May 18, 2010

Tomorrow (May 18) looks okay, with a narrow window of opportunity for supercells and possibly even tornadoes.

The opportunity will most likely be in the Texas panhandle along the dryline, later in the afternoon when better shear is forecast to come in.

Here's the SBCAPE forecast valid 00Z:



And the surface-500 mb bulk shear forecast:



The juxtaposition of CAPE and shear will make for perhaps an easier forecast because of the narrow opportunity area.

Here's a forecast sounding valid 00Z for the area, near Dumas, TX:



So I'd likely stick around Amarillo most of the day, try to be patient, and wait for initiation. The interesting thing for this setup is that as you go south the shear will decrease, so finding that fine balance will be key.

May 17, 2010

Today is a marginal day in many ways, but the play is actually pretty obvious.

This morning there was a cluster of storms in the central and northern Texas panhandle and it pooped out an outflow boundary. This boundary is moving southward through Texas and is just about at Midland. South of the boundary there's pretty good moisture and instability (2500+ J/kg SBCAPE), but shear is less than stellar (25 to 30 knots). So hoping for a mesoscale accident is pretty much what chasers can hang onto this afternoon.

But the reason I'm writing this is because I wanted to point out the outflow boundary, which is extremely obvious.

First, the RADAR with surface observations overlaid:



And now the visible satellite image:



Easy boundary to find. Now, can storms go on it? Time will tell.

May 14-16, 2010

The next few days look sort of interesting from a chasing perspective. I say sort of because of the location.

See, a couple of years ago Paul and the gang went chasing into Mexico, however briefly. The storms on that side of the border often look really juicy on the RADAR, but the road network (not to mention the not-getting-shot-at network) leaves something to be desired.

The pattern the next few days looks to be a deep south Texas/Mexico chase time. Good moisture off the Gulf of Mexico beneath some okay flow aloft and, like can happen in Alberta, magic could ensue.

The NAM is forecasting SBCAPEs on the order of 1500 to 2500 J/kg. Pretty decent, if you ask me. Not great, not early this week kinds of CAPEs, but still.

I wish my friends at the College of DuPage well, safe chasing and lots of good steak.

Wednesday May 12, 2010...Early tornado threat followed by damaging winds and hail!

I'm pretty tired at this time, but I thought I'd talk about tomorrow quickly.

In short I'd target Kansas City, Missouri for a start location tomorrow. A Surface Low is forecast to develop and move Northeast to lie somewhere just NW of Kansas City by the late afternoon. Storms should initiate near the center of the low somewhere NW of Kansas City initially then develop down the cold front/wiper blade. The warm front looks to be draped over Northern Missouri oriented West-East with the cold front located near St. Joseph oriented NE to SW.

A narrow window of time will exist for tornadoes before storms move and compete with each other and eventually merge to form a giant squall line along the cold front. The orientation of the wind vectors with height show this merging tendency. So in short, be there early for initiation, witness a tornado then enjoy the light show and gust front as the sun drops. Storm motion won't be terrible...about Northeast at 40-50 km/hr

Here is a NAM 00z forecast sounding from just West of Kansas City at 7pm CDT. Cooling aloft along with forcing along the cold front should allow the CINH to weaken and storms to develop.

Low level clouds will likely linger in this area as moisture streams northward with the low level jet. They should burn off sometime after lunch allowing for sufficient heating to take place. This combined with great moisture will allow for great instability to set up with CAPE values >3000 j/kg.

As mentioned a few days ago, all facets of severe weather can be expected, but expect mainly a strong wind/hail threat...but be there early for a chance to see a tornado.


I haven't looked at what the future holds beyond tomorrow but if it looks good, I'll post about it. Tomorrow's cold front looks to flush everything out (bring order back) for a short while...but that's all I got for now!

Cheers,

Tuesday, May 11

I think SPC is going to go with a moderate risk for a relatively small area. Looking at the information, including the satellite imagery and upper analyses, as well as the moisture in place, severe storms look to be on tap for southwest Oklahoma and adjacent parts of Texas. The only thing is that it'll be a more conditional threat, conditional only on whether storms go.

So here goes. First the satellite imagery and 500 mb chart.





100 knots at Oakland, CA. That even looks real, especially when you add in the water vapour image.

Now for the surface.



Moisture's there, all right. And a tight moisture gradient, to boot. Solenoidal circulations along the dryline (especially anywhere it surges) are really good for convective initiation.

So how about a couple of maps from the NAM? First the SBCAPE forecast.



That looks pretty interesting, especially the gradient. That indicates a dryline to me. How about a prog sounding from within the juicy air?



The CAPE is great, and the shear OK; this to me looks more like a sounding for HP supercells, which will primarily give some medium-large hail (let's say 3 inches) and a lot of rain; a tornado cannot be ruled out, although I don't know about the potential being there for long-track, damaging tornadoes.

If I were a chaser, I would be a bit more excited about Tuesday than Monday, primarily because of smaller geographical coverage of storms as well as the slower motion of the storms. I would park myself in Frederick OK (where the prog sounding is from) and see how things evolved throughout the daytime.

This doesn't look like a huge outbreak kind of day, but any storms that do go in that environment look to be serious supercells, more chaseable and probably more picturesque. I think Tuesday is going to be a "sleeper" day in terms of chasing. Only time will tell.

Wrap-up of May 10, 2010

Well, sort of a wrap-up. Storms are still going and likely producing as I type this. But the daytime show is done. And was it ever a doozy. Justin called me this afternoon and we briefly debated, once again, his term. Don't worry, we're not coming to blows over it. I just like to razz him a little bit and he is very adept at razzing right back.

I still think it wasn't a tornadopocalypse, though. :P

Anyhow, as I type this there have been 37 tornado reports (reports on this may or may not be duplicates) and 57 hail reports including 10 larger than 2 inches, and 3 at 4 inches or larger.

Here's the map I have to work with at this time:



The storms went a bit farther east than expected and, unlike the NAM was depicting last night, did actually go into Texas. This just tells me to be skeptical of model output. As if I weren't already.

Anyhow, this was a well-forecast event. The moderate risk issued yesterday and the high risk issued today really brought this to the fore. Unlike previous high risks I've seen (and chased) where relatively little went on, this one panned out pretty close to the forecast. VORTEX2 likely got some great data from the day. Chasers were likely upset about the storm speeds.

In other words, a classic severe weather setup in the southern plains.

Monday May 10, 2010

So the big day is just about upon us. It looks really promising for big storms. All severe modes.

I'll start off by looking at the conditions this evening. First, let's look at the water vapour satellite image and the 500 mb chart:





The main thing I'm looking at is that big trough over the southwest states. It has it all: cold temperatures (-26°C) and a strong jet (78 knots, gleaned from the text data). The NAM was pretty consistent in painting this kind of wind speed over the region of interest, and I was shocked because this is really strong. But it's actually there; there is, therefore, no reason to believe it won't be in place for tomorrow's storms.

Now how about the surface:



Check out that moisture having made its way as far north as just south of Lubbock. I had had my concerns about the moisture being in place, but this makes me think that maybe it won't be a problem.

So what are the potential problems? First off, wave timing. The location of the wave right now tells me that it will likely be in a pretty good place for the storms. But who knows? What if there's an unresolved little wave before it that messes up the atmosphere?

Second, how about wave strength? What if there's too much lift and storms go everywhere?

Moisture, like I mentioned before, was a concern I had had. But now, not so much.

Why do I have the reaction that I do to the pseudo-word "tornadopocalypse"? I think it's because I'm a grammar nerd and I'm not a fan of the forced portmanteau.

All this said, I suspect that the SPC will go to high risk for day 1. The new NAM run is quite different from previous runs in that it doesn't paint a lot of instability along the warm front. Check this out:





Interesting. And also, it paints good instability and shear all the way down into Texas. Here are some forecast soundings. First I'll show you Oklahoma City:



And somewhere west of Dallas, about 50 miles west:



Weird, that OKC one. The Texas one is nice, though. And the NAM isn't dropping a convective signal here, either.



Curious. Is this a real thing or is it just something goofy going on in this run of the model? I mean, the GEM-regional is certainly painting precipitation there:



I can't really believe that with such a strong jet core coming in that the synoptic lift won't be enough to pop big storms down to at least the Oklahoma-Texas border.

So what would I do? Analyze, analyze, analyze.

But seriously, it depends on what my goal is; if I were chasing I'd probably hang out just south of Oklahoma City and maybe a bit west and wait for the dryline to fire things off. If I wanted to see severe weather no matter what, I'd probably stick to the city itself, perhaps north.

Monday is going to be an analysis-heavy day. Every piece of data should be gleaned for clues to how the day will evolve. Where will the 500 mb jet core go? Where will the moisture pile up most? Which area will get the most sun? Who will see the best juxtaposition of convergence and nearly-breaking cap?

I still take issue with Justin's sort-of word, but I cannot deny that it will be a big day for chasers, VORTEX2 and citizens alike.