8/28/2004 FCST: Plains

This is early, but by request and because it's fun to think that 2004 will never end convectively, I've opened this thread. Don't know if I can transfer Justin Teague's post over here, so I'll paste it below:

Somebody should open a thread for the weekend of the 28th. Interesting pattern change by the middle of next week. I like what the CPC has to say......

"With the forecasted upper-level pattern, there is a chance of a severe weather outbreak in the middle of the country"

and also the following week....

"Despite disagreement on the exact position of the western trough, it is expected to persist during this forecast period. If its axis is centered inland, then shortwaves moving through the trough could lead to widespread severe weather outbreaks in the middle of the country."

180 hour maps show a vigorous trough approaching the central plains and develop an 850 mb low in eastern CO, always a bell-ringer for southern plains chasers. Who knows if it will verify, but it's fun to speculate. Looks like 2004's fat lady has a frog in her throat.
 
Thanks Amos. I have been watching this for a couple of days now. It's a little glimmer of hope for those of us who live in the southern plains. I would make a weekend trip to Nebraska or N. Kansas for a late season event.

I don't rely heavily on long range model data(or short range for that matter)but the upper pattern is just begging to be noticed. I will definitely keep an eye on it. All of the plains chasers need to keep their fingers crossed!
 
Agreed. I glanced at the spaghetti plots and they have some signal of height falls in that period, so this isn't complete fantasy. We'll know a little more every day I guess!
 
The spaghetti plots are indicating height falls by later in the week, they have also been fairly consistant, but we all know how fast things can go the other way. It's not a dry topic, that's for sure, but like Amos said.....we'll know a little more every day.

I have tentatively scheduled a vacation day for next friday. Let's hope mother nature will make something of it.
 
I hate to sound like a total idiot but can someone point me in the direction of data for the 28th? I've lost all my bookmarks and stuff.
 
If the models continue to verify, I wouldn't rule out some supercells due to the neutral tilt of the trough. The MRF still has a 1001mb low over SW Kansas. It has 850mb winds out of the SSW at 20-30knt and 500mb winds out of the SW at 30 and 40knts in S. Nebraska. This would yield favorable shear profiles for supercells. The models also indicate a good thermodynamic profile. Timing is always an issue, but should these parameters actually come together as the models indicate, I will be in Nebraska this weekend.

I have been burned every August when I don't go to Nebraska or S. Dakata for similar setups. I don't want to get burned for a 3rd year in a row.
 
Isn't wind shear this time of year more conducive to damaging wind events rather than tornadic supercells? If I am correct, shear plays a large part in the convective mode. When wind is SW at the surface and the jet stream is more westerly, I'm thinking tornaodes. The wind direction and speed are quickly changing with height. When the surface wind is nearly parallel to the upper level wind, there is more change in speed than change in direction. Doesn't this increase chances of a less tornadic convective mode? If I am wrong, my bad, this site is a learning experience for me as are my upcoming college courses.
 
Chase Prospects for this week: 8/23, 24

Amos,
Things are looking promising for early this week. Could you please start a NOW thread for Mon & Tuesday's system, as I'd like to get some other opinions before I start making any definite plans...
Thanks!
Jon
 
That's a very good question. There is a fine line between supercells and squall lines. Consider a typical squall line event in August.......they are usually motivated by NW flow in association with a cold front and associated short waves. This particular setup includes the formation of a sharp dryline in association with a surface trough. The winds should back to the SE in advance of the dryline causing more convergence in the area south of the cold front. Squall lines are also accompanied by higher windspeeds in the upper levels of the atmosphere, the winds are actually drawn to the surface by the downdrafts in the storms.....its a very complex process that would take alot of time do describe in a forum, I will try to find some links for you.

Here are some links to the data i have been watching......

http://weather.cod.edu/forecast/MRF/mrf_nh...500_spd_168.gif
http://www.rap.ucar.edu/weather/model/disp...wnd&hours=hr156
http://www.rap.ucar.edu/weather/model/disp...slp&hours=hr156

Please excuse some inaccuracy in my last post.....I described a 1001mb low...that was data for 0ZWed. 1004mb for 0z Sat. There are still many uncertanties as to what we should expect, long range models are rarely correct in exact placement and timing. 2 days it could look like a major wind event, or nothing at all. I also ignore some common model errors and place my own more reasonable parameters in place when I interpret any model data, long or short range. If the front takes over and dives south, we have a quall line......if convection fires closer to the low and parallels the front, we could be looking at supercells. Its a roll of the dice!

I would also expect SE winds underneath that 850 jet. (last minute though that I forgot to include above)
 
Amos,
Things are looking promising for early this week. Could you please start a NOW thread for Mon & Tuesday's system, as I'd like to get some other opinions before I start making any definite plans...
Thanks!
Jon


I agree....thread for tuesday please!
 
Re: Chase Prospects for this week: 8/23, 24

Amos,
Things are looking promising for early this week. Could you please start a NOW thread for Mon & Tuesday's system, as I'd like to get some other opinions before I start making any definite plans...
Thanks!
Jon

NOW threads are only for once the actual convection fires, isn't it?
 
Thats true...

That's true, you have to know what you are talking about. I see there's a FCST thread set up for 08/23/04 already. So this is a "beating on a dead horse" issue...subject closed.
 
Isn't wind shear this time of year more conducive to damaging wind events rather than tornadic supercells? If I am correct, shear plays a large part in the convective mode. When wind is SW at the surface and the jet stream is more westerly, I'm thinking tornaodes. The wind direction and speed are quickly changing with height. When the surface wind is nearly parallel to the upper level wind, there is more change in speed than change in direction. Doesn't this increase chances of a less tornadic convective mode? If I am wrong, my bad, this site is a learning experience for me as are my upcoming college courses.

David, I think the Weather Service in Wichita summed it up well......

THE
FRONT SHOULD MOVE ACROSS CENTRAL AND SOUTHEAST KANSAS FRIDAY AND
FRIDAY EVENING. LOOKS AS THOUGH THE MAIN ENERGY WITH THIS SYSTEM
WILL BE IN THE NORTHERN PLAINS. HOWEVER, THUNDERSTORMS ALONG THE
FRONT ARE A GOOD BET. WILL NEED TO WATCH THIS FOR THE POTENTIAL OF
SEVERE WEATHER BECAUSE AS THE PREVIOUS MIDNIGHT SHIFT INDICATED,
LOOKS MORE LIKE A SPRINGTIME FRONTAL SYSTEM RATHER THAN LATE SUMMER.
 
After a pretty quiet August, we are about to see some storm action around Saskatoon today. A week cluster of cells is growing up just west of the city at this hour and it should become severe over the next few hours. CAPEs are around the 1500 range so it likely will not be much to get excited about but I did see some lightning to my west already. The end of our storm chasing season on the Canadian prairies is coming fast so I hoping to get at least one good storm in before the snow flies!

Jared

Update:

CAPEs are 2500 in SE Saskatchewan so that will be the area to watch this evening....not much wind shear though...
 
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