ATL: LAURA - Post-Tropical - Discussion

[Do_For_Love]

It seems like Laura has pulsed a bit in strength since this morning, but there is a newish burst of convection with pink cloud tops on the IR. She's only predicted to be at 85 mph by 11pm according to the NHC, so she doesn't have to strengthen much today in order to be on track for major status.

[aspen]

Higher stability air is wrapping around right now, which could reduce significant intensification in the short term (the next few hours). Once that is mixed out, we could see faster RI. Luckily, this means that Laura will have less time to take advantage of perfect conditions - I'd estimate a C3 or low C4 at landfall. Anything higher is still possible (but looking less likely with this short pause in intensification), since it would require a herculean bout of RI. Luckily, C5 is looking unlikely now. (That being said, storms have done this before, so it is still important to be vigilant).

It seems like a 930-945 mbar storm is looking more likely than <930 mbar. If Laura will have a similar RI phase to Katrina in the next 36 hours (~1.4mbar/hr pressure drop), it’ll bottom out in the high 930s or low 940s. However, if it’s like Rita’s RI phase (~2.4mbar/hr), it could go below 910 mbar.

If it were to exceed all of our expectations and go for a completely bonkers RI phase like Amphan this May (~3mbar/hr), it could drop below 900-890 mbar. It’s safe to say something like that is extremely unlikely.

[Kazmit]

Looking a lot like it did yesterday with that dry slot.

[psyclone]

It's the organizational process happening today that will permit the strengthening down the road. Laura has been taking her time over the course of its life but it gets the work done over time. She's a cat 5 in terms of tenacity.

[Blow_Hard]

A lot of the models that show more pronounced RI start doing so late tonight after 03z, and continue through late tomorrow. Likewise, the NHC only is forecasting 'modest' strengthening (10 mph increase for a total of 85mph sustained) over the next ~10 hours, before doubling that rate (a 20 mph increase to 105mph by 15z tomorrow) overnight. Laura doesn't look fantastic right now (which isn't to say she looks unhealthy by any stretch) due to the slight weakness in her NW region, but she's probably just tabled off for now. While she may not blow up this afternoon/evening, it probably means little if anything in regards to her chances to drastically intensify after the next 10 hours.

I still unfortunately expect this to get to high Cat 4 if not Cat 5 before starting to slowly going down in strength right before landfall in between Sabine Pass and Grand Chenier, La.

Wouldn’t a Cat 4 or 5 push the storm west?

Not necessarily that but if it goes more westerly that means more time over warm water = stronger storm

[Blow_Hard]

It's the organizational process happening today that will permit the strengthening down the road. Laura has been taking her time over the course of its life but it gets the work done over time. She's a cat 5 in terms of tenacity.

Agree...Michael didn't take right off after it entered the GOM. Over the last 36 hours of it's lifetime the RI was phenomenal and pressure was still dropping as it came ashore.

[Highteeld]

Would appear to be intensifying again.

[GCANE]

CAPE increasing to 6000 NW of the CoC.
Likely thunderstorms will fire here in a few hours and moisten the mid-levels where it appears to be currently dry.

[aspen]

 https://twitter.com/TropicalTidbits/status/1298297843531354113

[FLpanhandle91]

I don’t think it’s going to look like this much longer, there are some subtle hints on visible this has bottomed out. For one, outflow is improving in all quadrants, even on the west side, if only gradually. Second, the area where the southern eyewall should be is starting to fill in a little bit. There was some weird vort on the nw side as well that seems to have largely dissipated.

I believe some were confusing that vort with the center. The LLC is pretty much underneath all of the expanding CDO.

[hurricaneCW]

Outflow is beginning to expand on its northern side, a good indication of shear relaxation and a moistening atmosphere.

[Sanibel]

How it reacts to passing over the Loop Current coming up from the Yucatan Channel will tell you a lot...

[Hypercane_Kyle]

Outflow is beginning to expand on its northern side, a good indication of shear relaxation and a moistening atmosphere.

Yea, you can see the cirrus clouds starting to move away to the north. One of the things to watch for is if it can develop polar outflow channels today.

[psyclone]

It's the organizational process happening today that will permit the strengthening down the road. Laura has been taking her time over the course of its life but it gets the work done over time. She's a cat 5 in terms of tenacity.

Agree...Michael didn't take right off after it entered the GOM. Over the last 36 hours of it's lifetime the RI was phenomenal and pressure was still dropping as it came ashore.

You're right. You need to construct a foundation before you can build that jenga tower of steam (which is the goofy way i envision a cane). Michael looked grungey and smudgey relative to its strength until it neared landfall. So did Joaquin in 2015. This system has the comma shape that often (but not always) precedes significant intensification. A major or near major hurricane still seems like a reasonable bet. I'd need to see a lot more before buying into the extreme solutions. thankfully those don't happen very often.

[sponger]

Time for model runs! I would give a fiver to take a peak at this afternoon's FSU ensemble! This is the time where the track really firms up and this 5pm update is the most critical since Michael and Dorian.

[bella_may]

Pretty intense band heading towards mobile in a few hours. We’ll see if it holds together

[p1nheadlarry]

FWIW, the cold pool is depicting total heat content. The areas near the cold pool are still >= 79 C.

Perhaps a cooler boundary layer => lower enthalpy flux => low entropy air at the low levels but this is likely sufficient to maintain it's current intensity.

edit units

[crimi481]

Has it been moving more n.n.w?

[GCANE]

Wow that was really quick.
Laura swallowed that high CAPE air like there was no tomorrow.
Up to 3000 in the core in the matter of 15 minutes.
Ice imagery showing CDO expanding to the NW.

Afraid to think what happens tomorrow when she starts swallowing the really heavy-duty CAPE air off the TX / LA coast.

[jlauderdal]

Time for model runs! I would give a fiver to take a peak at this afternoon's FSU ensemble! This is the time where the track really firms up and this 5pm update is the most critical since Michael and Dorian.

we know where its going...less than 75 miles either side of the NHC line...getting in the time frame where NHC is superior to the models, they can fine tune far better than nay model at this range