Arriving at the Station BEFORE the Train...

[Keith Mullen]

I hope I can convey my question clearly enough to get the answers I am looking for, lol.

When looking at all the factors for the days set-up starting in the wee hours of the morning (say 7am... that's early enough for me), taking into account: dryline position, skewT, warm front, mixed cape, surface conditions, convergence zones, upper divergence, and on and on...

...how do you determine or forecast where these conditions will be situated by 3 in the afternoon? (best preliminary forecast of prime targets).

Caveat: Without having an electronic arsenal of gizmos and gadgets to take on the road.

What factors do you look at to guesstimate how strong and far north the good deep moisture will push; If the dryline will remain somewhat stationary, push east, recede, etc; What are the key influences on all these ingredients that you then need to refer back to, in order to determine which way they will push-pull, peter out? (aside from stopping at every wi-fi and library en route)

I really am a little puzzled at how to take current conditions - and know how best to interpret where they will be later.

 

[Chad Cowan]

What factors do you look at to guesstimate how strong and far north the good deep moisture will push; If the dryline will remain somewhat stationary, push east, recede, etc

From "Dryline Magic" by Tim Marshall:

"In order to determine the probable movement of the dryline, I check the morning weather balloon soundings to see how deep the low-level moisture is east of the dryline. A moisture layer only a few thousand feet thick will tend to mix quickly, allowing the dryline to advance eastward rapidly. I have seen some drylines reach speeds of 50 m.p.h, when there is little low-level moisture in their paths. On the other hand, a moisture layer around 5,000 feet thick will tend to slow down the mixing process and could bring the dryline to a halt."

 

[Jason Harris]

Where does one go at noaa.gov or weather.gov to find the daily soundings to check on moisture?

 

[Jason Boggs]

Jason, there are many sites you can go to and get the daily soundings. Here are a few of them for you:

http://www.rap.ucar.edu/weather/upper/

http://weather.cod.edu/analysis/analysis.sound.html

http://weather.unisys.com/upper_air/skew/index.html

http://www.stormchaser.niu.edu/machine/sound.html

Hope these links help you out.

 

[Jason Harris]

Great: thanks for those links to sounding data!

 

[Keith Mullen]

Thank you! So dryline movement makes a lot more sense to me now.
So that is a fair indicator of dryline movement (which I am sure one would get a feel for over time).

What about heavy moisture and a stalled or otherwise stationary dryline? What would you double-check or reference to see how far north the good heavy moisture from the s/se would travel by later in the day - or conversely, what forces might be in place to cause it to not advance further?

Particularly in situations where there is a lack of a strong or otherwise significant Low to pull around?

(Sorry to sound ignorant, but I am still trying to wrap my head around surface obs/LLJ/mid&upperjet as they force their wills upon the ingredients for convergence.)

 

[Keith Mullen]

Wow, sorry to continue sounding ignorant, but I thought perhaps this might have been a subject that might have garnered more data for those of us that the difference between 6 hours guesstimate and 18 hours guesstimate would make or break a chase. Am I missing something here (not being higher-educated in meteorology or in forecasting otherwise)?

Thanks and apologies.

Keith

 

[Bill Tabor]

Generally Keith, in order to determine the location of the 'action' most of us predict where that will be by using weather models. Typically we want to back that up by surface data, or soundings to see the quality and nature of the air mass. This helps to verify whether what we are seeing predicted on the models is correct. So, with that in mind you might for instance check UCAR model link (previously given) for dewpoints, winds, temps, etc for the various hours. For short term day of we typically look at RUC info. Also keep an eye on SPC mesoanalysis parameters. I sometimes also use Tim Vasquez's Digital Atmosphere program to plot various elements. Also visible, water vapor, and infrared satellite imagery for location of features, or the development of them before they begin to show on radar.

But yes, you should be focused on atmospheric features more than just data such as identifying a dryline, warm/cold front, low, triple point, meso lows, dryline bulge. Keep in mind, that weather forecasting, while science still contains a lot of 'art' and interpretation, or comprehension of the big picture. You have to ask yourself how these elements are acting / reacting together based on the set up, time of year, and perhaps climatology. For all of us - even experienced forecasters the positions of these elements is always to a degree unpredictable. The further out in time the less accurate the data and model interpretation will be. That is because the algorithms aren't perfect and neither is the data sample being pulled in for analysis. This is typically why if you watch SPC's Convective Outlooks the position and strength of the outlook area will often change - sometimes dramatically over a period of days. For the day of things are fairly accurate position wise, but there is still variance. Pick your model, tool, and model data. Look at where the real features are early on and keep an eye on them throughout the day as things develop.