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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Quoting MississippiWx:


It's not over yet, my friend. Also, Haiti has reported at least 17 dead from Isaac.

Oh' Lordy. Havent looked at it today...
Hearts go out to Haiti.
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Quoting Bobbyweather:
SFMR Peak Surface Wind:
54 knots
(~ 62.1 mph)
(in the 850 mb levels)
Who cares? I mean, really, why are you posting 850 mb winds?
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Quoting MississippiWx:


Looks that way.


That's what I thought. Isaac might just be a hurricane. He's trying his hardest to become one that's for sure.
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Quoting TropicalAnalystwx13:
979 millibars with 21 knot surface winds.

Isaac is essentially a WPAC storm in the Gulf. Most bizarre storm in a while.
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1450. emcf30
Quoting SouthDadeFish:
You found one of the cyan ring? Usually, that is a telltale sign of an oncoming RI event.

Research on the Cyan Ring has shown normally you can see a 15 to 20mph increase in windspeeds in a relative short period of time.
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I think Isaac is more likely to be paralleled with Ike. It's winds speeds are probably going to be at the very most 110-115, and pushing a lot of water over a large area ahead of it. I hope people are taking the surge threat seriously...
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1448. GatorWX
Great sunset behind Cantore! Pretty darn red.
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Quoting oceanspringsMS:


NO got hit from gradual flooding due to levee failure not 20+ storm Surge driving houses off foundations
Not so gradual, but otherwise, yeah.

Quoting osuwxguynew:


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.
I agree on the eastern band theory. Isaac has had a problem with a band to the S or E pretty much since it got into the CAR... it was a rather ungainly two-lobed thing at one point...

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1446. guygee
Quoting keno66:

He also said last night that there are two types of levees - those that have failed and those that will fail.
A little too cute for me. That is like saying there are two kinds of empires, those that have fallen and those that will fall...there are two kinds of buildings, those that have crumbled and those that will crumble...there are two kinds of species, those that are extinct and those that will be extinct...ad infinitum...ad nauseum...
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Quoting HurricaneDean07:

I have to say...
The US is one lucky little Mo' Fo' Right now...
Gah, This sucker could've been HUGE. Isaac has failed his bretheren... No retirment...

90 Mph Landfall.


It's not over yet, my friend. Also, Haiti has reported at least 17 dead from Isaac.
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Quoting TropicalAnalystwx13:
979 millibars with 21 knot surface winds.

977. 75 Mph Hurricane?

This is the lowest pressure I've ever seen a TS get to...
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Quoting Jedkins01:
I'm pretty sure Isaac can be named the most "unpredictable" storm in a while, for both intensity and path. Seriously, Isaac has proved me wrong more times than the days I've been alive it seems, lol.
Actually for the path I will say Debby for intensity Isaac.
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Note how the high has finally moved closer to Isaac's position.

This thing could really bomb tonight.



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Quoting tornadolarkin:


Sign of MLC and LLC alignment like the HH said earlier?


Looks that way.
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Quoting MississippiWx:
Winds have certainly mixed down to the surface. Lots of 60+ mph readings north and west of the center.

I have to say...
The US is one lucky little Mo' Fo' Right now...
Gah, This sucker could've been HUGE. Isaac has failed his bretheren... No retirment...

90 Mph Landfall.
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1439. txjac
Quoting literacycoach:
Welp, long time observer here. What a way for me to celebrate my 50th! At least I get the day off.


Happy 50th!
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979 millibars with 21 knot surface winds.
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Link delete the first 2/3 of the frames then increase the speed. NNW for that time.
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Kermit's headed back through the center on its way back to base, at 10,000 feet, just as the Air Force makes its first center pass of the night at 5,000 feet. Both aircraft are finding that the non-contaminated surface winds peak around 50kts, at least so far. We should have two new center readings in the next 10-15 minutes, and I doubt we'll see the 11pm advisory come before the top of the hour, because the NHC will want the new data.

But, based on Kermit's 980.6 center pass, we're not going to see a hurricane at 11pm - just a bizarrely sprawling, stubbornly unwilling to strengthen tropical storm.
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Quoting MississippiWx:
Winds have certainly mixed down to the surface. Lots of 60+ mph readings north and west of the center.


Sign of MLC and LLC alignment like the HH said earlier?
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Welp, long time observer here. What a way for me to celebrate my 50th! At least I get the day off.
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Quoting emcf30:


Yea, I was hoping to find the one with a perfect Cayan Ring that it currently has. Guess it is not available over the public domain yet.

HH's are reporting a vertically stacked system with deep thunderstorm convection building over the center. We will see if it maintains.
You found one of the cyan ring? Usually, that is a telltale sign of an oncoming RI event.
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Quoting TomballTXPride:
Wow. That's is unbelievable. "I better wake up and find a category 3" WTF?

Unreal. Un-freaking real.

The guy is nuts...
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Winds have certainly mixed down to the surface. Lots of 60+ mph readings north and west of the center.
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SFMR Peak Surface Wind:
54 knots
(~ 62.1 mph)
(in the 850 mb levels)
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Quoting TropicalAnalystwx13:
BULLETIN
TROPICAL STORM ILEANA ADVISORY NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL EP092012
800 PM PDT MON AUG 27 2012

...TROPICAL STORM ILEANA FORMS...NO THREAT TO LAND...


SUMMARY OF 800 PM PDT...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...15.5N 107.7W
ABOUT 330 MI...530 KM SW OF MANZANILLO MEXICO
ABOUT 530 MI...855 KM SSE OF THE SOUTHERN TIP OF BAJA CALIFORNIA
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...WNW OR 290 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...1000 MB...29.53 INCHES

I didn't even realize the EPAC was alive...
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Quoting CosmicEvents:
Words from the wise, he's been proven right most if not all of the time, as far as I know.


He said Katrina was headed up the east coast....
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1426. emcf30
Quoting SouthDadeFish:
This image is a few hours old and was taken at about 3:30pm CDT but did show good organization at the time, which has since faded.


Yea, I was hoping to find the one with a perfect Cayan Ring that it currently has. Guess it is not available over the public domain yet.

HH's are reporting a vertically stacked system with deep thunderstorm convection building over the center. We will see if it maintains.
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Quoting TomballTXPride:
Wow. That's is unbelievable. "I better wake up and find a category 3" WTF?

Unreal. Un-freaking real.


hes trying to be cute...its his role here.
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Quoting Stormchaser121:
Ensemble members...now what??










With its enormous windfield pulling so much dry air off the SEUS, it could be a moot point.......starting to wonder if we'll have a cat1 @landfall.
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Quoting Masquer08er:
When it floods, I'll be on Spring Beach near Wilmer Hall down the hill a little ;-)


it will probably flood out by USA at Old Shell and University..sure glad the bank moved!..lol
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I'm pretty sure Isaac can be named the most "unpredictable" storm in a while, for both intensity and path. Seriously, Isaac has proved me wrong more times than the days I've been alive it seems, lol.
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1420. keno66
Quoting CosmicEvents:
Words from the wise, he's been proven right most if not all of the time, as far as I know.

He also said last night that there are two types of levees - those that have failed and those that will fail.
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Quoting TropicalAnalystwx13:
Recon should find Isaac with a sub-980 millibar central pressure. That's what Kermit found (980 millibars with 20 knot surface winds).

What is this, the Western Pacific? A minimal hurricane/strong TS does not have pressures of less than 980mb! Seems Isaac is in the wrong basin.
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Quoting Pcolanyc:


Weird because on the bluffs in East P'cola it's horribly humid and the winds are close to TS levels.

And we're kinda balmy and breezy on the Westside.

Weather's a bear, isn't it?
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BULLETIN
TROPICAL STORM ILEANA ADVISORY NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL EP092012
800 PM PDT MON AUG 27 2012

...TROPICAL STORM ILEANA FORMS...NO THREAT TO LAND...


SUMMARY OF 800 PM PDT...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...15.5N 107.7W
ABOUT 330 MI...530 KM SW OF MANZANILLO MEXICO
ABOUT 530 MI...855 KM SSE OF THE SOUTHERN TIP OF BAJA CALIFORNIA
MAXIMUM SUSTAINED WINDS...45 MPH...75 KM/H
PRESENT MOVEMENT...WNW OR 290 DEGREES AT 12 MPH...19 KM/H
MINIMUM CENTRAL PRESSURE...1000 MB...29.53 INCHES
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Quoting GeoffreyWPB:
Bob Breck..Fox 8 out of Orleans...Isaac could be a glorified thunderstorm.
Words from the wise, he's been proven right most if not all of the time, as far as I know.
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So I am guessing the models all predicted the frontal boundry to give way to the High pressure to the north which would allow Isaac to head nw west until it interacted with the high then off as a low to the extreme NE. I think the front will hold up or the high will not build strong enough to continue NW. Isaac will stall or head N then NE...The stronger faster predicted storm may have very well followed the predicted path but Isaac fizzled as of yet and will float if it does not get its act together.
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Any body have a link to the hurricane chaser who did coverage of Beryl.The guy was funny as hell.
Member Since: September 18, 2010 Posts: 0 Comments: 5248
This storm is crap...not the I name I expected...doubt it would make it to hurricane...

Im focusing on Kirk now...
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Quoting emcf30:
This image is a few hours old and was taken at about 3:30pm CDT but did show good organization at the time, which has since faded.
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1411. guygee
Quoting WDEmobmet:

Those are from early this morning... your link even identifies them as the 06z...nice try
Guess I better start reading the fine print with my anti-aliaser glasses before I comment on these colorful miniaturized graphics people are posting lately.
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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!



They are moving NNW at my house as well. I live about .5 miles SSE of the airport in Cordova Park.
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Hi y'all...

Meanwhile, back at the ranch.......



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I'm very curious to see if the section on the SW side wraps around or gets cast off like Florida blob and the part left south of Cuba. Isaac so far seems some odd kind of storm that never fixes itself in the center, it just flings things off and starts over with more convection. Right?
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1407. emcf30
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Quoting Unfriendly:


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


I meant the weather,,thunder storms,,I caught myself after I posted that,,,
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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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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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