• After witnessing the continued decrease of involvement in the SpotterNetwork staff in serving SN members with troubleshooting issues recently, I have unilaterally decided to terminate the relationship between SpotterNetwork's support and Stormtrack. I have witnessed multiple users unable to receive support weeks after initiating help threads on the forum. I find this lack of response from SpotterNetwork officials disappointing and a failure to hold up their end of the agreement that was made years ago, before I took over management of this site. In my opinion, having Stormtrack users sit and wait for so long to receive help on SpotterNetwork issues on the Stormtrack forums reflects poorly not only on SpotterNetwork, but on Stormtrack and (by association) me as well. Since the issue has not been satisfactorily addressed, I no longer wish for the Stormtrack forum to be associated with SpotterNetwork.

    I apologize to those who continue to have issues with the service and continue to see their issues left unaddressed. Please understand that the connection between ST and SN was put in place long before I had any say over it. But now that I am the "captain of this ship," it is within my right (nay, duty) to make adjustments as I see necessary. Ending this relationship is such an adjustment.

    For those who continue to need help, I recommend navigating a web browswer to SpotterNetwork's About page, and seeking the individuals listed on that page for all further inquiries about SpotterNetwork.

    From this moment forward, the SpotterNetwork sub-forum has been hidden/deleted and there will be no assurance that any SpotterNetwork issues brought up in any of Stormtrack's other sub-forums will be addressed. Do not rely on Stormtrack for help with SpotterNetwork issues.

    Sincerely, Jeff D.

Impulse mixed down

Helge Tuschy

EF0
Joined
Jan 28, 2005
Messages
39
Location
Innsbruck,Austria
Hi everyone,

I'm wondering about this question:
Question.jpg


This sounding shows the prefrontal situation immediately in front of an eastward racing cold front over Greece ( Athen, at 15Z ). Well, the cold front was driven by a very strong jet system ( 700hPa up to 25m/s and 500hPa up to 40m/s ---> deep layer shear (DLS) up to 35m/s / 70kt ).
Steep low level lapse rates present and I think impulse can be mixed down fine.
My question will be if someone of you knows a calculation, where you can guess the expected surface wind along the cold front ( squalline ) and how much influence this inversion will have for weaken this downward impulse somewhat...?Models forecast 925hPa wind speeds of about 25 kt ( ~ 13kt ) behind the cold front, not sampling the mesoscale convective wind field very well.
Maybe someone of you knows an abstract or a letter, which describes the problem.

Best regards,

Helge
 
I don't see any downward mixing of winds (downward transfer of momentum) here, because the winds throughout the steep lapse-rate portion are pretty much the same (30 kt). The winds at 500+ mb are too high and are not being tapped by a column of steep lapse rates.

This appears to be more an environment that favors linear storms along the front. Now WITHIN the storms you can assess the potential for convective gusts:
http://meted.ucar.edu/mesoprim/cape/print.htm
http://www.wdtb.noaa.gov/courses/dloc/svrp...s/svrparams.htm (#15)

The marginal upper lapse rates, warm upper wet-bulbs, and poor instability appear to suggest weak convective gusts.

It appears that the existing pressure gradient would almost exclusively drive the winds at the surface.. I'd be looking at hand mesoscale analysis to pull out any features that might drive the winds higher.

Tim
 
Hello Mr. Vasquez,

"I'd be looking at hand mesoscale analysis to pull out any features that might drive the winds higher.
"

*puh....I know that this can be done in North America, but here in Europe it is nearly impossible to draw a map with mesoscale features ( especially over the Mediterranean area ). I often get incomplete sounding reports ( like today, Athen ):
http://weather.uwyo.edu/upperair/images/20...16716.skewt.gif

But thank you very much for your answer. I see what you mean.

Helge
 
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