ATL: MARCO - Remnants - Discussion

[Michele B]

SW FL here....so all this rain on my house....hard rain followed by quiet.....followed by another round of hard rain.....a little thunder.....quiet....you get the idea. Been going on for hours now.

Is this outflow from Marco? All the way over here?!?!

If so, I expect it'll go on till he's up past our latitude. But by then, Laura will be on her way through FL straits.

GOOD TIMES!

[TheStormExpert]

No freaking way Marco is a hurricane at landfall with the kind of shear environment it’s entering! May even be a remnant low by then. On top of that you have mid-level dry air streaming from West to East in the Gulf.

[gatorcane]

I literally did a double-take when I looked at the NHC 85mph hurricane forecast. I don’t see that happening. Just took a peek at the WV loop which says it all. Lots of dry air and shear ahead. Plus Marco is small so even more susceptible. Looks like 00Z guidance agrees and is coming in less intense than the 12Z. Maybe the NHC will lower their guidance since they didn’t have this guidance for the 5pm package.

http://rammb.cira.colostate.edu/ramsdis ... display=24

[USTropics]

I literally did a double-take when I looked at the NHC 85mph hurricane forecast. I don’t see that happening. Just took a peek of the WV loop says it all. Lots of dry air and shear. Plus Marco is small so even more susceptible. Looks like 00Z guidance agrees and is coming in less intense than the 12Z:

http://rammb.cira.colostate.edu/ramsdis ... display=24

Yea I think the NHC was erring on the side of caution, even they stated in the discussion their intensity forecast was above the consensus models and the FSSE (FSU Super Ensemble). These small circulations can be difficult to predict as far as when/how much they weaken or strengthen. Earlier today when Marco quickly strengthened, flow due to the upper-level trough was essentially SSW to NNE:


As the trough has been backing out:


The upper-level flow has become a bit more west to east in the GOM:


As you can see in the GFS sounding, some shear has ensued:

[wx98]

I agree. I believe myself that we will see a mid-grade TS coming into LA, but the hurricane center usually gets it close, so wouldn’t be totally surprised to see a minimal hurricane before landfall.

[hohnywx]

No freaking way Marco is a hurricane at landfall with the kind of shear environment it’s entering! May even be a remnant low by then. On top of that you have mid-level dry air streaming from West to East in the Gulf.

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Hmm...I think I'll listen to the NHC's take on this:

Marco is beginning to move into a zone of moderate
southwesterly shear, but otherwise favorable conditions of warm
ocean water and some upper-level divergence are expected to foster
strengthening during the next day or so. With the exception of the
HWRF, the other intensity models show Marco reaching hurricane
strength, and the NHC foreast continues to show that possibility
while Marco moves over the central Gulf. The shear is still
expected to strengthen in 36-48 hours when the system is approaching
the northern Gulf Coast, but with the shift in the forecast track,
now there may not be enough time for Marco to weaken below
hurricane intensity before it reaches land.

[Kingarabian]

Shear level is important. If it's mid level shear then yeah, expect weakening up until land fall. If it's deep layer, airliner level shear, then that type of shear takes a while to do a number on the storm. With sufficient warm water, moderate strength system although will look lopsided, can actually still strengthen.

[CrazyC83]

Marco is probably a fairly shallow storm given the size and strength. It may not reach to the level of the shear if it is high level.

[TheStormExpert]

I literally did a double-take when I looked at the NHC 85mph hurricane forecast. I don’t see that happening. Just took a peek at the WV loop which says it all. Lots of dry air and shear ahead. Plus Marco is small so even more susceptible. Looks like 00Z guidance agrees and is coming in less intense than the 12Z. Maybe the NHC will lower their guidance since they didn’t have this guidance for the 5pm package.

http://rammb.cira.colostate.edu/ramsdis ... display=24

My post above yours tells the story though mid-level will likely be problematic too. Definitely looks like something you'd see in October with a trough digging into the Western Gulf.

[Kingarabian]

I literally did a double-take when I looked at the NHC 85mph hurricane forecast. I don’t see that happening. Just took a peek at the WV loop which says it all. Lots of dry air and shear ahead. Plus Marco is small so even more susceptible. Looks like 00Z guidance agrees and is coming in less intense than the 12Z. Maybe the NHC will lower their guidance since they didn’t have this guidance for the 5pm package.

http://rammb.cira.colostate.edu/ramsdis ... display=24

My post above yours tells the story though mid-level will likely be problematic too. Definitely looks like something you'd see in October with a trough digging into the Western Gulf.

[url]http://tropic.ssec.wisc.edu/real-time/atlantic/winds/wg8midshr.GIF[/ur]

That's pretty favorable mid level shear up until landfall which is exactly what the NHC mentioned.

[FixySLN]

I literally did a double-take when I looked at the NHC 85mph hurricane forecast. I don’t see that happening. Just took a peek at the WV loop which says it all. Lots of dry air and shear ahead. Plus Marco is small so even more susceptible. Looks like 00Z guidance agrees and is coming in less intense than the 12Z. Maybe the NHC will lower their guidance since they didn’t have this guidance for the 5pm package.

http://rammb.cira.colostate.edu/ramsdis ... display=24

My post above yours tells the story though mid-level will likely be problematic too. Definitely looks like something you'd see in October with a trough digging into the Western Gulf.

http://tropic.ssec.wisc.edu/real-time/atlantic/winds/wg8midshr.GIF

I'm inept, apparently. Will that steer Marco to the east or encourage more of a Western shift? The results of the interaction itself are confusing me...

[USTropics]

In my personal opinion 85 mph will be the theoretical max this can reach, and it'll need to do so in the next 24 hours. DMAX is quickly approaching, which will provide another boost going into tonight and tomorrow morning. There is some lingering dry air to the west, but so far it has walled it off decently at the mid-levels. GFS sounding still shows the western semicircle of Marco to be at ~55% RH values, while the eastern semicircle is near ~85% RH.



My guess is tonight it will pulse with DMAX, which will allow it to strengthen a bit. The issue will be it likely pulls in some dry air as the inflow increases, which will put a cap on things. late Sunday night/early Monday morning is when we start to see issues, as mid-upper level flow will be from the S to SW (and the storm will be positioned to the NE of the dry air mass as well):

[USTropics]

Right now degradation of structure is being attributed to upper-level shear:

Marco has taken on distinctly sheared appearance. Reports from an
Air Force Reserve Hurricane Hunter plane, microwave imagery, and
radar imagery from Cuba all indicate that deep convection is limited
to the east side of the tropical storm and that it no longer has a
nearly closed eyewall. The degradation of Marco's structure appears
to be primarily due to strong upper-level southwesterly flow.
Despite the shear, the plane still measured SFMR winds near 55 kt
and the intensity is held at that value.

I still think we get a decent convective burst tonight/morning that lets Marco strengthen some more. For landfall in 48 hours, difference between a strong TS/minimal hurricane means nothing.

[tailgater]

If you go the band 8 water vapor loop set at 60 mins for 30 frames, you can see the 1st trough lifting out the lower Mississippi valley and the next one diving down through RGV. Also the dry slot in the lower GOM/BoC is dissipating

https://rammb-slider.cira.colostate.edu/?sat=goes-16

[hurricanehunter69]

Yep...an excerpt from the movie Jaws...."you say Barracuda" ( crickets ) "you say Shark" ( everybody takes notice! ). It would make sense to err on the side of caution here with the wording of hurricane. Let us not forget how Cristobal brought a 7.5 foot storm surge to this area!

[Steve]

HMON looks to be heading to the MS Gulf Coast on its trajectory at 33 hours. Most of the bad weather is in Florida, but it's got weather with it on the model which it shows at 991mb.
https://www.tropicaltidbits.com/analysi ... 2300&fh=33

But then 39 hours it's going for Mobile Bay but still offshore @ 998mb so weakening coming in.

[Steve]

HMON goes up Mobile Bay but continues to weaken. That's a nightmare scenario dodged because of a weaker storm, but there are lots of homes along the rivers and places subject to tidal flooding.
https://www.tropicaltidbits.com/analysi ... 2300&fh=45

[Steve]

HWRF comes up toward Empire and Grand Isle but the low center moves west weakening and mostly around the coast.

Looks like weather and bands from NWFL through here .
https://www.tropicaltidbits.com/sat/sat ... product=ir

[dexterlabio]

What a difference 24hours can make. Last time I checked in here, Marco had the closest shot at hurricane status. Now Laura is the one to watch in the gulf.

[Blinhart]

What a difference 24hours can make. Last time I checked in here, Marco had the closest shot at hurricane status. Now Laura is the one to watch in the gulf.

I think Recon missed the point that Marco was a hurricane before the effects of the weather around him got to him and got him back under Hurricane level, but he still has a slim chance of making back up because of the hot water he is over.