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Katrina weakening--but still of catastrophic intensity

By: Dr. Jeff Masters, 4:31 AM GMT on August 29, 2005

The 10:36pm EDT Hurricane Hunter mission found a central pressure of 908 mb, up 6 mb since this afternoon's minimum of 902 mb. The maximum flight level winds in the northwest quadrant were 122 knots, which translates to a Category 3 intensity at the surface (130 mph). However, Katrina's strongest winds are in the northeast quadrant, and the Hurricane Hunters have not sampled that quadrant yet. Winds of 160 knots were found there by the previous mission at 8pm EDT. The rising pressure implies that we should see some diminishing of the winds in the next few hours, making Katrina a strong Category 4 hurricane. Hurricanes rarely maintain Category 5 intensity for more than 12 hours, and that is how long Katrina has been at Category 5.

I have been expecting Katrina to undergo a shrinking of the eye and an eyewall replacement cycle tonight, but instead the eye diameter has increased to 30 nm (35 miles). This is an incredibly large eye for a storm with a pressure this low, and makes me very uncertain about what intensity fluctuations Katrina may undergo in the next few hours before landfall. I see nothing to change the label of "catastrophic" for Katrina at landfall.

The eye is now clearly visible on long-range New Orleans radar. This view may not be around too much longer, I expect Katrina will destroy the radar site. This happened to the Miami radar during Hurricane Andrew, when a 160 mph wind gust ripped the radar ball from its rooftop mooring. When one looks at this radar image animate, considers the forecast track, and sees the huge size of the eye, it is very difficult to imagine that New Orleans will not get a portion of the eyewall. New Orleans will likely flood, causing immense destruction and heavy loss of life.

I just received this email from user Adam Henderson: "My friend is stuck on I-10 and has just called me saying there is a 12 car pile up. His CB is buzzing with news that a 18 wheeler is involved." At this stage, it might be best not to try to evacuate. Being stuck in a traffic jam on I-10 when the winds start blowing 130 mph is probably more dangerous than riding out the storm in the Superdome.

Tropical Depression 13
A new tropical depression formed in the mid-Atlantic today, and is headed northwest over open ocean. This is one we definitely do not need to worry about for now. The storm may even dissipate due to hostile wind shear within the next few days.

See you in the morning. My prayers to all in the path of Katrina.

Dr. Jeff Masters

The views of the author are his/her own and do not necessarily represent the position of The Weather Company or its parent, IBM.