05/21/05: TALK: KS/NE/IA

I;m at a Flying J just SW of Omaha checking data. Trying to decide whether to stay here or go to the Sioux City area. Also, waiting for Earl's update. Still worried about the cap and whether the winds will stay backed.

Bill Hark
 
Cirrus deck rolling in over the Southern Nebraska area, could limit any real activity if it persists. On the other hand, could help keep temps down a touch by not allowing heating thoughout the day, lower LCL's. Always a fine balance. W Iowa clearing as Mike mentioned looks to be good. Only downside, the moisture tongue well be a bit further west into E Nebraska.
 
Well, shoot, looks like RUC forgot to take his meds again. Boy oh boy do I hope RUC is out to lunch on moisture return. Looking at the forecast soundings around here (KLNK), give me the RUC's hodo and the NAM's energy and eroding CAP and I'll be happy. ;) The OAX radiosonde hodo from this morning doesn't look depressing at all. Unfortunately, it looks like all the good outflow boundaries are going to be floating around in NW Iowa and NE Nebraska.

If I'm gonna bust, I'm gonna bust close to home on this one, so I'm leaning towards sticking around here (and maybe heading over the Nebraska City -- if nothing else, I'll meet a few chasers today while waiting on the cap's mercy.) Plus, I'll be that much closer to I-29 if it looks like that's the only sane path to take.
 
I'm at Sapp bros truck stop just off I-29 (heading to Nebraska City). We're waiting for some new data before we decide where we need to be next. I'm not sure if north or west will give us the best results yet.

I'm on 146.520 and 146.550. In my Nissan Xterra in the parking lot right now. KC9GAV or KC9HGR.
 
I am in Lincoln NE taking a look at the data. LCL is better for low based storms to the east a little bit while cape seems better here. So the battle is CAPE and strong high based storms vs Lower storms and less cape... too close to call in my opinioin.

Hoping to avoid Omaha and maybe stay put till things fire. Might join you all in Nebraska city but then might stay put. I have decent expectations that today wil produce. Tough call on exact target just hope to be close enough when the storms fire. I expect that right along the MO river will be where the action is.

Good luck to all.

--
Tom Hanlon
 
Uh oh I think we may have ourselves an out flow boundary in w IA, e NE for today now. Stay north.
 
Uh oh I think we may have ourselves an out flow boundary in w IA, e NE for today now. Stay north.
Click to expand...

Well put Mike...the outflow boundary could be key later. My model of choice thus far has been the WRF which you can access at http://rain.mmm.ucar.edu/mm5/. I am using the 12 km nest. Looks like widespread initiation will occur between 18Z and 21Z along well-defined wind shift line from DVL to JMS to 9V9 to 15 E ANW or basically in the Eastern Dakotas and Northeast Nebraska. As of 16z RUC analysis, atmosphere was still highly unstable. I have determined two major target areas that people may want to hit...

(1) Outflow Boundary Mike Mentioned: This is where the RUC is placing EHI values in excess of 4 and WRF is placing EHI values in excess of 3 by 00Z. These high values...generally indicative of strong tornado potential coincide with highest SBCAPE values which could exceed 2500 j/kg. Looks like there may be an enhanced potential of tornadoes about 40 miles either side of a Mitchell SD to Harlan IA line or basically the I-29 corridor from Sioux Falls to just north of Omaha. Only real negative could be rather high LCLs...favoring more hail/wind producing supercells with higher bases.

(2) Far Northern Minnesota: Not exactly good chasing terrain or area but enhanced pocket of strongly veered profiles likely with strong ULJ plowing into the area...40-45 knot LLJ lifting northeast and backed sfc flow from the southeast could favor supercells. 500 mb height falls will be incredible and as large UL cyclone shifts east, vertical motions over N MN should be very strong. Thinking a few storms will at least exhibit supercellular characteristics. At least in this area LCLs will be lower...favoring more of a tornado threat.

Best of luck to all chasing!

...Alex Lamers...
 
Almost appears to be a gravity wave of some sort. Noticed that too. Looks to be oriented the wrong way to be an outflow boundary (outflow in this region is oriented NW-SE).

Here is some basic information about them if you didn't know what they were...

Amplitudes of 1-15 hPa/MB and Wavelengths of 50-500 KM (Uccellini and Koch, 1987) Periods of 1-4 HR

Strongest upward motions with Gravity Waves occur just following the surface pressure trough and lead to maximum precipitation rates just ahead of the ridge.

Gravity waves typically form within or near the back edge of a precipitation shield.

Gravity waves can affect an existing cloud pattern in several ways as they propagate through.....

* Modulate the cloud pattern with the development of wave cloud formations
* The wave and cloud can propagate in tandem with little affect on the overall cloud pattern
Click to expand...

In addition, in order to maintain a gravity wave, the same source says you will need wave ducting to be efficient and this can be achieved by having an asbolutely stable sounding in the lower levels. There have also been studies linking gravity waves to wake low events...and given that the cloud pattern is "modulated" in that area...people along the NE/IA border and into SE SD may want to watch out for some briefly gusty winds through 18-19Z until stable layer mixes out.

Whatever the case, there is outflow in that region...just not visible by that feature attm.

...Alex Lamers...
 
Satellite is showing clearing across the IA/NE border... Looks like there is an outflow boundry in SE SD right now on the view as well.

Brief gusty winds is an understatement, we have had winds here constantly at 35-40. Gusts I'm estimating of 45-50 mph...

With those low level winds, that should enhance the hodographs in this area. If those outflow boundries end up on the IA/NE/SD/MN area it could be a heck of a show up here...
 
Did not notice this before, but a large pressure fall bullseye of about 0.10 mb/hr over Jackson/Martin Counties in Minnesota and Dickinson and Emmet Counties in Iowa has developed. I can see why you're getting gusts that high. Looks like a wake low has indeed developed. Could even see some isolated damage reports from that area for non-precip gusts. Apparently my theory was correct. Wake lows are typically not long-fused and therefore the winds should slacken some into the mid afternoon hours.

...Alex Lamers...
 
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