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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1754. will40
Quoting moonlightcowboy:



Atmos, my answer would be this to the dilemma, and a question. First the question. When a dropsonde is dropped into the eye is pressure measured at the sfc or the mid-levels, or all along the way? If it's at the sfc, then Isaac's llc has been really intense today, more so than at any other time I've noticed according to vorticity charts and observations.

The MLC has been the dominant, broad circ throughout his life, and the smaller llc, trying as it may now, is having an awfully tough time trying to spin that broad mid-level circulation.

May be a bad question, but it's one I've never considered before now. TIA, friend.


i think it is measured all along the way
Member Since: September 19, 2005 Posts: 2 Comments: 4266
Cue the shower curtains... jesting.. please don't.
Member Since: October 1, 2007 Posts: 81 Comments: 26516
1752. GPTGUY
They just did a story and interviewed cyclone oz on the local tv station here in biloxi
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1751. IMA
Quoting LurkyMcLurkerson:
Yeah, I want to skin him some days, but it's not like it makes him the devil (just don't ask me to say that after he's eaten _another_ pair of shoes, because then I'm pretty sure I'll call him worse.)


Taz has been eating your shoes??

Uh, oh. The warm feelings I'm getting from seeing so much of the ol' gang is making me silly -- either that or the muscle relaxers & pain pills
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1750. Walnut
Quoting Orcasystems:


I so wanted to say that... but I remember its taboo :)
along with a certain person with several different logins containing the name Ja$on.
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1749. Caner
most recent microwave:

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Oz is running east & west along the coast line looking for Isaac!
Quoting JeffM:


CycloneOZ I believe it was.
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Quoting caneloader:


If I'm correct (tired) they've got gates now to shut off the Industrial Canal - the lack thereof during Katrina which was what sank New Orleans East.


Sort of.....it was a barge that sank the Lower Ninth. New Orleans East just got surged.....Chalmette got MRGO'ed.

Member Since: June 16, 2006 Posts: 0 Comments: 1565
Does anyone know what happened to TurtleHurricane?
Member Since: August 3, 2006 Posts: 133 Comments: 20639
Quoting atmosweather:


I still can't fathom Isaac's pressure dropping to 979 mb and RECON unable to find hurricane force winds. This wind field is so broad and the thermal gradient so modest that he just cannot spin up those winds any faster. Unbelievable storm, and with the amount of HH and NOAA G-IV data that has been taken from this storm, one that I hope will provide much needed education on the complex internal processes of tropical cyclones. Somehow, we need to gain a better grasp of intensity forecasting and Isaac keeps bringing it to light over and over again.



Atmos, my answer would be this to the dilemma, and a question. First the question. When a dropsonde is dropped into the eye is pressure measured at the sfc or the mid-levels, or all along the way? If it's at the sfc, then Isaac's llc has been really intense today, more so than at any other time I've noticed according to vorticity charts and observations.

The MLC has been the dominant, broad circ throughout his life, and the smaller llc, trying as it may now, is having an awfully tough time trying to spin that broad mid-level circulation.

May be a bad question, but it's one I've never considered before now. TIA, friend.
Member Since: July 9, 2006 Posts: 184 Comments: 29610
1744. Gaara
Quoting Jwd41190:


Wikipedia is wrong and is never a reliable source look at image below



Re: leslie..

Uh.. let's go with the most reliable source of all: Link

Read every advisory and then read the last discussion.. I'm guessing the 973 was after it went extratropical.
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This is the strangest, most confusing storm!
Quoting Orcasystems:
Ummmm not to be a tad on the alarmed side... but 983-981-980-979 in 2.5 hours....
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Quoting IMA:
Awwww, so good to see so many old, uhm, I mean "familiar" faces :) Where's ***, though? heehee I couldn't resist!


I so wanted to say that... but I remember its taboo :)
Member Since: October 1, 2007 Posts: 81 Comments: 26516
1741. will40
Quoting atmosweather:


Wasn't it Cyclone Oz?


yes atmo thats him
Member Since: September 19, 2005 Posts: 2 Comments: 4266
Quoting IMA:
Awwww, so good to see so many old, uhm, I mean "familiar" faces :) Where's JFV, though? heehee I couldn't resist!


Ohh no you said his name!! You know he's gotta be lurking just waiting for someone to tempt him into annoying everyone again ;p
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1739. MrsOsa
Quoting saltydog1127:
so...pascagoula is out of the worst part?


I wouldn't count Pascagoula out just yet. I'm here and not overly worried, but the forecasts are calling for a good bit of rain combined with a decent surge.
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1738. snotly
Perhaps that pressure was over the north Atlantic when the storm became extra-tropical or merged with a polar low.

Quoting Jwd41190:


Wikipedia is wrong and is never a reliable source look at image below

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1737. JeffM
Quoting will40:


his name was OZ someting i think


CycloneOZ I believe it was.
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1736. will40
Quoting HopquickSteve:

Or sometimes users cite the XTRP just to troll. :p


well believe it or not it is a kewl forecasting tool
Member Since: September 19, 2005 Posts: 2 Comments: 4266
1735. MrsOsa
Quoting HopquickSteve:

Or sometimes users cite the XTRP just to troll. :p


Lol I considered that possibility but went with the side of caution in case anyone actually took him seriously.
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Quoting will40:


his name was OZ someting i think


Wasn't it Cyclone Oz?
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Quoting DFWjc:


How much deeper are the Levees now? Are the gates to block more water coming into the Lake?


If I'm correct (tired) they've got gates now to shut off the Industrial Canal - the lack thereof during Katrina which was what sank New Orleans East.
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Hmmm, haven't seen Adrian...
Pat is on vacation or was. I don't think he is home yet.

Quoting jake436:
I started lurking here in 2004. Joined in 2006. Posted quite a bit for quite a while, but finally just went back to lurking. I lurked for so long I forgot my username...lol. Jake was my dog for 13 years, died in 2009. I had forgotten I used his name in my username. Finally remembered yesterday. Whatever happened to Hurricane23...Adrian? I know Patrap still posts, but where is he at the moment?
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Quoting moonlightcowboy:


Hey, Kman! Will you straighten this all out, please? TIA :)


LOL. One look at the AVN imagery tells the tale. All of the deep convection has been off to the SW of the circulation all day. With the center near the NE edge it has repeatedly tried and failed to develop and maintain a solid eyewall. Until that happens it will continue to struggle.

I thought we would see Cat 1 late this afternoon but have not given up on that happening over night.
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Isaac is pushing against the ridge to the north also causing his northern half to be "squashed" as it were. Also causing all these wobbles west-northwestward. IMO
Member Since: May 31, 2011 Posts: 57 Comments: 572
Quoting will40:
XTRAP is never wrong


lol...Rand taught me about the xtrap
Member Since: August 3, 2006 Posts: 133 Comments: 20639
1728. will40
Quoting drs2008:
kind of like a fat guy trying to get up from the couch.



lol exactly
Member Since: September 19, 2005 Posts: 2 Comments: 4266
1727. IMA
Awwww, so good to see so many old, uhm, I mean "familiar" faces :) Where's JFV, though? heehee I couldn't resist!
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Yeah, I've been lurking here long enough to recognize all of you oldsters. I was reading during Katrina, been reading on and off ever since.

And it's kind of amazing how huffy over really trivial crap some people can be. Taz has been here forever. He reminds me of one of my dogs, who is full of mischief and likes to push people's buttons, but is a damn lovely little guy. Yeah, I want to skin him some days, but it's not like it makes him the devil (just don't ask me to say that after he's eaten _another_ pair of shoes, because then I'm pretty sure I'll call him worse.)

But it goes past stuff like people being thin skinned about Taz into the "OMG you're wishcasting! You're downcasting! You were wrong that one time about the 5 day later path of a big storm effected by a really complicated set of factors and so you're a stupidhead! Blarg!"

Which has been true for a long time, too. I try to just keep finding it sort of funny. :P
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Quoting caneloader:
I'm a long-time lurker - trying to remember when I found this blog...I remember now.... I joined 7 years ago tonight... different screen name, with an e-mail account lost to time. Cannot believe it's been 7 years since Katrina. Seems like yesterday - and a lifetime ago.

I think Taz wuz here, too.


I was here. :-) Been lurking so far this year. I don't remember when I started my account, but it was probably before Ivan.
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so...pascagoula is out of the worst part?
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Quoting RTSplayer:
Apparently the attempt at El Nino is failing.



It may even swing back to a La Nina at this rate...


[from earlier....had trouble getting this to load]

Looks like EL NINO is going LA NADA!....

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Quoting MrsOsa:



The XTRP is not a forecast model. It simply shows where the storm would go if it stayed going in exactly the same direction that it is now.

Or sometimes users cite the XTRP just to troll. :p
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Quoting will40:



he is just so large he is having a time getting the winds up



That was forecast by Dr. Masters when the storm was clearing Haiti......
Member Since: June 16, 2006 Posts: 0 Comments: 1565
Quoting kmanislander:


Indeed it does. It seems that the winds just cannot respond due to the lopsided structure of the system combined with periodic dry air ingestion.

Perhaps another year where either dry air or shear continously prevents the storms that do develop from intensifying significantly. I still believe that we will see a hurricane from this one though.


Thanks, Kman, so what about landfall, coordinates and intensity. We're hanging on here! We've got all this Spam and all this Cold Beer, but we're not sure we bought enough! Do tell, friend. ;)
Member Since: July 9, 2006 Posts: 184 Comments: 29610
Some kinda of secreat code
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Quoting Thrawst:
This has got to be the lowest pressure ever recorded for just a tropical storm.
I agree I have been here a long time and have never seen a Pressure this Low and "Not" be a Hurricane.... Just saying :o)

Taco :o)
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1717. drs2008
Quoting will40:



he is just so large he is having a time getting the winds up
kind of like a fat guy trying to get up from the couch.
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1716. Caner
Quoting caneloader:


Jeez, I remember StormTop. Seem to remember controversy about someone spoofing his name or something... Man... Katrina seems like yesterday - and here we all are. Y'all don't remember me - I was a lurker - but I remember you. Hope life has treated you well.

i know this isn't a chat blog... I'm just really tired from hurricane prep and have more to do early tomorrow.. just winding down and taking a breath, here in Lafayette, La.


Hurricane Hugo seems like yesterday... LOL
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Member Since: August 2, 2010 Posts: 21 Comments: 9882
1714. snotly
ah, I see the ULL swung around up to the NE of Isaac, so the circulations are competing for energy, causing sinking air on the lee side where the two lows clash at upper levels... supposed to move over the center of circulation. What happens then?
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Quoting moonlightcowboy:
The stars are starting to line up now for Isaac, getting that neast wall closed off from the dry air. Shouldn't be long now. IMO, this takes anything west of NOLA and anything east of Pascagoula out of the picture towards landfall. So, MS, you are likely it, A G A I N!

WATER VAPOR LOOP


I still can't fathom Isaac's pressure dropping to 979 mb and RECON unable to find hurricane force winds. This wind field is so broad and the thermal gradient so modest that he just cannot spin up those winds any faster. Unbelievable storm, and with the amount of HH and NOAA G-IV data that has been taken from this storm, one that I hope will provide much needed education on the complex internal processes of tropical cyclones. Somehow, we need to gain a better grasp of intensity forecasting and Isaac keeps bringing it to light over and over again.
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Quoting Thrawst:


Checking Wikipedia, it says 1006mb for that storm o.O


Wikipedia is wrong and is never a reliable source look at image below

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1711. BlxMS
Quoting caneloader:
I'm a long-time lurker - trying to remember when I found this blog...I remember now.... I joined 7 years ago tonight... different screen name, with an e-mail account lost to time. Cannot believe it's been 7 years since Katrina. Seems like yesterday - and a lifetime ago.

I think Taz wuz here, too.


Think I joined that night too....I'm 57 and have to admit....seven years ago right now, I was as afraid as I had ever been...and experienced nothing like it since..
Member Since: Posts: Comments:
I remember exactly where I was the first time I posted in 2004. Did not join until a year later. Since then I have made a lot of friends as a result of the love of weather and the relationships founded on these blogs.
Quoting atmosweather:


Lol I thought about that the other day...I lurk more now than I ever did back then. But it's awesome to have so many bloggers still sticking around and making this community great after 8 hurricane seasons.
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1709. will40
Quoting mtyspider:
Do anybody remember a crazy guy waiting for a landfall in a jeep and a camera pointing to a umbrella or gas station canopy. Somebody remember the name??? am pretty intrigued ,maybe he would pull that stunt again. Not pretty smart or hurricane savie ..but really funny to listen to.


his name was OZ someting i think
Member Since: September 19, 2005 Posts: 2 Comments: 4266
1708. cjnew
Foxx the dry air has really made it not bad here. we barely got any rain. waiting to see if that stays through tomorrow.

Does anyone remember when Dr. Masters blog was lucky to break 50 comments? ha. who knew.
now he's on TWC.
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The only good thing about Isaac is that the people of New orleans and Mississippi maybe could play Kayak in the streets
I post this yesterday This was here in Dominican Republic


And sorry, because this storm maybe will cause severe flooding
Member Since: June 20, 2012 Posts: 0 Comments: 2169
1706. acl8610
Quoting texascoastres:
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

Thats a good point and i agree with questioning that. Hurricane force winds were there at the surface (although briefly) per recon and were present a few hundred feet above the surface after that. Odds are Issac is a hurricane and will be officially at 2am. If the winds were there at 11pm it would have made more sense to upgrade it earlier without a second confirmation, before more people went to bed in the warning areas. People obviously take the word hurricane much more seriously than tropical storm... It is only five mph... As i was told as a freshman met major, a meteorologist in the 21st century needs to also be a psychologist, an economist, and computer engineer. I think issac has proved that point so far...
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Quoting caneloader:


Jeez, I remember StormTop. Seem to remember controversy about someone spoofing his name or something... Man... Katrina seems like yesterday - and here we all are. Y'all don't remember me - I was a lurker - but I remember you. Hope life has treated you well.

i know this isn't a chat blog... I'm just really tired from hurricane prep and have more to do early tomorrow.. just winding down and taking a breath, here in Lafayette, La.

Good Luck to you!
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1704. DFWjc
Quoting MrsOsa:



The XTRP is not a forecast model. It simply shows where the storm would go if it stayed going in exactly the same direction that it is now.


Thank you MrsOsa!!
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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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