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 Tazmanian:
i got a new name for Isaac


am calling Isaac the joker


Dry Air joker?

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Quoting RTSplayer:


Two days ago GFS said this was going to happen. It was off on track by about 1 degree N though.


This is going to be pretty nasty once the eye passes to our west and starts dumping tens of inches of rain on NOLA and the Northshore and Livingston Parishes.

If it gets far enough west and floods the Amite basin too, then it could be very wide spread river flooding.


Another thing, since the Mississippi is so low from the early melt and the drought in the tributaries in the northern states and central plains states, the storm surge is going to screw up the fresh water environment.

there was already a salt water wedge moving upstream in the Mississippi just due to normal high tides, and that was over a week ago.

A really high storm surge with this track might push salt water all the way back up to Baton Rouge, or maybe at least half way there, since the river level is only like 4 feet at Baton Rouge last I heard...


Anyway, with this kind of forward speed we are going to see very wide spread 10 inch or greater totals, I think.


They were interviewing the Army Corp of Engineers yesterday on this very issue. They said there will be no problem, since the heavy rain will raise the Mississippi River and push the freshwater back south again.
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Looks pretty. Beautiful-looking system on (HD-looking) visible loop. LINK

Isaac seemed to strengthen at the spot I mentioned at about 28n,88w. More thoughts when the fog clears! ;P
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Quoting MississippiWx:
Lol. Wow, NHC. Surface winds of 80mph and flight level winds of 100mph aren't good enough???

One would think so, I would love to hear the NHC reasoning behind this.
Member Since: March 16, 2012 Posts: 127 Comments: 7940
3550. Gearsts
Quoting Felix2007:

What did I tell you? This thing will never become a hurricane...
But it is a hurricane and is still deepening. Or it is the strongest TS i ever seen.
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Quoting weatherh98:
storm pro, the lake is normal level.

this northeast windsare throuwing it to the south shore

it should gradually rise as the windshits

and eventually slosh it back up here witht he south wind


Thankf for the answers guys. My family and I are going to walk down there in a few...look for the bald tattooed guy in a black tank top lol
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Can't they just upgrade it to hurricane just so that people will take it seriously???
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For the folks that live in this area

Houma, LA (70364) Weather Map

Link
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Quoting sar2401:


Let's put this into perspective. Katrina had a maximum storm surge of 27.8 feet at Pass Christian MS. Average storm surge was in the order of 15 to 18 feet. The Grand Isle LA area had a storm surge of 16.2 feet. 6-12 feet is still a lot of water but it's not Katrina.

I don't under stand why everyone keeps wanting to compare to the worst natural disaster to hit our country. That is like saying the Iraq war wasn't bad let me put it into perspective and compare it to the Vietnam war. They are both bad and destructive just not as prolific but needs to have the proper attention paid to it just the same.
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What is going on in TWC studio....? Someone is not prepared!
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3544. ncstorm
two blobs on the east coast and tropical storm in the GOM..


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3543. Patrap


URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 591
NWS STORM PREDICTION CENTER NORMAN OK
945 AM CDT TUE AUG 28 2012

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

SOUTHWEST ALABAMA
WESTERN FLORIDA PANHANDLE
SOUTHEAST LOUISIANA
FAR SOUTHEAST MISSISSIPPI
COASTAL WATERS

EFFECTIVE THIS TUESDAY MORNING AND EVENING FROM 945 AM UNTIL 700
PM CDT.

TORNADOES...HAIL TO 0.5 INCH IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 55 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 15 MILES WEST OF NEW ORLEANS
LOUISIANA TO 20 MILES EAST OF PANAMA CITY FLORIDA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU1).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS.

DISCUSSION...A SLOW INCREASE IN CONVECTION HAS BEEN NOTED THIS
MORNING ON OUTER PERIPHERY OF ISAAC WHERE BREAKS IN THE CLOUDS ARE
SUPPORTING AIR MASS DESTABILIZATION. THIS TREND SHOULD CONTINUE
THROUGH THE REMAINDER OF THE MORNING AND THIS AFTERNOON WITH AN
INCREASED RISK FOR MINI SUPERCELLS AND AN ASSOCIATED TORNADO THREAT.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
450. MEAN STORM MOTION VECTOR 11040.


...MEAD
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Don't worry there is a crow buffet somewhere around here.Well have a nice day :).
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Well that's great news!! Still just a TS!! YEA for us!! Get the popcorn this blog is about to go supersonic.
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Isaac is still at TS status based on max sustained winds, which I believe is decieving.

The pressure, storm surge, rain, track, and forward progression once Isaac makes landfall will be comparable to a Cat 1/ 2.

Is there a chance that this hits the mouth of the Miss river?
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Just a tropical storm folks, carry on as this will be a non event.....

lol
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Lol. Wow, NHC. Surface winds of 80mph and flight level winds of 100mph aren't good enough???
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3535. Levi32
Quoting reedzone:
I have lost all confidence on the NHC... I'm done.


Too far Reed. Too far. The NHC is the best we have. I don't understand why they have not upraded Isaac any more than you do, but they deserve and have earned the public's confidence. At least hurricane warnings have been out on the coastline for a long time now.
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Quoting K8eCane:

if a-holes could fly, i swear sometimes this place would be an airport. never, ever underestimate a tropical system


I have 125 people on ignore now. lol

Anyway, GFS says eye wall of Isaac will be coming near me in SW LA.
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Quoting tkeith:
I think SJ looks a little smarter now Press...not any better, but a little smarter :)


lol. Hey tkeith! How are ya? Got the preps ready?
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Quoting osuwxguynew:
Radar shows inner eyewall/core died due to dry air entrainment. They may not upgrade after all...



look at post 3482,eye almost complete.
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3531. Patrap
Quoting presslord:
Cool live video here right now...Link


Big Duke NOLA 7..nice video..Hwy 90 at Biloxi..Beau Rivage as well. Nice stuff SJ.
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i got a new name for Isaac


am calling Isaac the joker
Member Since: May 21, 2006 Posts: 5091 Comments: 114910
Quoting MysteryMeat:
STILL not a hurricane

10:00 AM CDT Tue Aug 28
Location: 28.1°N 88.5°W
Moving: NW at 10 mph
Min pressure: 976 mb
Max sustained: 70 mph


That's just stupid then.

They ignore the radar and their own dropsondes.

What's the point in the instruments if they aren't going to use their data?
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Quoting reedzone:
I have lost all confidence on the NHC... I'm done.


Lol
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The discussion contradicts itself.

SFMR SURFACE WINDS HAVE ONLY BEEN AROUND 60-62 KT...
WHICH CORRELATES WELL WITH DROPSONDE BOUNDARY LAYER-DERIVED SURFACE
WINDS.
AS SUCH...THE INTENSITY OF ISAAC IS BEING MAINTAINED AT 60
KT...WHICH IS JUST BELOW HURRICANE STATUS.

Dropsondes say 80mph.
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3525. junie1
SUPER TROPICAL STORM ISAAC
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New frame.

Wide spread plus 64kts winds and still has the minus 64kts too.

The left side of the eye wall may actually be stronger than the right side at the present time.
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Click image for text and probabilities
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Quoting Levi32:
They didn't upgrade Isaac. Unbelievable.


I had a feeling that they wouldn't.. I hear ya tho..
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Quoting wayfaringstranger:


Reed, just let it roll off your back. I enjoy reading your posts. Your one of the few still on here from way back.

Too bad Destin J isnt back on here.



Isaac will be interesting in post analysis. Big mystery why he couldn't get stronger in ripe conditions in the GOM.

Yeah Destin Jeff was a really funny guy. He should be lifetime member in my book. Don´t know if he was banned or just got bored here.

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I also think ACE is a little weird. It is based solely on wind speed so large storms like Isaac that have incredibly low pressures (for they're winds)still get the ACE of a TS
I think pressure could be included somehow
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Still a TS, according to TWC......
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From the Louisiana Department of Transportation: LA 1 in both directions: Bridge closed at West 170th Street (near Golden Meadow). The bridge is closed. A Hurricane Warning is in effect. The Galliano Pontoon is closed on LA 1 (W. Main St.) at W. 170th St. for hurricane warning.


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haha @ TWC on air talent...
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I wonder if these trolls ever been in actual hurricane or any strong tropical storm.. probably not.. The ones that do the mocking really don't know what they r talking about.. I say if u r on here mocking then thats a new low for the ones r doing so.. Well I c more idiots come out everyday, know wonder this world is crazy..
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I don't care. Regardless of what they say, this thing is a hurricane with 80 MPH winds. Period. End of story.
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11 am. Isaac still a ts. Twc is going to be upset
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Just below...
Member Since: July 12, 2007 Posts: 0 Comments: 6004
still no hurricane!!!!!
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I have lost all confidence on the NHC... I'm done.
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Quoting Felix2007:

Watch Isaac still not become a hurricane.

What did I tell you? This thing will never become a hurricane... but if it doesn't then I think it must be upgraded in post-season analyis.
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I give up, how is not a hurricane. Flight level and surface winds support a hurricane.
...ISAAC STILL JUST BELOW HURRICANE STRENGTH AS IT CONTINUES
NORTHWESTWARD...


SUMMARY OF 1000 AM CDT...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...28.1N 88.5W
ABOUT 80 MI...125 KM SSE OF THE MOUTH OF THE MISSISSIPPI RIVER
ABOUT 165 MI...260 KM SE OF NEW ORLEANS LOUISIANA
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...NW OR 310 DEGREES AT 10 MPH...17 KM/H
MINIMUM CENTRAL PRESSURE...976 MB...28.82 INCHES
Member Since: March 16, 2012 Posts: 127 Comments: 7940
3507. Skyepony (Mod)
Quoting Charliesgirl:


oh well, anyone know how to post a photo? I put it to my photos on here.


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darn you Isaac..become a wave crappy storm!!!
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Quoting Patrap:


The forecast calls for

HAZARDS AFFECTING LAND
----------------------
STORM SURGE...THE COMBINATION OF A STORM SURGE AND THE TIDE WILL
CAUSE NORMALLY DRY AREAS NEAR THE COAST TO BE FLOODED BY RISING
WATERS. THE WATER COULD REACH THE FOLLOWING DEPTHS ABOVE GROUND IF
THE PEAK SURGE OCCURS AT THE TIME OF HIGH TIDE...

* SOUTHEAST LOUISIANA AND MISSISSIPPI...6 TO 12 FT
* ALABAMA...4 TO 8 FT
* SOUTH-CENTRAL LOUISIANA...3 TO 6 FT
* FLORIDA PANHANDLE...3 TO 6 FT
* FLORIDA WEST COAST INCLUDING APALACHEE BAY...1 TO 3 FT

everything I see for my area shows about 5 to 8....I am a ways from the lake. 1/2 mile. But I can look down the street and see it. Truck is full of gas if we gotta go . What time should the surge hit its peak here in the middle of the northshore?
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Quoting Felix2007:
How ironic that a storm that was once moving at 23mph has now crawled to the pace of a snail.


Two days ago GFS said this was going to happen. It was off on track by about 1 degree N though.


This is going to be pretty nasty once the eye passes to our west and starts dumping tens of inches of rain on NOLA and the Northshore and Livingston Parishes.

If it gets far enough west and floods the Amite basin too, then it could be very wide spread river flooding.


Another thing, since the Mississippi is so low from the early melt and the drought in the tributaries in the northern states and central plains states, the storm surge is going to screw up the fresh water environment.

there was already a salt water wedge moving upstream in the Mississippi just due to normal high tides, and that was over a week ago.

A really high storm surge with this track might push salt water all the way back up to Baton Rouge, or maybe at least half way there, since the river level is only like 4 feet at Baton Rouge last I heard...


Anyway, with this kind of forward speed we are going to see very wide spread 10 inch or greater totals, I think.
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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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