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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1604. dader
Does anyone know how to decipher Joe Bastardi's "power scale" for cyclones? This guy is a complete lunkhead- no wonder he only appears on Fox Business News.
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Quoting Orcasystems:


You guys are going to start confusing me again with this one word stuff again... like you did with "word" last year... I am to old for that stuff.


{{ORCA}}!!..lol

Will and I have been friends since I joined in '06..lots of fun times!
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Quoting greene47:


I was agreeing with you...have you never heard the statement "some people's kids"?..not dismissive towards you but towards Issac's inability to get it's act together..In other words..Issac is that kid that doesn't behave...all over the place..and not conforming


Ah, I understand now. Just not used to thinking of cyclones as wayward children. Although it's not a terrible way to anthropomorphize Isaac. Just hoping he doesn't throw a tantrum when he gets to shore.
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Quoting jake436:
Guys, Taz has been Taz here since long before I joined the blog. It used to drive me nuts too, but you get used to it. He's the resident...er...Taz. Take it with a grain of salt.


right. like the little Tazmanian Devil. just picture that whenever you read his posts. he's fun
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1600. txjac
Quoting chicagowatcher:

ditto the ditto, of course.

Good gravy, an old building (Grand Palace) in nola on canal street that was imploded some time ago is now a massive pile of rubble and sheet metal that some are concerned may become airborne tomorrow...


Yikes ...thats not good
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Quoting JeffM:
Isaac has easily overtaken Ernesto as the most annoying "storm" of 2012.
Certainly the most deadly one, with 22 death , 19 in Haiti, 2 in Dominican Republic and one in Puerto Rico...
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Quoting fldude99:


The blog moves so fast it's hard to find a single post
Just put him on ignore if he's that annoying to you. It really does make things smoother all around. Despite the fact that he makes interesting observations I've had him on ignore a few times in the past. I suspect people do at some point or other.

I have a hard time parsing what he writes and when he posts a lot, goes off on a tangent or does the whole "blog cop" shtick .... But like someone mentioned he has his moments of contribution and insight.

At first I assumed his communication style was due to a learning or physical disability until someone mentioned that it's due to English not being his native language. It could be all three for all I know but his intent doesn't seem to be to hurt anyone and the weather seems to be his life.
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If you don't like Taz, just put him on ignore

Also, it will shorten the blog by about 15%, which can come in handy sometimes when you are trying to get caught up on things.

Of course I love Taz, as do most who have been here a while.
Member Since: December 21, 2009 Posts: 0 Comments: 93
Quoting AllyBama:


{{WILL}}!!!!


You guys are going to start confusing me again with this one word stuff again... like you did with "word" last year... I am to old for that stuff.
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Quoting txjac:


This what chicago? lol ...

ditto the ditto, of course.

Good gravy, an old building (Grand Palace) in nola on canal street that was imploded some time ago is now a massive pile of rubble and sheet metal that some are concerned may become airborne tomorrow...
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Amen!
Quoting AllyBama:


maybe you should do the same!
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Quoting CloudGatherer:
What's with the dismissive comment? I'm hardly the only poster here who's been finding Isaac maddeningly difficult to comprehend. If you'd like to add your thoughts, please do - but I'm not really sure what your post adds to the conversation.


I was agreeing with you...have you never heard the statement "some people's kids"?..not dismissive towards you but towards Issac's inability to get it's act together..In other words..Issac is that kid that doesn't behave...all over the place..and not conforming
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Chill out - he is a good soul. Let him be!
Quoting fldude99:


That's no excuse. He needs to find another place to spew his hateful, or at best ignorant garbage
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Quoting fldude99:


That's no excuse. He needs to find another place to spew his hateful, or at best ignorant garbage


maybe you should do the same!
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Quoting will40:
Rita Taz knows more about the weather than you will ever comprehend


That's what I was trying to say........
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1589. will40
Quoting AllyBama:


{{WILL}}!!!!


!!!!! ALLY!!!!!!
Member Since: September 19, 2005 Posts: 2 Comments: 4225
Dr. Neil Frank says he wants to know what/why the NHC has not called this a hurricane. that it should be as many people are not taking te storm seriously because they wont upgrade issac
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Quoting will40:
Rita Taz knows more about the weather than you will ever comprehend


{{WILL}}!!!!
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1586. JeffM
Isaac has easily overtaken Ernesto as the most annoying "storm" of 2012.
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Quoting greene47:



SMH....some people's kids
What's with the dismissive comment? I'm hardly the only poster here who's been finding Isaac maddeningly difficult to comprehend. If you'd like to add your thoughts, please do - but I'm not really sure what your post adds to the conversation.
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1584. snotly
What did they get wrong? Was it the ULL to the SW that got dragged into the circulation? Made Isaac cough up a lung.
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1583. txjac
Quoting chicagowatcher:

this


This what chicago? lol ...
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This storm has been weird on so many levels.
Member Since: March 16, 2012 Posts: 127 Comments: 7942
Quoting Beachfoxx:
Agreed... Taz is part of WU. Accept him and his love of weather. He's been a friend to many and a special part of WU for many years. We love & support the TAZ!


Ditto Beachfoxx!
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Quoting fldude99:


That's no excuse. He needs to find another place to spew his hateful, or at best ignorant garbage


Hey check WU mail Please!!
Member Since: May 31, 2011 Posts: 57 Comments: 571
Quoting Orcasystems:


Ditto... what she said :)

this
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1578. will40
Rita Taz knows more about the weather than you will ever comprehend
Member Since: September 19, 2005 Posts: 2 Comments: 4225
Quoting Beachfoxx:
Agreed... Taz is part of WU. Accept him and his love of weather. He's been a friend to many and a special part of WU for many years. We love & support the TAZ!


Ditto... what she said :)
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Quoting CloudGatherer:
So...two new Vortex messages.

The Air Force reports an eye that it's open in the south, (The south? That's what it says) and circular, with a diameter of 28nm. Pressure is at 979mb, confirmed by dropsonde. It also continues to find a very sharp temperature gradient (16/22 degrees) but maddeningly, only 50kt surface winds. Isaac's a tough storm to figure out.

NOAA, flying at 10k feet, finds a poorly defined eye, a lower gradient (12/15) and 980mb of pressure.

Go figure. Strangest tropical storm I've ever seen.

Quoting CloudGatherer:
So...two new Vortex messages.

The Air Force reports an eye that it's open in the south, (The south? That's what it says) and circular, with a diameter of 28nm. Pressure is at 979mb, confirmed by dropsonde. It also continues to find a very sharp temperature gradient (16/22 degrees) but maddeningly, only 50kt surface winds. Isaac's a tough storm to figure out.

NOAA, flying at 10k feet, finds a poorly defined eye, a lower gradient (12/15) and 980mb of pressure.

Go figure. Strangest tropical storm I've ever seen.




SMH....some people's kids
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Oh my! Those goats! O just loved them!
Quoting EcoLogic:

Ferral goat southern end of Aruba
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1572. FOREX
Quoting greene47:
Question...Did the blob on the peninsula officially break away, of is it still considered part of Issac?


distant cousin.
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So...two new Vortex messages.

The Air Force reports an eye that it's open in the south, (The south? That's what it says) and circular, with a diameter of 28nm. Pressure is at 979mb, confirmed by dropsonde. It also continues to find a very sharp temperature gradient (16/22 degrees) but maddeningly, only 50kt surface winds. Isaac's a tough storm to figure out.

NOAA, flying at 10k feet, finds a poorly defined eye, a lower gradient (12/15) and 980mb of pressure.

Go figure. Strangest tropical storm I've ever seen.

Member Since: Posts: Comments:
Quoting Beachfoxx:
Agreed... Taz is part of WU. Accept him and his love of weather. He's been a friend to many and a special part of WU for many years. We love & support the TAZ!



Yeah, DON'T mess with TAZ! :)
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1569. FOREX
Quoting WeatherNerdPR:

Maybe then we'll have a cat 1! A 960mb 75mph cat 1!


Joe Bastardi predicting intensification once it moves inland.
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Quoting RitaEvac:
flag Taz's post, he'll be perma-banned for good, and never be back.


Obviously the blog is losing interest in this storm if a Taz post is the most dramatic thing going on...

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Agreed... Taz is part of WU. Accept him and his love of weather. He's been a friend to many and a special part of WU for many years. We love & support the TAZ!
Quoting jake436:
Guys, Taz has been Taz here since long before I joined the blog. It used to drive me nuts too, but you get used to it. He's the resident...er...Taz. Take it with a grain of salt.
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Quoting AussieStorm:
Carriere, Mississippi is going to get 16.92".



Isaac will be known as a rain maker and not for his wind .

ick, thats where i am. guess i need to get my boat out. :)
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Good Evening..Central LA here. We are prepared...prepare for the worst and hope for the best...All loose objects brought inside, got non-perishable foods,dog food, LOTS of water, batteries, flashlights, etc...I guess you CAN SAY....WE are ready!!!! :)
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In the WV Loops, Isaac seems stationary?? ...or slight Jog to the W (could be a convective blob..)

Link
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1563. jake436
Quoting Stormbugn:
t

I believe he was joking and BECAUSE of his illiteracy we lose the intent behind his attempt at sarcasm. However, he tries which is more than many of us "lurkers" do. I have only recently started posting. I also mentor mentally challenged people. I do not feel that we have the right to ask them to permabann him. If someone explains to him how offensive that post was, I am sure he would apologize for it. I live in MS close to the coast and expect major damage and flooding. But I don't hold his words against him. Some will because they find him annoying but it seems this blog is his life.
Warrants repeating.
Member Since: August 31, 2006 Posts: 0 Comments: 271

Isaac in Upstate NY...Kirk north of Hispaniola...Irene's path
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Tropical storm Leslie of 2000 had a low pressure of 973mb with Max's winds of 70 mph
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Question...Did the blob on the peninsula officially break away, of is it still considered part of Issac?
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Winds at several offshore stations 40-50 kts and some are a good distance North west of Isaac.
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Quoting fldude99:


I've noticed that people on this blog give this guy a pass, in spite of his illiteracy and idiocy..my question is why. This kind of comment shows no respect for those that have to live with these storms in real life
t

I believe he was joking and BECAUSE of his illiteracy we lose the intent behind his attempt at sarcasm. However, he tries which is more than many of us "lurkers" do. I have only recently started posting. I also mentor mentally challenged people. I do not feel that we have the right to ask them to permabann him. If someone explains to him how offensive that post was, I am sure he would apologize for it. I live in MS close to the coast and expect major damage and flooding. But I don't hold his words against him. Some will because they find him annoying but it seems this blog is his life.
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1557. txjac
Quoting EcoLogic:

Ferral goat southern end of Aruba


It's cute!
Thanks for responding
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TomballTXPride and RitaEvac check your WU Mail Please!!
Member Since: May 31, 2011 Posts: 57 Comments: 571
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Quoting Stormchaser121:

Ensembles saying....west again?? what on earth is this storm gonna do.


He won't go back east. IMO, the landfall threshold now moves to a less likelihood of Mobile and is a bit further west. Just for saying sakes it takes a really strong storm to push up against 1016mb. Isaac has squeezed every inch it can up against 1012mb. See the SFC MAP - 1012mb is wrapped totally, almost in a circle around the storm, and it's still having trouble getting northwards, hence the slowed motion to 10 mph. Even if it strengthens a bit (and should, despite the dry air) it's still going to have a tough time getting ashore unless that shortwave trough trailing now over eTX further erodes the western periphery of the eConus ridge.

With Isaac's dry air/subsidence troubles on the northeast side he's only going to gradually strengthen having missed the warmer neast corner of the loop eddy. There's still a fair channel of warm water that runs swest to neast that should allow for some strengthening, but now I'm not thinking it'll be overly significant. We can't forget Humberto, but he was also much closer to shore (if I remember correctly), so there's still room, time for intensification; but, a 3 is likely not in the cards at this point.

Earlier I mentioned that this "stall" was beginning to concern me, having mentioned it yesterday too. If the plains high squeezes the swave trough and it lifts out to the neast or gets more lateral, we're looking at the makings of a blocking high northwards. Isaac could actually make landfall where it would eventually spin down, OR it could move back over open waters again. Not much chance of this I know, models probably not suggesting either, but I think it's possible. Call me crazy! ;)

Weaker is west, stronger is wnw, nw and then almost due north. Current motion at nw at 10 mph means Isaac is trying to escape, pushing as hard as he can, but he can't get there, so he'll creep westwards slowly, trying to put on some more armor and get poleward.

The circulation is too strong. And, he's trying harder to get symmetrical and vertical. Earlier this evening the MLC had broadened with the llc more intense for a change. The levels are getting symmetrical now, but the mlc and upwards are still a bit linear southwards. If that improves he'll be able to close off that neastern side and grow an eyewall. Lots of ifs!!!! ;P

With that vigorous a circulation and with no upwelling with slowing or stalling, I'm fairly confident Isaac will get to cane status and maybe to a low 2. He's going to slow even further, look for 5/6 mph at the next update or the next one.

The key bit here is still going to be surge (underestimated imo) and Isaac's strength to push poleward. A weaker, leveled off intensity storm will either weaken more and move further west, or it'll pop more northwards at the slightest bit of weakness that the shortwave trough may give it.

....slow, slow, slow deal developing
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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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