Quincy

The last month of May in the U.S. with less than 100 tornadoes was 1970 with 88. http://www.tornadohistoryproject.com/tornado/1970/5/map

Started in Wyoming today. Chased a couple of initial supercells forming near the Laramie Mountains. Not much worth sharing. Next, dropped into the Nebraska panhandle into a more moist low-level environment, but the linear convection kept unzipping southward. Finally watched a tail end transient supercell put on a lightning show in northeastern Colorado. One of my goals this year is to step up my lightning photography game, which could use some work.

The setup tomorrow is a bit similar with a bulge-type feature leading to a locally enhanced area of low-level shear. Wonder if it’s a repeat, but will keep that talk to the other thread. I bailed on the Montana chase idea today. They did have a few transient supercells, but didn’t want to get too far out of position for tomorrow or play around with the complications that come with out of state travelers there. Even though I barely had any contact with anything there, outside of my shoes on the ground.

I’ve had an opportunity to look more closely at progs for tomorrow. Upper level winds are unidirectional and display some VBV characteristics, especially across the northern High Plains. It does not help that deep shear vectors will be nearly parallel to the initiating boundary in most cases. Low-level CAPE looks minimal at best. With that said, wind profiles show enlarged low-level hodographs with 850mb winds SSE/SE. My guess is there could be a few initial supercells before storm mergers and surging outflow turn the storms into a linear mess. CAMs are varied with where CI will occur, but really a tall swath up and down the High Plains could see activity.

The synoptic pattern favors episodes of severe thunderstorms from the High Plains, across the central/northern Plains through mid to late week and potentially continuing through this weekend. The trough axis over the Rockies early this week should initially favor the High Plains Wednesday/Thursday and gradually shift east across the central states in the 2-3 days following. I’ll defer further discussion to y’all from here on out, as I’m trying to not get too caught up in the medium range. Wednesday features an enhanced (ENH) over the far eastern Wyoming and adjacent areas...

Quick glance for the deadly Louisiana tornado... About 35 knots of bulk shear with 500mb winds out of the NW, backing to SW at the surface. Marginal MLCAPE ~500 J/kg, however there was sizable 0-3km MLCAPE around 100 J/kg. A localized area of 200-300 m2/s2 0-1km SRH was also noted. LCH didn’t launch a RAOB, but the 00z 5/18 SHV sounding gives a rough idea of the mid to upper profile. There was more backing of low level winds where the tornado occurred, resulting in larger 0-1km hodographs. https://www.spc.noaa.gov/exper/soundings/20051800_OBS/

I’ll take a look into this... Had a few transient supercells in Montana today, but the instability axis was too narrow and meager to support anything more. Tomorrow’s setup is in the same general area, except moisture return should be better.

Dragged myself up to Montana for a couple of days... Never chased this far NW before. Today might see a high based supercell. Tomorrow looks more favorable. Either way, deep layer shear is impressive and it doesn’t take much moisture at these elevations... Wednesday looks like a mess up and down the high plains with unidirectional mid/upper level winds. There should be some backing of low-level flow, but I’m not overly excited at this point.

Caught a shelf cloud in Iowa before it got dark:

I followed that storm into Iowa. It looked really interesting for a while, but low level rotation was not very focused. Did see a lot of very low hanging appendages though. It died upon crossing into Iowa.

The Arklatex setup has some tropical characteristics to it. Definitely not something you’d usually see in May.

It does. I haven’t cracked its code yet... Today looks interesting, but I do see a few potential caveats. First, low-level instability looks good, but CAPE profiles aloft should be quite skinny. Second, low level winds are backed, but forecast soundings show only modest enlargement of 0-1km hodographs. Moisture looks sufficient and breaks in the clouds are allowing for some destabilization. Forcing is a little bit nebulous prior to 00z, but storms could initiate in three regimes: 1. In the narrow warm sector as capping is minimal. 2. Near an effective warm front. 3. On the SW flank of ongoing convection. It looks like the strongest forcing does not arrive until after sunset. I still think a few storms can initiate, but if upper level support was just a bit faster, I think we’d have a higher ceiling. On the flip side, modest forcing might save this from rapidly blowing up into a sloppy mess. I’m interested to see how it turns out.

Heading toward northeastern Colorado. Not the most impressive setup, but wind profiles along with modest instability might support a supercell or two. Not playing with that junk in Oklahoma. Deep layer wind profiles are hideous for mid-May.

I caught the beginning stages of that storm:

A few areas to consider today... The most obvious seems to be southeastern Kansas. With strong/extreme instability and modest shear, I’m not sure if we’ll see a clustered mess or a slow-moving supercell just before 00z. It could go either way. The dryline/front intersection out west looks interesting, but large T/Td spreads and marginal shear could lead to junk as well. Keeping an eye on Colorado and Nebraska as well for good measure.

Feel free to ask questions too, that’s one of the best ways to learn.

Looks like a few storms went up right before sunset. Not a complete bust. Tomorrow could feature some fun in Kansas or possibly even eastern Colorado...

Shear remains unfavorable for supercells:

HRRR still only shows 25-30kt shear at CI, but it does increase to 30-40kt by 22-23z. It will be interesting to see if a storm can manage to form between GAG and DDC. There hasn’t been much CAM support for that, but the environment would be conditionally favorable for a discrete supercell. Otherwise it looks like a sloppy storm mode with rapid clustering.

One of the key factors to consider tomorrow is deep layer shear. Sure, instability will be there and critical angles look good (favorable turning with height), but 30 knots of shear is very marginal/borderline. 12z 3km NAM shows only 25-30kt deep layer shear along the dryline at CI time. HRRR is not much better at around 30kt. Sure, you could get a storm or two to take on supercellular characteristics, initially, but a rapid transition to messy/clustered storm modes looks likely. Edit to add graphical support:

This can be a thread for some of the less significant severe weather days... Took a gamble and went out to West Texas today. Missed the supercell up near Amarillo and nearly busted the whole chase. Did have some redemption at sunset as a QLCS intensified not far from Lubbock.

Flipped to snow as far southeast as MMK. Been snowing at Danbury for a bit too. Almost kinda miss Connecticut in a weird way at the moment...

Still chasing this as it’s gradually turning right.

Getting into position near CDS now.

Based on short term CAMs, convective temperatures (91-92F) are almost reached near/just NW of CDS and this is supported by agitated cu fields east of AMA.