If a storm were to come now, the Army Corps would close off the canals using sheet pilings, as they did during Hurricane Rita. The new gates are designed to be closed when a hurricane threatens to bring a storm surge over five feet, and thereby keep waters from Lake Pontchartrain from flowing deep into the city along the drainage canals. It was the failure of the levees along these drainage canals that primarily responsible for the flooding of New Orleans during Katrina. However, closing the drainage canals means that the city will flood due to excessive rains, since it is these canals that take all the rainwater out of the below sea level areas of the city and dumps it into the Lake. (Thanks to wundermember mrpember for posting this info).

New Army Corps of Engineers report issued (repeat from this morning's blog)
A long awaited Army Corps of Engineers report on Louisiana coastal protection and restoration came out this week. The report had no specific recommendations on immediate actions to take to protect New Orleans from the next hurricane, saying another 18 months was needed to study the problem. Politicians and scientists immediately criticized the plan, saying that action is needed now. In particular, Governor Blanco of Louisiana and Louisiana's Senators were upset that five specific recommendations that they had agreed on with the Corps in May were stripped out of the proposal:

-- Beginning design work on a barrier and gate plan to protect the New Orleans area from major hurricanes.

-- Closing the Mississippi River-Gulf Outlet (MR-GO) to major ship traffic and beginning environmental restoration of the wetlands adjacent to it.

-- Design work on a plan for rebuilding eroded barrier islands and headlands and building new ones in the Barataria basin, which includes parts of Jefferson, Lafourche and Terrebonne parishes.

-- Authorizing the Morganza-to-Gulf hurricane levee project that stretches along much of the same area and has been awaiting congressional approval for several years.

-- Approval and financing for a variety of smaller restoration projects in southwestern Louisiana.

"These critical projects cannot wait another 18 months to be considered for action by Congress," Blanco said in a statement released Monday.

In the report, the Corps say they have completed emergency repairs to 169 miles of New Orleans levees, which are now as strong or stronger than before Hurricane Katrina. I can't tell from news reports what levee work--if any--is currently going on, I'd be interested to see if any of you know. In particular, is the $3 billion plan to move the pumping stations on the 17th Street Canal and London Avenue Canal to Lake Pontchartrain being worked on? It seems to me that this work is the most critical flood protection measure that needs to be undertaken.

Jeff Masters