ATL: ISAAC - Post-Tropical - Discussion

[6SpeedTA95]

But wouldn't the 100mph storm have winds of 100mph, sustained?

Again, sustained is defined as a 1 minute average. It could be 100mph dead on for 60 seconds or 50mph and 150mph for 30 seconds each giving you a 100mph average. Which one do you think would do more damage?

[fci]

To the folks who are going to experience Isaac in a stronger form, might be helpful to know that the Palm Beach Post has a lead article on their site called:

Did forecasters adequately warn this area about Isaac? by Opinion Staff

Palm Beach County and the Treasure Coast were out of Isaac’s “cone” well before the storm approached the Florida Keys. There was a tropical storm watch as far north as Jupiter Inlet, but the models were in ever-better agreement that the storm would cross the Keys going west-northwest, and head out into the Gulf of Mexico a good distance from Florida’s west coast.

So how bad could it be way over here on the east coast? Pretty bad, as it turned out.

There were tropical storm force gusts, but the rain was the real surprise. Even as the storm was hitting Key West on Sunday, there seemed to be nearly as much rain in Palm Beach County. Then, as the storm moved beyond Key West on Sunday evening and overnight, there was much, much more rain in Palm Beach County. And the rain didn’t stop on Monday. Into the afternoon, a long “snake” of heavy rain extended from Melbourne down to Miami, inundating areas just west of the coast. A curving swath of heavy rain also curled across the northern part of the state. Forecasters had predicted rain. And the official forecasts included the expectation that some of the storms “could produce heavy rain.”

The National Hurricane Center’s graphics also had warned that even though most of Florida was out of the cone, “The cone contains the probable path of the storm center but does not show the size of the storm. Hazardous conditions can occur outside of the cone.” Certainly Palm Beach County and the Treasure Coast experienced plenty of those “hazardous conditions outside of the cone” on Sunday and Monday.

But were we adequately warned?


Several readers have posted comments like the excerpt below:

Hi. I’m looking out my window; my house sits atop a tiny island that I hope remains above the water level as the afternoon progresses. It’s never been this deep and I’ve been in this location nearly a decade and a half. I did not anticipate this much water, nor did those nearby that I’ve discussed it with. I can’t say that I wasn’t warned; anyone who’s lived here for a while knows that tropical drenchers frequently bring extensive flooding.
I’d also appreciate some detailed local information regarding when to expect water levels to drop enough that I can get my car out of my driveway. Do we know when which canals and drainage areas will subside below street level again? I’d really like to let my boss know whether I’ll be able to make it to work tomorrow or not

NHC and Local NWS office predicted upwards to 12 inches of rain and that's what we received.
The media, including The Palm Beach Post; could do a better job of explaining what "the cone' is.
Most of us on S2K understand it and accept that there is a lot of damage that can occur outside the cone.
Plus, we were told in advisories that Tropical Storm winds extended outwards to over 200 miles to the NE and that was where our county was located relative to the ill-defined center of circulation.
So, I think that when the question is answered, the NHC DID give adequate warning. Please just didn't heed them.

[monicaei]

But wouldn't the 100mph storm have winds of 100mph, sustained?

Again, sustained is defined as a 1 minute average. It could be 100mph dead on for 60 seconds or 50mph and 150mph for 30 seconds each giving you a 100mph average. Which one do you think would do more damage?

Is that a realistic example? Winds 80 mph, gusting to 150? Does lower/falling pressure really equate to these dramatic kind of numbers?

[6SpeedTA95]

But wouldn't the 100mph storm have winds of 100mph, sustained?

Again, sustained is defined as a 1 minute average. It could be 100mph dead on for 60 seconds or 50mph and 150mph for 30 seconds each giving you a 100mph average. Which one do you think would do more damage?

Is that a realistic example? Winds 80 mph, gusting to 150? Does lower/falling pressure really equate to these dramatic kind of numbers?

I already gave a realistic example. You can have an 80 or 90mph rated storm cause more damage then one rated at 100mph because of extreme gusts in the eyewall that are a result of deep convection in a strengthening storm.

You have a lull of 60 or 70mph and then a massive gust to 120mph versus a weakening storm that may be more constant (for a variety of reasons) but lack the gusts. This was first really explored after Andrew.

edit: so no my 50 to 150mph example was not realistic it was to make a point because the realistic scenario obviously didn't get the job done. It'st he gusts that can cause a LOT of damage, especially if they're high. A lot of homes have no issues with 90 to 100mph winds, go up much higher than that though and many roofing materials begin to have big problems. Windows break, debris breaks them etc...as speeds ramp up in excess of 100...there are various breakpoints for all kinds of things...windows, roof material, trees of various sizes, structural damage etc. Gusts can cause more havoc in some situations then a sustained wind, even though the gust only lasts for 5 or 6 seconds.

[windnrain]

If I am correct, I think a falling pressure storm will not weaken as fast once inland as a rising pressure storm. A falling pressure storm will probably have a higher wind radius too.

Or am I completely wrong?

[Janie2006]

Well, I'm going to trust the observations and recon data....and that is one ugly looking tropical storm. So far he's been the "little engine that couldn't". Always a bridesmaid and never the bride, so to speak. Still having the same issues he's been having, well, most of his life.

[Blinhart]

I'm shocked no one has stated that this sort of looks like a sub-tropical system. The way it is shaped with most of the action to the West and South of the center, it has to look of one.

[Wx_Warrior]

Well, I'm going to trust the observations and recon data....and that is one ugly looking tropical storm. So far he's been the "little engine that couldn't". Always a bridesmaid and never the bride, so to speak. Still having the same issues he's been having, well, most of his life.

That made me laugh out loud. Needed that for all the watching and wondering.

[Blinhart]

Question for the pro-mets that have the time to answer me. If the High that is over Texas and Oklahoma moves more to the North East and closes off the weakness, what will be the end results for the movement of Isaac in the future?

[jinftl]

Been on and off this thread all evening and there has been no real dialogue (other than a mention here and there that garners little/no response) about the surge threat to New Orleans, SE LA, and the MS coast, some of the most surge prone areas in the U.S. And all the while, the NHC continues to highlight the surge risk in the last several advisory headings.

Folks are 'over it', underwhelmed, and anxious for Isaac to 'get going' once and for all. Dr. Jeff Masters discussed earlier today how Isaac, as is, could produce a higher surge than Hurricane Gustav did in the same areas. We are talking about a system already capable of producing a Cat 2 surge, but it is the wind mph that need to go up to make Isaac legit in most folks' eyes.

Downed trees and power lines, signage blowing away, roof shingles and some minor roof damage won't have near the damage and lethal impact as a surge that could rival or pass Gustav's if people aren't thinking along those lines.

From Dr. Masters:


Storm surge is the primary damage threat from Isaac. Isaac is a huge storm, with tropical storm-force winds that extend out 205 miles from the center. For comparison, Hurricane Katrina at landfall had tropical storm-force winds that extended out 230 miles from its center. Isaac's large size will enable it to set a large area of the ocean into motion, which will generate a large storm surge once the storm approaches land on the Gulf Coast. Water levels at Shell Beach, Louisiana, just east of New Orleans, were already elevated by 1' this morning. Conversely, water levels have fallen by 2' this morning at St. Petersburg, Florida, where strong offshore winds due to Isaac's counter-clockwise circulation have carried water away from the coast.

The latest 6:30 am EDT Integrated Kinetic Energy analysis from NOAA's Hurricane Research Division put the destructive potential of Isaac's winds near 0.6 on a scale of 0 to 6, but the destructive potential of Isaacs's storm surge was 2.1 on a scale of 0 to 6. I expect this destructive potential will rise above 3 by time Isaac makes landfall, making Isaac's storm surge similar to that generated by Category 2 Hurricane Gustav of 2008, which followed a path very similar to Isaac's predicted path. Gustav brought a storm surge characteristic of a Category 1 hurricane to New Orleans: 9.5' to Lake Borgne on the east side of the city. A higher Category 2-scale surge occurred along the south-central coast of Louisiana, and was 12.5' high in Black Bay, forty miles southeast of New Orleans.

Recent model runs indicate Isaac may slow down to a forward speed under 5 mph on Tuesday evening and Wednesday morning, close to the coast. If Isaac is just offshore at this time, the coasts of Southeast Louisiana, Mississippi, Alabama, and the Florida Panhandle will be exposed to a large storm surge with battering waves for two high tide cycles. This sort of extending pounding will be capable of delivering more damage than the storm surge of Hurricane Gustav of 2008.

[Janie2006]

Well, I'm going to trust the observations and recon data....and that is one ugly looking tropical storm. So far he's been the "little engine that couldn't". Always a bridesmaid and never the bride, so to speak. Still having the same issues he's been having, well, most of his life.

That made me laugh out loud. Needed that for all the watching and wondering.

We need a laugh now and then!

I was talking with a good friend of mine in the Atmospheric Sciences department (okay, that's what I call it) this afternoon and we were looking over the plain old sat pics and water vapour imagery of Isaac and tracking the recon missions at the time. While I was almost certain it was a Cat 1 at that point I was simply underwhelmed by its overall presentation. I've seen nothing since to change my impressions. If anything, he's even worse right now.

Just my opinion and YMMV.

Edited to add: The storm surge is, of course, an issue of great concern. The official predictions at Dog River in Mobile County, for instance, are 7-9 feet. I'm sure you can imagine that it would be considerably worse elsewhere. I'm in agreement that storm surge will be the greatest threat, but that's in line with most tropical systems.

[PTPatrick]

Well the convection seems to have wrapped around the center. There's nice ball over it now ...will it keep what's left of that dry out? I dunno. Just saying. Looking better by the minute. But then it has all day.


Other than that Mrs. Lincoln....how was the play?

[WeatherGuesser]

Anybody notice they've got this thing going almost to Chicago by Saturday night?

[pledger28]

This has been the most exhausting storm I have ever watched.

[fasterdisaster]

Recon flying towards the center again, let's see what they find.

[Wx_Warrior]

This has been the most exhausting storm I have ever watched.

You're a newbie pledger...get used to this. It's a norm around these parts.

[Camille(CaneOnAPill)]

-NOT AN OFFICIAL FORECAST AND SHOULD NEVER BE TAKEN AS SUCH, JUST AN OPINION FROM AN AMATEUR WEATHER ENTHUSIAST-

Looks like the dry air to its northeast is going to rotate around the northern side and get ejected to its northwest, at least most of it.

[deltadog03]

Recon still suggests at least a NW movement...

[ncweatherwizard]

Been on and off this thread all evening and there has been no real dialogue (other than a mention here and there that garners little/no response) about the surge threat to New Orleans, SE LA, and the MS coast, some of the most surge prone areas in the U.S. And all the while, the NHC continues to highlight the surge risk in the last several advisory headings.

Folks are 'over it', underwhelmed, and anxious for Isaac to 'get going' once and for all. Dr. Jeff Masters discussed earlier today how Isaac, as is, could produce a higher surge than Hurricane Gustav did in the same areas. We are talking about a system already capable of producing a Cat 2 surge, but it is the wind mph that need to go up to make Isaac legit in most folks' eyes.

Downed trees and power lines, signage blowing away, roof shingles and some minor roof damage won't have near the damage and lethal impact as a surge that could rival or pass Gustav's if people aren't thinking along those lines.

From Dr. Masters:


Storm surge is the primary damage threat from Isaac. Isaac is a huge storm, with tropical storm-force winds that extend out 205 miles from the center. For comparison, Hurricane Katrina at landfall had tropical storm-force winds that extended out 230 miles from its center. Isaac's large size will enable it to set a large area of the ocean into motion, which will generate a large storm surge once the storm approaches land on the Gulf Coast. Water levels at Shell Beach, Louisiana, just east of New Orleans, were already elevated by 1' this morning. Conversely, water levels have fallen by 2' this morning at St. Petersburg, Florida, where strong offshore winds due to Isaac's counter-clockwise circulation have carried water away from the coast.

The latest 6:30 am EDT Integrated Kinetic Energy analysis from NOAA's Hurricane Research Division put the destructive potential of Isaac's winds near 0.6 on a scale of 0 to 6, but the destructive potential of Isaacs's storm surge was 2.1 on a scale of 0 to 6. I expect this destructive potential will rise above 3 by time Isaac makes landfall, making Isaac's storm surge similar to that generated by Category 2 Hurricane Gustav of 2008, which followed a path very similar to Isaac's predicted path. Gustav brought a storm surge characteristic of a Category 1 hurricane to New Orleans: 9.5' to Lake Borgne on the east side of the city. A higher Category 2-scale surge occurred along the south-central coast of Louisiana, and was 12.5' high in Black Bay, forty miles southeast of New Orleans.

Recent model runs indicate Isaac may slow down to a forward speed under 5 mph on Tuesday evening and Wednesday morning, close to the coast. If Isaac is just offshore at this time, the coasts of Southeast Louisiana, Mississippi, Alabama, and the Florida Panhandle will be exposed to a large storm surge with battering waves for two high tide cycles. This sort of extending pounding will be capable of delivering more damage than the storm surge of Hurricane Gustav of 2008.

Freshwater inland flooding will be an equal, if not bigger, problem for such a slow moving storm. The rain will be a blessing for many folks farther north though.

[MHurricanes]

Been on and off this thread all evening and there has been no real dialogue (other than a mention here and there that garners little/no response) about the surge threat to New Orleans, SE LA, and the MS coast, some of the most surge prone areas in the U.S. And all the while, the NHC continues to highlight the surge risk in the last several advisory headings.

Folks are 'over it', underwhelmed, and anxious for Isaac to 'get going' once and for all. Dr. Jeff Masters discussed earlier today how Isaac, as is, could produce a higher surge than Hurricane Gustav did in the same areas. We are talking about a system already capable of producing a Cat 2 surge, but it is the wind mph that need to go up to make Isaac legit in most folks' eyes.

Downed trees and power lines, signage blowing away, roof shingles and some minor roof damage won't have near the damage and lethal impact as a surge that could rival or pass Gustav's if people aren't thinking along those lines.

From Dr. Masters:


Storm surge is the primary damage threat from Isaac. Isaac is a huge storm, with tropical storm-force winds that extend out 205 miles from the center. For comparison, Hurricane Katrina at landfall had tropical storm-force winds that extended out 230 miles from its center. Isaac's large size will enable it to set a large area of the ocean into motion, which will generate a large storm surge once the storm approaches land on the Gulf Coast. Water levels at Shell Beach, Louisiana, just east of New Orleans, were already elevated by 1' this morning. Conversely, water levels have fallen by 2' this morning at St. Petersburg, Florida, where strong offshore winds due to Isaac's counter-clockwise circulation have carried water away from the coast.

The latest 6:30 am EDT Integrated Kinetic Energy analysis from NOAA's Hurricane Research Division put the destructive potential of Isaac's winds near 0.6 on a scale of 0 to 6, but the destructive potential of Isaacs's storm surge was 2.1 on a scale of 0 to 6. I expect this destructive potential will rise above 3 by time Isaac makes landfall, making Isaac's storm surge similar to that generated by Category 2 Hurricane Gustav of 2008, which followed a path very similar to Isaac's predicted path. Gustav brought a storm surge characteristic of a Category 1 hurricane to New Orleans: 9.5' to Lake Borgne on the east side of the city. A higher Category 2-scale surge occurred along the south-central coast of Louisiana, and was 12.5' high in Black Bay, forty miles southeast of New Orleans.

Recent model runs indicate Isaac may slow down to a forward speed under 5 mph on Tuesday evening and Wednesday morning, close to the coast. If Isaac is just offshore at this time, the coasts of Southeast Louisiana, Mississippi, Alabama, and the Florida Panhandle will be exposed to a large storm surge with battering waves for two high tide cycles. This sort of extending pounding will be capable of delivering more damage than the storm surge of Hurricane Gustav of 2008.

This was posted today by Joe Bastardi:

https://twitter.com/BigJoeBastardi/stat ... 53/photo/1