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  • Sailing is all about the Weather.

    Big into the exploration of Atlantic Hurricanes since Katrina came uninvited into his world, James (Jim) Gurley (JamesG161) has followed every Tropical Storm birthed in Atlantic, Gulf and Caribbean waters since. Being a boater, he knows that we often need more time to prepare than we get from the TV weather folk. Jim relies on the science of storm development to share early warning info with friends and fellow boaters.

    Early in 2018, Jim and John Shepard, (JSSailem) started to chat about the weather data available. John asked Jim to help forecast Pacific NW storms, and this morphed into discussions on weather forecasting.

    For John, sailing in the PNW is sometimes hit and miss. One day is ugly, then a string of beautiful days but no wind, followed by a series of blue-sky days and 12 knot breezes. Being ready for those great sailing days means you need to look to the Pacific Ocean and what is brewing. John has been into Pacific NW Weather since the 1970’s when his first PNW November storm hit bringing more than 40 days and 40 nights of continual rain.

    Together we want to share information, new APPs, safety, and thoughts about letting the weather help you. Identify some of the resources for sailors and help prepare you for your next sailboat outing.

    It is far better to go out on the water knowing what to expect in weather terms, than to be out on the water and see dark ominous clouds suddenly appear, unprepared.

Storm Surge versus Storm Tide

Feb 14, 2014
4,744
Hunter 430 Waveland, MS
We should know the difference.

I have seen posts on the best ways to tie up your moored or berthed boat.

To understand the "slack" needed on the mooring lines, you need to understand the terms used by NOAA,

Storm Surge Overview

NOAA has an Experiment Model for this called...

SLOSH

Sea, Lake, and Overland Surges from Hurricanes (SLOSH)

They will only run SLOSH for local officials, as of now.

So your local officials will alert you as a Hurricane approaches.
My experience is the forecast is 2-4 foot higher than actual, thus experimental.

They used historical data to improve results.
This is Hurricane Katrina real data in the SLOSH model.

slosh_2005_katrina307.gif

Guess where I live?:facepalm:
_____
Our boat was ready for a 10' surge, but we got 6', for Hurricane Nate.
NateReady.JPG

There are many Articles on boat mooring lines for a storm.

Feel free to post them here.

Jim...

PS: Hurricane Nate holds the record for the fastest moving storm in NOAA history at 29 mph. Another factor for Storm Surge Modeling.:cool:
 
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Likes: Dave Groshong
Jan 1, 2006
4,840
Slickcraft 26 Greenport, NY
Far be it for me to start an argument, as I'm likely to be yet more homebound, :stir: but that SLOSH (Geez, do these Gov workers spend most their time making up acronyms?) graphic shows what I've been saying since Katrina. The coast of Alabama took the worst conditions, not New Orleans. The reason the death toll was so high in New Orleans is because the levee failed and flooded a city that is below sea level. The death toll would have been in line with other hurricanes if the levee held. In the interest of truth the death toll in New Orleans should be blamed on poor planning and not Katrina.
 
Feb 14, 2014
4,744
Hunter 430 Waveland, MS
New Orleans is because the levee failed and flooded a city that is below sea level.
My City, Waveland, MS, what hit the worst and listed a "Ground Zero" by Wikipedia. 45 minute drive East of NOLA.

Water that Flooded the 9th Ward of New Orleans came in from Lake Pontchartrain and over the levee behind them.
The Eye of Katrina split, caused by the LA boot.

The largest part went between Waveland MS and Slidell, LA. Barometric pressure at my home 820 millibars and my ears popped as it passed nearby.

The smallest part went ashore near MS-AL border.

Bourbon Street in The French Quarter in NOLA, was up and running in 2 days.
We got power 30 days later.

Thus began my scientific hobby of meteorology.;)

The Storms Surge in Waveland was 42 feet high and came in three waves.
Here is where my office was, and it was 1000 feet from the beach in Waveland.
KatrinaOffice.jpg
The 2x4 on the slab was where my desk was. You could not see the Water Tower [in back of pict] before. Notice that no mud or sand is around?

So Storm Surge and Not Storm Tide wiped Waveland off the map.

So that 42 ' Storm Surge went through Lake Borgne and into Lake Pontchartrain to get NOLA.
______

Back to how to prepare you boat for Storm Tide/Surge


Anyone have links to boat mooring for best practices in a Storm?


Jim...
 
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Jul 27, 2011
3,891
Bavaria 38E Alamitos Bay
What I remember reading is that the levee was built to withstand up to Cat 3 hurricane conditions. Katrina was stronger than that, so the levee could not hold back all of the water. Everything is a risk calculation, just like the purchase of safety gear for your boat. Spend excessive amounts of money to cover the risk for an event of very high magnitude but that almost never occurs, or less money to cover the risk of events with low to medium-high magnitude that are likely to occur within a certain time frame at a certain place; say, within a half century. There’s a mathematical relationship between the magnitude of events and the frequency of their occurrences. Small versus very large earthquakes, small versus very large storms, small versus very large meteor impacts, etc. So, planners built the levee they intended to build to meet the likely conditions. When it becomes evident that the levee will be breached; yes, there needs to be a plan to evacuate. And the residents must have the willingness, the means, and the opportunity to do so, etc. Yet, it reduces to the same problem as with the levee itself. The cost of a plan for an event of high magnitude with a very low probability of occurrence.
 
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Jan 1, 2006
4,840
Slickcraft 26 Greenport, NY
My inexpert analysis was that the eye(s) landed East of NOLA and therefore the winds should have been Northerly in NOLA. So is it that the storm blew so much water into the delta that even when they shifted North the surge couldn't recede very quickly - or at all?
I'm not familiar with many geographical features in that area. And, most people don't realize that Katrina was a Cat III at the time it made landfall. Anyway the SLOSH chart above shows a surge of 16' - something you would think a city at the mouth of the largest river in the country, which drains water from 1/2 the country would be able to handle.
How does Storm Tide produce a sandy surface and a Storm Surge doesn't?
 
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Feb 14, 2014
4,744
Hunter 430 Waveland, MS
How does Storm Tide produce a sandy surface and a Storm Surge doesn't?
Actually you have that reversed.

The Surge washed away all sand and mud from my office slab. In fact it looked like someone had pressure washed it.
Grass nearby was very clean, but if you went 2000 feet north and the other side of the railroad track...

STINKY MUD!

The levee on Lake Pontchartrain flowed over the top and it took a long time before the dam was breached to flood the 9th Ward.
It is almost impossible to rise the height of the Levee.
So this is the solution...

Storms SURGE Barrier

________
It is almost impossible to moor you boat for major STORM SURGE, but STORM TIDE is possible.

Jim...

PS: That picture of my Office was taken the day after Katrina.
 
Jun 21, 2004
1,512
Beneteau 343 Slidell, LA
The coast of Alabama took the worst conditions, not New Orleans. The reason the death toll was so high in New Orleans is because the levee failed and flooded a city that is below sea level. The death toll would have been in line with other hurricanes if the levee held. In the interest of truth the death toll in New Orleans should be blamed on poor planning and not Katrina.
Would definitely disagree about the coast of Alabama experiencing the worst conditions; as Jim mentioned, Mississippi was ground zero and definitely impacted more severely than any area of the coast, with regards to wind, surge, and catastrophic physical damage. Agree with you that with regards to New Orleans, the death toll would have been negligible had the levees not failed. All govt levels failed miserably from FEMA, LA state and New Orleans in pre planning & managing the aftermath. With a metro area of some 2 million people it is a monumental effort to evacuate the city and surrounding area. Complicating matters worse is the high poverty situation in New Orleans with substantial numbers lacking transportation and $ to evacuate for several days/weeks hundreds of miles away. A couple years after Katrina, the area was threatened with another storm and FEMA/LA/NO got their collective acts together and evacuated the city effectively; so with proper planning, the death toll can be mitigated.

Finally, with all the technology & forecast models, storms are tricky to predict; therefore, making full scale evacuations difficult.
The weekend of Katrina, I was moving into a newly constructed home. A few days before the Katrina hit, I knew that there was a storm brewing near the Bahamas and kept it on my "radar". On Friday AM moving day, I checked the Weather Channel, and noted that the storm was to clip South Florida and eventually make landfall around Apalachicola, FL on the North East Florida panhandle, on Monday AM. We had movers scheduled to move the heavy stuff and worked all day Friday moving. Early Friday evening I got a call from a relative, informing me that the storm trajectory had shifted some 400 miles westward toward the greater New Orleans/Mississippi Coast. So, within a ten hour time period, the forecast changed drastically. We worked frantically to finish the move by Midnight on Saturday, allowing about 2 hours early Sunday AM to secure the boat. We hit the road around 5 AM on Sunday to evacuate, and 24 hours later, on Monday AM, the storm was making landfall.

So, there was a 48 hour window to evacuate 2 million people. Bumper to bumper traffic on interstates that were reconfigured for contra-flow traffic schemes and hotels booked for 500 miles. Easier said than done to accomplish a mass evac; however, I think that all govt levels are better prepared and have better evacuation plans in place. This year is the 15th anniversary of Katrina; hopefully, complacency has not set in.
 
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Likes: JamesG161
Jun 21, 2004
1,512
Beneteau 343 Slidell, LA
My inexpert analysis was that the eye(s) landed East of NOLA and therefore the winds should have been Northerly in NOLA. So is it that the storm blew so much water into the delta that even when they shifted North the surge couldn't recede very quickly - or at all?
I'm not familiar with many geographical features in that area. And, most people don't realize that Katrina was a Cat III at the time it made landfall.
ONE problem with Katrina is that it downgraded to a Cat 3 at landfall; however, it was pushing a Cat 5 surge.
Interesting phenomenon occurs in Lake Pontchartrain, once the lake fills and wind direction changes, there is a secondary wind driven surge that piles up on the leeward shore. Depending on the extent of the initial surge and the wind intensity, there can be an additional surge height of several feet.
Yes, with the topography of the Lake Pontchartrain basin, it takes several days for the water to drain from the area, unlike an area that is directly on the coast. In the case of New Orleans, once the areas that are protected with levees flood, the only manner in which to dewater the flooded area is by intentionally breaking the levees or pumping. I may be mistaken; however, I seem to recall that it took 2-3 weeks to get all parts of the city dry again. Pumping stations in New Orleans were drastically improved in the years following Katrina; however, there are still problems present.
With regards to the new surge barriers and improved levee system around New Orleans, I would guestimate that it would be adequate for a Cat 3 storm; however, I would not bet my life that it would be adequate for a storm of higher intensity.
 
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Jan 1, 2006
4,840
Slickcraft 26 Greenport, NY
Thank you for that post. I've shuttered up my house in Jensen Beach and am awaiting Isais. So hurricanes have my interest today. Having never been to NO, or in MS or AL my geographical awareness of the area is not very good. Yes, I meant MS. I've been looking at maps of NO for the last 1/2 hour and still don't really get the relationships of the various waterways. It is stunning that 15 years have past since that awful event.
BTY, I've always thought the idea of evacuating Long Island NY was ridiculous.
 
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Likes: JamesG161
Jun 21, 2004
1,512
Beneteau 343 Slidell, LA
Yes, with the population of Long Island, vertical evacuation would be the only practical manner in which to keep people safe. The aftermath would not be good; however, survivable.
Hopefully Isais will not strengthen appreciably and damage will be minimal. "Hunker Down" and be safe!
 
Jun 2, 2004
2,959
Hunter 23.5 Fort Walton Yacht Club, Florida
I lived in Biloxi and moved to FLA just a few years prior to Katrina. I believe there was a huge difference in the local governments between Alabama , Mississippi and Louisiana which accounts for the difference in the preparation and for the relief following the storm, more so than the physical geography. Is Mayor Nagin still in jail?
 
Jun 21, 2004
1,512
Beneteau 343 Slidell, LA
I believe there was a huge difference in the local governments between Alabama , Mississippi and Louisiana which accounts for the difference in the preparation and for the relief following the storm, more so than the physical geography. Is Mayor Nagin still in jail?
No, I think he was released to home incarceration recently.

Rick, I am not from New Orleans & don't live there, so I think that I can be objective about the situation. As far as evacuation is concerned there is a much greater population in the NO metro area than in coastal MS & AL combined, that translates to much more difficulty in evacuation. Lets face it you only have three choices when dealing with a hurricane; you can stay home & hunker down, you can go to a shelter, or you can get the hell out of Dodge and evacuate to a safer place. And again with the poverty level in NO, many didnt have the means to evacuate except to shelters in the city that flooded or were cut off by flooding. As I stated previously, NO stayed flooded for a few weeks after the storm. Flood waters in coastal MS & AL receded in a day. That made relief efforts immediately after much more difficult in NO. I didn't see any helicopter evacuations of people from rooftops occurring in MS & AL for days following the storm. Needless to say there were exponentially more homes destroyed in the NO metro area that were destroyed or flooded, as compared to MS & AL, that required much longer to rebuild. Yes, politicians like Nagin didnt help matters; however, you can believe that the same was going on in other states as well.
 
Jun 2, 2004
2,959
Hunter 23.5 Fort Walton Yacht Club, Florida
No, I think he was released to home incarceration recently.

Rick, I am not from New Orleans & don't live there, so I think that I can be objective about the situation. As far as evacuation is concerned there is a much greater population in the NO metro area than in coastal MS & AL combined, that translates to much more difficulty in evacuation. Lets face it you only have three choices when dealing with a hurricane; you can stay home & hunker down, you can go to a shelter, or you can get the hell out of Dodge and evacuate to a safer place. And again with the poverty level in NO, many didnt have the means to evacuate except to shelters in the city that flooded or were cut off by flooding. As I stated previously, NO stayed flooded for a few weeks after the storm. Flood waters in coastal MS & AL receded in a day. That made relief efforts immediately after much more difficult in NO. I didn't see any helicopter evacuations of people from rooftops occurring in MS & AL for days following the storm. Needless to say there were exponentially more homes destroyed in the NO metro area that were destroyed or flooded, as compared to MS & AL, that required much longer to rebuild. Yes, politicians like Nagin didnt help matters; however, you can believe that the same was going on in other states as well.
What I remember was empty school buses left in the city and Amtrak offering trains out of the city that could have taken people out before the storm. I realize that begs the question to where? In Mississippi it was apparent that those in office were constantly thinking about the next big storm perhaps because Camile was so prevalent in their young live it was an innate response. What was obvious was the city, parish and state had no contingency plan for evacuating the area. They seemed to rely on the levees and pumps to keep everyone safe and were dumbfounded at the circumstances they faced when those systems failed.
 
Jul 27, 2011
3,891
Bavaria 38E Alamitos Bay
They seemed to rely on the levees and pumps to keep everyone safe and were dumbfounded at the circumstances they faced when those systems failed.
Probably discovered too late that the system was not designed or built to handle a Cat 5 storm even if it came ashore as a “Cat 3” in the last few hours. Once the streets were under water, there’s no wholesale evacuation, etc.
 
Oct 22, 2014
12,581
CAL 35 Cruiser Portland OR, moored EVERETT WA
The levee on Lake Pontchartrain flowed over the top and it took a long time before the dam was breached to flood the 9th Ward.
A couple of years ago, when James first got me to conspire with him on Weather watching, He asked me to read a book. "Rising Tide: The Great Mississippi Flood of 1927 and How it Changed America". It was an incredible examination of the river management history. The Army Corps of Engineers have been in the middle of this adventure for eons. They are still today a controlling entity of levee construction.

Katrina hit the levee's in a couple of ways.
  • SURGE over the top of the not yet completed construction projects
  • Destruction of the pumps designed to control the water behind the levees
  • Water pressure subsurface infiltration and shifting.
The levee's failed.
"As Katrina's storm surge filled the canal, water pressure rose in the soil underneath the wall and in the peat layer. Water moved through the soil underneath the base of the wall." (wiki - 2005 levee failures in Greater New Orleans - Wikipedia)​
This destroyed some of the levees in much the same way they failed in 1926 and 1927. Water pressure finds weaknesses in the sub soil in the peat layers or the sand pockets. The foundation of a levee is weakened and whoosh... Water, water everywhere.