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WxWatcher007

Major Hurricane Laura

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It's most likely inconsequential, but the appearance of Laura with the Comma shape reminds me of Katrina when it was traversing S Florida and heading into the loop current. 

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49 minutes ago, vortex95 said:

Although Laura is better organized than yesterday with decent banding and an inner core, I still see continuing issues for RI anytime soon.  First is that the core convection keeps pulsing up and down.  That says dry air is still entertaining into the core.  You can see on the 15z mid-level WV image dry air to its NW and NE.  Second, this elongation N-S.  It is has been very persistent in the last 24 hr and the large area of strong convection separate from the core is really not a good thing to have as it does not allow symmetric circular banding and outflow to take shape.  This southern blob of convection is also pulsing which continues to send low-level outflows N into the LLCC. 

One of the more bizarre hurricanes I have seen, esp. with the elongation N-S of the deep convection.

12z SHIPS guidance here. 

http://hurricanes.ral.ucar.edu/realtime/plots/northatlantic/2020/al132020/stext/20082512AL1320_ships.txt

Mid-level RH stays 61% or below up until landfall, and you can see a jump in shear to 22 kt just before landfall.  This suggests that significant or rapid intensification is going to be hard to come by.

 

 

goes16_ir_13L_202008251707.gif

g16wvmid.jpg

There is dry air in almost every sector except to the south and the air over Florida is very dry for now this has to be a huge limiting factor over the next 10 hours.

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Appears as though we have some hot towers trying to go up on the SW side of this ragged eye feature. If these manage to stick around and help tighten up the core, Laura may well be shaking off the persistent shear and entering a period of quicker intensification.

EDIT: Gif not looping. Use this link: https://rammb-data.cira.colostate.edu/tc_realtime/loop.asp?product=4kmirimg&storm_identifier=al132020&starting_image=2020al13_4kmirimg_202008251640.gif

 

RAMMB Laura.gif

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1 minute ago, Kevin Reilly said:

There is dry air in almost every sector except to the south and the air over Florida is very dry for now this has to be a huge limiting factor over the next 10 hours.

As someone said before, if the shear is low then dry air will not penetrate the core. 

Shear is dropping off right now. We're starting to see banding on the western side and better outflow to the north.

Also a huge hot tower is firing near the center. This in all likelihood will go boom tonight into tomorrow.

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Laura might be going bombs away. Looks much more symmetrical and outflow expanding in all quadrants. Yes there’s some dry air, but convection has wrapped almost all the way around the eye feature. I think this is the critical point we’ve been waiting on. I’d expect significant pressure falls with the next recon mission 

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Given the lightning flashes on the SW side do we still think this is not a sign that the clearing in satellite imaging is due to beginning of eye formation and its just a dry air patch ?  When or how can we tell for certain? 

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2 minutes ago, NorthHillsWx said:

Laura might be going bombs away. Looks much more symmetrical and outflow expanding in all quadrants. Yes there’s some dry air, but convection has wrapped almost all the way around the eye feature. I think this is the critical point we’ve been waiting on. I’d expect significant pressure falls with the next recon mission 

Probably mid 970s if I had to guess

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Big time convection wrapping around the SW side of the eye.  Is it about to take off?

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2 minutes ago, Hotair said:

Given the lightning flashes on the SW side do we still think this is not a sign that the clearing in satellite imaging is due to beginning of eye formation and its just a dry air patch ?  When or how can we tell for certain? 

Wait and see if it turns into an eye.  ;)

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She's definitely about to blow up now huge explosion of thunderstorms wrapping around the southwest side of a developing eyewall.  I take back my 10 hours lack of development due to dry air looks like Laura is breathing pretty good now all sectors she's coughing out the last bit of dry air around the center. 

 

https://www.tropicaltidbits.com/sat/satlooper.php?region=13L&product=vis

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Just now, Windspeed said:

Laura's structure is improving significantly.
0f12cf4cc0da8eab6bf9242379048300.gif

rapidly too!!!  She's just sucking in everything right into the center.  She's about to take off clearly shear has diminished and high pressure is building right over the top.

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44 minutes ago, HKY_WX said:

Pretty clear it is going to strengthen significantly tonight/tomorrow. It has been since yesterday. Shear will be negligible for the next 24 hours. Only issue I can see is dry air in the mid levels.

There are three key things that have to be ideal for an intense hurricane: 1) warm enough SSTs, 2) low shear, and 3) a moist column.  If any one of these three is not ideal, it is difficult to get anything higher than a strong Cat 2 IMHO.  Occasional dry air intrusions are going to likely be persistent issue up until landfall for Laura. And just the elongated structure N-S that has persisted, that isn't a overall good sign for significant intensification anytime soon.  Latest EIR loop shows irregular strong bursts of very cold IR tops in the S quad of the circulation.  These irregular bursts have been an issue for days now.  Is there any real reason to expect they will stop since mid-level RH will remain a bit too low (60% or less)?
 

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Lol at how quickly this thread went from "There isn't going to be RI, it's probably not even going to make major" to "Bombs away!!!"

 

 

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Just now, vortex95 said:

There are three key things that have to be ideal for an intense hurricane: 1) warm enough SSTs, 2) low shear, and 3) a moist column.  If any one of these three is not ideal, it is difficult to get anything higher than a strong Cat 2 IMHO.  Occasional dry air intrusions are going to likely be persistent issue up until landfall for Laura. And just the elongated structure N-S that has persisted, that isn't a overall good sign for significant intensification anytime soon.  Latest EIR loop show irregular strong bursts of very cold IR tops in the S quad of the circulation.  These irregular bursts have been an issue for days now.  Is there any real reason to expect they will stop since mid-level RH will remain a bit too low (60% or less)?
 

So your forecast is for cat 2 at landfall? I think she has more going for her than against her. I don't think there will be much weakening near landfall. Today's Euro kept her intensifying right up until then. 

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Just now, vortex95 said:

There are three key things that have to be ideal for an intense hurricane: 1) warm enough SSTs, 2) low shear, and 3) a moist column.  If any one of these three is not ideal, it is difficult to get anything higher than a strong Cat 2 IMHO.  Occasional dry air intrusions are going to likely be persistent issue up until landfall for Laura. And just the elongated structure N-S that has persisted, that isn't a overall good sign for significant intensification anytime soon.  Latest EIR loop show irregular strong bursts of very cold IR tops in the S quad of the circulation.  These irregular bursts have been an issue for days now.  Is there any real reason to expect they will stop since mid-level RH will remain a bit too low (60% or less)?
 

We've discussed the RH issue a bit.  I don't think this will be a huge hinderance to strengthening so long as shear is low.  Dynamically, the pulse-like nature is more connected to shear than to RH.  Now, when shear is present, low RH probably has a more deleterious effect than high RH.  But it does look like the system is trying to get its act together, in a way that It hasn't throughout the entirety of its life up to this point.  For instance, the new pulses of convection are forming a concentric ring.

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Just now, jpeters3 said:

Lol at how quickly this thread went from "There isn't going to be RI, it's probably not even going to make major" to "Bombs away!!!"

 

 

We knew it was possible, but it was struggling through much of the day. A lot has changed in the last 1.5 hours. Rapidly expanding outflow, appearance of an eye, huge blow up of convection in southern region of circulation, and finally a circular structure (not the n/s tilt we’ve seen for 48 hours). This has the earmarks of, at a minimum, a quick strengthening trend. 

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1 minute ago, jpeters3 said:

Lol at how quickly this thread went from "There isn't going to be RI, it's probably not even going to make major" to "Bombs away!!!"

 

 

Honestly bombs away and RI are too overused. Not every tower firing means RI. Would be a good drinking game for sure on this board. 

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20 minutes ago, HKY_WX said:

It's most likely inconsequential, but the appearance of Laura with the Comma shape reminds me of Katrina when it was traversing S Florida and heading into the loop current. 

I was going to ask about the comma shape. It seems when storm gain that shape on the east coast they're never able to revert back to a symmetrical look even when conditions greatly improve. I assume that isn't usually the case in the gulf?

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Just now, TradeWinds said:

Honestly bombs away and RI are too overused. Not every tower firing means RI. Would be a good drinking game for sure on this board. 

Every hot tower = RI, and every minor warming of the cloud tops or slight degradation of the satellite presentation = weakening.

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Just now, Dunkman said:

I was going to ask about the comma shape. It seems when storm gain that shape on the east coast they're never able to revert back to a symmetrical look even when conditions greatly improve. I assume that isn't usually the case in the gulf?

I suspect the comma shape was due to northerly shear.  It's possible that this will go away as the shear abates. 

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10 minutes ago, vortex95 said:

There are three key things that have to be ideal for an intense hurricane: 1) warm enough SSTs, 2) low shear, and 3) a moist column.  If any one of these three is not ideal, it is difficult to get anything higher than a strong Cat 2 IMHO.  Occasional dry air intrusions are going to likely be persistent issue up until landfall for Laura. And just the elongated structure N-S that has persisted, that isn't a overall good sign for significant intensification anytime soon.  Latest EIR loop shows irregular strong bursts of very cold IR tops in the S quad of the circulation.  These irregular bursts have been an issue for days now.  Is there any real reason to expect they will stop since mid-level RH will remain a bit too low (60% or less)?
 

Patience is a virtue. Currently nothing signifying the system won't take off this evening. Still early. Best RI periods characterized on SHIPS have been consistently between Midnight and 8pm tomorrow before it hits a bit of shear prior to landfall. Today was all about getting its act together. 

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12 minutes ago, vortex95 said:

There are three key things that have to be ideal for an intense hurricane: 1) warm enough SSTs, 2) low shear, and 3) a moist column.  If any one of these three is not ideal, it is difficult to get anything higher than a strong Cat 2 IMHO.  Occasional dry air intrusions are going to likely be persistent issue up until landfall for Laura. And just the elongated structure N-S that has persisted, that isn't a overall good sign for significant intensification anytime soon.  Latest EIR loop shows irregular strong bursts of very cold IR tops in the S quad of the circulation.  These irregular bursts have been an issue for days now.  Is there any real reason to expect they will stop since mid-level RH will remain a bit too low (60% or less)?
 

I disagree w/ your premise that you cant have a Cat 3 or 4 with some mid-level dry air around. It's happened many times. Almost all major hurricanes that track north of 25 Latitude will likely face dry air problems. If we're talking about achieving  Cat 5/historical wind/pressures, sure I would agree the environment would need to be pristine.

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1 minute ago, HKY_WX said:

I disagree w/ your premise that you cant have a Cat 3 or 4 with some mid-level dry air around. It's happened many times. Almost all major hurricanes that track north of 25 Latitude will likely face dry air problems. If we're talking about achieving  Cat 5/historical wind/pressures, sure I would agree the environment would need to be pristine.

You're hard pressed to find large scale anticyclone with very high RH in the middle troposphere within it... And large scale anticyclones are favorable regions for TC intensification.

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4 minutes ago, jpeters3 said:

Every hot tower = RI, and every minor warming of the cloud tops or slight degradation of the satellite presentation = weakening.

Rapid very cloud top convective development in a blob fashion in one quad isn't generally a good sign overall for significant intensification. You want to see a smooth ring of convection gradually develop, and cool with time, and wrap around the center, and most importantly, persist for more than just a couple of hours.   At that point, RI is much more likely.

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Much of it is probably bias and selective memory on a small sample size but in my head a storm in this area of the GOM without any major inhibitors seems almost certain to strengthen rapidly.  Warm water and no more islands in the way from here on out.  I'll take the over.

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Laura's structure is obviously improved, but the core is still pretty loose.  It's only over the last several hours that a ribbon of solid moisture was able to wrap around the west and south sides, and the new "hot tower" convection is pretty new and hasn't even had time to pinwheel around the center, yet.  I'm guessing the pressure is mid 980s now.  Give the new structure several more hours before we go all in on "bombs away".

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There will be no recon at all before 5 PM, that's for sure. Kind've surprising lack of recon today. Maybe they're prepping to do continuous recon missions from tonight through landfall or something. 

In any case, this means the intensity estimate at 5 will be a guess. If I had to guess, I'd say high cat 1, like 90 mph. 

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