TD 15? And, New Orleans NWS survives

The New Orleans NWS office, located in Slidell, LA, was knocked off-line Monday by Katrina as her northern eyewall hammered Slidell and a 15-foot storm surge crashed ashore. The building and radar survived the hurricane, and the staff continues to work there, although all communications remain down. The radar was damaged but is repairable, and a repair team is on the way to work on it. All but one of the employees are accounted for, and the missing employee is assumed to be in a shelter. Meteorologists generally have enough sense to leave evacuation zones, unless of course they are Weather Channel personalities or storm chasers. Most of the employees had their homes destroyed or damaged. A number of satellite phones have arrived at the office, and limited communications are now possible. The Mobile, Alabama NWS office is assuming responsibility for issuing forecasts and warnings for the New Orleans area until full communications can be restored.

Four weather radars in Louisiana, Mississippi, and Florida that were down due to communication infrastructure failures are now back up. Only the Lake Charles, LA radar and New Orleans radar remain down. Communications are still out to the Lake Charles, LA and Jackson, MS NWS offices, and their forecasts and warnings are being issued by other NWS offices until MCI can repair the communications infrastructure. The repair time needed is estimated to be one week.

Tropical update
The most significant threat in the tropics may be from a tropical wave that is spinning midway between Africa and the Leeward Islands, near 9N 36W. This system has gotten much better organized in just the past two hours, and will probably be classified as TD 15 by tomorrow. There is a moderate amount of deep convection near the center, but this is being disrupted some by wind shear. A large area of improving upper-level outflow on the north side and east sides exists, and Quikscat winds are already over 55 mph on the east side. The disturbance is far enough south that it will not get recurved out to sea by the mid-Atlantic trough. The early track models (below) show it moving west-northwest and threatening the Leeward Islands by Tuesday. Virtually all the the computer models forecast the shear over the system to lessen, and develop it into at least a tropical storm. The GFS continues to forecast that this will be a major hurricane. I believe that this will be at least a Category 1 hurricane by Tuesday, and might be trouble for the Leeward Islands.


Figure 1. Forecast track of tropical wave I expect to be TD 15 by Friday.

Development by the Bahamas
An area of concentrated clouds has developed northeast of the Bahamas, but the wind shear is too high here now for any tropical development to occur. However, the shear will decrease over the next few days so that by Sunday or Monday tropical depression could develop in the waters between the Bahamas and Bermuda. This is the same location that Katrina developed. This development would occur at the tail end of a cold front that is expected to push off of the East Coast. The latest GFS model run is showing two possible areas of formation, one near Bermuda, and one near the east coast of Florida. If a depression does form near the east coast of Florida, the likely track would be across Florida and into the Gulf of Mexico. If formation occurs closer to Bermuda, the likely track would be northeastward away from land. I think it is unlikey that two systems would form in the this region; the energy for storm formation will probably concentrate in one area and create one storm. Let's hope that if this occurs, the formation region will be closer to Bermuda and the storm will head out to sea.


Figure 1. GFS forecast for 2am Monday, showing two possible locations a tropical depression may form.

TD Lee and TD 14
Tropical Depression Lee and Tropical Depression 14 are of little concern at this point. Both are weak, sheared systems that are tracking out over open ocean, with little chance of impacting any land areas.

Blog comments
Please continue to post non-weather related comments to this blog for now. In a national emergency like this, it is important for us to communicate freely. Keep it positive! The best way to deal with this unbelievable horror is to be positive and supporting of one another. If you find yourself wanting to make a post that insults another blog poster, please refrain. Criticism of politicians is OK, but remember we elected them!

Jeff Masters