ATL: ISAAC - Post-Tropical - Discussion

[rainstorm]

indications are its slowing quite a bit, and wrapping up.

[gboudx]

Here's the HRRR at the end of its run so far:
Without a doubt we're going to be seeing some sort of intensification tonight and tomorrow.

How good has the HRRR been to this point?

Excellent, so something to strongly consider.

Thanks. Let's hope this is the time it's wrong.

[Macrocane]

This is from a recent HDOB:

021230 2744N 08750W 8433 01443 9962 +167 +130 054051 058 061 024 00

Seems to be unflagged, and there are reports of almost 75 kt at flight level, probably there will be an upgrade. I am not forecasting, it's just a personal opinion.

[wxwatcher1999]

im am seeing where some are saying its stalling...anyone have any comments?

[SunnyThoughts]

Wasn't this about the time (during the past model runs) where the storm slowed down and we all waited to see if it would head north (towards the weakness) or the ridge would build back in and send it west? Just saying if it has indeed come close to a stall or a drift...that is probably where we are...that fork in the road. Good luck everybody in the path. I'm sure everyone is prepared and ready for whatever comes their way.

[thatwhichisnt]

Where does the HRRR show landfall?

[tailgater]

Are the winds closer to the northeastern eyewall slower than, say, 35 miles east of the northeastern eyewall?

I ask because WWL TV just showed a graphic of predicted winds where Hammond, La. which will be about 5 miles east of the northeastern eyewall has top winds of 56mph, Mandeville which is about 20 miles east of the NE eyewall has 62mph, and Slidell which is about 35 miles east of the NE eyewall has 68mph.

I thought the fastest winds were in the eyewall itself.

Probably because they are closer to open water. Hammond would have a lot more land interaction.

[jasons2k]

Where does the HRRR show landfall?

It's a short term model only; it doesn't run that far out. But it's great to use for short term intensity and structure changes.

[SunnyThoughts]

979.4 pressure reading at the recon thread. Man, sure is low for a TS. Crazy storm, I'll be glad when its over.

[Jake8898]

Are the winds closer to the northeastern eyewall slower than, say, 35 miles east of the northeastern eyewall?

I ask because WWL TV just showed a graphic of predicted winds where Hammond, La. which will be about 5 miles east of the northeastern eyewall has top winds of 56mph, Mandeville which is about 20 miles east of the NE eyewall has 62mph, and Slidell which is about 35 miles east of the NE eyewall has 68mph.

I thought the fastest winds were in the eyewall itself.

[EDR1222]

To the untrained eye, the latest satellite images look as if the storm may be suffering from some dry air entrainment.

Any thoughts from the pro mets ?

[FutureEM]

979.4 pressure reading at the recon thread. Man, sure is low for a TS. Crazy storm, I'll be glad when its over.

Not as low as a fellow Gulf of mexico struggler, i.e. Alex (2010)

01L ALEX 100630 1200 23.5N 95.2W ATL 70 958

[thatwhichisnt]

Where does the HRRR show landfall?

It's a short term model only; it doesn't run that far out. But it's great to use for short term intensity and structure changes.

Great, thanks for the clarification.

[JamesCaneTracker]

IF this thing ever decide to develop an eye it's going to strengthen quickly with that low of an pressure...

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[PTPatrick]

Yeah often times cat2's are in the 970s...that's why I think this still has a chance at cat 2 I know low pressure in a big storm like this won't support as high of wind...but nonetheless there is time for it to get to cat 2

[rainstorm]

Yeah often times cat2's are in the 970s...that's why I think this still has a chance at cat 2 I know low pressure in a big storm like this won't support as high of wind...but nonetheless there is time for it to get to cat 2

if it comes onshore with a 960 pressure and its deepening at landfall it will do 960 damage.

[WxGuy1]

Current IR satellite imagery continues to show relatively unimpressive structure. As we've seen through the past 36 hours, there is intense convection in only ~1/2 of the circulation. Yesterday, it's was primarily located in the northwestern 1/2 of the storm. This morning, most of the convection was "lop-sided" to the western 1/2 of the circulation. As of the latest image I've seen, nearly all of the precipitation is located in the southern semicircle. The upper-level anticyclone associated with Isaac is dislocated to the north of the center of circulation, resulting in some ~10 kt northeasterly shear over the center (and more over the western side of the storm). Although current precipitation water satellite data doesn't really suggest much in the way of dry air in the northern half of the storm, Isaac's appearance on satellite through the past couple of days certainly has shown signs of significant dry air entrainment.

So, the question is whether or not conditions will improve. Considering the warm water and "only" 10 kts of deep vertical wind shear, I would have expected to have seen appreciable intensification already if you had asked me a couple of days ago. However, the storm has looked "off" for the past few days, with strange wind structure as observed by recon (a few days ago, it was a very large area of weak winds near the center of circulation -- yesterday it was multiple eddies flying around). The structure of the winds around the circulation has improved and looks more "classic" now, but the lack of much convection in the northern semicircle doesn't bode well for significant intensification. I'm still waiting for the hammer to drop, so to say, and I'm waiting to see a symmetric blowup of convection around the center, but it's uncertain whether that will happen.

The longer Isaac stays in this 50-60 kt sfc peak wind state, the less time it has over water to intensify. Since I'd rather not see an intensifying hurricane slam into southeastern LA or coastal MS, this is probably a good thing. Landfall may not be that far off; each additional hour that recon flies through and sees only 55-60 kt surface winds is one less hour that intensification can occur. We can hope that Isaac maintains status quo of slow intensification and it makes landfall as a Cat 1. Considering the potentially "worst case scenario" track of putting New Orleans in the front right quad of the storm, this is much better than a major hurricane...

[Sonica]

Wasn't this about the time (during the past model runs) where the storm slowed down and we all waited to see if it would head north (towards the weakness) or the ridge would build back in and send it west? Just saying if it has indeed come close to a stall or a drift...that is probably where we are...that fork in the road. Good luck everybody in the path. I'm sure everyone is prepared and ready for whatever comes their way.

This ain't no thing. Maybe some slight flooding around the lake but shouldn't be too bad here in Baton Rouge.
I guess if your the one to flood it is horrible but not too scarey for me this time.
IMO

[timeflow]

Hey Kool Aid Man!



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[Kennethb]

Wasn't this about the time (during the past model runs) where the storm slowed down and we all waited to see if it would head north (towards the weakness) or the ridge would build back in and send it west? Just saying if it has indeed come close to a stall or a drift...that is probably where we are...that fork in the road. Good luck everybody in the path. I'm sure everyone is prepared and ready for whatever comes their way.

This ain't no thing. Maybe some flight flooding around the lake but shouldn't be too bad here in Baton Rouge.
I guess if your the one to flood it is horrible but not too scarey for me this time.
IMO

Per NWS, here in BR we could have a period of 50-75 mph sustained with 90 mph gusts.