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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1304. Reb74
Quoting treehuggingsister:


It IS lovely outside.

Not sure where you are but it is stifling compared to most nights lately. Absolutely "still" feeling even if the winds are not!
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Recon is reporting 45kt surface winds and a 1001mb pressure well away from the center and in no convection.
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Quoting wilburo33:


I googled it but i could not find any information about dish providing this service. Directv also did this during Katrina and all big storms since that time. They did it for people who evacuate and want local news from their home area.


Thank you! I haven't been able to find any info either, and I have been wondering.
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1301. MZT
He hs a lot of dry air in him, but he is BIG. You can see the circulation affecting weather from Texas to South Carolina, and down to Florida.
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1300. WxLogic
Quoting TomballTXPride:

I will say you called this and have been showing those mid-level charts all quarterbacking how dry air is really playing a role in Isaac's intensity. Gotta give you props because at the end of the day that's what ultimately deterred our him from becoming a category 3 beast.


I'm glad this one is being kept in check. Things could have been a lot more worst. Of course, still over water and still has time to get its act together, but I personally don't see this as being a Cat. 3 and may be it has a shot at a low Cat. 2 if it's able to close the eye real good.
Member Since: August 14, 2008 Posts: 4 Comments: 4927
1299. jake436
Quoting azduck:


Also, to the person claiming similarity to Ike - Ike was a strong CAT 4 prior to hitting Cuba dead-on, and maintained some semblance of his structure the whole time. That also meant he was pushing CAT 4 surge out in front of him. Isaac pushed 1-2 feet of surge sideways into Tampa Bay today. So, lets be generous and say he's pushing 4x that out in front - that is still only 4-8 feet.



I agree with this. The comparisons to Katrina, Ike, Gustav, all silliness. Every single one of those storms was already VERY WELL DEVELOPED in this location. Isaac has yet to develop and maintain an eyewall structure for more than an hour. I believe the surge with this storm is going to be impressive, for a Tropical Storm/light CAT 1. But it's still going to be less than half of anything seen during Katrina. The over-dramatization is ridiculous. "Peoples lives and the lives of their children"...come on guys. I'm a NOLA native that has lived in South Mississippi for 16 years now, but let's be realistic here. Elena/Georges/Frederic...all those were infinitely more impressive than Isaac, and those things didn't happen.
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Quoting TropicalAnalystwx13:
Everybody welcome the East Pacific's tenth named storm, Tropical Storm Ilena.

EP, 09, 2012082800, , BEST, 0, 153N, 1072W, 40, 1000, TS, 34, NEQ, 40, 30, 0, 30, 1006, 200, 40, 0, 0, E, 0, , 0, 0, ILEANA, M,

Hmmm... I was wondering if this would make it to TS status, or just waft off into the sunset...

Quoting aislinnpaps:


Sad
True. But at the same time I'm glad there's no charge to blog here.
Quoting cajunkid:
Funny how cranky the blog is in the evening.

GO EAT, then come back.
100% agreee... just took a food break, and now am too sleepy to argue with anybody... lol
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1297. scott39
Quoting SouthDadeFish:
I see your point, but what do you think about all that dry air around Isaac?
Isaac is building a shield around his center. Dry air is not going to keep him from strengthening.
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Quoting Caner:
current microwave, still a beeline for just south of New Orleans:

Not that it means anything, but based on many storms I've seen, there will be a northerly turn at Grand Isle. There is an adjustment seemingly to avoid land. If I'm wrong, big deal. Has anyone noticed this? Jamaica has dodged storms due to this phenomenon a couple of times I've seen.
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Quoting oreodogsghost:
If the Mississippi coast is affected, please consider helping out through the Back Bay Mission in Biloxi. Not taking anything away from Portlight, but Back Bay is a Biloxi institution and is always there helping those in the Gulfport-Biloxi area who lack the means to recover from disasters - natural and man-made.

Self-bump
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goodnight all. I hope preparations are complete and everyone is as ready as possible for what tomorrow brings.
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1293. SirCane
Link

Click this satellite loop and then click on the "Forecast Pts" option you will see the center of Isaac is East of the forecast at this moment.
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Issac reminds me of a Western Pacific tropical cyclone. Very large, with a barometric pressure lower then you'd expect for its sustained wind speed because of its size. The good thing is that any wind damage may be less than expected, but the bad things are the large water surge from the Gulf on the right side of it and the copious amounts of rain associated with this system.
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Now as of 01:57:30 UTC, Mission 29 is near the 850 mb level.
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Looks like the Gulf Coast is going to dodge bullet only because our buddy Isaac couldn't get his act
together yesterday & is going to run out of time. If he had another 24 hrs. before landfall, I think we would be looking at a Cat. 3. Thank the gods for dry air..
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1289. GetReal
Member Since: July 4, 2005 Posts: 204 Comments: 8806
Biggest threat of Isaac is not the winds, but STORM SURGE and HEAVY RAINFALL AMOUNTS LEADING TO FLOODING.
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Quoting WxLogic:
OK... back to PC ( at least for a bit ). Was checking out the moisture levels vs dry air and we still have dry air issues being pretty much enhanced by land (in this case CONUS).

Below you'll see that there's an area of quite pronounced drying to the NE of Isaac at around 400/500MB:



Also noticed that below the 500MB level, at 600MB there's more dry air but appear to be a thing layer.

This falls quite in line with the latest RAOB obs from KTBW:



I'll continue to expect Isaac to be at a border line TS/HURR like earlier until is able to manage this dry air accordingly. Almost had it earlier today but convection collapsed prematurely due to an intake of dry air. As discussed before.

On a side note... the more Isaac delays on moving quick enough the more time it gives the steering currents a chance at changing in configuration and therefore the path.
Great analysis, thank you for sharing this.
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this new burst may sustain it until the dry air hits again
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1284. guygee
Jogwatchers note the last 20 miles where Isaac gains about 10 degrees more northwards component, so clearly he must be going north now (not).
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Apparently my boss knows something I don't. Just got word that the office (in Pensacola, right on the bay) is closed tomorrow, and I've gotta go in and shut down the servers and move computer equipment to high ground (ie. on top of everyone's desk, LOL).
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Quoting osuwxguynew:
For those downplaying the heat content available to Isaac, they just have to look at where Gordon went from a tropical storm to a strong Cat 2 (possibly post season upgrade to Cat 3).

See above and east of 30N 50W in this TCHP map. Certainly more available in the Gulf on its future track according to SHIPS...


Also, while outflow was good in all quadrants for Gordon, it did not have quite the outflow channels that Isaac does to rapidly remove mass from the eyewall that will form.


I see your point, but what do you think about all that dry air around Isaac?
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I think Chicklit has it right: Isaac is going to be mainly about water.

Meanwhile, up North:

Arctic sea ice 'hits record low'

Link

"...The Arctic sea ice fell to 4.10 million sq km, some 70,000 sq km less than the earlier record charted on 2007, the lowest since satellites began measuring the ice in 1979, according to the US National Snow and Ice Data Center on Monday...."
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Hurricane-force winds being reported in the 951 mb level.
951mb 160° (from the SSE) 65 knots (75 mph)
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Quoting Stormbugn:
Ouch...people are a little cranky tonight. Grothar...did you forget to hand out the happy meds again?

On a more serious note...I live 50 miles north of Gulfport and just getting some gusty winds that came through here. I also have about 50 ducks and cranes in my pond...weird. Thanks all for the updates!
Grothar has happy meds? I didn't get that memo. Where do I sign up?
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Quoting SirCane:
Sure are some testy people on here tonight. SHesh


Just don't post the models and comment on where the majority of them point. ;-)
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1276. azduck
Welp thats bad news from the HH team... still, my thought is that the size of the storm and short time left to it, combined with the (relatively) lower heat potential of the Gulf this year will keep Isaac from RI and getting much past CAT 1.

Also, to the person claiming similarity to Ike - Ike was a strong CAT 4 prior to hitting Cuba dead-on, and maintained some semblance of his structure the whole time. That also meant he was pushing CAT 4 surge out in front of him. Isaac pushed 1-2 feet of surge sideways into Tampa Bay today. So, lets be generous and say he's pushing 4x that out in front - that is still only 4-8 feet.

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1275. GetReal
There is ONLY one track that counts, and that is the FINAL track and we will have that answer in the next 30-40 hours tops.... Buras or Waveland it is only a wobble or two differnce in the end. Some area is going to get dumped on with rain, and hopefully no more than a Cat 1.
Member Since: July 4, 2005 Posts: 204 Comments: 8806
Quoting WXGulfBreeze:
Here's a nice little radar loop that shows clearly that Isaac is sucking in dry air. For having a TS right offshore, Pensacola is unusually un-humid tonight.

Link


Isaac is not exactly a 'go-getter.'
Keeps to himself, drinks a lot...
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Quoting presslord:
OK...we're all set. Gonna have a crew (including 2 EMT's) at the Biloxi Special Needs Shelter from tomorrow morning until the storm passes. They will be caring for shelter dwellers, as well as assisting with evacuations. They will also be doing rescues of people who call for help.

Another team will be surveying all the shelters in the area to ensure that they are accessible to all people.

John Wilbanks will be hunkered down in a Biloxi parking garage live streaming video. He's gonna be able to give great real time, on scene reports.

Wednesday we will begin doing needs assessments and start to engage in the relief phase of our work.


Good luck and stay safe!
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Quoting BiloxiBlues:
East side is the beast. I lived through Katrina and Mississippi got hit harder than any other state, although the media, for the most part, focused only on New Orleans.


NO got hit from gradual flooding due to levee failure not 20+ storm Surge driving houses off foundations
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1270. SirCane
Sure are some testy people on here tonight. SHesh
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Cyclone Oz is broadxasting from the Waveland Ms pier.

Crazymother.tv
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1268. jake436
Quoting MississippiWx:


Lol. Actually it was Buras. Grand Isle is further west. Katrina made its third and final landfall in Mississippi at Bay St. Louis. I know this very well.
This is correct...except technically it was Ansley, MS. Either way, this storm is nowhere NEAR Katrina in any way shape or form.
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Quoting keithneese:


Does anyone know if Dish Network is doing the same thing?


I googled it but i could not find any information about dish providing this service. Directv also did this during Katrina and all big storms since that time. They did it for people who evacuate and want local news from their home area.
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Quoting Grothar:


No, I am not on vacation. My family is away for awhile.

I am usually a paid member, but this year when I went to go on PayPal, I got a message that read "Expired". At first I wasn't sure they meant me or the account. I will try again this week.
Never like to see "expired". Can really ruin your entire day.
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Quoting osuwxguynew:
For those downplaying the heat content available to Isaac, they just have to look at where Gordon went from a tropical storm to a strong Cat 2 (possibly post season upgrade to Cat 3).

See above and east of 30N 50W in this TCHP map. Certainly more available in the Gulf on its future track according to SHIPS...


Also, while outflow was good in all quadrants for Gordon, it did not have quite the outflow channels that Isaac does to rapidly remove mass from the eyewall that will form.




Yeah. 970mb storm in like 10 TCHP.

So much for the TCHP argument.

I question whether it's even a scientifically valid measure for predicting intensity.

Certainly the correlation is far closer to 0 than to 1.
Member Since: January 25, 2012 Posts: 33 Comments: 1520
1263. IMA
Quoting Grothar:


I am usually a paid member, but this year when I went to go on PayPal, I got a message that read "Expired". At first I wasn't sure they meant me or the account. I will try again this week.

I paid my $5 on the day I was notified to renew, have the PayPal receipt to prove it, but it still says "renew". I have sent multiple messages to support but have not had a reply. It's been 19 days since the first message was sent. I'm so disgusted right now! It's not about the ads, I have ABP, but not being able to get more than 6 frames on the animated radar & not getting assistance is maddening!
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Mission 29 now heading towards the surface...
It has moved from 484.9 mb at 01:38 UTC to 748.8 mb at 01:47:30 UTC.
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Quoting gustaveye:
Katrina track...mississippi bound...some of you say it won't make a difference it is still close to NO...b.s.....makes a big difference...i ain't afraid to tell you how it is going to be...unlike these meteo clowns on TV....all saying the same thing when water vapor shows a totally different story...


Live in Ocean Springs, MS. we had an 18 ft + storm surge surge 60 miles from the LA/MS state line that is a fact
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Quoting scott39:
What we have to remember with Isaacs landfall, that Al/MS/LA arent that far apart. Any variation in track could easily have Isaac make landfall in any of those states.
and the actual eye landfall isnt so important in the grand scheme of things. Is it? Anyway, bed for me. Good luck to all in La and Ms and surrounding areas :)
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East side is the beast. I lived through Katrina and Mississippi got hit harder than any other state, although the media, for the most part, focused only on New Orleans.
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Quoting WXGulfBreeze:
Here's a nice little radar loop that shows clearly that Isaac is sucking in dry air. For having a TS right offshore, Pensacola is unusually un-humid tonight.

Link


It IS lovely outside.
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Ouch...people are a little cranky tonight. Grothar...did you forget to hand out the happy meds again?

On a more serious note...I live 50 miles north of Gulfport and just getting some gusty winds that came through here. I also have about 50 ducks and cranes in my pond...weird. Thanks all for the updates!
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Quoting gulfbreeze:
He has slowed down to 10mph. Could be about to stall or change direction .Models do seem to be going back to the east. Wind here is p/u.


I thought he might have had a little eastward movement to Isaac's track,but looking at a loop someone posted,it appeared not so. We will see.
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Quoting sunlinepr:
Looks split in two pieces...


haarp
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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.