Forecasting the Dryline

[Tim Vasquez]

So, I was wondering, how do some of you locate the dryline when you do a surface analysis?

Hi Jason,

I think a good way to approach this problem is to recognize the trap of getting into a cookie-cutter or object-based mindset. What you're really after is what the dryline represents: vertical circulations, the nose of deep mixing, the easternmost extent of the surface-based EML, the northwestmost extent of high theta-e's under the weakest portion of the cap, and so forth. A good, thorough analysis will delineate all significant moisture gradients as candidates for the above. During analysis, everything is important. Then as your diagnosis process solidifies you can evaluate each zone and try to figure out what bearing it has on the forecast. If you can link them up into a dryline, more power to you... the easternmost gradient is probably the correct one for dryline placement. But sometimes you'll have multiple moisture gradients and it's worthwhile to keep an eye on all of them and dig in a little bit with satellite imagery, radar, and continuity.

The key thing is to keep your dryline symbol on the moist side of any given dewpoint or mixing ratio gradient, as within the transition zone the dryline has already done its thing and has passed eastward. I'd say there's room for flexibility with this at nighttime when the dryline is retreating westward under the effect of advection... this is probably when the gradient as a whole needs to be monitored.

Tim

 

[Bob Schafer]

Thanks, Tim! Might as well lock the thread now. (j/k)

 

[Tim Vasquez]

Not really... I certainly make my share of stupid mistakes on the analysis.

Tim

 

[David Drummond]

That's one of the things I really like about the mesonet systems. From the right source, you can get updated data every 5 minutes. With that you can get surprising accuracy on dryline location. Unfortunately, as far as I know, they are limited to the TX Panhandle/South Plains, and Oklahoma. I used these considerably on chase days when chasing in those areas.