Sunday, August 29, 2010

Continuing to Remember Hurricane Katrina...

Sunday, August 29, 2010

The third and final entry to remember Katrina is posted below. This entry is as is from one year ago, with some edits at the end. The forecast discussion and regular blog entry will be forthcoming tonight. Please check back for that a little later on.

As we all know, Hurricane Katrina, was one of the worst natural disasters in our nation's history, and it was also one of the worst natural disasters in state history, and was the worst man-made disaster in history. This is a chronological history of Hurricane Katrina.

Hurricane Katrina formed on August 23, 2005 from a tropical wave that had actually originated off the coast of Africa on the 13th and was originally classified as T.D.10, but degeneration occurred as the system moves towards the Lesser Antilles. A new circulation developed as the system approached the Bahamas, and Tropical Depression 12 was born near the Bahamas on the 23rd. T.D. 12 was forecasted to steadily move Westward and strengthen into Tropical Storm Katrina as it approached South Florida and the Florida Keys.

Katrina was a very favorable environment for development once it got going over the Bahamas. A period of rapid intensification began during the early morning hours of August 24th, and was officially upgraded to Tropical Storm Katrina at 10 a.m. when it centered over the Central Bahamas. The initial motion of Katrina was off to the NW, but a building ridge of high pressure would force Katrina to make a left hand turn into a more W to eventually WSW direction still aiming it at South Florida. Steady-state intensification continued through the day on the 24th and 25th. Katrina became a category 1 hurricane shortly before its first landfall in South Florida. First U.S. landfall of Katrina was near the Miami-Dade and Broward Country, Florida line. Katrina began to develop an eye just as it moved onshore and remain well-defined as it moved through the Everglades. The eye of Katrina actually passed right over the National Hurricane Center. Katrina's center only spent about 6 hours over land in South Florida. As typical with a tropical system over land, Katrina weakened, but not as much as one might suspect after being over land. It only weakened to a 70 mph tropical storm. The center of Tropical Storm Katrina emerged over the warm Gulf of Mexico waters on the evening of the 25th. From this point on, Katrina would grow into an unprecedented storm.

The environment over the Gulf of Mexico was one that was primed for a strengthening system. Katrina didn't waste any time at all becoming a hurricane once again, and achieved category 1 status once again on the night of the 25th just as it was situated WNW of the Dry Tortugas. Katrina underwent 2 periods of rapid intensification while it was over the Gulf. Katrina intensified from a 75 mph-category 1 storm to a 110 mph-category 2 within a 24 hour period from the 25th to the 26th. I should note here, that at this time the official forecast track for Katrina was for landfall over the weekend in the Florida Panhandle near Pensacola or possibly as far West as Mobile, AL, however the strengthening Atlantic ridge continued to force Katrina to the WSW and models would soon latch on to this idea. The concern was growing for a direct hit from a major hurricane near the city of New Orleans. The intensification processes continued, and Katrina strengthened into a major hurricane at category 3 strength about 435 miles SE of the Mouth of the Mississippi River.

Katrina leveled off for a time at this point as it went through an eyewall replacement cycle. During this same time, the wind field and diameter of Katrina increased in size to nearly double what it had been. Katrina finally began to make a turn to the WNW as the ridge shifted slightly to the East over Florida. As Katrina began to make this turn, another period of rapid intensification would ensue. Amazingly, Katrina strengthened from an already dangerous category 3 with 115 mph to a potentially catastrophic category 5 hurricane with 165 mph winds in about 12 hours. On the night of August 27th, hurricane warnings were issued for a large portion of the Central and Northern Gulf coast from Morgan City, LA to the Florida/Alabama border. On Sunday morning, August 28, Katrina peaked in intensity reaching sustained winds of 175 mph. This occurred as Katrina was only about 170 miles SE of the Mouth of the Mississippi River. This was setting up to be the absolute worst case scenario for SE Louisiana and Southern Mississippi, including New Orleans.

It was then mentioned that Katrina could possibly make landfall on Monday the 29th as a category 5 hurricane, if it did this it would be only the 4th hurricane to make landfall as a category 5 in the U.S., and the first since Andrew in 1992. Fortunately, Katrina underwent a period of rapid weakening as it moved closer to the coast, and began a turn to the North around the periphery of the Eastern Gulf ridge. It would still come ashore as a major hurricane, and bring with it lots of devastation. The weakening period began as another eyewall replacement cycle occurred. The large eye that Katrina had at peak intensity contracted, and eroded on the Southern side, thus weakening it from the category 5 that it once was earlier in the day on Sunday the 28th. The weakening trend continued through landfall, and Katrina made landfall as a category 3 storm with 125 mph winds near Buras, LA around 6:10 a.m. on Monday, August 29. The eye of Katrina moved Northward over SE Louisiana, passing just East of New Orleans, and very near Slidell. Final landfall occurred near the LA/MS border with 120 mph winds. While, Katrina may have only made landfall as a category 3 officially, a category 5 storm surge occurred. This resulted in the highest storm surge ever recorded in the United States with an amazing 32' storm surge along the Mississippi Coast at Long Beach. The storm surge was highest along the entire Mississippi Coast with surge readings higher than 20' for the entire length of the coastline as this was the area just to the East of the eye. Lower SE Louisiana saw a surge of 12-15' causing major damage. Severe structural damage occurred across the entire area of SE Louisiana, Southern Mississippi, and Southern Alabama from the storm surge and the wind. The worst wind damage was over Mississippi and across the Northshore of Lake Pontchartrain, and through the New Orleans Metropolitan Area. Katrina caused widespread damage with tree and power line damage through a large portion of Mississippi. The eye of Katrina moved near Jackson, MS as a category 1 on Monday evening, and weakened to a tropical storm as it began a NE movement to the NW of Meridian.

There are many meteorological explanations as to why Katrina weakened so rapidly after reaching its peak intensity. It should be noted, that it is very rare for storms to maintain a category 5 intensity for a very long duration.

The National Hurricane Center cites that the weakening may have been
aided by entrainment of dry air that was observed to be eroding the deep convection over the western semicircle while Katrina approached the coast. Gradually increasing wind shear, slightly lower ocean temperatures, and (following the first Gulf landfall) interaction with land each could also have played a role. Without extensive investigation, however, it is not possible to assess the relative roles played by these various factors. The weakening of major hurricanes as they approach the northern Gulf coast has occurred on several occasions in the past when one or more of these factors have been in place. Indeed, an unpublished study by the National Hurricane Center (NHC) reveals that, during the past 20 years, all 11 hurricanes having a central pressure less than 973 mb 12 hours before landfall in the northern Gulf of Mexico weakened during these last 12 hr. Much research is being conducted on this topic.

Now, I will touch on what happened in New Orleans. The disaster that unfolded in New Orleans really didn't happen until several hours after the worst of the storm had passed the city. During the storm, winds near 100 mph occurred inflicting structural damage, but not to the extent that everyone expected or what it could've been if the eye had passed just West of the city as opposed to just East. However, the storm surge piled up in Lake Pontchartrain and battered the Northshore from Mandeville to Slidell with readings of 12-16'. As the storm moved inland over Mississippi strong Northerly winds across the Northshore and New Orleans caused water levels to rise on the southern end of the lake. This led to breaches and breaks in the New Orleans levee system, and water began spilling into the city which is largely below sea level. The highest surge readings were on the East side from New Orleans East to St. Bernard and Plaquemines Parish. A surge of almost 20' occurred in these areas, and a surge of 12-16' occurred further West. Many of the breaches to the levees appear to have occurred during the morning of the 29th. Nearly 80% of the great city of New Orleans was flooded. Water was as deep as 20' in some locations, and this was all within a couple days of the storm. It took over a month (43 days) for all the water to be removed from the city. The removal of water was briefly delayed 3.5 weeks later during Hurricane Rita. The flooding in New Orleans made the city uninhabitable for weeks, and changed the way of life for thousands and left thousands homeless. Over 1,500 people perished in New Orleans as a result of the flooding. The suffering inflicted by Katrina is by far the worst created by any hurricane to strike the United States, likely in history.

In closing, I send out my prayers and thoughts to all of those directly and indirectly affected by this disaster. Many many people will never go back to the New Orleans area, and part of the area may never be the same again. I know it was a rough time physically and mentally for lots of people after seeing what happened in New Orleans and on the Mississippi Gulf Coast. There is much to be learned from Katrina, and much much research is yet to be done on this most devastating storm. Much work has to be done within the city of New Orleans to prevent such a man-made disaster from occurring again. It is inevitable that a hurricane will strike the area again, but no one knows when. Hopefully, it will be many many years before it does. I have included the official post-storm reports from both the National Hurricane Center and the NWS Slidell office. God bless all those still recovering from the storm, and we pray for those who lost their lives during the storm. In remembrance of this terrible day in weather and American history, let us all stop a moment to reflect and pray. Join me in saying the Prayer for Hurricane Season. I will post it underneath the links below.

NWS Slidell Hurricane Katrina Post Storm Report

You Can Find the NHC Post Storm Report Here


Prayer for Hurricane Season

O God, Master of this passing world hear the humble voices of your children. The Sea of Galilee obeyed Your order and returned to its former quietide. You are still the Master of land and sea. We live in the shadow of a danger over which we have no control; the Gulf, like a provoked and angry giant, can awaken from its seeming lethargy, overstep its conventional boundaries, invade our land and spread chaos and disaster. During this hurricane season we turn to You, O loving Father. Spare us from past tragedies whose memories are still so vivid and whose wounds seem to refuse to heal with passing of time. O Virgin, Star of the Sea, Our Beloved Mother, we ask you to please with your Son in our behalf, so that spared from the calamities common to this area and animated with a true spirit of gratitude, we will walk in the footsteps of your Divine Son to reach the heavenly Jerusalem where a stormless eternity awaits us.

In the name of the Father, the Son, & the Holy Spirit...Amen!

God bless everyone affected by Katrina & all those who continue to recover. 8-29-05...We Will Never Forget!


-DM-

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