9 days out

I've been monitoring the GFS for the last few days, and the swings in the solutions it comes out with every successive run are amazing. All that tells me is that the models cannot be trusted with anything this far in advance. A fact that I already knew, anyhow.

But just for fun, why not?

Here's a rundown of what the 10/00Z run of the GFS is saying we will be looking at for day 1 of our chase, May 19.

Moisture: we should be good, with an open Gulf and southeast winds all the way down south. A low is progged in northwest Kansas with an obvious dryline to its east. The dewpoint gradient isn't likely to be as slack as shown here--the GFS is notorious for a) not being moist enough, and b) smearing out gradients over too far an area. One caveat, though: that area has been under a terrible drought, and unless it rains there, a lot, between now and then, the dryline could end up being farther east.



850 moisture looks good, all advected on the nose of a 50 knot low-level jet.



CAPE looks okay, albeit not great. Again, this could be real or it could be something to do with the GFS being notoriously dry. We'll see, when the time gets closer. But still, in excess of 1500 J/kg is nothing to sniff at.



Lift should be easy to come by. A short-wave trough is forecast to move through the area, with 50 knots at 500 mb and cooling aloft.



Wind shear will, of course, be fine. With the aforementioned upper trough as well as the low-level jet, we should be in business.



So we'll see how this evolves over the next couple of days. I'm sure the model will paint a different scenario tomorrow, the next day and the next. What matters to me is what scenario is painted by Mother Nature.

Today: wow

Today is one of those days I wish I could be chasing. However, were I chasing today I would be facing a monumental decision. Let's take a look.

First off, there's good moisture return to the central plains, with dews in the mid to upper 60s.



Second off, there are crazy lapse rates out there.



Deep wind shear is not going to be a problem, as there is plenty of strong wind off to the west, with a deep trough in place.



Lift is the key here, and there are 2 places for it. This is what I really want to talk about.

Days like this really aggravate me. I am torn when two distinct locations for chasing are evident. What are you talking about, Dave?

Today is a classic plains cyclone setup. A low has formed in Colorado and will move eastward today and deepen, drawing moisture northward with it. To its east will be a fairly strong warm front, to its southwest a cold front, and to the south will sit a dryline. This is the concern.

See, the typical area to chase, the place where most chasers would aim for, is the triple point--the intersection of all three, which is likely to be somewhere northwest of Omaha, Nebraska. This is where you get the best juxtaposition of all the necessary ingredients. Let's have a look at all of these from the 12Z NAM, courtesy of Twister Data.

Surface map with temperatures, showing the warm front


500 mb winds and temperatures


Surface map with dewpoints, showing the dryline and warm front


SBCAPE, CIN and EHI





As you can see, the SBCAPE is progged to be rather big today, over 2000 J/kg over a huge area, the cap is forecast to be minimal or break completely over the whole area, and EHI values show good potential for storm rotation.

But where to go, where to go?

Conventional wisdom, like I mentioned before, would favour the triple point. It has a few things going for it:

1. High likelihood of storms
   
2. High likelihood of tornadoes, including maybe some strong ones
   
3. Good chase country

It also has a few things against it:

1. Possibility of storms being on the warm front, close to being mired in low cloud and fog
   
2. Too many chasers going to be there
   
3. There could be a lot of storms

All that being said, here are forecast soundings for the triple point and the dryline, respectively.




I would say wow for either of these, but the triple point one has my jaw on the floor with a YOWZA.

So I think that today, despite the potential negatives, and despite my nickname, I couldn't pass up the golden opportunity to chase a classic plains cyclone setup. This looks too juicy a setup not to chase. If, though, I got some information saying that this area would be less perfect, I would book it to north-central Kansas and chase the dryline. The storms there will be more isolated and likely more photogenic. That being said, water vapour imagery shows a good wave heading toward the Nebraska target area, making storms there much more likely.



Happy and safe chasing to everyone out there!

Getting antsy

So there have been a few good outbreaks in the south, including this incredible day of over 1000 severe reports.



I have the new laptop and I have loaded all the software onto it. I have been practicing my forecasting and soon I'll be in top shape. Now all we need is chase-able storms.

This weekend looks like a good few-day setup. The moisture is just beginning to creep northward, so it looks like the threat will be in the southern plains. until our chasecation I don't think I'll have enough time to go chasing, although there's a short time period that would work if things come out just right.

Bring on May!!!

Equipment

So I think we're going to have all the equipment we need for this summer. Justin, let me know if you can think of anything else we'll need.

Here's the list thus far:

• Fast laptop with
  
  • GRLevel3 with alternate, reliable data feed
    
  • Live maps (for navigation)
    
  • GPS Gate
    
  • Firefox
    
  • Spotter Network
    
  • BUFKIT
    
• Laptop stand for in-truck
  
• North America-wide internet
  
• GPS
  

I can hardly wait!

Late-season event on Monday?

In the wake of my previous, depression-inducing post, it's only fitting that a severe weather event is potentially going to occur tomorrow. And of course, it's made all the more likely due to the fact that I have a dentist appointment in the afternoon.

Once more, with feeling:

Moisture - the forecast dewpoints are up there around 20, and there's no problem with that, as the dewpoint outside today is in the upper teens (or actually 21 at my backyard weather station).



Instability - it should be there, just by virtue of the fact that the surface will be warm and moist. The forecast MLCAPE is over 1000 J/kg and there are even some hints of over 2000. Looking at the 500 mb map (below, after "shear") I see that there will be slight warming. Will that be enough to suppress storm development?





Lift - there appears to be a warm front progged somewhere over southeastern Manitoba. This will provide lots of convergence. Will it be enough?



Shear - This is a bit of a weakness, as the winds through much of the atmosphere will be aligned (save for at the warm front, where they will be backed) and not terribly strong.







So the question is whether storms will go. I just don't know if it will, but if it does it could be pretty serious. As soon as I get out of the dentist's chair I will likely be off in my car, chasing those elusive severe storms.

What do you think?

On the winding down of severe thunderstorm season

I've been putting off writing this post for a little while now. It sucks to think about it.

When I say "it" I mean the end of severe thunderstorm season. This of course happens every year, and every year I get the blues about it. It's not only the winding down of severe thunderstorm season but also the winding down of summer itself. Now, last year proved that summer can extend almost into October, but severe thunderstorm season isn't so generous. Usually.

Still, the latest in the year I've ever heard thunder in Winnipeg is the end of November. Not severe, but rumbly.

In 2008 and 2009, my melancholy was exacerbated by the fact that I didn't see any tornadoes those years. This year I had exactly one tornado day (although I could have had 4, had the right decisions been made) and that beats the crap out of zero. That day produced 4 tornadoes from 2 storms, what we call the Campo day.

I will miss you, summer and severe thunderstorms. Until next year.

Quiet August; SD chance today and tomorrow

I can't speak for Justin, but I'm in Saskatoon for most of this month and it seems that the severe weather taps got turned off as soon as I got into town.

If I were able to go, though, I would camp out in South Dakota for the next couple of days. Here's today.

Moisture: the morning analysis has surface dewpoints in the upper teens. They should get to 20 no problem this afternoon.



Instability: lapse rates are great across the area 700-500 delta T of 25 degrees at Rapid City), so instability should be easy to realize. In fact, there have already been thunderstorms this morning in southeast North Dakota.

Lift: there's a warm front draped across the ND/SD border that will likely get shunted southward a bit this morning because of outflow from the morning convection. But the convergence along the front should provide plenty of lift.

Shear: the deep shear will be plentiful, as the 500 mb flow is around 40 knots, and with the warm front in place the directional shear looks to be pretty good.



An added bonus is that there's ACC this morning over northwestern South Dakota, a sign that midlevel instability release is occurring.



So as a start I would set today's initial target as Huron, SD.

Tomorrow looks pretty good, too. Great, actually, if the cap breaks.

Moisture will be easy to find, with dewpoints progged to be in the low to mid 20s. Instability should therefore reach MLCAPEs of 4000 J/kg. Lift - a warm front in place. What do you think? And shear will be fine, with a midlevel jet streak progged to come across with winds from 40 to 60 knots. Capping will be an issue, but if a storm goes it will a) likely be along the warm front, and b) likely go explosively. My target: Yankton, SD.