csnavywx

We're at/near peak shear and Henri seems to be holding up. 27kt analyzed on the 06z GFS and 31kt on CIMSS. It decreases through today and into tomorrow, dropping to or below 20kt by 06z tonight and down to 10-15 by tomorrow evening.

Regardless of track, if this thing does hit NE, it won't be trucking along. The trough is weak and trapped underneath a ridge. It'll be over cold water for a while, which caps LF strength.

As OSU pointed out, this thing is already pretty far east. Much will depend on how Henri gets through the next 24-48hr. Shear peaks in the ~36hr timeframe at around 25kt (from 16 now). That's probably not enough to decouple it completely, but depending on how convective trends end up, we could see some further southwesterly adjustments -- albeit the ensemble spread suggests not as much as we've had over the past day or two.

The airmass getting entrained via shear isn't particularly dry during max shear either, so I'm leaning stronger than I would normally.

They're late to the punch. It's already happened twice in the last couple of weeks. EOSDIS shows that pretty well. And I don't know about the "first time" part. Been some pretty big fire seasons up there the past few years.

24 minutes ago, Typhoon Tip said:

Through both indirect and direct geo-physical various circuitry ...the following article probably is more connected/suitable for this thread. Example, "..Complex interplays between the AMOC and North Atlantic sea-ice cover in conjunction with salinity and circulation changes have been proposed as physical causes underlying the DO cycles..."

https://www.nature.com/articles/s41558-021-01097-4.epdf?sharing_token=qWMQcnRcVRZQmZ_yahYbd9RgN0jAjWel9jnR3ZoTv0ODQw4Na6S4LwvIIwjZ_S3NdBoG6pi8c5NBfIwoUKp1VK_OHHszXMnB3OMoyz8L8emOhG-hoDsJyn1YMubz_IampYbIRg_8P9vjnfIPPzRQwm6m9BfwEGfoLu0JsB4E2trSfyu4r947mOz1oZQlyxQxZLxaMkEINR4Wt7XEIrPrRkahci-lKgCSTZahFzlH7wM%3D&tracking_referrer=www.washingtonpost.com

"...Here, a robust and general early-warning indicator for forthcoming critical transitions is introduced..." c/o above -

I'd also point out that we in the field began involved in conjecture as well as reading formulated papers/science on the subect matter all the way back to the early 1990s.   Really interesting embedded statements, like:

"...Different lines of evidence from palaeoclimate proxy records indicate that Northern Hemisphere temperatures have varied abruptly at millennial time scales during previous glacial episodes, with corresponding changes of the AMOC between its weak and strong modes1,15,16...."

Read through that paper once this morning. Will be combing it a few more times before I make up my mind on it. It obviously needs more confirmation and research, but if Rahmstorf et. al and now Boers are on to something with AMOC stability states, this is extremely bad news. AMOC instability falls into the category of low prob. but very high impact. Whelp, the probability might be higher than we appreciate.

Reminds me of a paper not too long ago, but it was more focused on the sub-polar gyre. Boer's paper is making the case that *most* CMIP models are too stable.

Link to that one: https://www.nature.com/articles/ncomms14375

On 7/20/2021 at 6:46 PM, A-L-E-K said:

Naso keen on our new summer doldrums smoke watching season 

Gonna be a LOT more of that this year and in the future. While the stuff out west is going first, as the Manitoba fires show, those jack pine forests can go up in smoke too.

3 minutes ago, BuffaloWeather said:

https://en.wikipedia.org/wiki/Year_Without_a_Summer

That was mainly via SO2 forcing via the stratosphere.

18 hours ago, donsutherland1 said:

This is another bad break on the climate change front. There had been some hope that cloud changes could somewhat dampen the warming. Research by Jessica Tierney et al., hinted at amplification from the paleoclimate record, but there was no direct evidence. This paper provides that evidence. Its findings underscore the urgency of moving faster rather than more slowly in curbing greenhouse gas emissions.

Yeah, that's almost a complete shutout of ECS <= 2C by their calculations. While the mean looks to be around 3.2, that PDF is .... not great. Anything under 2.5 is pretty unlikely and pretty decent probs of something closer to 4.

From what I'm gathering, that's also just from the observational record. Paleo suggests ECS itself might be variable depending on the state (higher during warmer climates for instance). https://advances.sciencemag.org/content/5/9/eaax1874

Having said all of that -- I'm also wondering if the laser-like focus on ECS is a bit troublesome in itself. It's possible, for instance, that we're focusing a bit too hard on global temps and not enough on downstream effects -- like asymmetric hemispheric response. All evidence points towards the NH losing ice much faster than the SH and indeed paleoclimate tends to suggest that the NH and SH can exist in a "decoupled" state where most of Antarctica can still be relatively cold and glaciated and the NH is essentially much closer to something resembling a greenhouse climate. The GIS will still be around for quite a long time but the amount of resistance it can put up pales in comparison to the combination that the circumpolar current and EAIS can put up. It's worth noting that Antarctica glaciated pretty early on (30-40mya at around 650 ppm I think?). I'm sure the isolating power of the circumpolar current helped, but if folks like Tierney are right, that doesn't have as much of an effect as one might initially think.

1 hour ago, WxUSAF said:

It was pretty evident driving home that the smoke is reducing visibility at ground level as well.

Yep, HRRR has some pretty nasty (4-6SM vis) smoke descending to the surface tomorrow and especially late Wed. I would expect a lot more smoke haze aloft over the next couple of days, but the weak cold advection behind Wednesday's little front will probably help drag more of it to the surface. Not going to be great for folks with respiratory issues.

Can't imagine what later this summer and fall are going to look like with the way it's going out West this year.

16 minutes ago, George BM said:

That 25-27K theta-e difference. Is that between the 1000mb and 500mb level?

I generally use the difference between the mixed boundary layer and a representative sample of the theta-e minimum aloft (generally 700-600mb), though there are a few effective methods to choose from depending on the situation.

Latest skew-T fcst soundings spitting out widespread 45-55kt wind gusts (and theta-e differences between the mid-levels and boundary layer of about 25-27K, which matches) so probably a good call there by the SPC on emphasizing the wind potential. Though I think it'll mostly be outflow dominated by the time it approaches the bay, wouldn't be surprised to see some weak rotation in any discrete activity and a bit better organization in general as the windfield is already backed and dews are higher there. We're at the time of the year where the Bay is very warm (80+F) and tends to help convective activity by pumping dews and providing instability after sunset.

Convective initiation west of IAD and down closer to CHO. The cell west of IAD started putting off quite a few strikes before there was much of a BR signature. Some high grade instability to work with today and a strong sign that today's storms will likely be electrically active.

90/77 here. Absolutely soupy and miserable.

5 hours ago, mappy said:

def need some rain. very crunchy up my way. 

Such a huge difference from here. At 6.70" on the month already at NHK. Almost certainly going to add to that total tomorrow. Outside shot of reaching 10" this month.

Yep, fat CAPE profiles tomorrow with some solid 2500-3000 values showing up on fcst soundings this morning. There's *just enough* shear for high CAPE to mostly compensate, so wouldn't be surprised to see a similar setup to Wednesday, if a bit less organized.

Edit: Theta-e profiles indicate about 25K/C in between the boundary layer and mid-levels and combined with PWATs around 2", that argues for some wet microburst activity tomorrow as well. There's very little to no capping, so I would expect a bit earlier of a start time for initiation than usual. Any storms that fire early will have a good chance of being able to pulse to severe limits before weakening.

23 hours ago, bluewave said:

Very unusual to get such a low a mid-July extent with a strong reverse dipole.This used to be a cold regime that was great for sea ice retention. But the NSIDC noted how its been warmer than expected for a strong low pressure pattern. 

https://nsidc.org/arcticseaicenews/

Unusually strong low pressure (up to 10 hPa below average) near the North Pole dominated the average atmospheric circulation pattern for June

Air temperatures near strong low pressure areas over the Arctic Ocean have historically been associated with relatively cool conditions. However, June temperatures in the vicinity of the low-pressure pattern were near the long-term average.

 

Combined with winter temps, that'll end up being the kill-shot in the long run (few decades). Easy to forget that diabatic processes only go so far during the summer. If you keep mixing in much-above normal airmasses into an otherwise favorable ice-retention pattern, the lower limit is raised and the window shifts towards melting, even in good patterns. We may yet stay in this "transitional plateau" for a while longer but the creeping risk of a rapid collapse will eventually catch up as winter freezing degree days drop below a critical threshold and summer T-min increases during low pressure regimes, narrowing the stable space upon which the current pack is balanced. My eye is on the mid-2030s for something like that.

Might be faster if we don't figure out why CH4 seems to be taking off again over the last 10-15 yrs (and subsequently stop it). It rose 15 ppb last year and we might beat that this year. That's going to significantly bolster warming at those rates. I don't think any of AR5's scenarios -- aside from RCP 8.5 -- had it rising like this. (RCP 8.5 had 1923ppb for 2020 actual, and we were at 1880ish; no other scenario is as high as current until after 2040).

55 minutes ago, donsutherland1 said:

 

AGW and the severe multi-year drought can't fully be disentangled. While internal variability leads to drought conditions, AGW increases the probability of such outcomes through shifting precipitation patterns and greater drying of soil from higher temperatures. How much is climate change contributing?

Detailed multi-model analysis, which is utilized during attribution studies, would provide a good answer. But a rough approximation is possible from the following approach:

(Probability of an event under the current climate - Probability of an event under the baseline climate) / Probability of an event under the current climate

This formula provides a good approximation, because climate science has concluded with very high confidence that most of the recent warming has resulted from growing anthropogenic greenhouse gas forcing (actually > 100%, because a small decline in solar irradiance has led made a negative contribution).

I ran some numbers for Seattle. For the baseline, I used the June-August 1951-80 period (the GISS baseline, as the Seattle-Tacoma record only goes back to 1945). For the current climate, I used the 1991-20 base period.

Probabilities:

100-degree day: 1951-80: 0.035%; 1991-20: 0.078%

Actual: 1951-80: 0%; 1991-20: 0.07%

Then using the probabilities, I got: (.0078 - .0035)/0.0078 = approximately 55%. Climate change made such events 55% more likely

For 105-degree days, the climate change contribution was 61%

The actual probabilities could be somewhat higher, as climate change has made the kind of resonance events involved in this epic heat event more likely. @bluewaveposted a good paper on this topic earlier in the thread.

 

 

I'm gonna add on just a bit to what Don said for this particular event. In this case, the incredibly strong Rex block that is baking BC and WA/OR had its origin in an unusually juiced episode of convection along the Meiyu/Baui front in E. Asia. Moisture transport for that event likely originated over the SW Pac and E Indian Ocean, both of which are running above normal over a very wide area (and abnormally high ocean heat content to boot), which very likely contributed to amp'ing the intensity of the event. The latent heat release from that event helped boost the N.Pac jet significantly, causing a big downstream rossby wave break and the big ridge/block. So in a way, there's even an entangling between enhanced and extreme rainfall events and this heatwave. It's just not the kind of thing that's inherently obvious until you start digging.

After the miserable bust of Saturday, it looks like we've got a somewhat better chance today. Issues include a cap and some deep mixing potential. We're also going to probably be a bit dependent on LEWPs or bows surging well out ahead of the front to get the job done, since forcing locally will be pretty weak.

Some high-based shallow convection (just showers for now) SW of DC on the lee side. It's possible this activity could become surface based as it gets further east.

CI appears likely soon W and SW of DC.

So far, so good. That mass of convection will probably produce a coherent MCV for the region later on today. 

SPC keeping an eye out as well:

Quote

   Another likely influential thunderstorm complex will be ongoing at
   the start of the period across southern IN/OH. In all likelihood one
   or more MCVs will evolve from this activity. These storm-induced
   eddies will likely contribute to further thunderstorm development
   downstream later in the day. Too much uncertainty exists regarding
   these yet-to-develop features to warrant more than low severe
   probabilities. 

New MCS is up and going over OH and IN. Initiation likely in the next few hours over IA. HRRR really pressing this (in the form of an MCV or remnants) as a viable trigger for tomorrow. It looks like the current MCS may track far enough south to prevent it interfering with insolation too much tomorrow morning.

1 minute ago, Stormheartgypsy said:

Good to know and thanks for the info.

Is the ENSO being a neutral position playing into the "fun" weather? Or it strictly how the jet streams wobbles so far north and south and the moisture pumped in the from Gulf?

There tends to be a delay of several months between when an ENSO phase begins and ends and the atmosphere responds. It lags by 2-4 months or so. So, we're still probably feeling some of the effects of the faded Nina. The current drought episode in the West is probably being exacerbated by it (by helping shift the jet north and imparting extra subsidence). Sometimes those effects "spill over" downstream into the Plains.

3 hours ago, Stormheartgypsy said:

Just curious if this drought has to do w/ (possibly) climate change and or the ENSO has moved from what I've read to a neutral (La Nina seems to be over - for now)...

 

Would love some rain here in the MidWest (skip hop away from St Louis)...

Nina years tend to have a higher chance for summer drought but this isn't always a given.

As far as climate change goes, the trend has been for (so far) has been for relatively rapid increases in rainfall and absolute humidity (dewpoint) in the STL area but relatively modest increases in temperature. There's some evidence to strongly suggest this is due to the rapid increase in corn planting area and density, which transpires rapidly and has served to keep temperature increases somewhat muted at the expense of increasing humidity. Since corn and crop land area has reached near its maximum nowadays, I would expect temperature increases to start taking over. If that's the case, the future may include a bit more rainfall on average, but with ever bigger swings between wet and dry. Increasing whiplash or flickering, if you will. Drought sets in and ends quicker, rainfall tends to come in bigger bursts and less towards gentle, soaking rains.