8/4/2004 FCST: Upper Midwest

[nickgrillo]

SWODY2: "THE COMBINATION OF BOUNDARY LAYER DEWPOINTS IN THE 70S AND THE INTENSE VERTICAL SHEAR WOULD APPEAR TO FAVOR A SIGNIFICANT TORNADO THREAT E OF THE SURFACE LOW"

The latest ETA is very promising for tornado potential... With substanial low-level moisture advecting into the Great Lakes region, leading to very strong instability (>2500j/kg CAPEs) and very strong helicities (>500m2/s2 0-3km layer). Hopefully something will turn out tomorrow...

..Nick Grillo..

 

[Robert Dewey]

Well, I originally thought this situation was very intense convective feedback in the ETA, but ALL of the 00Z suite (Canadian models/Euro models) show a very similar solution. The 06Z models are even stronger, with the GFS being most cosistant, while the ETA has pushed a little further south somewhat.

12Z models starting to roll in, and the ETA has the 250MB/500MB jet stronger at the 12Z analysis than the pervious 12HR forecast had, so it may yet again be a little stronger this run. If any of the situations were to verify, I would go as far as saying a significant outbreak of severe thunderstorms and tornadoes (maybe even strong tornadoes given the pretty intense shear for this time of year/good instability/SFC td's). My bet, is if anything close to these solutions occurs, expect at least a strongly worded MDT risk day... The GFS is even more ominous, and has been more consistant (its also in agreement with the Euro models). This may all be one big coincidance, and it may ALL be convective feedback, but thats just too many models (ALL) showing the same solution!

If I live in central or northern OH/IN, I would definately keep an eye on the situation, I may even decided to hit I75 and track on down there...

 

[Jon Miller]

I'm defintely keeping an eye on tomorrow as I live real close to the sig. tornado bullseye in Ohio- about 2 or 3 counties sw of it :

http://198.63.55.43/CENTRAL_ETA212_ATMOS_STP_48HR.gif
http://198.63.55.43/CENTRAL_ETA212_ATMOS_SCP_48HR.gif
http://198.63.55.43/CENTRAL_ETA212_ATMOS_S...SIGSVR_48HR.gif

I'm a little skeptical right now - having a potential spring type of set up in August is way out of the ordinary here in the Ohio/In area- will see what the SPC says in their 1:30(1730 utc`) Day 2 outlook. But I am making preliminary chase preparations - "Be prepared"-Scout motto !

 

[rdale]

12Z Eta rocking the world to my south - helicities of 1000+ along the MI border with CAPEs to 3000 just south of the boundary. 9Z SREF from SPC also shows good agreement over IN/OH, I'm concerned if anything develops at all though along the boundary in extreme southern MI.

SREF also shows that all of the various schemes develop this system fairly close - 50% chance of SigTor > 3, Supercell index of 12, SigSvr 90% chance of being > 40000. My target right now is NW Ohio, where I can hit the stuff along the boundary or head south for the "typical" storms if nothing happens there.

- Rob

 

[Robert Dewey]

I'm gonna side with Rob, I will most likely be heading down into OH for this one... Also, that heavy QPF in MI is interesting (probably overdone, maybe)...

Man, these are some good probablities:

I suspect the afternoon AFD packages will feature more of the severe weather concern over that region (a 180 degree turn from there previous discussions of whether or not to add showers :lol...

[Broken External Image]:http://www.spc.noaa.gov/exper/sref/gifs/forecasts/SREF_prob_supercomp_3_f036.gif

 

[rdale]

I feel the pain... Sunday I had showers in the Wed forecast then Sunday night I went partly cloudy, then yesterday for the 6p I had mostly cloudy then added showers back in for the 11 ;>

GFS just trickling in now.

- Rob

 

[Robert Dewey]

I feel the pain... Sunday I had showers in the Wed forecast then Sunday night I went partly cloudy, then yesterday for the 6p I had mostly cloudy then added showers back in for the 11 ;>

GFS just trickling in now.

- Rob

LOL, what else can ya do though - The models went from nothing to an outbreak in less 06 hours, one must take that with a grain of salt...

 

[tom hanlon]

I feel the pain... Sunday I had showers in the Wed forecast then Sunday night I went partly cloudy, then yesterday for the 6p I had mostly cloudy then added showers back in for the 11 ;>

GFS just trickling in now.

- Rob

LOL, what else can ya do though - The models went from nothing to an outbreak in less 06 hours, one must take that with a grain of salt...

Haven't the models been a little flaky in general lately? I am fairly new to weather forecasting but the SPC and the other forecasts that I have been watching have seemed to change dramatically from one day to the next in the last week. Is all the moisture at the surface to blame for the confusion or is it a problem with the upper level ?

I am cancelling any work for wednesday and hoping for the best, an outbreak in unpopulated areas with high visibility. I70 from Springfield OH to Indianpolis IN or I75 from Toledo to Cincinnati. If it turns into a bust it will be a 600 mile bust rather than a 1500 mile bust.

Visibility declines in Southern OH and IN. So the N 2/3 of either state is a better chase area. Corn and Soybeans in the North, trees and hills in the South.


I am uncertain about how to predict storm motion.
http://www.wxcaster.com/modelskewts.php3?f...STATIONID=_KIND

Shows storm direction/speed at 276 degrees and 26kts . Translated into english that is almost straight south ? and 27 MPH ? is that correct.

 

[Ben Pinette]

NW OH target certainly looks like the place to be. Everything seems to be in place, unless this is ALL convective feedback, which doesn't seem warranted like Robert said.

Initial target at this hour is somewhere around the Fulton, Hancock, Putnam county area. Leaving work at 13:00 so should be in the area around 14:30 at the latest.

 

[Dan Robinson]

OK, this could be the late-season Ohio chase I have been waiting for. Pending a data check in the morning, I will be out the door heading northwest on Route 35. Prelim target is somewhere NW of Columbus, the farther N and W the better. The uncertainty of tomorrow's situation has me a little concerned about making the drive, we'll see in the morning.

 

[Robert Dewey]

SPC still calling possible convective feedback, but they now mention a possible situation for if the models are correct...

...IF
MODEL GUIDANCE IS CORRECT...SUPERCELL TORNADO POTENTIAL WILL BE HIGH
OVER PARTS OF THE AREA ESPECIALLY WITH INITIAL TSTM DEVELOPMENT.

Guess the 18Z and 00Z guidance will make the final decision...

 

[Robert Dewey]

It's beyond my mind why the SPC would even consider not upgrading this area to a MDT risk... which they just did. It's still a slight risk? Unbelievable.

Probably because of the big swing in model guidance - To go from a "partly cloudy with showers forecast" to a "severe thunderstorms with tornadoes" is a bit dramatic for 6 hours, the difference between yesterdays 18Z and 00Z Init. One has to make sure, since the situation can flip just as fast - i.e the 18Z data may show nothing...

 

[Amos Magliocco]

I'm trying to figure out exactly which features are suspected of over-amplification due to convective feedback. The low level wind fields?

 

[Ben Pinette]

They're still highlighting as a Slight due to the convective feedback problems with all of the models. Too much uncertainty, as whatever happens tomorrow will be solely based upon what does or doesn't happen today.

Sorry, a little late there. Robert already has it covered.

 

[rdale]

It wraps up some VERY strong winds in the low-levels, and the GFS does the same but not with that intensity. SPC should not upgrade to MDT given the unlikeliness of this event.

- Rob