Quincy

It’s the 84hr NAM. That’s all we need to know. Plus that sounding is a bit contaminated. So much can change this far out, especially with earlier season events. The potential spread for Saturday is quite large. We first need to see how the next couple of days evolve, then focus shifts toward the potential for early initiation on Saturday.

Two part post, first focusing on recent and short-term severe threats, then addressing Thursday and beyond. Yesterday I headed out to West Texas for a conditional supercell threat. Storms initiated near a triple point in the afternoon and one transient supercell evolved. I tracked the storm across Fisher and Nolan Counties, before calling it a day when the storm passed over I-20. Structure was as expected, noteworthy and interesting, but nothing super crazy or "epic." If anything, the scene from the backside of the storm with mammatus and nearing sunset was the most photogenic. Today I'm focusing on West Texas again, albeit slightly farther west than yesterday. Moisture and instability should be more favorable today, although forcing is a bit more nebulous. 500mb height tendencies should be fairly neutral, although there are hints of a weak disturbance ejecting off the Southern Rockies later today. Convergence will be maximized near the dryline and there is the potential for isolated convection around 00z. For several runs, the HRRR was very consistent showing convective initiation, although recent runs have backed off a bit. Other high resolution guidance is mixed, but seems to argue against a storm being able to form. The 12z 3km NAM shows attempted, but ultimately failed CI. The SREF is more mixed, but several members do show convection in West Texas between 00-03z. I'd say the odds are close to 50/50 at sustained convection forming. Given the setup, any convection should be very isolated. If a storm does form, with better low-level moisture and a larger warm sector than yesterday, it will likely become severe. Now that I've had an opportunity to actually look at Thursday in some detail, here's what I think: Thursday Synoptic pattern certainly suggests a threat of significant severe. Some of the surface features still need to be resolved, but the expectation is for lee cyclogenesis off the Front Range late Thursday. At least isolated convective initiation seems likely from eastern Colorado into western Kansas and possibly parts of southwestern Nebraska/panhandle. The increasing low-level jet and strongly backing flow in the boundary layer suggests significant severe will be possible, including a strong tornado potential. If there's any caveat for the Central Plains portion of the threat area, it's that early day convection on Thursday could play a role on the quality and size of the warm sector. Some guidance shows widespread morning precipitation over Kansas, which could narrow the warm sector, especially if outflow surges far enough south. Still, even the worst case scenarios manage to form isolated storms in western Kansas late Thursday. Further south into the Oklahoma/Texas panhandles and far western Oklahoma... convective initiation is much more uncertain. While many of the global models show convection, high resolution models either show weak/failed or no attempts at sustained convection. The background environment would conditionally favor convective initiation, given substantial height falls, large buoyancy and favorable low-level moisture (much better than last week). With that said, I pulled some forecast soundings and it appears that residual capping tries to preclude storms. The new 12z 3km NAM has taken a step toward more storm potential, showing a narrow sliver of eroded convective inhibition just ahead of the dryline. This is reflected with attempts at CI in the reflectivity fields. One last observation for Thursday is that the analog guidance is surprisingly wimpy looking. A few analogs do point toward enhanced (for the lack of a better word) events, but several show little to no severe storms. Obviously, that extreme seems unlikely, but the most probable solution is that severe storms are isolated to scattered, rather than widespread up and down the entire length of the dryline. Most of the analogs narrow in on northeastern Colorado into Kansas, which makes sense given the setup. Again, activity farther south is more uncertain, but if a sustained storm is realized down there, significant severe would also be possible. Friday A surface low deepens and occludes across Nebraska during the day with a pronounced shortwave impulse. Model guidance shows a robust daytime low-level jet ejecting east, in excess of 50 knots across Missouri, but also becoming increasingly displaced from better buoyancy to the west. Convective initiation seems likely from eastern Nebraska, southeast across the Lower Missouri Valley. Storms farther south toward the Ozarks and eastern Oklahoma is a bit more uncertain. Either way, even if storms do form, they'll be pushing into an increasingly hostile environment for storm chasing. Saturday I try not to get caught up in details this far out, so I'm not going to analyze this potential threat too much. There is also great uncertainty and wide model spread with convective evolution through the day. On the heels of Friday's shortwave, a deeper shortwave is forecast to dig across Colorado/New Mexico, ejecting across the Plains. The most glaring red flag that I see at this juncture is for the potential for widespread early day precipitation/convection. That could really throw a wrench in this threat, as if there is more capping and limited daytime precipitation, the setup otherwise looks like it could have a high ceiling across much of Kansas/Oklahoma/Texas. We'll have to stay tuned and see how things evolve.

The synoptic pattern has multiday potential, but I’ve learned to be skeptical until the day of. All of the hype lately (mainly talking about social media and news outlets, not here) is way overblown. Last week was supposed to be some historic event and it was mostly a dud. Every forecast trough is supposedly the “best setup in years” according to some. It’s really muddying the waters and desensitizing the general public. Big trough in spring ≠ mega outbreak. Despite living in Oklahoma, I’ll most likely be sitting these events out. With the hype and potential location, it will be a zoo storm chasing anyway. Being the rebel that I can sometimes be, I’ll be out in West Texas today and tomorrow. There’s a low probability for an isolated supercell both days. Sure, nothing might happen, but I’d prefer to be out when it’s quiet, rather than a circus.

12z 3km NAM has very good verification with Oklahoma dew points, as moisture is over performing many progs. On the other hand, most models (NAM included) show cloud cover, midday/afternoon precip and limited instability across central Oklahoma on Monday. One area to watch may be western Kansas, as some CAMs try to initiate isolated storms around 23-00z. I think it was two or three years ago where an early season event looked like a CAP bust, except an isolated storm blew up and went nuts over western Kansas. The timing of everything seems to be slightly late for widespread CI, but if moisture is over performing and more CAMs are coming onboard with isolated convection, watch out. Monday is quite a complex setup with many different areas to watch. I’m not really concerned about Oklahoma (prior to 01-02z), but aside from isolated dryline storm potential in western Kansas… storms also appear likely near the warm front in Nebraska, while some guidance suggests CIN may erode enough for storms farther SE into northeastern Kansas. West/NW Texas could see afternoon storms, although the parameter space seems disjointed enough to suggest mixed/messy storm modes there. Hell, you could even see a storm near the triple point in the Nebraska panhandle or just downwind of the Black Hills. More widespread convection appears plausible after dark across Kansas and surrounding areas. It feels like an event that will probably see wide gaps in storm coverage. To a point where swaths of the ENH risk may see nothing at all, while an isolated storm or two could be prolific. It’s still a wait and see type of setup, so I won’t try to nail down any specifics. Confidence is lower than usual given the synoptic pattern. I remain pessimistic, but not as much as say 24 hours ago.

I’ve mostly stayed quiet on Monday because the models keep shifting. Just looking at the last few runs of the 3km NAM, now that it’s in range… the warm sector ahead of the dryline keeps narrowing, to a point now that the 48hr prog for 00z Tuesday looks bleak for pre-sunset convective initiation prospects. At this point, daytime initiation in Nebraska seems more plausible than OK/TX, closer to the surface low. Tuesday is also getting more intriguing, particularly around the lower Missouri Valley vicinity, but maybe around Arkansas too. The slower progression of the system seems to suggest Tuesday *might* be the main show. If trends have taught us anything, it’s that nothing is set in stone, especially several days out. Things may continue to change. By the way, last check for Monday is that 4/26/14 showed up as a top analog. That event featured isolated severe storms going up around 01-02z in far northwest Texas. The next day… that featured isolated intense (tornadic) supercells in Arkansas, as well as severe storms north into Missouri and Iowa. Take analogs with a grain of salt, because 4/14/12 was showing up for a while with Monday.

Interesting, yes, but I’m not on board with a high-end event yet. Still early in the season, so smaller scale variables could still throw a wrench in it. Models are waffling on timing and while it doesn’t look perfect, I don’t see any harm in starting a discussion this far out. Analog guidance suggests a Day 6 30% contour is warranted. In fact, just looking at the medium range models, this could be a multi day threat that also includes Tuesday and/or Wednesday.

Pretty meh so far across the Oklahoma/Ozarks portion of the threat some. Messy storm modes and somewhat veered low level winds. It will be interesting to see if anything goes up near the Red River later as the low-level jet increases. Otherwise the near-term tornado threat in Oklahoma is quite low.

12z soundings show an unseasonably unstable air mass already in place (for early day, mid-March standards) with some capping. However, guidance erodes capping quite quickly with some model solutions initiating storms prior to midday. Wind profiles aren’t ideal, but should be sufficient for initial supercells. Given the background environment, you could see a few intense supercells form. I’d expect complex storm modes/interactions with time, but if a storm can thread the needle, significant severe is certainly a possibility.

Kansas and Missouri are the areas to watch late this afternoon into this evening. A tornado threat could develop near I-70 along the warm front, but we’ll have to see how narrow the warm sector is and if storms outrun the front. Right now, dew points are confined to the 40s across much of Kansas, but lower 60s dews have surged into northeastern Oklahoma. At one point there was some concern about convective initiation near the dryline in Oklahoma. That seems unlikely at this point. A non-zero shot, as a few outlier models (6z RGEM) still try to convect there. Very shallow moisture will likely preclude any development. Even if something were to initiate, it would likely be short lived. Tomorrow looks interesting over a larger area with a broad warm sector anticipated. Evolution of overnight storms into early tomorrow morning will be a factor to watch. Stay tuned.

Not common for an essentially straight north from Bermuda with no recurve. As modeled, it even bended back NNW a bit. It’s a good thing it wasn’t a 200 miles west or it would have been a much higher impact event for the I-95 corridor.

Wow. No kidding. PWs mostly below an inch, outside of the Cape/isIands. That’ll do it.

Did Kev write this headline? https://grist.org/extreme-weather/its-gigantic-hurricane-lee-heads-for-new-england-and-atlantic-canada/

A nudge west, but still avoids US landfall. Curves right up into Fundy.

12z 3km NAM shows several hours with gusts over 60 mph on the outer Cape. Probably a bit overdone, but wouldn’t be surprised to see a few obs with gusts over 50 mph.

Even the SREF is east. Maybe it ends up being a dry weekend for TOL with just an occasional light breeze?

The outliers are shifting east and there’s more support for a wide right turn, than a rogue landfall left. I’d stick near the mean. Of course it could waffle a little either way, but there’s a higher probability for this to hit NS than for the Cape to see landfall. SREFs are going the same way. A few kept showing a left hook into SNE. Now those have tightened up to the east.

A tighter look at the 18z GEFS at 78 hours shows about half of the members east of the mean. Those to the west are relatively tight. Only about three members bring the center close to Cape Cod. None show a landfall there.

That’s what I mean. The totality of the runs over the past few days did not show a landfall. Kudos to NHC for not waffling and sticking closer to the consensus with continuity. Live and die by the model runs. Another great example that ensemble means can be very helpful when there’s uncertainty.

Granted the track with Lee is unique, we’ve seen this same thing play out almost every year. A tropical system threatens the East Coast. It’s not unprecedented for landfall, but it’s relatively uncommon in most cases. Model noise shows a few runs that either make or threaten landfall and people start freaking out. I did play into the hype a bit, but it’s time to accept that any substantial westward trend is done What percentage of the model runs/ensemble members showed a New England landfall over the past 3-4 days? 10%? 20%? 5%? I still think there’s a legit possibility that the Cape and parts of coastal Maine are affected with tropical storm force conditions and some flooding, but anyone hoping for a repeat of Bob, Gloria or Sandy are going to be disappointed.

GEFS is way SW from 06z, but a tick east of 00z. Solutions are consolidating and intensity has notched up slightly. (Mainly due to less spread dampening the mean)

GFS ever so slightly east. The wind field is still fairly intact. One of the stronger runs. Verbatim, looks like a cat 1 cane just SE of Maine, if the run is taken literally. There’s a little tease jog NW between 72-78hr before it makes the NNE turn into the Bay of Fundy.

You actually want slower movement now, so there’s less interaction with the initial exiting shortwave. Less opportunity to get tugged east. The models seek to be locking in. There’s some noise, but I don’t think there’s room for any major shifts west or east now that we’re getting inside of 72ish hours.

Keep in mind, this thing is going to bend back N and possibly even NNE for a time around the Atlantic ridge, before a likely shift back N/NNW. Not seeing any interaction with an approaching shortwave across the Upper Midwest/Great Lakes. That will be key if there are any hopes left for a westward turn. I imagine it won’t go much more west than the current consensus, but you never know.

Through 72 hours, it’s basically between 00z and 06z runs. Heading for Bar Harbor it looks like.

No big changes, almost identical to the 00z run thru 57hr