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 wxchaser97:

Right now I've just been stumped on Isaac. I decide to join WU this year and this is what I have to track/ forecast.


Yea i had a year to "work out the problems" your sharkbait
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Quoting nigel20:
Good night/morning fellow bloggers!

Good morning Nigel. Isaac has been a "fun/interesting" storm to look at over the past few days.
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Quoting xtremeweathertracker:


Idiocy.....hmmmm....Wow!! Just discussing the weather thats all!! I have seen some idiocy on this blog...I didnt think Orca or I were on the verge of idiocy! He was just pointing out long term motion where as i was refering to a short term jog! LOL


im quitegrumpy
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Quoting weatherh98:


but its done the best lol

Strangely, I've seen everything with Isaac.
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Nobody should be called a wish, west, doom, zoom caster here.....y'all have good opinions and give out valuable info with out the commercials...if i wanted bs i'd watch TWC..keep up the good work.....long time lurker

thanks again
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It looks like NCEP's run got slowed down during the 48hr products and then that has precipitated in later products. This seems like it might be a bit of a problem for this run especially since the amount of time it's taking for the next data set (84-120hrs) is now 1 to 2 hours late...

I suspect this run is going to be either very very late or terminated, better wait for the 06Z data if you're sleepy.
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Quoting wxchaser97:

XTRP is not a model, its just an extrapolation of the current heading.


but its done the best lol
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Quoting xtremeweathertracker:


Thanks, but i was refering to the latest fixes from the current mission!! I understand the overall general motion!!


What i was trying to tell you is you cannot use two fixes... you have to use at least three. If you used only two... your not telling anyone anything... you just sound like a wishcaster.

Using your theory.. two of those fixes would have had it going to Mobile earlier. If your going to post something base it on a valid point or supporting data.
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting weatherh98:



It will steadily deepen through landfall, because the pressure could get as low as 970

the fact that the nhc cant find high winds is perplexing

Right now I've just been stumped on Isaac. I decide to join WU this year and this is what I have to track/ forecast.
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Quoting weatherh98:
This is idiocyand nitpicking

its all based on perspective. if you wanna look at 2 center fixes fine if you wanna make it 5 thats great too. you are both right according to perspectivepersonally the storm is making a few hundred s curves


Idiocy.....hmmmm....Wow!! Just discussing the weather thats all!! I have seen some idiocy on this blog...I didnt think Orca or I were on the verge of idiocy! He was just pointing out long term motion where as i was refering to a short term jog! LOL
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Quoting Terradad:
I think the XTRP model has performed the best over the last several days.


It has exhibited amazing continuity, at least....



damn right

if theres an eye in landfall, ill see it with this track

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2093. nigel20
Good night/morning fellow bloggers!
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2092. sar2401
Quoting stormchaser19:
This is the most stressful Season that i've seen


Certainly one of the most confounding. It looks like some models really need some serious work done if they are to deal with large, weak storms better.
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Sitting here in West Monroe, LA and "frustrated" is an understatement. We are now lying just west of the line track. We are in desperate need of rain. My family is from Little Rock. They need even more than us.
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Quoting Terradad:
I think the XTRP model has performed the best over the last several days.


It has exhibited amazing continuity, at least....


XTRP is not a model, its just an extrapolation of the current heading.
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Quoting sar2401:


I think it dropped around 10 millibars yesterday also. I expect that he will finally make cat 1 status at 0200...and that's as far as he gets.



It will steadily deepen through landfall, because the pressure could get as low as 970

the fact that the nhc cant find high winds is perplexing
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Much better consensus tonight then in recent days.

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Quoting RTSplayer:


I'm already using that site, and it's not updating.


The 00Z GFS run is stalled.
Link
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2085. EvilGN
Quoting Terradad:



Things are looking better now than they were earlier today.

Even a small shift east can greatly benefit NOLA. And there has been no intensification so far (for like the last 5 days or so...)


I agree, the past 6 hours have been a slight relief for us, and knowing that between cuba and right now, it hasn't gained an ounce of strength, and FYI I am an avid WX type, I taught aviation WX for the Navy for almost 6 years, and have been watching Canes since Georges (my first)
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Quoting sar2401:


Best site around:
http://www.americanwx.com/raleighwx/models.html


I'm already using that site, and it's not updating.
Member Since: January 25, 2012 Posts: 33 Comments: 1520
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I think the XTRP model has performed the best over the last several days.


It has exhibited amazing continuity, at least....

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2081. salgrl
Long time lurker here and live in the Mobile, AL. area. Not liking what i'm seeing on here or what i've seen on TV about the surge around here. Just how far west would this thing have to go for it NOT to give us that kind of surge ? The winds wouldn't bother me so much. Someone pls give me a clue !!! TIA
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This is idiocyand nitpicking

its all based on perspective. if you wanna look at 2 center fixes fine if you wanna make it 5 thats great too. you are both right according to perspectivepersonally the storm is making a few hundred s curves
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2078. sar2401
Quoting TexNowNM:



I'm really concerned they got him banned.


Why do you think "they" got Taz banned?
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000
URNT12 KNHC 280515
VORTEX DATA MESSAGE AL092012
A. 28/04:26:50Z
B. 27 deg 17 min N
087 deg 27 min W

C. 850 mb 1253 m
D. 52 kt
E. 065 deg 25 nm
F. 137 deg 60 kt
G. 063 deg 30 nm
H. 979 mb
I. 18 C / 1514 m
J. 22 C / 1519 m
K. 19 C / NA
L. OPEN SW
M. C40

N. 12345 / 08
O. 0.02 / 1 nm
P. AF309 2909A ISAAC OB 10
MAX FL WIND 70 KT E QUAD 03:39:00Z
MAX OUTBOUND FL WIND 62 KT SW QUAD 04:54:00Z
Member Since: September 24, 2005 Posts: 33 Comments: 9265
Quoting Orcasystems:




Thanks, but i was refering to the latest fixes from the current mission!! I understand the overall general motion!!
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2075. sar2401
Quoting weatherh98:


Its dropped about 10 millibars today, it is intensifying, expect upgrades soon


I think it dropped around 10 millibars yesterday also. I expect that he will finally make cat 1 status at 0200...and that's as far as he gets.
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2074. JLPR2
Possible future 98L taking shape south of the CV islands.

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Quoting weatherh98:

Wheres taz when you need him



I'm really concerned they got him banned.
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This is the most stressful Season that i've seen
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Quoting RTSplayer:
Does anyone have a link to a site hosting the actual graphical outputs from the 0z GFDL and HWRF?!

The site I was using has not updated anything.


GFS is having a hard time this evening getting past 54 hours for some reason. The official status isn't much help either. But apparently it's late, very late.
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Quoting AussieStorm:

It's probably due to Isaac being so lopsided. making the centre move around so much.


Agreed :)
Member Since: October 1, 2007 Posts: 81 Comments: 26511
Quoting xtremeweathertracker:



Although i couldnt get it to save the text box that line heading is 292 degrees...take it or leave it!!
img src="Photobucket">




Click on image to enlarge
Member Since: October 1, 2007 Posts: 81 Comments: 26511
2068. sar2401
Quoting RTSplayer:
Does anyone have a link to a site hosting the actual graphical outputs from the 0z GFDL and HWRF?!

The site I was using has not updated anything.


Best site around:
http://www.americanwx.com/raleighwx/models.html
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Quoting Terradad:



Things are looking better now than they were earlier today.

Even a small shift east can greatly benefit NOLA. And there has been no intensification so far (for like the last 5 days or so...)


Its dropped about 10 millibars today, it is intensifying, expect upgrades soon
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Nite, geeks! ;) Y'all try and keep the door closed, will ya? ;P
Member Since: July 9, 2006 Posts: 184 Comments: 29594
Quoting jake436:
Give up. Obvious westcaster is obvious.

who is west-casting. I am just going on the centre fixes.
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Quoting xtremeweathertracker:



Although i couldnt get it to save the text box that line heading is 292 degrees...take it or leave it!!
img src="Photobucket">


The red line is the center's track from mission 28 & 29(in progress)Also recon finding 60-70mph about 100 miles from the center. They are in the SW quadrant but rain rates are pretty high.

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Sitting on a offshore supply vessel just outside of galveston waoiting on isaac to pass, right now very flat seas relatively no wind... Do not expect this to last, but nice at the moment
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Quoting sar2401:


Kind of looks like a chicken embryo now. :) I really think he's still sliding west and will make landfall somewhere around the LA/TX border. Isaac has been the most contrary storm I've seen in 50 years of tracking tropical systems.


Gonna bring up Lee again but...

I remember when we were all nitpicking the track of Lee, it would jog to the left and all of the HGXers would start flipping out. Then it would jog to the right, and all of NOLA would start flipping out.

And then when it finally made landfall, the state of Texas burst into flame. Whoosh.

Contrary these badly-made storms with poor steering are and contrary these badly-made storms will be.
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What a bizarre storm. Highest SFMR winds so far on this recon pass are being reported 120 miles SW of the centre!
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Quoting EvilGN:
Long time lurker here, have posted once or twice, was around for Ivan/Dennis in pcola, now live in new orleans, SE algiers area.
Unfortunately we left NOLA 9 days ago on vacation and are now stuck in the midwest. Its been a mind numbing couple of days wondering how/if/when/what we are coming home too, even a bad rain event will cause minor flooding in our house. (happened a couple weeks ago)
So far we have had some relief in seeing the lack of development, and I am wishcasting that to continue, please let that dry air disrupt things! All I can do now is sit and wait to see how things turn out in our part of town, and hope we can get home soon, and hope we have power and water when that happens. Hope everyone in the area is ready for the worst just in case though. Will be glued to the WC and this site for the next 48hrs obviously :P



Things are looking better now than they were earlier today.

Even a small shift east can greatly benefit NOLA. And there has been no intensification so far (for like the last 5 days or so...)
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2059. sar2401
Quoting Whoduguru:
Isaac is a tired old dog.....someone put him out of his misery
Unfortunately Arkansas aint gettin any rain


At least it looks like we're not going to have the multiple names we had with Ernesto. :)
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Quoting Orcasystems:


The average course over the last 7 vortex reports is 312... almost bang on the projected course plus or minus (east or west) 10 miles.


That may very well be true...my point was that the latest fix compared to the previous fix is exactly 32 miles apart at a heading of 292 degrees!!
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Quoting Orcasystems:


The average course over the last 7 vortex reports is 312... almost bang on the projected course plus or minus (east or west) 10 miles.

It's probably due to Isaac being so lopsided. making the centre move around so much.
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Does anyone have a link to a site hosting the actual graphical outputs from the 0z GFDL and HWRF?!

The site I was using has not updated anything.
Member Since: January 25, 2012 Posts: 33 Comments: 1520
2055. jake436
Quoting Orcasystems:


The average course over the last 7 vortex reports is 312... almost bang on the projected course plus or minus (east or west) 10 miles.
Give up. Obvious westcaster is obvious.
Member Since: August 31, 2006 Posts: 0 Comments: 271
Quoting weatherh98:


Lets look shall we...



its growing
]

In the morning, I meant.
Member Since: June 16, 2006 Posts: 0 Comments: 1560

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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.