WeatherArc

May 12

Current sat view

May 12

That went up very quickly

May 12

LIGHTNING ACTION Look at the amount of lightning they are pumping out aswell!

May 12

Some towers really trying over south Birmingham

May 12

Hmmm, cell north of Bristol looking a little suspicious on radar for a second. Would keep an eye on it, shear is supportive of mini-supercells.

May 12

Now surrounded by towering cumulus, some developing big bases.

May 12

Some lovely bubbling cumulus just south of Birmingham, tell tale signs of the cap weakening, keeping an eye on that Bristol cell. Further development looking likely.

May 12

Some great soundings from the Arome tonight, liking shear profiles. Real potential for 2,000+ sbcape in some areas.

Soundings taken from midlands, wales and Bristol areas.

Honestly i dont mind whether i get hit or not tomorrow, just looking forward to seeing those distant towering cumulus.

May 11

The Tall Weatherman that 3cape tho

Considering global models underdo instability, 1500-2000 sbcape looks likely. That combined with a capping inversion breaking would lead to some explosive development, shear weak but nice veering of winds from the surface to 500mb, high 3cape will slightly compensate for the lack of shear.

May 10

Wow

May 10

About 20 mins ago from my mate in Yardley Wood

Defo can see something from my room but very faint, might try to go out tomorrow night if its still hopefully around.

May 10

Wow, look at the cape in Northern Mississippi last night! I can only imagine how humid that would of felt.

Some massive hailers around in Texas last night aswell with all that instability

May 10

Sprites Thank you very much, no my username has always been weatherarc.

May 10

Nice to see the return of +15 degree dewpoints, that combined with surface heating into the low to mid 20 degrees should yield some decent cape values for this time of the year (800-1400 j/kg sbcape)

Could lead to a few thunderstorms sunday afternoon.

Despite some low level curvature present i suspect these will be pulse storms, bulk and 850mb shear is weak

Mid level lapse rates not amazing but may change models very uncertain, gfs not amazing but other models such as GDPS is more favourable (6.4+)

Low level lapse rates seem good though, gfs has 7.2 0-3km, leads to some high 3cape values.

imo cloud cover and saturation of the profile overdone by gfs, gdps likely has a better handle on coverage.

If cloud cover is sorted out and lapse rates improve i wouldnt be surprised to see 1,500 to maybe even 2,000 sbcape with much more active thunderstorms.

Heres latest UKV

Will also be watching northern France for possible development.

May 8

Sprites Your right on both reasons, its a very fine balance. I believe it was simply too much dry air, so stronger downdrafts cutting off inflow. I suspect it wouldnt of been as much of a problem if cells were discrete, but we had 2-3 cells basically congealed into a single line, i mean the forward flanks of one cell was literally the rfd of the one infront, the circulations were completely rained out and inflow kept being choked off by those massive rfd surges.

Radar image from last night, these 3 cells are all training and interfering with each other

Profile from last night, lots of very dry air at 500mb downwards. Honestly, despite what i said, looking at that sounding even discrete cells would struggle with very strong downdrafts

We like some dry air to steepen lapse rates but too much=more evaporative cooling so large cold pools.

Compare that sounding to the ones above from the may 24th 2011 outbreak (taken from Treys great vid about it) much less dry air.

I dont think dry air was the only reason it underperformed but i do think it likely played a major role.

May 7

Tornado emergency in Michigan

May 7

With the exception of the Barnsdall tornado yesterday thankfully underperformed when compared to what was expected, one of the core reasons tornado events interest me is days like this, knowing how and why these days failed means we can be better prepared for those that dont.

Really great thread on twitter by Cameron Nixon here going over the event and comparing it to the significant may 24th 2011 outbreak which did verify. He highlights subtle fail modes that were difficult to forecast but combined to hinder storms.

Main reason though was storm mode, its no coincidence that the Barnsdall storm was the only cell that managed to retain its discreteness. The cell near Wakita, Oklahoma kept trying to put a large tornado down but its rear flank downdraft kept being impinged on by the forward flanks of the cell behind, leading to weaker, rained out circulations that only lasted for a few mins before dissipating. This was on top of the dry air aloft, reports of virga ahead of some supercells, this is explained in Camerons thread but essentially this led to rear flank downdrafts being stronger with excessive precip, choking off cells inflow, this is all while they are likely competing with a cell infront or behind them.

Honestly in my opinion it was a combination of 'smaller' fail modes aswell as the slower trough ejection that led to this event underperforming.

Saying that im once again not particularly impressed by models, especially the HRRR showing low level lapse rates at 7 degrees celcius a few hours before the event when in reality they were under 6.4, once again no coincidence that the Barnsdall storm produced as low level lapse rates began to increase after dark.

The best area for discrete cells was southern Oklahoma, storms didnt fire there and in northern Oklahoma shear vectors were way more parallel to the dryline than perpendicular, leading to training storms.

Shows that we still have ways to go in fully understanding the internal dynamics of thunderstorms and tornadogenisis, some things we just dont know yet.