Forecasting the Dryline

[Jason Boggs]

I've been reading a lot the past few days so I can be better prepared for next season. I have been reading about dryline forecasting and analysis for most of the night. I got into an interesting read on dryline dynamics and forecasting. So, I was wondering, how do some of you locate the dryline when you do a surface analysis? I found several different methods of locating the dryline in this particular study. I may try to keep it simple and use the 50 degree F isodrosotherm, although other methods can be used.

This is really a great read if anybody is interested in learning more about dryline formation and forecasting. The study was conducted in the Lubbock area.

http://dspace.lib.ttu.edu/bitstream/2346/1135/1/Mark_Conder_Diss.pdf

 

[Jay McCoy]

Jason.. I hope you mean 50 degree F not C!! Actually when plotting on a map the 50 degree line is the standard for most since 50 is the magic number needed on the caprock. If I am heading off the caprock into the east pahnadle I bump it to either 55 or 60.Ofcourse you cant always just go with DP's since they can pool shallow in certain areas and give false readings. Wind shifts and topography have to be factored in. And ofcrouse anmything Borger reports throw out since their statio always overdoes Td and temp.

here is the easiest way jason..

When your driving east and the dust turns to haze you have crossed the dryline!!

By the way Jason give me a call on my cell soon as you can. I need to talk to you about something.

 

[Shane Adams]

I don't know if what I do isn't forecasting so much as nowcasting, but I basically just use the 60-degree dewpoint line for my preferred dryline area for a chase. I also use a mesonet for surface wind obs, which IMO are probably a better indicator than dewpoints about the nature of the dryline (i.e., how veered are the winds behind it, are they SWerly or more due west, how strong [how fast is the DL moving, is it moving at all, is it retreating?]). I guess that really isn't much of an answer, but that's my thought process as I do a DL check in the morning. Also, I'm always looking for any buldge or ripple along the dryline, as I have had my best days traditionally just east or northeast of those kinds of kinks (again, this is where I prefer surface obs to a dewpoint map). All of this is done over the course of a few minutes, about every half hour to hour in the morning from awake time to leaving for the chase.

As far as old school forecasting, I don't really know if I can even do that LOL.

 

[Mikey Gribble]

Here is some information from one of Doswell's books that I took some notes on...

"the convergence of the observed surface wind field reaches its maximum somewhat behind the dryline, while the moisture covergence maximum is right along the boundary"

"the convergence of the surface winds is used here for velocity and directional changes. Although the dryline may be located at the area of rapid directional changes, the convergence is usually dominated by the speed changes upstream".

When forecasting and targetting I always use a combination of the 50 degree F line for dryline placement and the surface wind shift (there are exceptions obviously, but that is generally how I do it). I'll put myself about thiry miles ahead of this line and then watch visible satellite and get exact placement of the dryline off of that once a cu field builds back to it. Once I know the exact location of convergence then I get right on it (assuming storm motions aren't really fast that day).
Be really careful moving in that close to the dryline, before storms are firing, when you have strong mid-level winds mixing down and a bulge forecast that day. You'll get your pants pulled down and end up on the wrong side of the dryline if you aren't careful. It happened to me a couple times when I first started chasing and if the dryline movement and storm motions are quick enough that day it will ruin your chase.

 

[David Drummond]

I'll go by the 50 degree line up until late April, then I start looking more at the 55 degree line. This may vary by the setup of course. My very best dryline chase days are when I have been able to hand analyze a surface map hourly during the day and really pinpoint things.

 

[Jason Boggs]

Jason.. I hope you mean 50 degree F not C!!

I have no idea why I wrote Celsius in there! I guess I was up too late reading and turned into a zombie! Wow, just think what kind of storms would form in a 50C environment!! LOL

 

[Martin North]

I was gonna suggest 'around' 55F, but as been said before you do need to be flexible day to day.

The thirty mile (East) suggestion/rule is a good one imo. Also...decent sat imagery for once heating has got the Cu field bubbling well.

 

[David Drummond]

The 30-50 miles east of the dryline is good on days progressive forward movement of the dryline is expected. Don't forget there are days the dryline will stall and even start retreating, even by late afternoon. The big Lubbock tornado so long ago now was from a storm that fired on a retreating dryline.

 

[Martin North]

Aye...but I'd rather take my chances being East and having a bit of driving to do than play catch up.

50 miles is too far maybe. Well it would be for me.

 

[Willie Dines]

I agree with you on that Martin, perhaps about the +/- 20-30 mile mark, would seem about right, but like David has said, it would depend on the conditions for that day

Willie

 

[David Drummond]

Keep in mind out here on the plains guys, someone living 30 miles over is practically your neighbor. That is almost no distance at all. In the Texas panhandle, that is about the width of your average county, for a quick reference.

 

[Willie Dines]

That's a good point, I've seen the google earth maps of in around the plains lol

Willie

 

[Martin North]

That's just a personal preference/opinion for me Dave. If you're on a good East/West highway waiting for things to begin moving...60+ miles would be fine...

 

[David Drummond]

That's just a personal preference/opinion for me Dave. If you're on a good East/West highway waiting for things to begin moving...60+ miles would be fine...

Yep, I've sat right on it, and way east of it. Just depends on what was going on that day. I prefer the days it's stalls, or maybe never even advances at all. Nothing like a nice, tight, dryline in West Texas. Go from 20s dewpoints to 60 dewpoints in a matter of miles.

 

[Bob Schafer]

I find the DL one way or another (visual, data, nowcaster, hygrometer or just plain smell it as I cross it...sometimes the windshield fogs up, LOL)), then look for hard cu. If there isn't any yet, I either hit a library or find a nice shady spot for a nap. My personal rule #1: If I'm under stratus, MOVE! Oh, you can watch which way the flags are blowing as you drive, too.