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Pastimes : Hurricane and Severe Weather Tracking -- Ignore unavailable to you. Want to Upgrade?

To: John Vosilla who wrote (2224)	8/27/2005 10:59:54 AM
From: Road Walker	Read Replies (1) \| Respond to of 26015

Hurricane Katrina Discussion Number 17 Statement as of 10:00 am CDT on August 27, 2005 reports from an Air Force Reserve hurricane hunter aircraft indicate that the central pressure of Katrina dropped to 940 mb at 0932z. Since then...the hurricane has started a concentric eyewall cycle...with a filling of the eye and warming of the cloud tops in satellite imagery. The initial intensity remains at 100 kt based mainly on satellite intensity estimates of 102 kt from TAFB and AFWA...and 115 kt from SAB. It should be noted that the maximum flight-level winds reported by aircraft so far are 106 kt...which are lower than would normally be expected for a 940 mb hurricane. The initial motion is now 275/6. Katrina is south of a deep-layer ridge over the northern Gulf Coast. This ridge is forecast to weaken as a strong deep-layer trough develops over the central United States...and a new deep-layer ridge forms over the Florida Peninsula and the adjacent Atlantic. This pattern change should cause Katrina to turn northward during the next 72 hr and make landfall over the northern Gulf Coast. All track guidance agrees on this scenario...although there remains some spread... particularly from the NOGAPS and GFDN models which call for landfall near Morgan City and Intracoastal City Louisiana respectively. The other guidance is clustered with landfall between Grand Isle Louisiana and Pensacola Florida. The official forecast remains close to the model consensus...calling for landfall in southeastern Louisiana in 48-60 hr. The new track is basically an update of the previous package. Katrina should strengthen slowly for the first 12 hr or so as the concentric eyewall completes and some residual northerly shear affects the storm. After that...it should strengthen in a light shear environment over very warm water. The intensity forecast calls for the hurricane to reach 125 kt in 48 hr as a compromise between the 120 kt GFDL...the 126 kt GFDN...the 127 kt SHIPS...and the 132 kt FSU superensemble models. However...it is not out of the question that Katrina could reach category 5 status at some point before landfall. There is a possibility that southerly or southwesterly shear could affect Katrina starting at 48 hr...and as always happens in hurricane of this intensity additional concentric eyewall cycles could occur. The new forecast track and wind radii require a Hurricane Watch for portions of southeastern Louisiana at this time...including metropolitan New Orleans. This watch will likely need to be extended along the coast later today or tonight. Forecaster Beven forecast positions and Max winds initial 27/1500z 24.5n 85.0w 100 kt 12hr VT 28/0000z 24.6n 86.0w 105 kt 24hr VT 28/1200z 25.3n 87.6w 115 kt 36hr VT 29/0000z 26.7n 89.0w 120 kt 48hr VT 29/1200z 28.6n 89.9w 125 kt 72hr VT 30/1200z 33.0n 89.5w 60 kt...inland 96hr VT 31/1200z 37.5n 86.0w 30 kt...inland 120hr VT 01/1200z 41.5n 80.0w 25 kt...extratropical

To: John Vosilla who wrote (2224)	8/27/2005 4:12:34 PM
From: patron_anejo_por_favor	Respond to of 26015

>>So Patron, would New Orleans then be off the hook from serious flooding if the eye hits at least say 40 miles to the east or west of the city?<< I would say yes, as long as the storm surge into Lake Ponchartrain wasn't too bad (ie, as long as the storm didn't make landfall at high tide). There is a hitch though...the last time a really big storm hit directly (Betsy in 1965) the wetlands were much more intact and provider a larger buffer for flood waters. A natural levee if you will. Over the past 40 years, that buffer is largely gone, so it would take a smaller storm or storm surge to produce the same effect. Mitigating this a bit is that the levee system has been built up somewhat since then. The real answer is "no one knows", and we may find out with Katrina. The problem is if major flooding (say, 3-4 feet citywide) does occur, the water may be high enough to knock out the pumping system. Getting that back would require a massive undertaking, and the water would have no place to go until it's pumped out. So instead of having a flood that receds, you'd have a flood that persisted for weeks, which obviously would have major implications to infrastructure as well as immediate loss of life. The "Washing Away" series in the NO Times-Picayune really did an outstanding job of describing what they're up against, if anyone's interested it's well worth a read (it's a 5-part series and pretty long): nola.com Here's the latest reports on evacuation orders, etc from the Southeast Louisiana civic leaders, New Orleans mayor, etc: nola.com

To: John Vosilla who wrote (2224)	8/27/2005 4:23:42 PM
From: energyplay	Read Replies (1) \| Respond to of 26015

Near Miss Question - "...would New Orleans then be off the hook from serious flooding if the eye hits at least say 40 miles to the east or west of the city? " Katrina was a Cat 1 when it went near you. It is both stronger and bigger now. If I have read some of the New Orleans disaster preparation documents correctly, New Orleans is so vulnerable that it could be flooded by a strong Cat 2 Hurricane in exactly the right that moves with the tide. I think your observation would be true for Cat 1 (which you experienced) Cat 2 and some weaker Cat 3. Hurricanes usually have an intense wind & rain area off to on side of the eye, instead of being symmetrical. Bigger means not only wider, but the Hurricane will take longer to pass over a given point - so instead a 50 knot wind pushing a storm surge of water for two hours, you get 65 knots for three hours. More time for the wave to break over the levees, and with higher waves with higher winds. Hurricane Intensity Scale - Note the right hand columns on how high the water can go - srh.noaa.gov The Boat US has a diagram of the current wind field - boatus.com ******* So with Katrina being about a Cat 4, and considerably larger the answer is No - even at 40 miles, there will significant risk (way more than 10%) that New Orleans gets flooded.