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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If Isaac is not a Hurricane in the morning I really doubt it will ever reach that sataus before landfall.
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Last 3 fixes show isaac moving at a heading of 290 degrees or west-northwest!
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04:26:00Z
27.300N 87.400W
844.2 mb (~ 24.93 inHg)
1,311 meters (~ 4,301 feet)
979.4 mb (~ 28.92 inHg)

No change yet pending dropsonde data.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting Skyepony:


No need if you're okay with some tropical storm winds (60% chance for Pensacola) & 8-10" of rain.


Meh - we had 15" with a lot of flooding a few months back, and had a line of thunderstorms through here recently that clocked north of 80MPH winds. It's been doing nothing but raining here for the past month, almost every day. The past couple of days of sunshine and no rain have been very pleasurable.
Member Since: March 9, 2012 Posts: 0 Comments: 150
Quoting will40:


wow i guess that stuff FLA got went off to the east
Yeah it got pulled into the trough off the East Coast it was a surface convergence line that set up from the high pressure to the east and Isaac to the west.
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Who was that guy either in 2004-5 or 2007-8 that had those rose colored glasses and his own blog, had some type of time with Coast Guard I think...and would quickly introduce himself to all new females?

Forget his name....Would normally post a list of definitions for all newbies, and give a morning update?



Sorry if someone answered...StormW I believe...
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Pressure looks to still be 979mb
Extrap. Sfc. Press: 979.6 mb (~ 28.93 inHg)
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Quoting Beachfoxx:
1895. moonlightcowboy 11:22 PM CDT on August 27, 2012

You see that dry air to my south and eas - keep it coming my way so I can get some rest!

So good to see so many old friends! Stay safe - the anticipation, watching & waiting for Issac to pound on my door has deprived me of much needed beauty sleep!
I'm crashing.....

Night all!


Get some rest Beachfoxx, and great to see ya :)
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Time: 04:19:00Z
Coordinates: 27.4667N 87.0333W
Acft. Static Air Press: 842.9 mb (~ 24.89 inHg)
Acft. Geopotential Hgt: 1,378 meters (~ 4,521 feet)
Extrap. Sfc. Press: 987.4 mb (~ 29.16 inHg)
D-value: -
Flt. Lvl. Wind (30s): From 141° at 54 knots (From the SE at ~ 62.1 mph)
Air Temp: 18.0°C (~ 64.4°F)
Dew Pt: 15.5°C (~ 59.9°F)
Peak (10s) Flt. Lvl. Wind: 56 knots (~ 64.4 mph)
SFMR Peak (10s) Sfc. Wind: 52 knots (~ 59.8 mph)

Its trying
Member Since: October 1, 2007 Posts: 81 Comments: 26511
1944. will40
Quoting AllyBama:
Good night Beachfoxx!

Will, we have had no rain today - just some breeze and LOTS of sunshine - was beautiful!


wow i guess that stuff FLA got went off to the east
Member Since: September 19, 2005 Posts: 2 Comments: 4251
Been two hours since the last VDM. It will be interesting to see if the pressure has fallen.
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Okay, this is interesting.
Hurricane Gert (1999)
70 mph 110 kph 964 mb Tropical Storm
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Good night Beachfoxx!

Will, we have had no rain today - just some breeze and LOTS of sunshine - was beautiful!
Member Since: August 3, 2006 Posts: 132 Comments: 20635
Quoting will40:


yes the site i use quit sending images
Ok because I tried both Allan Huffman and NCEP and it stops at 54 hrs.
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1939. tkeith
Quoting CosmicEvents:
Before I put my foot in my mouth...I hear the bed calling. Good night all.
peppermint flavoured Dr. Shoals should do the trick...
Member Since: November 1, 2004 Posts: 25 Comments: 8936
Quoting atmosweather:


A little thing that made it more scary was...the old satellite blackout used to start at 11:45PM eastern and end at 2:15AM, and when Katrina completed its eyewall replacement cycle, it was during the exact blackout time, so the last image before blackout showed sprialing strong convection with no eye, and the 1st one out of the break showed a complete monster hurricane with the clearest roundest eye possible.
Yep, that was an "oh crap" moment... stupid sat blackouts
Member Since: August 28, 2005 Posts: 0 Comments: 153
weather near Asheville NC - clear and calm. No lunar halo at all, no clouds.


2 days ago we were forecast to get 6 inches or more of rain over the next few days.


My, how times have changed....
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1936. dipchip
Seems to me Isaac is going to slide along the South shore of La. and go into Cameron south of Lake Charles La.
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Quoting GTcooliebai:
Anyone else having problems running the GFS past 54 hrs.?

Mine hasn't updated past 54hrs for a while now.
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1933. zillaTX
Looks like just more hot dry air for Texas.. I hope everyone else east is well prepared!
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1932. tkeith
Quoting nola70119:
Starting to get tropical clouds streaming in low from the south here.....breeze is definitely picking up, too.
yes...
Member Since: November 1, 2004 Posts: 25 Comments: 8936
Quoting Beachfoxx:
1895. moonlightcowboy 11:22 PM CDT on August 27, 2012

You see that dry air to my south and eas - keep it coming my way so I can get some rest!

So good to see so many old friends! Stay safe - the anticipation, watching & waiting for Issac to pound on my door has deprived me of much needed beauty sleep!
I'm crashing.....

Night all!


Nite, sweets! ;)
Member Since: July 9, 2006 Posts: 184 Comments: 29610
Quoting vis0:
IMAGES of Issac make it look Extratropical ...sure its scientifically incorrect & impossible but makes a great news headline; nor'easter hits the gulf then blame it on slippey oil blended at 75degrees.



They could start a new concept called sout'easter.
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1929. cjnew
Quoting atmosweather:


A little thing that made it more scary was...the old satellite blackout used to start at 11:45PM eastern and end at 2:15AM, and when Katrina completed its eyewall replacement cycle, it was during the exact blackout time, so the last image before blackout showed sprialing strong convection with no eye, and the 1st one out of the break showed a complete monster hurricane with the clearest roundest eye possible.


I was wondering about the blackout the other night.It was awful.
But it doesn't happen anymore?
Member Since: July 22, 2005 Posts: 84 Comments: 2779
Looking good in the last frames....

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Before I put my foot in my mouth...I hear the bed calling. Good night all.
Member Since: August 3, 2005 Posts: 10 Comments: 5622
1926. jake436
Quoting nolarocks:


Hi all,

I've been a long time lurker and have always appreciated this site for its content. It really is my go to site for tropical weather.

The reason I wanted to write was to address what I feel are some common misconceptions. Am I an expert? No. But, being a lifelong resident of NOLA, I've seen some pretty ridiculous engineering ideas for combating flooding, particularly in Orleans Parish.

To be brief, Orleans Parish allows the lake to meander its way deep into the city at multiple locations with pumping stations at the termini of "outflow canals." These canals hold water at the same level as the lake and have historically been lined with small levees - the Army COE/Orleans Parish modified these levees with walls that were driven down on top of them. (I remember driving by the newly constructed walls and asking my wife if they were simply decorative since they had no buttressing, and thus, no obvious sign of being a retention wall).

Jefferson Parish, on the other hand, is situated exactly the same way as Orleans Parish with Lake Pontchartrain on its north side. Jefferson Parish does not allow the lake to intrude into its limits - it has pumping stations at the lake, which serve as damns/dikes (so to speak), and pump water that is collected in a network of canals throughout the Parish. There are no levees along these canals within the Parish nor along the canals that lead directly to the pumping stations.

The large levees, which most think of when the term is used, did not fail during Katrina. Yes, there was overtopping in locations, but the levees by large DID NOT FAIL. The flood walls protecting inland waterways connected directly to the lake did!! These flood walls were obviously not designed to hold back high water levels to even untrained eyes.

Orleans Parish has installed "temporary" pumps analogous to the locations of the pumping stations in Jefferson Parish. Yet, the stupidity persists in Orleans which relies on "outflow canals" to carry water that is pumped from stations miles inland.

We have perfect examples of how to protect ourselves using the Jefferson Parish model vs. how not to do it using the Orleans Parish system.

Don't allow the water in side the city limits in the first place!!!

Remember, Katrina's devastation was the result of flood wall failure (NOT levee failure!!) which is evidenced by Jefferson's relatively successful outcome post-Katrina - despite Jefferson Parish turning their pumps off during the storm!!

I certainly do not intend to be preachy - I simply want to clarify for those who want to know the difference, since many are completely unaware of the 2 systems sitting side by side with very very different approaches and successes/failures.

Thanks for your patience,

NOLARocks
BINGO!!!!! Thank you for preachin'!!! That's 100% correct!
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1925. will40
Quoting AllyBama:
Good night Kman...

Will - I can concur - I am close to odingslightning and no rain here..but the wind is nice! - helps blow the skeeters away!..lol


may just be me but that sounds weird that there is no rain there i guess you got it earlier today?
Member Since: September 19, 2005 Posts: 2 Comments: 4251
Starting to get tropical clouds streaming in low from the south here.....breeze is definitely picking up, too.
Member Since: June 16, 2006 Posts: 0 Comments: 1565
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1922. acl8610
Quoting WXGulfBreeze:


Hard to believe it took a "forced retirement" to finally get me off my butt and make the permanent move. The only thing I miss is close proximity to my kids (kids, heh, 32 and 25).

oddly and opposite enough for me, i decided to transfer schools and my family is following me from ohio. so far my parents are about to retire in cape coral, my sister is taking up a job in orlando, and younger brother is about to begin college next year in florida... that leaves only one sibling left up north now and i suspect that she will be down here too once shes done with college in pittsbugh
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1921. Skyepony (Mod)
Quoting gulfcoastmom:
So from the way I understand things those of us east of Pensacola can relax and not need to vacate these mobile homes? yes? No?


No need if you're okay with some tropical storm winds (60% chance for Pensacola), 3-7' surge & 8-10" of rain.
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Quoting wxchaser97:

I'll try to spare ya but no promises. I'm a crazy TS right now with a really low 979mb pressure but only 70mph winds. That surge+heavy rain/flooding will be very bad.


As we saw in Irene, a system with a large wind field will typically have lower winds even with low pressures. But in all reality 979mb is about on part for a strong tropical storm, anyway. I don't see the storm surge being very bad unless the maximum sustained winds increase. Even with the large wind field I think the most you would see with the current strength is a Category 1 style storm surge. Really the biggest factor with this cyclone, barring any rapid strengthening, will be the rain.
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Quoting louisianaweatherguy:
ya know on this night seven years ago, we went to bed with a pretty decent hurricane Katrina turning in the gulf, BUT the next mornin... was when we woke up to a monster (175 mph winds)... not saying Isaac is exploding into major hurricane, but I think Isaac is getting ready to explode into at least an 80+mph hurricane... satellite imagery has improved dramatically over the last 3 hours.... have a feeling the morning will bring us a little surprise... :)


I am in Belle Chasse. I was thinking the same thing... Where are you and are you staying????
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1895. moonlightcowboy 11:22 PM CDT on August 27, 2012

You see that dry air to my south and eas - keep it coming my way so I can get some rest!

So good to see so many old friends! Stay safe - the anticipation, watching & waiting for Issac to pound on my door has deprived me of much needed beauty sleep!
I'm crashing.....

Night all!
Member Since: July 10, 2005 Posts: 157 Comments: 29384
Quoting TxIkeJoe:
Dry air......has this years drought cause more ULL s. with so much dry air?
Can you even imagine what this storm would be like if the dry air wasn't there....


Interesting theory. Isaac has been sucking dry air since he rolled out of Africa, but he's still hanging out like the guest that won't go home when everyone else has left the party.
Member Since: March 9, 2012 Posts: 0 Comments: 150
Good night Kman...

Will - I can concur - I am close to odingslightning and no rain here..but the wind is nice! - helps blow the skeeters away!..lol
Member Since: August 3, 2006 Posts: 132 Comments: 20635
1915. will40
Quoting GTcooliebai:
Anyone else having problems running the GFS past 54 hrs.?


yes the site i use quit sending images
Member Since: September 19, 2005 Posts: 2 Comments: 4251
Anyone else having problems running the GFS past 54 hrs.?
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1913. will40
Quoting tomas5tex:
Not sure if the name is right but what happen to Weather456


he left to spend more time with Family i think
Member Since: September 19, 2005 Posts: 2 Comments: 4251
1912. drs2008
In biloxi,we will all have PTSD,from this storm.
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From LSU Earth Scan Laboratory. It's a little slow to load.
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The alleged eye-wall will be rotating into NOLA radar view soon.

I can see a piece of it, I think, from Tallahassee Radar, but Mobile and Nola are still out of range, since the moved the NOLA radar to Slidell.

Still, you can see some faint outlines of the suspected eye-wall approaching.
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Quoting Beachfoxx:
Nothing here either (Destin area) hot humid, no breeze, in fact still air... all most freaky!


Schooners Sunset Cam is showing more wind and wave action
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting louisianaweatherguy:
ya know on this night seven years ago, we went to bed with a pretty decent hurricane Katrina turning in the gulf, BUT the next mornin... was when we woke up to a monster (175 mph winds)... not saying Isaac is exploding into major hurricane, but I think Isaac is getting ready to explode into at least an 80+mph hurricane... satellite imagery has improved dramatically over the last 3 hours.... have a feeling the morning will bring us a little surprise... :)


A little thing that made it more scary was...the old satellite blackout used to start at 11:45PM eastern and end at 2:15AM, and when Katrina completed its eyewall replacement cycle, it was during the exact blackout time, so the last image before blackout showed sprialing strong convection with no eye, and the 1st one out of the break showed a complete monster hurricane with the clearest roundest eye possible.
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting acl8610:

know the feeling... youngstown, oh to port orange, fl in 2010


Hard to believe it took a "forced retirement" to finally get me off my butt and make the permanent move. The only thing I miss is close proximity to my kids (kids, heh, 32 and 25).
Member Since: March 9, 2012 Posts: 0 Comments: 150
Quoting weatherh98:


9-12 feet for me!

I'll try to spare ya but no promises. I'm a crazy TS right now with a really low 979mb pressure but only 70mph winds. That surge+heavy rain/flooding will be very bad.
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Not sure if the name is right but what happen to Weather456
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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.