Isaac approaching hurricane strength

By: Angela Fritz , 9:14 PM GMT on August 27, 2012

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Isaac is walking the line of hurricane status this afternoon after a hurricane hunter mission investigated the storm and found winds of 80+ mph with the SFMR instrument, which looks down at the surface from the plane and estimates what wind speeds are. This instrument has a notoriously rough time in doing so when there's heavy rain, and since the strongest winds were recorded coinciding with the strongest rain, you can imagine that this region of high wind speed could be suspect. The hurricane hunter mission is still in the storm, so I imagine they will issue a special update if needed. Currently the best estimate of wind speed within the storm is 70 mph. Isaac's pressure has been dropping today as well and is now 981 mb. Isaac is moving northwest at 12 mph--no change since this morning. Satellite loops show that Isaac remains large, though asymmetric, with most of the strong thunderstorm activity on the west and southwest side. Isaac's southeast side continues to struggle with dry air and wind shear, which could help to moderate Isaac's intensity as it approaches the coast.

An oil platform in the northern Gulf of Mexico is reporting sustained winds from the north-northeast at 40 mph this afternoon. A buoy west of Tampa, Florida is recording sustained winds around 30 mph, and platforms south of Louisiana are recording winds from 35-40 mph. The widespread heavy rain of yesterday has lightened up in Florida, but a strong line of thunderstorms in one of Isaac's outer bands is training northward along and offshore of the east coast of Florida, affecting everyone from Miami to Jacksonville.

This afternoon the AP reported that Isaac's death toll in Haiti jumped to 19, which puts Isaac's total death count at 21. It appears most of the deaths in Haiti were due to collapsing structures.


Figure 1. Satellite imagery of Tropical Storm Isaac around 3pm EDT on Monday.

Track forecast:
Models seem to be coming into better agreement today on where Isaac will make landfall, closing in on Louisiana and New Orleans as most likely landfall point. The ECMWF, HWRF, and UKMET all suggest New Orleans as the landfall location. The GFS is only slightly west of that. The GFDL is the farthest west, predicting landfall near the Louisiana-Texas border. Landfall timing remains Tuesday night. Beyond landfall, Isaac is expected to move north toward the Midwest through the rest of this week, however, models are showing that the system will likely slow down around landfall time, prolonging impacts like surge and inland flooding.

Intensity forecast:
The closer Isaac gets to landfall without having formed an eye, the better it is for intensity at landfall. Isaac has strengthened only modestly in the past 24 hours, and is still struggling with a less-than-conducive atmospheric environment. The HWRF remains on the high end of the intensity spectrum, suggesting Isaac will be a weak category 2 upon landfall. Other models suggest it will be a strong category 1, but the difference is splitting hairs. The National Hurricane Center's official forecast is for Isaac to continue strengthening over the next day, reaching category 2 at landfall.


Figure 2. Tide gauge data from St. Petersburg, Florida. The green line shows the storm surge. As Isaac's counterclockwise winds blew offshore this morning, water levels feel two feet at St. Petersburg. The winds switched to onshore this afternoon as the center of Isaac moved more to the northwest, bringing a storm surge of two feet to the city.

Storm surge observations from Isaac
This morning, as Isaac's counter-clockwise winds brought offshore winds to the Tampa/St. Petersburg area, ocean waters fell two feet along the coast. This afternoon, winds have shifted to blow onshore, and a two foot storm surge has been observed at Naples, Fort Meyers, and St. Petersburg on the west coast of Florida. Water levels have also begun to rise along the coast of Louisiana, with a storm surge of 1.5 feet already occurring at Shell Beach on the east side of New Orleans in Lake Borgne.

Angela and Jeff

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And there we go. Kermit's made its pass through the center. Minimum extrapolated surface pressure is back down to 980.6 - and there's a temperature differential of 12/13 outside the core to 16 degrees in the middle. Winds are still moderate for a tropical storm, though.
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Quoting MississippiWx:


So you're picking individual members and different runs that put Isaac close to Texas? You're just going to confuse the blog doing that. Isaac is not going to Texas unless he makes landfall in Louisiana, then moves west for a while.

and thats what the ensembles are saying. 1st LA then it moves west to TX
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Quoting BahaHurican:
Sigh. Final landfall was on the LA/MS border... look at the map again. Basically just short of the Pearl River, IIRC, in between Slidell and Bay St. Louis...
You're both right:
http://www.nhc.noaa.gov/pdf/TCR-AL122005_Katrina.p df

"Katrina turned northward, toward the northern Gulf coast, around the ridge over Florida early on 29 August. The hurricane then made landfall, at the upper end of Category 3 intensity with estimated maximum sustained winds of 110 kt, near Buras, Louisiana at 1110 UTC 29 August. Katrina continued northward and made its final landfall near the mouth of the Pearl River at the Louisiana/Mississippi border, still as a Category 3 hurricane with an estimated intensity of 105 kt."
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Quoting IMA:

I paid my $5 on the day I was notified to renew, have the PayPal receipt to prove it, but it still says "renew". I have sent multiple messages to support but have not had a reply. It's been 19 days since the first message was sent. I'm so disgusted right now! It's not about the ads, I have ABP, but not being able to get more than 6 frames on the animated radar & not getting assistance is maddening!


Make sure you are logged in when you access the radar loop. The very top should show your screen name.
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Recon should find Isaac with a sub-980 millibar central pressure. That's what Kermit found (980 millibars with 20 knot surface winds).
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1399. keno66
Quoting BahaHurican:
Sigh. Final landfall was on the LA/MS border... look at the map again. Basically just short of the Pearl River, IIRC, in between Slidell and Bay St. Louis...

The initial landfall was in Buras. That's where I grew up and lived until everything was completely and totally destroyed. Imagine driving into an area in which you spent 38 years living and not knowing where you were because there weren't any recognizable landmarks.
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Quoting CoastalAlabama:
I'm getting a bit tired of...

"...it looks like we are in an intensification stage right now..."

then...

"...it seems that there is an eyewall trying to form..."

then

"...dry air continues to be coming in from (pick a direction) and it's important to remember that it is not just all about the wind, but the length of time for the rain (or the size of the impact area means (pick a result))."

...on the Weather Channel.

Loved the Mobile Bay, Mississippi by Vivian earlier today...over and over...without any corrections from editors or producers in the earpiece. Doh!
Quoting CoastalAlabama:
I'm getting a bit tired of...

"...it looks like we are in an intensification stage right now..."

then...

"...it seems that there is an eyewall trying to form..."

then

"...dry air continues to be coming in from (pick a direction) and it's important to remember that it is not just all about the wind, but the length of time for the rain (or the size of the impact area means (pick a result))."

...on the Weather Channel.

Loved the Mobile Bay, Mississippi by Vivian earlier today...over and over...without any corrections from editors or producers in the earpiece. Doh!






Yea...that aggravated me too. "Mobile Bay, MS"...Really? Alabama coast is always forgotten.
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Quoting Dunkman:


It's not old school it just makes no sense for a hurricane. They rotate....
If you watch the clouds the low ones are cir, and the high ones are the motion. Somthing I have been doing for years and sometimes I am right!
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Quoting Reb74:

Not sure where you are but it is stifling compared to most nights lately. Absolutely "still" feeling even if the winds are not!


Weird because on the bluffs in East P'cola it's horribly humid and the winds are close to TS levels.
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Quoting odinslightning:
thank god im near the top of Spring Hill here in Mobile..... :::phew:::
When it floods, I'll be on Spring Beach near Wilmer Hall down the hill a little ;-)
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Quoting gulfbreeze:
Ok this may be old school but some time you need to go out side and just look up at the clouds. I am about a mile from the Gulf and in MHO I think he is moving NNW!


how can you tell the heading of a storm thats 250 miles south of you by clouds moving above your head?

Also, Taz, once again (as ALWAYS) you're passive agressively hoping for a massive catastrophic storm. I think you're too immature to realize that in doing so, you're causing distress to people who might. lose. everything. Think before you speak, boy.
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980.6 mb
(~ 28.96 inHg)
(From 1 hour 12 minuts ago)
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Quoting gulfbreeze:
Ok this may be old school but some time you need to go out side and just look up at the clouds. I am about a mile from the Gulf and in MHO I think he is moving NNW!


I was just outside with my daughter doing that, and looking at the trees and telling her about, that what my Moma always said about the upside down leaves,,,,,, 47years here,,, Zachary La
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1391. guygee
Quoting nola70119:

True, either way, I have no confidence in his "high confidence"....

Fair enough.
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Quoting Stormchaser121:

Actually its 00Z 06Z 12Z and 18Z its ALL of em.


So you're picking individual members and different runs that put Isaac close to Texas? You're just going to confuse the blog doing that. Isaac is not going to Texas unless he makes landfall in Louisiana, then moves west for a while.
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Quoting SouthDadeFish:
I think the more likely scenario is that the windfield is still really large, and Isaac probably still lacks a tight inner core.

Exactly. Isaac doesn't seem much better organized than earlier. If anything, it's core is as disorganized as ever since recon had reported in an earlier VDM that the eyewall had fallen apart.
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1388. guygee
Quoting Stormchaser121:
Ensemble members...now what??
Maybe some of the runs are noticing the giant continental high rolling in...if Isaac lollygags too long in the Gulf, some of the ensemble members would bring it more west.
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Bob Breck..Fox 8 out of Orleans...Isaac could be a glorified thunderstorm.
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Where is all this dry air coming from that Issac is sucking up? Is it coming from the drought stricken midwest (the midwest is dryer than it's EVER been in some regions, (mine))?? That would be neat if our misery could keep Issac from getting stronger...
On that note WHAT was the hurricane that came onto land and got stronger like in Oklahoma?? It's been since Katrina cuz I didn't pay attention before then...wouldn't it BE COOL if Issac pulled a landcane thing like that and dropped like 20 inches of rain over say like 3 days with Missouri as the center after just dropping a few inches and some mild breezes on the coast??
Now back to real life....
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Quoting SouthDadeFish:
I see your point, but what do you think about all that dry air around Isaac?


I think the dry air is signficant when the storm is being sheared, much less so when the shear weakens.


With this big of an anti-cyclone aloft causes divergence and rising motion over a large, nearly synoptic scale area.


I also believe the band east of Florida finally dying will help convection on the eastern side of the storm. This band was hurting low level convergence as well as probably causing a bit of subsidence on it's periphery, including the eastern side of Isaac.
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Quoting SouthDadeFish:
I think the more likely scenario is that the windfield is still really large, and Isaac probably still lacks a tight inner core.


Possibly. The thing is recon never got winds like this outside of the convection earlier.
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Quoting guygee:
To paraphrase Freud, sometime a "high confidence" is just a "high confidence".

Somewhat tangentially, I can remember when a judge ruled that IBM had exclusive rights to the number "2" after IBM introduced their PS2 product. That ruling didn't stick.


True, either way, I have no confidence in his "high confidence"....
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Sure, Isaac had troubles with dry air earlier, but I think he looks way better now than he did an hour ago, and even better than two to three hours ago. It looks like the dry air stabbed him because, from what I can see, his eyewall is established enough that it's wrapping around the very prominent COC and mixing out the dry air, of which there is only a sliver left, quite quickly.

Once he closes it off completely, which seems to be happening as we speak, I have a feeling he will explode. I have a feeling we will see a jump in a couple of categories over the day tomorrow, especially when those winds respond to that pressure.
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Goodnight everyone. To my fellow Mobilians and Gulf Coasties, stay safe.
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Quoting Masquer08er:
bwahahahaha
I would give that credence.
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Quoting WDEmobmet:


Those are from early this morning... your link even identifies them as the 06z...nice try

Actually its 00Z 06Z 12Z and 18Z its ALL of em.
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Quoting nola70119:


Katrina came ashore at Grand Isle or Buras, not Mississippi.

Sigh. Final landfall was on the LA/MS border... look at the map again. Basically just short of the Pearl River, IIRC, in between Slidell and Bay St. Louis...
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Quoting Stormchaser121:
Ensemble members...now what??



http://raleighwx.americanwx.com/models/gfsensembl e/members/06zensp004500mbHGHTtropical078.gif






Those are from early this morning... your link even identifies them as the 06z...nice try
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Am I the only one here wearing out their 'refresh' key waiting for Kermit to finally report in?
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1373. Melagoo


Looks like Isaac may be kicking out the dry air ...
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Quoting odinslightning:
thank god im near the top of Spring Hill here in Mobile..... :::phew:::


lol..me too but I am on the hill at Skyline! you and I live on the two highest points in Mobile!! ROFL
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Quoting TropicalAnalystwx13:
Flight level winds have crossed the hurricane threshold on the northern side of the circulation. Me thinks recon will find some 100 mph flight level winds on the south side.
I think the more likely scenario is that the windfield is still really large, and Isaac probably still lacks a tight inner core.
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Quoting BiloxiIsle:
It's really kind of scary to see the forcasted storm surge, and yet the Mississippi Gaming Commission has not closed the casinos. These things sets right on the coast. What are they thinking (that's right, they're not!).


WOW! amazing..I remember the times I had to shutdown a casino..ahhh, so much fun - lol..at least it is easier since they don't use tokens and coins anymore..
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Bryan Norcross' Official Blog entry 3

Isaac is less than 24 hours from its center's landfall on the Louisiana or Mississippi coast. The main computer-forecast models are finally in reasonable agreement on the location, although the small differences would change exactly who gets the worst storm surge.

The center has jogged a bit to the right tonight, likely due to the asymmetry of the system. If that trend continues, the surge will be higher in Mississippi, and the surge on the south-facing coast of Louisiana would be much less. This far out, however, more slight variations are possible.

The somewhat good news is that dry air continues to invade the core of the system, which is inhibiting or at least tempering the intensification process. Large-diameter storms like this generally intensify more slowly, as well. On the other hand, the pattern aloft looks very favorable for strengthening tomorrow, the heat content of the water will go up some, and the friction of the circulation's initial interaction with the coast can turn the winds in toward the storm's center kicking up the wind speed. Given the short window of time left before landfall, it looks most likely that Isaac will come ashore as a Category 1 storm, though Category 2 can't be ruled out.

The bad news is that the models are in lockstep on the LONG duration that the storm will batter areas near the coast, including the city of New Orleans. Tropical-storm force winds may continue over southeast Louisiana and Mississippi for 24 hours or more, with hurricane force winds for 8 hours or more. The storm is expected to move very slowly once it makes landfall, with tropical-storm force winds, at least in gusts, continuing into Thursday as the storm center moves away to the north.

If the storm tracks over or just west of New Orleans as is forecast, the heart of the city will experience stronger winds than it did in Katrina. And the duration of the strong winds will be far far longer.

The dry air in the circulation may temper the rain totals a bit, though there's no way to know it won't mix out before landfall. in any case, a foot or more of rain will fall along the coast and inland.

The levee and pumping system in New Orleans is NOT designed to keep the city dry in all eventualities. It's designed to keep the city safe. If a foot or more of rain falls on the area inside the levee, there will be flooding, just like there would be just about anywhere else. The difference is that the water is PUMPED out of New Orleans - one inch in the first hour and one-half inch each hour after. So people still need to use common-sense precautions in low-lying areas.

Elsewhere, the combination of heavy rain and storm surge is going to create an enhanced flood threat. The storm surge will push Gulf water up rivers, creeks, and inlets where the wind is onshore. The rainwater will want to drain out those same waterways. The storm surge will win and the rain water won't have anyplace to go.

Life-threatening storm surge will affect the coast for hundreds of miles east of where the center comes ashore. And, the slow movement is expected to hold the Gulf water over the coast and into inlets and bays for at least two high-tide cycles. The amounts at any one location will vary with the exact final track, but be ready for water higher than 6 feet above the land from Louisiana to Alabama, and dangerous surge in the Florida Panhandle as well.

The best we can hope for is that Isaac doesn't intensify, although at least some intensification is expected.

There is very little time to take precautions that will make a tremendous difference in how uncomfortable the period during and after the storm will be. Follow emergency instructions, use common sense, and stay safe.
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Quoting bluehaze27:
A few observations from Isaac: 1) Isaac reminds me that Florida is very fortunate that Hispaniola and Cuba are where they are. Without them I can foresee most storms hitting SE Fl at least two categories higher. When hurricane David hit many years ago, it was a 200 mph monster tempered by Hispaniola into a relatively tame 80mph storm. Once again these two countries kept a very large Isaac from spinning up.

2) Isaac was such a large storm that it has had a difficult time consolidating, especially, since it followed Saharan dust and relatively dry air.

3) Rainmakers can do lots of damage
4) forecasting intensity is still a (WAG) wild ass guess.
I have the same opinion. Haiti and Cuba saved Florida from a worse outcome. Perhaps some will realize the money they were saved and donate to the tent people.
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Ensemble members...now what??








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Quoting allancalderini:
Iliena is actually the 9th not the 10 ts of the eastern pacific Cody.

Thanks for the correction.
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Quoting Tazmanian:
Good night guys when i wake up I better find a cat 3 hurricane with winds of 120mph. If now I drop a cow on the nhc


You'll get a Cat 1 and like it
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1363. guygee
Quoting nola70119:


No problem here with data, you wrote "high confidence" without any explanation and that is a term the NHC uses and I associate it with their discussions.
To paraphrase Freud, sometime a "high confidence" is just a "high confidence".

Somewhat tangentially, I can remember when a judge ruled that IBM had exclusive rights to the number "2" after IBM introduced their PS2 product. That ruling didn't stick.
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Quoting oceanspringsMS:


Live in Ocean Springs, MS. we had an 18 ft + storm surge surge 60 miles from the LA/MS state line that is a fact


ocean springs here also...yall stay safe.
Member Since: June 28, 2009 Posts: 0 Comments: 79
Quoting ThePass:
At my house in Pass Christian, 2nd Street. Just walked down to parents (which is south of second). Very light winds almost calm. Will keep y'all posted as long as cableone is up lol

I was just telling son how houses in Pass Christian held up better than some of the others because of the steps which helped break up the water (my private theory) Stay safe, we used to live up on Alcede Lizana road...Thinking about everyone down there!!
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Iliena is actually the 9th not the 10 ts of the eastern pacific Cody.
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1359. Dunkman
Quoting gulfbreeze:
Ok this may be old school but some time you need to go out side and just look up at the clouds. I am about a mile from the Gulf and in MHO I think he is moving NNW!


It's not old school it just makes no sense for a hurricane. They rotate....
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Quoting gulfbreeze:
Ok this may be old school but some time you need to go out side and just look up at the clouds. I am about a mile from the Gulf and in MHO I think he is moving NNW!


It's an interesting evening. Was just outside watching the moon duck in and out of the bands coming in. Pleasant breeze, low humidity, and an "open up the windows and let some fresh air in" kind of evening.
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thank god im near the top of Spring Hill here in Mobile..... :::phew:::
Member Since: September 3, 2009 Posts: 0 Comments: 514
Quoting Tazmanian:
Good night guys when i wake up I better find a cat 3 hurricane with winds of 120mph. If now I drop a cow on the nhc

Why? It's not their fault Isaac is a troll that has failed to develop a good core.
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1355. Dunkman
I will say this about our awful looking storm, when the TS winds kick up on the coast in a few hours they aren't going to stop for a very long time. That howl is going to be a way of life for a couple days.
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Ok this may be old school but some time you need to go out side and just look up at the clouds. I am about a mile from the Gulf and in MHO I think he is moving NNW!
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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