csnavywx

Florence is looking pretty chunky on satellite. Been gorging on all that meaty OHC. Wouldn't worry about the satellite appearance too much. This is probably 125-130knots atm. It also has some time to complete another EWRC and expand even more if it decides to do so.

This is the nightmare scenario I was afraid of. That trend from 3 days ago never did stop and now with the midwest ridge helping out, we've got ourselves a coastal staller. An earlier stall isn't necessarily good either, because while there will be some extra time for wind shear to weaken it, I don't expect the shear to stay indefinitely and the Gulf Stream will abate some of the weakening associated with upwelling, especially if there actually is some slight southwest motion.

We're dangerously close to this thing not quite making it onshore on the last few runs. This weakening trend of the WAR is bad news. This also has implications for the track forecast since a stronger/offshore vortex will not be pushed by just the weak lower level southeasterlies and will have a propensity to stay offshore due to weak southerlies or southwesterlies aloft. The individual EPS members show just that and a decent minority now don't have landfall for several days, hovering offshore instead. Also a minor note since I brought up the EPS -- it's still displaying a small left of track bias. This morning's position is again on the right edge of the envelope. It's a relatively small track error and may not end up mattering, but given the situation later on, it might make a difference to landfall times, since the right side of the envelope is favoring closer to Morehead City, NC and a longer stall/loop.

The tendency is restrengthening after the completion of an EWRC, especially since it will be in ideal conditions over the next 48 hours.

Secondary wind max definitely showing up on that last pass. The wind max is out a ways, so this one may take quite some time to contract. The bad thing is that this is going to significantly increase the wind radii.

Not really much of an issue. There's some dry-moating going on due to internal processes (perhaps the start of an ERC since it appears there might be a secondary wind max trying to form further out).

Careful with that shear product. Some of that is contaminated due to storm outflow. Actual shear is only about 5 knots right now. There's a bit more on the southeastern side of the circulation (you can see the outflow restriction there) and that might be responsible for part of the more poleward motion than expected in the last several hours. Edit: The shear product lags the TC center since it is only updated every so often. You can see where the TC center was actually analyzed at the time.

18Z HWRF is notably slower and further northeast for landfall now -- matching the HMON. Uncertainty now abounds on what happens after landfall as steering collapses. Some southwesterly vertical wind shear is likely by this point, making me think the vortex will tend to favor turning a bit more poleward. It's not out of the question that it may be a bit of a struggle to get it onshore as frictional torquing and shear try and oppose landfall for a while.

That's true, although storage remains a huge issue and will for some time. Hence my personal support for nuclear baseload to avoid the issue. I do think there may be some potential for transitional and/or transient effects on the way to a greenhouse/hothouse state that may not take that long to take effect. There's some evidence that Northern Hemispheric and Southern Hemispheric base climate states were at least partially asymmetric during the Pliocene. Some of this may have had to do with different ocean currents (isthmus of Panama, etc), but I also think there's a part to play in the lack of widespread ice sheets in the NH. Because of this much smaller amount of persistent land ice, an equable climate state is probably easier to reach in the NH and Pliocene/Miocene high latitude temperatures seem to support that. Whereas with the SH, glaciation occurred much earlier, ice is much more extensive and will probably require CO2 north of 550-600ppm to deglaciate the EAIS, which will take centuries. We'll have significant problems well before that though. Aragonite undersaturation in surface waters will begin in the Southern Ocean under RCP 4.5+ starting in the 2030s and become widespread quickly. Coral reefs are already suffering significant mortality from bleaching events. Permafrost limits are reached en masse starting around +1.5C.

It's not much of a decrease. There were some recent papers on the issue, where emissions were increased and then suddenly "shut off" to zero. The result was a short dip followed by an extremely long plateau (think centuries) due to stored heat being released from the oceans, though the effect was considerably worse at RCP 4.5+ levels than RCP 2.6. CO2 concentration decreased slowly as well, due to Henry's Law, where the near-surface ocean dissolved CO2 started to come back out of solution and into the atmosphere, slowing the decline. None of those dealt with permafrost emissions, which have the potential to throw a wrench into any long-run calculations, even at the 2.6 level. The hidden, implicit conclusion is that NET (negative emissions technologies) and large-scale BECCS are going to be necessary to bring temperatures back down. Once you get above the ~450 level, you're more or less stuck with the temperature max you achieve for a very long time without explicitly drawing down carbon from the atmosphere.

Geopolitics is definitely a dark horse here, whether for good or ill, I can't tell yet for the long run. Recently, it's been decidedly negative. We've been following Shell's infamous "Scramble" scenario much closer than the "Blueprint" scenario so far. Incidentally, most of the heavier damage and risk curve steepening comes in above +1C, right around when emissions need to be headed sharply downward. I think some folks think that the impacts of moving from +1C to +2C or +2C to +3C will be like moving from 0C to +1C. If anything, the risk and damage potential increases by up to an order of magnitude for each step. It's generally hard for people to envision or deal with non-linear scenarios. Case in point: Ask someone to move two pencils together smoothly and they'll do well. Ask them to do it with some decent handheld magnets and they'll do well up until the magnets get fairly close, then they'll do pretty badly.

Yeah, RCP 8.5 is likely too high in the long run, but we're running ahead and will likely stay ahead of all of the other scenarios through at least 2030 if not 2040. Especially RCP 2.6, which is foisted as the hopeful scenario all the time. For reference: 2018 CO2 is 408ppm. At constant emissions, it will be ~438 in 2030 (+2.5 ppm/yr). At current rates of CH4 emissions, we'll be at ~1950ppb (interestingly only RCP 8.5 shows any increases in CH4 concentrations, all others show drops). RCP 2.6 at that time is 431 and flattens sharply right around this time. RCP 4.5 is 435 and RCP 6.0 is 429. RCP 8.5 is 449 ppm. Constant emissions and flat CH4 are probably optimistic scenarios at this point with emissions still rising, but that still places us above everything except 8.5. I'd wager the over/under is probably going to be in the 440-445 range in 2030.

I always love those GSM predictions. They're so bad that it ends up being good entertainment. I also love the incredulity at what +6-8C would do. We don't have to guess. That's what paleoclimate is for. Virtually all of the big extinctions are due to large excursions of carbon from igneous provinces. The trick is the atmosphere couldn't care less if the carbon is from Volvos or volcanoes. Wanna know what +6C can do? Ever heard of the end-Permian? The difference is the sun is brighter in this era (by 2.5% since the end Permian and 0.5% from the PETM), so not nearly as much carbon is needed to get those very high temperature levels.

Not unusual for a sheared TS to have convective bursts. Mid-level shear brings low theta-e air over a moist high theta-e boundary layer, causing convective instability to increase. A convective burst results. The burst can last a few hours, but often results in low theta-e air being dispersed into the boundary layer through downdrafts/microbursts (from the mid-level dry air), stabilizing it. The convection weakens and disappears. Over several hours, the boundary layer recovers and another burst ensues. This can continue so long as there's enough convergence and lift from the old vortex to initiate convection and as long as instability can be regenerated.

Definitely a hefty mesovortex in there. Probably some sig. winds ongoing over Prince George at the moment.

Healthy bow starting to develop. Low-level shear isn't anything to write home about, but average boundary layer flow is easterly, which should maximize convergence. Effective bulk shear is around 40 knots though, so this could become a prolific wind producer if that cold pool continues to develop and/or a nice bookend vortex can get going.

Yep. Fusarium root rot can do that as well. I had a real issue with that a couple of years ago. Had to start using RootGuard to keep it in check, which works well if you keep up with it.

Exactly. Thunderstorms and/or lightning strikes within 5 miles are considered to be "on station" per observation rules. Storms from 5 to 10 miles away are considered to be "in the vicinity". Either condition is good enough to trigger a SPECI (special) observation.

Full wipeout of the Beaufort is ongoing, per usual, along with all of the cycled MYI there. With the current clear conditions and forecast over the ESS, I doubt much of that ice survives past mid-August. It's already showing negative signs from just the past 2 days on Worldview. The big block will probably thin CAB ice as well, but there's some solid stuff left there, as mentioned earlier.

Worldview seems to corroborate the satellite data. Lots of soupy/ragged looking ice over there. Typically symptomatic of a reduction of floe size as it thins. It looked relatively fine up until the 15th or so, but deteriorated quickly after that.

Don't be fooled by surface temps. They never deviate much from about 1C at this time of year. This is due to heat exchange between the ice and the overlying atmosphere. 850/925 temps and winds are important. Even if 850s were at 20C with the sun out at full blast, surface temps would not rise much due to heat absorption from the ice phase-changing to water. It's the same principle as having ice in your drink. The temperature of the drink will not rise much until it is nearly all melted.

Bit of a convective feedback issue going on (especially on the 3km), so use with care. Low placement and strength scream issues with latent heat release.

SMB doesn't account for calving and discharge at the periphery, which is significant. Despite the cooler conditions, this surface melt season is still above the 1981-2010 average and with the oncoming melt in the next week or two, it will probably remain so for this season. The 2012 melt season was exceptional and doesn't (yet) represent the norm. When we get to the point where SMB can't crack positive (as it almost did that year), it'll represent the non-viability of the ice sheet in the long term and a permanent shift to widespread net ablation. I suspect that will happen consistently when we lose sea ice in the late summer.

Bluewave, You posted this paper earlier and the post is gone: https://www.nature.com/articles/ncomms14375 I meant to comment on it earlier but ran out of time that day. It's definitely an interesting and concerning paper. I've read it a couple of times before. I'm not sure that's what's going on here, as it seems that most of the cooling was from diabatic heat loss, but the mechanisms mentioned in the paper are definitely a concern down the road. It looks like most of the ones that predict deep ocean convection collapse in the SPG target right around mid-century. The SPG collapse happens almost regardless of emissions path too (happens in 2.6 and 8.5). The fact that only the higher skill models do it and it happens regardless of emissions scenario does set off an alarm bell that they might be on to something. The authors obviously thought so as well. It's interesting that the earlier paper you linked (from 2012) showed some SPG instability that the authors dismissed as a 'freak occurrence'. Perhaps not?

The flip side to this is the fact that the record +AO still isn't enough to get a recovery to pre-2007 levels -- only enough to mostly cover for the higher winter temps. You may be right that when we look back, 2007 may have been the most important point in the entire sequence. I'm sure we'll get to some point where extent drops out rapidly towards zero in late Aug in the future, but the biggest change was probably the Beaufort gyre turning from a nursery for ice to a MYI graveyard. That change looks irreversible at this point.