Model differences

The models seem to be settling on a scenario out to 6 days now, one that's favourable for our chase. However, at this time, I must state that the huge wildcard in the mix is moisture--that is, whether or not it'll be there in the abundance we seek.

After 7 days, though, they start to diverge and in a pretty fundamental way, one that would make for vastly different outcomes of the latter part of our chase.

The difference is outlined best by these two 500 mb forecast charts, valid next Saturday evening. The first one is from the GFS and the second is from the ECMWF.




At first glance, they appear pretty similar, both having upper circulations near the coast of California and another near New York City. But in between, the difference is huge.

The GFS has a positively-tilted lead trough over north Texas and the upper midwest, followed by a sharp short-wave ridge over Arizona. On the other hand, the ECMWF has a negatively-tilted trough over the northern plains followed by weak short-wave ridging in advance of the next impulse to be ejected. The difference is that the GFS solution would mean a longer time between storms and likely less low-level moisture availability, whereas the ECMWF solution would mean more low-level moisture and a near-constant barrage of storms, perhaps with a one-day break.

Forecasters far and wide perceive that the ECMWF is the superior model to all others in the mid-range. I have no lazy way of knowing if this is accurate; however, I do know that the wishcaster in me hopes that this is the case.

4 More Days...

Well the 5/15 00Z GFS is coming in and it looks like it's going to be a busy start to our chase trip...

An omega blocking pattern is setting up over N. America and it will hold for a few days or longer with impulses ejecting out of the base of the western trough daily. Wednesday looks to be the first of a busy chase period in SW Kansas, OK panhandle which we will have to miss since I land at 9pm in Winnipeg that night. I'm not worried because moisture will still be returning into that area meaning the tornadic potential for the storms won't be that great(LP Sups with large hail). As moisture continues to advect into the region, this should result in a bigger day on Thursday for north central Kansas vc triple point (classic sups with tornadic potential). We will have to drive a long way as quick as possible to get into position for Thursday if the latest runs verify. I figure we leave Winnipeg as soon as I land and head to Fargo for 1am. Get up at 6:30am, leave by 7:30am in order to be in position by 6:30pm which should be okay. I'd prefer 4pm but hey we are coming from Winnipeg. Friday looks bigger with a dry-line play over central Kansas/Oklahoma as moisture quality continues to improve. Last day I'll talk about is Saturday which again looks like a good dryline play over central Oklahoma.

Let's hope this run verifies...regardless...it looks like an active beginning is shaping up for our Tornado Hunt that runs from May 19-28th, 2011.

Only thing I fear is massive chaser convergence as we play in KS/OK...I'm still hoping for a warm front play over North Dakota near the end of our trip which should keep convergence to a minimum. I'm actually beginning to like Canada for chasing...even though we have fewer storms. It's cool knowing you might be the only one chasing it.

Is it really only a few days now?

It seems like we've been waiting for this time to come around for years. The drab day yesterday here in Winnipeg made storm chasing seem that much further away.

But it's almost here. A few more days, and I couldn't be happier.

So what do the imperfect models have in store? I will turn to the GFS for its "wisdom".

Day 1 (May 19):
This looks like a dryline/warm front intersection chase day. Western Kansas looks to be the place to be, although the moisture quality will be in question, seeing as how they're in the midst of a drought and the dewpoints haven't been as juicy as they normally are this time of year. There is a problem, though: we will most likely be starting off the morning in Fargo, so getting far enough south will be a challenge. Not to say that we won't try, though.





Day 2:
Another warm front and/or dryline chase, but I suspect this one will be more in the way of moisture-dependent.





Day 3:
This looks like the day, if it comes true, that we'll abandon the warm front. Reason being, a) it'll be getting farther and farther away from the good moisture, and b) the upper winds south of it are forecast to be much better. Still, though, this looks like a pretty good chase day, although the territory where the good stuff could happen isn't ideal (the Ozarks and the Ouachitas in eastern Oklahoma.)





Day 4:
Central Oklahoma. That looks better, although with this setup we'll have to deal with about 400 million other chasers. Le sigh.





Day 5:
This is as far as I'm going to go, as the models tend to go into la-la land at this point, and very often much much earlier. But nonetheless, it's a fun exercise. Oklahoma again, maybe a bit farther west.





After this, the GFS goes into a bonanza for us chasers, although at this point I'm going to give it the credit it's due (that is to say, none). But if I were a wishcaster (and some have accused me of it, and rightly so), I would hope for the 14/00Z GFS to be right.

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!